three gorges dam case study

Case Study: The Three Gorges Dam

The 3 Gorges Dam project - China

• This is an example of a large scale development project designed to:
• Create more jobs
•  Allow large ships to navigate the river and reach Chungong Create thousands of jobs Develop new towns and farms
• Provide 10% of China’s electricity through HEP Increase tourism along the river
• Protect precious farmland from flooding
• However it also has a number of disadvantages:
• Over 150 towns and 4500 thousand villages will be flooded displacing people from their homes
• 1.3 million people will be forced to move
• The river landscape will be forever changed
•  The lake which will be created could become very polluted from industrial waste

This video showcases the Chinese Three Gorges Dam Project

Project in-depth: The Three Gorges Dam, China

Introduction to the Dam

Three Gorges Dam, China is the world’s largest hydroelectric facility. In 1994, work on the project started with the goal of not only creating power to fuel China’s rapid economic expansion but also controlling the country’s longest river, protecting millions of people from deadly floods, and elevating the project to a point of great technological achievement and national pride. Initially, the entire project took about two decades to complete, Construction on the Three Gorges Dam was completed in 2008 it cost 200 billion yuan ($28.6 billion). The dam is significantly larger than Brazil’s 12,600MW Itaipu facility, standing 185 meters tall and 2,309 meters wide as one of the largest hydroelectric plants in the world.

NSPD: Water Quality, Ecosystems

Stakeholder Types: Federated state/territorial/provincial government, Sovereign state/national/federal government, Local Government, Environmental interest, Community or organized citizens.

Sun Yat-sen first stated his plan to construct the dam in 1919. In addition to endorsing the project to mitigate the ongoing threat of flooding, Mao Zedong also revealed his plan to construct the dam in one of his most well-known poems, “Swimming” (1956). At the end of the first phase, two Chinese equipment vendors were crucial. 

Working with the two foreign groups, Harbin Power Equipment and Dongfang Electrical Machinery benefited from stringent technology transfer rules. Dongfang collaborated with the Voith General Electric and Siemens consortium, while Harbin worked with the Chinese company Oriental Motor and the Alstom, ABB, and Kvaerner grouping. Nearly the construction of the final two units of the first phase took place in China. Chinese groups were given construction chores. Contracts totaling $800 million were awarded to Gezhouba Share Holding, Yichang Qingyun Hydropower Joint Management, and Yichang Three Gorges Project Construction 378 Joint Management just before the equipment announcements. The powerplant and dikes were constructed as part of the work.

Time of Construction 

Because the Three Gorges Project needed to manage flood discharge on a massive scale, if a typical architecture of the flood-discharge orifices had been used, a large leading edge would have been needed for the discharge sections. The length of the flood-discharge dam sections had to be as short as possible while still meeting the requirements of energy dissipation and anti-scouring due to the large installed capacity of the power station and the large number of installed units. In addition, construction diversion and navigation needed to be considered.

Excavation and earth-filling 

To build the plant, 102.83 million cubic meters of rock and soil had to be excavated, and 31.98 million cubic meters had to be filled in.

Concrete and metal placement 

Additionally, 27.94 million cubic meters of concrete had to be placed, and a 256,500-ton metal frame had to be installed. 

Hydro turbine generator 

Production of hydroelectric power started small in 2003 and grew steadily as more turbine generators were added over the years until 2012 when all 32 of the dam’s turbine generator units were in use. With those units and two more generators, the dam could produce 22,500 megawatts of energy, making it the world’s most productive hydroelectric dam. With an annual power generating volume of 111.88 terawatt hours in 2020, the hydropower project set a new world record.

The Three Gorges Dam is a gravity structure made of concrete that is straight-crested and spans 2,335 meters (7,660 feet) with a maximum height of 185 meters (607 feet). Its design calls for 463,000 metric tons of steel and 28 million cubic meters (37 million cubic yards) of concrete. Large portions of the Qutang, Wu, and Xiling gorges are submerged by the dam for around 600 km (375 miles) upstream. 

This creates a massive deepwater reservoir that enables oceangoing freighters to travel 2,250 km (1,400 miles) inland on the East China Sea from Shanghai to the inland city of Chongqing. The complex’s five-tier ship locks, which let vessels weighing up to 10,000 tons pass the dam, and ship lift, which enables vessels weighing up to 3,000 tons to bypass the ship locks and pass the dam more rapidly, aid in the navigation of the dam and reservoir. The lift was the largest ship lift in the world when it was finished in late 2015. It measured 120 meters (394 feet) long, 18 meters (59 feet) broad, and 3.5 meters (11 feet) deep.

Context and debate surrounding the Three Gorges Dam

The concept for the Three Gorges Dam was first floated by Chinese Nationalist Party leaders in the 1920s. However, it gained fresh momentum in 1953 when Mao Zedong, the Chinese leader, ordered feasibility assessments of several locations. In-depth project planning started in 1955. The dam was not without its critics, despite the claims of its supporters that it would prevent catastrophic floods along the Yangtze, ease inland trade, and supply much-needed electricity for central China. The Three Gorges project was criticized from the moment the designs were put forth until they were completed. 

The threat of a dam collapse, the 1.3 million people (some critics claimed the number was closer to 1.9 million) who were uprooted from over 1,500 cities, towns, and villages along the river, and the devastation of numerous unique architectural and archaeological sites along with breathtaking landscapes were among the main issues. 

In addition, there were worries—some of which came true—that the reservoir would become contaminated by industrial and human waste from towns and that the massive volume of water it contained may cause landslides and earthquakes. Several smaller, far less expensive, and less problematic dams on the Yangtze tributaries, according to some Chinese and foreign engineers, could produce as much electricity as the Three Gorges Dam and regulate flooding almost as effectively. Building those dams, would, they claimed, allow the government to fulfill its top priorities without taking unnecessary chances.

An Environmental Catastrophe?

Chinese officials assert that the Three Gorges Dam has been successful in preventing floodwaters from spreading, despite the destruction. China Three Gorges Corporation, the dam’s operator, informed China’s official news agency Xinhua that 18.2 billion cubic meters of potential floodwater had been caught by the dam. 

The dam “effectively reduced the speed and extent of water level rises” on the middle and lower reaches of the Yangtze, an official from the water resources ministry told the state-run publication China Youth Daily. However, some geologists claim that the poor effectiveness of the Three Gorges Dam in preventing flooding has been exposed, given that numerous gauging stations monitoring river flows in the Yangtze basin are witnessing record-high water levels this summer it involved uprooting over a million people along the Yangtze River.

Furthermore, the government’s claim that the dam could shield the nearby villages from a “once-in-a-century flood” has been contested on multiple occasions. The Yangtze basin experienced its highest average rainfall in over 60 years since June, which led to the river and its numerous tributaries overflowing, reinforcing those fears. Over 158 persons have lost their lives or disappeared, 3.67 million residents have had to relocate, and 54.8 million individuals have been impacted, resulting in horrifying financial losses of 144 billion yuan ($20.5 billion).

Concerns about sustainable development and proper water management have surfaced internationally due to the project’s far-reaching effects. All of the measures as mentioned earlier place a strong emphasis on cooperative fact-finding, mutual benefits discussions, technical expertise, inclusion, transparency, and collaborative adaptive management , all of which are progressively enhancing Chinese governance in the areas of water management and dam construction.

China: The Three Gorges Dam Hydroelectric Project (no date) China: The Three Gorges Dam Hydroelectric Project – AquaPedia Case Study Database. Available at: https://aquapedia.waterdiplomacy.org/wiki/index.php?title=China%3A_The_Three_Gorges_Dam_Hydroelectric_Project (Accessed: 01 December 2023). 

Hvistendahl, M. (2013) China’s Three Gorges Dam: An environmental catastrophe? Scientific American. Available at: https://www.scientificamerican.com/article/chinas-three-gorges-dam-disaster/ (Accessed: 28 December 2023). 

Three Gorges Dam hydroelectric power plant, China (2021) Power Technology. Available at: https://www.power-technology.com/projects/gorges/?cf-view (Accessed: 01 December 2023). 

Three Gorges Dam (2023) Encyclopædia Britannica. Available at: https://www.britannica.com/topic/Three-Gorges-Dam (Accessed: 01 December 2023). 

Gan, N. (2020) China’s Three Gorges Dam is one of the largest ever created. was it worth it? CNN. Available at: https://edition.cnn.com/style/article/china-three-gorges-dam-intl-hnk-dst/index.html (Accessed: 01 December 2023). 

 (2022)The Three Gorges Project. Available at: https://www.engineering.org.cn/en/article/35384/detail (Accessed: 01 December 2023). 

A recent graduate, passionate about learning tangible and intangible concepts and ideas relating to space, time and people, is mostly interested in looking at how built spaces is a medium of cultural and social identity. Architecture for her is constant search. she is interested in representing built designs better with graphics,drawings and writing.

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River management in an emerging country

Edexcel iGCSE > River Environments > River management in an emerging country: China’s Three Gorges Dam

China’s Three Gorges Dam

The Three Gorges Dam, located on the Yangtze River, is the largest multipurpose river management structure globally. The dam, over 2 km long and 100m high, was finished in 2009, forming a lake over 600 km long behind it. The Yangtze basin, home to 400 million people and providing 66% of China’s rice, covers 1.8 million km2 and releases 24,000 m’/second of water annually.

The Three Gorges Dam

The project boasts several benefits:

• Flood management, protecting 10 million downstream residents in cities like Wuhan, Nanjing, and Shanghai from the river’s seasonal floods.
• A massive electricity generation capacity of 22,500 MW, primarily powering Shanghai and Chongqing, making it the world’s largest power station.
• Incorporation of locks for navigation, promoting shipping above the dam and boosting tourism with the growth of cruise ships on the river.
• During dry spells, ensure downstream water supply for agricultural, industrial, and domestic uses.

However, the dam has also attracted criticism for several reasons:

• Over 1.25 million people were displaced to make space for the dam and lake.
• The dam sits in an earthquake -prone region, where landslides occur frequently.
• The dam’s silt trapping reduces the reservoir ’s capacity and the downstream farmland’s fertility over time.
• The dam disrupts aquatic ecosystems.

The Three Gorges Dam on the Yangtze River, the world’s largest river management scheme, provides flood control, powers cities, promotes tourism and shipping, and supplements water supply.

Over 1.25 million people were displaced due to the dam’s construction.

The dam’s location in an earthquake-prone region leads to frequent landslides.

Silt trapping by the dam reduces reservoir capacity and downstream farmland fertility and disrupts aquatic life.

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Original research article, case study: influence of three gorges reservoir impoundment on hydrological regime of the acipenser sinensis spawning ground, yangtze river, china.

• 1 Changjiang River Scientific Research Institute, Wuhan, China
• 2 Key Laboratory of River Regulation and Flood Control of MWR, Wuhan, China

After the construction of the Three Gorges Dam (TGD) in China, the downstream has been affected by the reduction in sediment discharge and regulation of flow processes, which have resulted in severe scouring and changes hydrological regime. Consequently, the spawning ground of Chinese sturgeon distributed along the downstream Yichang reach could be affected. This study examined the effects of TGD on the streamflow, sediment load and channel morphology downstream based on in situ measured data. Results showed that, after the impoundment of the TGD, sediment load at the downstream Yichang hydrological station decreased significantly, and the Yichang reach continued to be scoured. The distribution of erosion was uneven, and the scouring mainly occurred in the branching channels. The channel gradient and riverbed roughness increased with the erosion of the river cross section. After more than 10 years of erosion, the riverbed scouring and armouring in the Yichang reach was basically completed, thus we expected that the spawning grounds of Chinese sturgeon could be retain as the riverbed tends to be stable. The findings in this work have implications in the protection of the critically endangered Chinese sturgeon.

Introduction

The Three Gorges Reservoir (TGR) is one of the largest water projects in the world. While it plays an important role in flood control and water utilisation, the TGR dramatically changes the incoming water and sediment conditions in the downstream reaches ( Yang et al., 2007a ; Zhang et al., 2017 ; Guo et al., 2019 ). Owing to the storage and regulation performed by the reservoir, extensive sediment is deposited in the reservoir, thereby significantly reducing the sediment concentration of the flow discharged downstream. The sediment carrying capacity of the water flow is severely sub-saturated. Riverbed scouring and armouring critically impacts the flood control, navigation, ecology, and environment of the lower reaches ( Friedman et al., 1998 ; Yang et al., 2014 ; Zhou et al., 2014 ).

Global researches demonstrated that about 30% of fish species in freshwater have become endangered, threatened, or extinct in the past few decades, which is much worse than in marine ecosystems ( Liermann et al., 2012 ). Chinese sturgeon Acipenser sinensis , mainly lives in the mainstream of Yangtze river, the continental shelf of East China Sea and Yellow Sea. It is one of the first-class national protected animals in China, and has been classified as Critically Endangered in the IUCN Red List of Threatened Species. The spawning grounds of Chinese sturgeon were in the upper Yangtze river and the Jinshajiang river, covering a stretch of at least 600 km of the river length. However, after the construction of Gezhouba Dam (GD) in January 1981, Chinese sturgeon could not go to the previous spawning grounds and fish alternatively spawned within a 30 km section below the GD, which is much smaller than the original spawning ground in the upper reach of the Yangtze river ( Chang, 1999 ; Wang et al., 2013 ). In 2003, the TGR (∼38 km upstream of Gezhouba Dam) began to operate, resulting in a large change in the downstream hydrological regime ( Guo et al., 2012 , 2020 ). It is urgent to protect Chinese sturgeon from extinction as the population of this endangered species in the Yangtze river has declined remarkably in recent decades due to the influences of habitat loss, overfishing, and hydrologic regime changes ( Zhuang et al., 2016 ; Shen et al., 2018 ). The new spawning ground plays a crucial role in preserving Chinese sturgeon species. Thus, the conservation of this area is crucial.

Because of its importance, many researchers have studied the evolution and hydrodynamic characteristics of this reach. Li et al. (2011) analysed its flow-sediment conditions. Zhou et al. (2017) studied the shape of its cross section and variation in flat discharge and considered that the cross section tends to be narrower and deeper. However, other researchers ( Zhang et al., 2013 ; Han et al., 2017 ; Xia et al., 2017 ) focused on the entire middle and lower reaches of the Yangtze River. Most of the riverbed in the middle and lower reaches of the Yangtze River have sandy materials, which are easy to deform, while only the Yichang reach has a sandy pebble riverbed in the middle reaches. In addition to morphological changes, bed sediment armouring often occurs in the scouring state ( Doyle and Harbor, 2003 ; Yuan et al., 2012 ; Li et al., 2019 ). However, the impacts of the specific variations of hydraulic condition and channel morphology on the spawning ground of Chinese sturgeon just a few 10 km downstream of the GD remain unclear. Although the spawning behaviour in the downstream site next to GD has been detected after the impoundment of TGD, the spawning has been lowered in quantity and quality, moreover, the natural spawning activities of Chinese sturgeon has been interrupted for 3 consecutive years from 2017 to 2019. Therefore, it is necessary to figure out the effects of the newest changes in the river regime, riverbed materials, and response to flow conditions in the suitability of the only existed spawning ground for Chinese sturgeon. Our objectives were to analyse the impact of the impoundment of TGD on the water-sediment conditions and riverbed evolution of the Yichang reach and their influences on the spawning ground of Chinese sturgeon recently based on measured data from 2003 to 2018. It is expected to provide reference for the protection of Chinese sturgeon spawning grounds and the evolution of sandy pebble riverbed downstream of other dams.

Study Area and Methods

The Yangtze river is the longest river in China with a total length of ∼6,300 km, and it provides essential habitat for many fish species. According to the geographic and hydrological properties, the Yangtze river is usually divided into upper, middle and lower reaches with divisions at Yichang and Hukou ( Figure 1A ).

Figure 1. (A) Boundaries of the Yangtze River Basin. (B) Map of the Yichang reach. The yellow area in (B) shows the spawning ground of Chinese sturgeon, and red lines indicate the cross sections from Yi34-Yi51 without Yi35. DGB, Dagong Bridge; BTH, Baotahe; YZB, Yanzhiba; AJZ, Aijiazhen; LPL, Longpan Lake; MPX, Mopanxi; HYT, Huyatan; GLB, Gulaobei; HHT, Honghuatao.

The Three Gorges Dam (TGD) locates at the outlet of the upper Yangtze river, approximately 40 km upstream of the Yichang hydrological station. The storage capacity of TGR is about 393 × 10 8 m 3 , corresponding to its normal impoundment water level of 175 m. The GD locates about 38 km downstream of the TGD, and it is the largest runoff hydropower station with low water head and large flow discharge in the world. The GD was China’s largest hydroelectric facility with a total storage capacity of 15.8 × 10 8 m 3 until the completion of the TGR project.

As the spawning ground of Chinese sturgeon have been changed to downstream of GD since 1982, the Yichang reach was selected as the study area.

The Yichang reach is located at the entrance of the middle reaches of the Yangtze river, which is a transition section from a mountainous river to a plain river. Restricted by the low mountains and hills on both sides of the river, the trend of the entire reach is from northwest to southeast. This reach starts at the GD and ends near Gulaobei (GLB), with a length of ∼30 km. The Yichang reach is generally straight, with Yanzhiba (YZB) forming a river island. The deep channel is close to the left bank, which is submerged and exposed to water in normal water periods. Hence, the Yangtze river is divided into left and right branches. The left branch is the main branch, whereas the right branch is cut off in dry seasons ( Figure 1B ).

Data Acquisition

Streamflow and sediment in the Yichang reach mainly come from the upper Yangtze river. Annual hydrological data including flow discharge, sediment load, and median particle size since 1950 were collected at the hydrometric station of Yichang, which is located just a few kilometers downstream of the GD ( Figure 1B ). The data used in the present study were obtained from the Changjiang Water Resources Commission (CWRC) 1 , and their consistency was verified.

In order to calculate the cumulative volume of channel deformation and analysis the plane change, the post-flood cross-sectional profiles surveyed at 17 fixed locations annually since 2002 were collected in the study reach, with the section number ranged from Yi34- Yi51 (without Yi35). The distance between two consecutive sections varies from about 1–3 km, with a mean spacing of around 2 km.

This study analysed the erosion and deposition volume and morphological changes of the river channel, riverbed armouring, gradient changes, and resistance changes.

The cross-section morphology method could accurately reflect the volume changes and distribution circumstances along the main channel of the rivers, as well as the beach and whole reach area on the cross-sections. Thus, the volume of erosion and deposition was calculated using the cross-section morphology method ( Xia et al., 2017 ; Yuan et al., 2018 ). By cutting out several cross sections of the river channel, assuming that the changes between two adjacent sections are gradual. The storage capacity between sections Vi can be calculated using a trapezoidal formula as:

where A i and A i + 1 indicate the areas of the i th and i + 1th section, respectively. ΔL is the distance between the i th and i + 1th sections. Differences between Vi under varied years show the volume of erosion (negative) or deposition (positive).

When the circumstances of water and sediment changed, the river channel would usually gradually reach a new balance state through continuous self-adjustments. The fluvial facies relationship is known as a quantitative relationship between the section morphology and longitudinal profile ( Yuan et al., 2018 ). In this study, the fluvial facies coefficient ζ was used to represent the morphological variation, which was expressed using the width to depth ratio as:

where B is the river width, h is the water depth.

Riverbed armouring is reflected by changes in the characteristic particle size of the riverbed materials ( Doyle and Harbor, 2003 ).

The change in roughness was back-calculated using the Manning model:

where A ¯ = the mean area river of import and export cross section in the channel, m 2 ; Q ¯ = the mean discharge of import and export cross section, m 3 /s; R ¯ = the mean hydraulic radius of import and export cross section, m; and J = the flow surface slope.

Streamflow and Sediment Changes

The Yichang hydrological station is the control station. Figure 2 shows the variation in annual runoff and sediment load over time at Yichang station. The annual runoff at Yichang station fluctuated yearly with no clear trend, but the annual sediment load has been decreasing significantly since around 2001 when the TGD was closed to operation.

Figure 2. Annual runoff and sediment load at Yichang station.

Before the impoundment of the GD (1950–1980), the multi-year average runoff and sediment load at Yichang station was 4,518 × 10 8 m 3 and 5.15 × 10 8 t, respectively. After the impoundment of the GD and before the impoundment of the TGR (1981–2002), the multi-year average runoff at Yichang station was 4,348 × 10 8 m 3 , and the mean annual sediment load was 4.59 × 10 8 t. Before the impoundment of the TGR, the annual runoff and sediment load at Yichang station underwent minor changes. Since the operation of the TGR (2003–2018), the annual runoff at Yichang station fluctuated around the average value over many years with minor changes, while the annual sediment load declined sharply down to about 0.36 × 10 8 t.

The variations of impoundment phases of the TGR was as follows: the storage level was raised to 135 m in 2003, and the cofferdam power generation period was initiated (period A). Then in October 2006, the storage level reached 156 m, marking the start of the initial storage period (period B). Two years later, the TGR began to impound water to the normal level of 175 m on September, 2008, known as the 175 m trial storage period (period C) ( Ren et al., 2021 ). From 2003 to 2018, the outflow sediment became thinned. As shown in Figure 3 , during the power generation period at the cofferdam, the mean particle size of the outflow sediment decreased sharply from 0.044 to 0.014 mm. The proportion of particles finer than 0.031 mm increased from 75.3 to 86.7%, and the proportion of particles larger than 0.125 mm decreased from 14 to 5.4%. The mean and median particle sizes of the outflow sediment had minor changes in the period B of the initial storage period from 2006 to 2008, and the proportion of coarse sediment continued to decrease. While during the trial storage period from October 2008 to December 2018, the mean and median particle sizes of suspended sediment slightly increased. In 2018, the median particle size at Yichang station was 0.009 mm, and the coarse-grained sediment content was 0.5%.

Figure 3. Changes of the median and mean particle size of suspended sediment at Yichang station.

Since the TGR has been in operation, the changes in median and mean particle sizes of the suspended sediment during different periods basically demonstrated the same patterns. In other words, the discharged sediment became finer. During the power generation period at the cofferdam, the difference between the median and mean particle sizes of the suspended sediment discharged from the reservoir was large, indicating that the degree of non-uniformity of sediment gradation was large. However, in both initial and trial storage periods, the difference between the median and mean particle sizes decreased, indicating that, owing to the reservoir regulation, the non-uniformity of the suspended sediment discharged from the reservoir was reduced. From January 2013 to December 2018, the mean particle size of suspended sediment increased, but it was notably smaller than that during the cofferdam impoundment period. Further, the median particle size exhibited no significant changes.

Riverbed Erosion and Deposition

The shoreline of the Yichang reach is composed of hilly terraces with strong impact resistance. With the control of bedrock nodes along the course, the overall river regime has been stable over the years, and the main stream has been relatively stable.

Since the impoundment of the TGR, the channel was mainly in the scouring state. Analysis of the main flow line changes demonstrated that the flow in this section was relatively smooth, and no large backflow areas were observed. During the high water periods, the main stream was in the middle of the channel and could submerge the YZB. The maximum flow velocity was observed at the tail of YZB. During the normal and low water periods, branching flow was formed at the head of YZB, and the main stream flowed to the left channel. The maximum velocity happened at the head of YZB. During the low water period, the main stream started from the GD, and turned right to the head of YZB. After flowing out of YZB, the main stream slightly tended to the right bank during the low water period and tended toward the centre of the channel during medium and high water periods.

With the normal operation of the TGR, the scouring intensity of the riverbed in this section of the river gradually decreased, and the scouring slowly moved downstream. The scouring in the YZB reach was the most evident from 2002 to 2004, and the scouring intensity of the entire reach decreased slightly after 2004. Since the initial storage period of the TGR, the riverbed between the Yichang station and YZB presented a state of alternation of scouring and deposition until 2016, with a small change range. From YZB to Huyatan (HYT), the erosion remained dominant, and the location of erosion was significant in the YZB section. Table 1 shows the calculations of sectional erosion and deposition amount in the Yichang reach. It can be seen that from 2002 to 2016, the Yichang reach presented a scouring state, and the cumulative amount of erosion was 1,565 × 10 4 m 3 . Among them, the erosion in the YZB section was the most severe, and the total amount of erosion attained 47.5% of the entire Yichang reach ( Table 1 ).

Table 1. Statistics of the erosion and deposition volume in the Yichang reach at the water level of 43.3 m in different periods.

Plane Changes

The thalweg line of the Yichang reach started from the GD, and it went down along the left trough of YZB and then gradually transited to the right bank after leaving YZB. In the vicinity of Longpan Lake (LPL), the thalweg line transited to the left bank and then turned to the right bank. It gradually transited to the left bank until reaching the Mopanxi (MPX). This trend was basically consistent with that of the main stream and underwent minor changes over the years ( Figure 4 ). According to the change of main stream and thalweg, the interannual oscillation of the thalweg was small.

Figure 4. Thalweg variations along the Yichang reach before and after the impoundment of the Three Gorges Reservoir.

It was found that the river reach just downstream of the GD (sections Yi 34∼Yi 39) almost reached the bedrock, and the riverbed exhibited strong anti-scouring capability. The elevation variation range over the years was small, from 18 to 22 m. The changes of the thalweg were relatively large in the YZB reach (sections Yi 42∼Yi 44). From 2002 to 2008, the elevation of thalweg generally decreased by 2–5 m, while the descending rate of the thalweg slowed significantly from 2008 to 2010. In the reach below YZB, the thalweg descent slowed down after 2002, and the change of thalweg elevation was not significant from 2008 to 2010. From 2010 to 2016, the interannual variations of scouring and deposition of the reach increased, as well as the changes of longitudinal section of the thalweg.

Typical Marshland

The main river island of the Yichang reach is YZB, which is about 10.2 km away from the GD. YZB is a river island near the right bank, which stretches from Baotahe (BTH) down to Aijiazhen (AJZ). During both normal and high water periods, the YZB is submerged, whereas it is exposed during the low water period. After the normal impoundment of the GD and before the impoundment of the TGD, the YZB was basically stable, but the erosion and deposition processes were stronger than that of the natural river channel before the construction of the GD and TGD. In 2002, the 25 m contour lines of the upper and lower sections of the left branch channel were connected to form a complete 25 m deep channel. After 2002, the dam body of YZB was slightly scoured, and its area had been reduced, but the maximum length and width increased slightly. The maximum elevation of dam crest also increased slightly. After the impoundment of the TGD, the YZB was still generally stable, and its dam body erosion and shape change were relatively slow ( Table 2 ).

Table 2. Statistics of the characteristic values of Yanzhiba marshlands under the water depth of 39 m from 2002 to 2016.

Cross-Sectional Morphology

The cross-sectional morphology of the Yichang reach can be divided into three types: V shape for the curved section, U shape for the straight section, and W shape for the branching section. The main parts of erosion and deposition of each type of cross-section were the normal and low water parts of the main channel and side beach of the river bed, and the change of the part above the high water level is relatively small.

According to the analysis of the topographic data of the fixed section over time, the cross-sectional morphology of this reach changed greatly, and the fluvial facies coefficient was around 2–5. The width of the river changed from approximately 900 to 1,500 m, and the cross-sectional change was mainly reflected in the erosion and deposition in the deep channel. The statistics of cross-sectional elements of the normal-water channel in some sections of the Yichang reach showed that the fluvial facies coefficient in this section had a large change along the course and that of the YZB branching channel was large as the channel was wide and shallow. From 2002 to 2016, fluvial facies coefficient showed a decreasing trend, indicating that the river channel in this section tended to become narrower and deeper as the riverbed was undercut ( Table 3 ).

Table 3. Statistics of some cross-section elements of the Yichang reach under the water depth of 43.3 m.

As shown in Figure 5 , the left and right shorelines of the Yichang reach were relatively stable, and the riverbed evolution trend was dominated by deep channel scouring. The erosion range was large. The deep groove expanded yearly and became deeper and longer, while the horizontal dimension remained unchanged overall. The shoals in the whole reach shrank to varying degrees, and the shrinkage amplitude of the river island was slightly less than that of the side beach. With the operation of the TGR, the scouring intensity of the reach was gradually weakened.

Figure 5. Typical cross-section changes of the Yichang reach.

Riverbed Armouring

Since the operation of the TGR, an overall temporal fining trend of the suspended sediment was found, which was in consistent with the decreasing sediment load tendency ( Yang et al., 2014 ; Guo et al., 2020 ). In contrast, the riverbed materials coarsened significantly at Yichang station ( Figure 6 ). The median size of riverbed materials increased from 0.638 mm in November 2003 to 23.59 mm in October 2012. The riverbed composition gradually evolved from sand or sandy pebble before impoundment to pebble with sand. Before the impoundment of the TGR, 99% of riverbed materials ranged from 0.062 mm to 0.5 mm. From 2003 to 2005, 99% of riverbed material sizes were between 0.125 and 1 mm, approximately twice as large as before impoundment. After 2006, the trend of riverbed armouring was more obvious, and the proportion of coarser particles increased annually. The median size of riverbed materials coarsened to 10 mm with annual fluctuations. The coarsening of riverbed sediment at Yichang reach was ascribed to erosion, which tends to resuspend the finer grains and leave the coarser particles on the riverbed ( Yang et al., 2018 ). It was observed that the maximum coarsening of surficial sediment was immediately downstream of the TGD, and riverbed erosion has become the dominant source of suspended sediment in the middle and lower Yangtze reaches since the beginning of the TGD ( Yang et al., 2018 ; Guo et al., 2019 ). The size of riverbed materials at Yichang station increased to the maximum value in 2009 due to the 175 m experimental impoundment of the TGR in 2008, with pebbles as the main component. After 2010, there was more sediment deposition in the Yichang reach, with a slight increase in the content of fine-grained materials. From 2012 to 2014, the riverbed materials changed with the erosion and deposition conditions in the river reach. Gravel and pebbles were still the main components of the riverbed materials. The content of sand particles less than 2 mm was low. In 2015, due to the reduction in incoming sand from upstream, weak scouring occurred in the Yichang reach, and the proportion of gravel and pebbles increased. Thus, the riverbed at Yichang station coarsened significantly. The median post-flood particle size of riverbed materials at Yichang station in 2017 was 43.1 mm. Although the surficial sediment at Yichang reach has been coarsening significantly, it is expected that armouring of the coarsening reach will prevent further erosion.

Figure 6. Gradation curve of post-flood riverbed materials at Yichang station.

Changes in Gradient and Roughness

Changes in gradient.

The common result of riverbed undercutting erosion is water level drop. Since the GD has been in operation, low water levels at stations along the reach (Q: 5,000 m 3 /s) demonstrated a cumulative downward trend ( Table 4 ).

Table 4. Statistics of low water levels at each water level station along the Yichang reach under the flow discharge of 5,000 m 3 /s.

Figure 7 shows the water surface gradient of each section of the Yichang reach under different flow rates in 2012 after the impoundment of the TGR. The figure demonstrates that as flow rate increased, the overall gradient also increased. Gradients around YZB and MPX were small, which could control the low water level. For intermediate flood discharges, the control of YZB on the gradient is clearly weakened, while MPX has certain control at all discharge levels.

Figure 7. Water surface gradient of each section of the Yichang reach at different flow discharges in 2012.

Since the impoundment of the TGR, there has been a certain degree of adjustment in the water surface gradient in the Yichang reach ( Figure 8 ). In general, the gradient of the downstream reach of the dam is lower, however, the gradient of the Yichang reach increased, especially in the section from the GD to the BTH. A larger gradient indicates that the roughness of the section will increase. Accordingly, the gradient of the section from YZB to AJZ slightly increased.

Figure 8. Water surface gradient variation of each section in the Yichang reach at two different flow discharges: (A) 5,800 m 3 /s; (B) 10,000 m 3 /s.

Changes in Resistance After Riverbed Armouring

For sandy pebble reaches, the resistance of sand particles on the riverbed surface is a major source of resistance. Downstream of the TGD, the differences in grain size after bed surface armouring increased 100-fold, which inevitably led to a significant change in riverbed surface resistance ( Rinaldi and Simon, 1998 ).

Resistance adjustment can be visualized by the changes in the waterlines ( Zhou et al., 2018 ). Using the measured topographic and water level data of 2003 and 2012, the changes in channel roughness were analysed. The results showed that the channel roughness in 2012 increased significantly compared to that in 2003 ( Table 5 ), which was consistent with the riverbed surface armouring. The erosion of the cross section increased, and thus the hydrodynamic force was reduced. The roughness increase was beneficial to restrain the drawdown of normal and low water levels and reduced the flow rate. However, it was also likely to increase the turbulence near the riverbed, especially at the normal and low flow rates.

Table 5. Changes in topography and roughness before and after scouring.

Effects on the Spawning Ground of Chinese Sturgeon

After the construction of GD, the spawning ground of Chinese sturgeon located just downstream of the GD (Yichang reach) was the only natural one that had been found ( Tao et al., 2009 ). Thus it is crucial to retain the availability of this spawning ground for the sustainability of this critically endangered species.

Researches showed that sturgeons were selective in their spawning ground, and the specific spawning locations were generally around the sharp bends of river with complex flow patterns, with hard bed materials, and with water depth ranging from a few meters to 20–30 m ( Paragamian and Wakkinen, 2002 ). Some biologists held that there was a certain relationship between the spawning of Chinese sturgeon and the hydrology as well as the substrate types of the river bottom ( Chang, 1999 ; Zhang et al., 2011 ; Zhou et al., 2014 ). The spawn of Chinese sturgeon requires a series of certain environmental conditions, including water temperature, riverbed topography, substrate, hydrological and hydraulic conditions etc. ( Zhang et al., 2011 ; Shen et al., 2018 ). It was found that the preferred flow velocity and suspended sediment concentration for the spawning of Chinese sturgeon were in the range of 1.0–1.7 m s –1 and 0.2–0.3 kg m –3 , respectively ( Yang et al., 2007b ). Considering the water depth, the Chinese sturgeon appears more frequently in 6–15 m, regardless of whether it is male or female ( Yang, 2007 ).

Among the influencing factors, the topography of the riverbed plays a key role, as the change of it could lead to the variations of substrate, hydrological and hydraulic conditions to a certain extent. According to the results of filed surveys, it was found that the morphology, gradient, and roughness of the Yichang reach had suffered from significant changes due to the erosion by the clean water from the TGR. The channel gradient increased, especially in the upstream section of YZB. The riverbed roughness also increased accordingly. With the erosion of the river cross section, the hydrodynamic force of the reach was weakened, which brought new impacts on the spawning ground of Chinese sturgeon. Good news is that except for the branched section, the adjustment range of riverbed scouring in the Yichang reach was small and stable. Thus, it is expected that as the riverbed topography tends to be stable after more than 10 years of erosion since 2003, the spawning grounds of Chinese sturgeon could also be retained. Thoroughly evaluation of the ecological effects is required in future studies, and necessary measures should be taken to rehabilitate the spawning ground of Chinese sturgeon if the adverse effects on the survival and development of Chinese sturgeon continues.

This work examined the construction of GD and TGD and their impacts on the streamflow, sediment load and channel morphology downstream based on in situ measured data. The operation of the GD reduced sediment inflow to Yichang station and triggered the prevailing scouring of the Yichang reach, which is the only regular spawning ground of Chinese sturgeon after the construction of GD. The impoundment of TGD greatly altered the water-sediment conditions of Yichang reach, which is manifested in the flow process regulation, sharp sediment content reduction, and particle size decrease etc. Thus, the river channel was further eroded, especially in the form of undercutting.

In recent years, channel erosion has been uneven as there are some scour resistant nodes in the reach, such as YZB and MPX. The water surface gradient is controlled by such nodes, and the water level of each section drops unevenly. Overall, the low water surface gradient has decreased. According to the grading of riverbed sediment, the riverbed scouring and armouring in the Yichang reach was basically completed, and the riverbed material has been transformed from sandy gravel to pebble. The channel gradient and riverbed roughness increased with the erosion of the river cross section, especially in the upstream section of YZB. The hydrodynamic force of the Yichang reach was weakened, while the adjustment range of riverbed scouring was small and stable. It is expected that the spawning grounds of Chinese sturgeon could be retained as the riverbed tends to be stable. Further evaluation and necessary steps should be taken considering the influences of clean water erosion and related problems in the downstream ecological.

Data Availability Statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

Author Contributions

YZ was responsible for the writing and design of data analysis. ZL, SY, MS, and CG were responsible for data analysis and discussion. All authors contributed to the article and approved the submitted version.

This research was funded by the National Key Research and Development Program of China (2019YFC1510704 and 2016YFC0402300), the Fundamental Research Funds for Central Public Welfare Research Institutes (CKSF2019246/HL and CKSF2019171/HL), Natural Science Foundation of China (Nos. 51579014, 41906149, and 51609013), and the National Major Hydraulic Engineering Construction Funds “Research Program on Key Sediment Problems of the Three Gorges Project” (12610100000018J129-05).

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Keywords : Three Gorges Reservoir, Chinese sturgeon, spawning grounds, riverbed evolution, Yangtze river

Citation: Zhou Y, Li Z, Yao S, Shan M and Guo C (2021) Case Study: Influence of Three Gorges Reservoir Impoundment on Hydrological Regime of the Acipenser sinensis Spawning Ground, Yangtze River, China. Front. Ecol. Evol. 9:624447. doi: 10.3389/fevo.2021.624447

Received: 31 October 2020; Accepted: 22 January 2021; Published: 11 February 2021.

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Copyright © 2021 Zhou, Li, Yao, Shan and Guo. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Zhijing Li, [email protected] ; Chao Guo, [email protected] ; [email protected]

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Dams and Wetland Biodiversity: Impacts and Mitigating Measures

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• Published: 15 November 2017

Influence of Large Reservoir Operation on Water-Levels and Flows in Reaches below Dam: Case Study of the Three Gorges Reservoir

• Yunping Yang 1 , 2 ,
• Mingjin Zhang 1 ,
• Lingling Zhu 3 ,
• Wanli Liu 1 ,
• Jianqiao Han 4 &
• Yanhua Yang 1  

Scientific Reports volume  7 , Article number:  15640 ( 2017 ) Cite this article

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The Three Gorges Project (TGP) is the world’s largest water conservation project. The post-construction low-flow water level at the same discharge below the dam has declined, but there remains disagreement over whether the flood level has increased. Measured water levels and upstream and downstream flow data from 1955 to 2016 show that, post-construction: (1) the low-flow water level at the same discharge decreased, and the lowest water level increased due to dry-season reservoir discharge; (2) the decline of the low-flow water level below the dam was less than the undercutting value of the flow channel of the river; (3) the flood level at the same discharge below the dam was slightly elevated, although peak water levels decreased; (4) flood characteristics changed from a high discharge–high flood level to a medium discharge – high flood level; and (5) an expected decline in the flood level downstream was not observed. Channel erosion and the adjustment of rivers and lakes tend to reduce flood levels, while river bed coarsening, vegetation, and human activities downstream increase the flood level. Although the flood control benefits of the Three Gorges Dam (TGD) and the upstream reservoirs are obvious, increased elevation of the downstream flood level remains a concern.

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Introduction.

The huge storage capacity of a river-reach reservoir changes downstream flows and water quantities, intercepts downstream transportation of sediment, and leads to river erosion, water-level adjustments and other impacts, as stream reaches below the dam adapt to the discharge change and the sharp reduction in sediment supply. After construction of the Aswan Dam on the Nile River in Egypt, the average river channel undercut was 0.45 m, and the flow level at the same discharge showed a declining trend 1 . After the establishment of a reservoir on the Missouri River in the United States, the low water level dropped by more than 2.5 m, and the flood level increased by almost 1 m in the lower reaches around Kansas City 2 . In 2011, the Mississippi River flooded with a discharge lower than that measured during the 1927 and 1973 floods 3 , but due to the backwater caused by dense vegetation in higher parts of the floodplain, the flood level increased 4 , resulting in conditions of medium discharge but a high water level. Following r construction of the Danjiangkou Reservoir on the Hanjiang River in China, when the downstream discharge at Huangjiang port and Xiangfan Hydrological Station is less than 5,000 m 3 /s, the water level decreaseds by 1.5–1.7 m relative to pre-construction levels. When the discharge exceeds 10,000 m 3 /s, however, water levels are not significantly reduced compared to pre-construction values 5 . A review of the literature 6 , 7 indicates that following the construction of a reservoir, the low-water level below the dam decreases at the same discharge, while the flood level at the same discharge does not change significantly or increases only slightly, although this will vary due to the different hydraulic factors for different rivers.

The Three Gorges Project (TGP) is the largest comprehensive water conservation project in the world 8 . It has considerable comprehensive benefits, such as flood control, power generation, shipping, water supply, and energy savings 9 . The influence of its construction and operation on the regulation of the downstream river, flood water levels and other important factors has attracted significant attention from researchers. The low-flow water level downstream of the Three Gorges Dam (TGD) is decreasing 10 , 11 , which is consistent with predictions 12 , 13 and also with the decline of the low-flow water level downstream of the world’s other large reservoirs 6 , 7 . At these large reservoirs, downstream flood levels generally increase only slightly or do not change significantly 6 , 7 . As of yet, there is no common understanding of the variation in the downstream flood level before and after construction of the TGD, and it is not certain whether data show a decrease in the downstream flood level 14 ,a small or non-significant increase 15 , or a rising trend 16 , 17 .

Recent studies have shown that, at times when the river downstream of the TGD was actively eroding, the flood level was not reduced. Instead, the flood diversion from the Jingjiang reach to Dongting Lake decreased, and the flood discharge capacity declined further 16 . Comparing the 2003–2013 and 2000–2002 periods, when the flow rate at Hankou Station was 50,000 m 3 /s, the corresponding increase in the water level was 0–1.0 m 17 . During July 2016, flood control water levels were exceeded at the lower sections of Jianli Station in the middle and lower reaches of the Yangtze River, and also at Dongting Lake and Poyang Lake. The total alarm period was 12 to 29 days, the longest since 1999, and in the reach from Hankou to Datong reach and Poyang Lake, the water level was the highest measured since 1999 18 . In 1954 and 1998, the maximum flow rate at Luoshan Station was 78,800 m 3 /s and 67,800 m 3 /s, respectively, and the corresponding water levels were 33.17 m and 34.95 m. Comparing 1954 and 1998, the maximum flow rate had decreased by 11,000 m 3 /s, and the water level had increased by 1.78 m 19 . In 2016, the maximum flow rate at Luoshan Station was 52,100 m 3 /s and the corresponding water level was 34.86 m, indicating that the flow rate had decreased by 15,700 m 3 /s and the water level had decreased by 0.09 m in comparison with those of 1998. After construction of the Three Gorges Reservoir (TGR), a consensus was reached that the lowest water level at the same discharge had decreased. Although it remains controversial whether the flood level has increased, it is necessary to study the characteristics, regularity, and genesis of the changes of the flood level downstream of the TGD. In general, siltation of the shoreline, decline of the branch river, shrinkage of the flood channel, and increased resistance in the river channel caused by coarsening of the river bed and encroachment of vegetation into the river channel are the main factors affecting flood-level elevation 20 , 21 . Following construction of the TGR, the erosion downstream of the dam intensified 22 , and the impact of factors, such as the coarsening of the river bed 23 , 24 , the variation in the number of days of floodplain inundation 23 , and the effects of human activities 25 , 26 , on the flood level is apparently increasing. Therefore, it is very important to conduct the relevant analysis as soon as possible.

The present study uses measured data from the period 1955–2016 to analyse the variation and regularity of the flood level and the low-flow water level below the TGD and to discuss the underlying causes, clarifying the relationship between changes in the low-flow water level and the increase of waterway depth, and the relationship between the change in the flood level and flood-control scenarios. The results obtained in this study provide important reference points for further optimization of the joint control of the TGR and the upstream cascade reservoirs, and prediction of the flood-control scenarios, well in advance of flood events.

Study area and dispatching process of the runoff at the TGR

On the Yangtze River, the main stream above Yichang is the upper reach, with a length of 4,504 km. The middle reaches extend for 955 km from Yichang to Hukou, in which the section Zhicheng – Chenglingji is known as the Jingjiang Reach, which is further divided into the Upper Jingjiang Reach (UJR) and the Lower Jingjiang Reach (LJR) at Ouchikou. The river below Hukou is the lower reach, which is 938 km long (Fig.  1 ). The length of the Yichang–Datong reach of the Yangtze River downstream from the TGR is 1,183 km. The Yichang–Dabujie segment is a sandy cobble reach, 116.4 km long, while downstream from Dabujie is a sandy reach of 1,066.4 km (Fig.  1b ). The main stream of the river in the study area includes the hydrological stations at Yichang, Zhicheng, Shashi, Jianli, Luoshan, Hankou, Jiujiang, and Datong. Flood diversion channels to Dongting Lake include Songzikou, Taipingkou, and Ouchikou, which are known as the three mouths of Dongting Lake. The Xiangjiang, Zishui, Yuanjiang, and Lishui Rivers converge at Dongting Lake and are known as the Four Rivers of Dongting Lake. The Chenglingji Hydrological Station controls the discharge from Dongting Lake into the main stream of the Yangtze River. The Hanjiang River confluence is controlled by Huangzhuang Station. Hukou Station controls the discharge to the river from Poyang Lake, which is fed by the Xiushui, Ganjiang, Fuhe, Xinjiang, and Raohe Rivers, known as the Five Rivers. The impact of the TGR is most significant in the Yichang–Datong reach, which corresponds to the middle and lower reaches of the Yangtze River.

Location map ( a ), and detailed study area ( b ), with hydrologic distribution. Note: The figure shows: ( a ) the geographical location of the Yangtze River reaches, and the study area; ( b ) the study area in more detail, including the length of the reaches, the location of the hydrological stations mentioned in the text, and the compositional information of the riverbed geology; and ( c ) the main water system of the study area. (YZR denotes Yichang to Zhicheng Reach (61 km); UJR denotes Upper Jingjiang Reach (175 km); LJR denotes Lower Jingjiang Reach (173 km); CHR denotes Chenglingji to Hukou Reach (546 km); HHR denotes Hukou to Datong Reach (228 km). Figure  1 Location map ( a ), and detailed study area ( b ), generated using AutoCAD 2009. Then Fig.  1 ( a ), ( b ) and ( c ) were joined by the software of CorelDRAW X6.

Data sources

The hydrological stations involved in this study are Yichang, Zhicheng, Shashi, Jianli, Luoshan, Hankou, Jiujiang, and Datong. Also involved are the three diversion channels to Dongting Lake, and the discharge channels from the Dongting and Poyang lakes, respectively controlled by the Chenglingji and Hukou stations. Runoff rates, flow rates, sediment transport data, and water-level data for the period 1955–2016 were collected from each of the hydrological stations. Deposition, erosion, and cross-section data were collected from the Yichang–Hukou segment from 1987 to 2014. Water-level data were collected along the Yichang–Hankou segment from 1981 to 2016. Information on the depth and width of the shipping channel from 2002 and 2015 was also collected. Data collection times vary, but all data sets end within the past three years, and so include recent information. Table  1 shows the source of each type of data.

Flow regulation of the TGR

The TGR began impounding water in June 2003, reaching an impoundment level of 175 m in three separate stages (Fig.  2 ): (1) June 2003–September 2006; (2) October 2006–September 2008; and (3) October 2008–present. These are distinguished as the cofferdam stage, initial stage, and pilot impoundment stage, with corresponding water retention levels of 135–139 m, 144–156 m, and 145–175 m, respectively. Regulation of water level in the TGR is based on flood peak reduction and drought flow recharge. Thus, during the flood season, the upstream flood peak is drastically reduced to alleviate the pressure of downstream flood prevention, and during the drought season, the discharge is supplemented with the goal of alleviating downstream drought conditions, while increasing channel depth and improving its ecology. Since reaching the 175 m pilot retention stage in 2009, both flood peak reduction and runoff recharge for drought season have become increasingly important. For example, in 2010 the maximum reduction of peak flow reached 30,000 m 3 /s, which ensured that the reservoir discharge rate did not exceed 40,000 m 3 /s. Since 2009, the number of drought season runoff recharge days has increased every year; it reached 189 days during the period between 2015 and 2016, indicating that the flow recharge regulation lasted for more than half of the year (Table  2 ).

Inflow and outflow during the pilot impoundment stage of the TGR, showing the runoff regulation process (2009–2016).

Changes in the flood and low-flow water levels in the reaches below the TGD

Variation of the highest and lowest water level.

The TGR reduces the peak flow so that the corresponding flood level decreases, while allowing an increase in the low-flow water level during the dry season 27 , 28 . The highest and lowest water levels in the reaches below the dam after reservoir construction show the combined effects of reservoir runoff regulation, climate change, channel scouring and silting, human activities and other factors. The occurrence of extremely low runoff and water levels cannot be attributed entirely to the reservoir, climate change is not a negligible factor 29 , 30 .

Minimum water levels

Before construction of the TGR, there was a fluctuating downward trend of minimum water levels at the Yichang, Zhicheng, and Shashi hydrological stations, and the corresponding minimum discharge did not change significantly. After impoundment began at the TGR, the annual minimum water level and minimum flow began to increase (Fig.  3a,b, and c ). The Yichang, Zhicheng, and Shashi stations showed a decreasing trend in the corresponding water levels at the same flow rate in the 4 time periods of 1955–1968, 1969–1987, 1988–2002, and 2003–2016. The minimum water levels and minimum flow rates at Luoshan Station and Hankou Station increased steadily, both before and after the TGP was implemented (Fig.  3d and e ). This change is related to the decrease of the shunt flow volumes of the three outlets of Dongting Lake along the south bank during the same period 31 . The increase or decrease in the corresponding water levels at the same flow rate at Luoshan and Hankou stations in the 4 time periods of 1955–1968, 1969–1987, 1988–2002, and 2003–2016 was not significant.

Minimum water levels and corresponding flows at the hydrologic stations downstream of the TGD.

Maximum water levels

Changes in the maximum water level are shown in Fig.  4 . Before the impoundment at the TGR, the highest water level at Yichang, Zhicheng, and Shashi stations showed fluctuating but generally decreasing trends. After impoundment began, there was no significant trend, but the maximum water levels measured were lower than the pre-impoundment maxima. Before construction of the TGR, the maximum water levels at Luoshan Station and Hankou Station increased slightly, but there was no significant elevation change post-construction. A comparison between the water levels during the 2003–2016 period with the water levels corresponding to the same flow rates before construction of the TGR shows that post-construction water levels were all elevated, and the expected decline did not occur.

Maximum water levels and corresponding flows at the hydrologic stations downstream of the TGD.

Variation of water levels at the same discharge

The years 1998, 2003, 2010 and 2016 were selected as representative years (Fig.  5 ), during which the water levels of the dry-season discharges dropped, while discharges during the flood season showed an increasing trend. For each station, there is a critical discharge below which a declining trend is observed, while discharges greater than this value increased over time. Comparing the 2010–2016 and 2003–2010 periods, the value of this critical discharge showed a decreasing trend, indicating that the flood characteristics had changed from a high discharge and high flood water level to a moderate flood discharge and high flood water level.

Relationship between the water level and flow in reaches below the TGD.

Reasons for the variation in the flood and low-flow water levels and their influence on the flood control situation and channel water depth

Analysis of the causes of the variation of the flood and low-flow water levels.

Before and after construction of the TGR, the adjustment trends of the low-flow water level and flood level of the river channel were different, suggesting that the influentian factors driving the variation of these water levels were also different. After the impoundment was completed, scouring in reaches below the dam mainly occurred as a result of the basic flow channel, and the expansion of the water area below the low-flow water level was the main factor driving the water-level decline 10 . In addition to exceptional reasons, such as elevation of the erosion datum by sedimentation and flooding at the confluence with tributaries, the increase in river channel resistance due to the coarsening of the bed and increased growth of vegetation in the river channel are the major factors leading to higher flood levels at the same discharge 20 , 21 . Due to the combined effect of natural and human factors, the decrease in the water level corresponding to the same flow was greater than the increase in water level. The water level with the same flow exhibited a decreasing trend, which should otherwise have increased. Based on this concept, we analysed the effects of changes in any of the influential factors on the drought and flood water-levels under the same flow-rate conditions in the lower reaches of the Three Gorges Dam.

Effect of river channel geometry adjustment

According to the statistics of the Bureau of Hydrology, Changjiang Water Resources Commission, from 1981 to 2002, the volume of erosion of the Yichang to Hukou reach from the basic flow channel was 4.91 × 10 8 m 3 , the sediment volume of the basic flow channel-bankfull channel was 5.05 × 10 8 m 3 , such that the sediment volume of the bankfull channel was 0.14 × 10 8 m 3 , and the average annual sediment volume was 67.23 × 10 4 m 3 (Fig.  6 ). During the period from October 2002 to October 2015, the cumulative volumes scoured from the basic flow channel and the bankfull channel in the Yichang–Hukou reach were 15.16 × 10 8 m 3 and 15.88 × 10 8 m 3 , respectively, the annual scouring amounts were 1.16 × 10 8 m 3 and 1.22 × 10 8 m 3 , respectively, and 95.46% of the river erosion occurred in the basic flow channel (Fig.  6 ). Before construction of the TGR, sediment deposition in the middle and lower reaches of the Yangtze River was the main reason for the increasing flood level at the same discharge 15 , 32 . After construction of the TGR, erosion in reaches below the dam (Fig.  6 ) could reduce the flood level in theory, but the trend of river bank erosion was opposite to the elevation of the flood level at the same discharge, indicating that river erosion did not cause the decrease in the flood level. The maximum discharge and water levels at the Yichang and Zhicheng stations, both within the sandy cobble reach, were reduced (Figs  3 and 4 ). Even if the flood level increased at the same discharge, the pressure on flood control systems in this section was effectively weakened, due to runoff regulation by the TGR. The increase in the area of the river channels in the upper reaches and the reach-scale bankfull channels of the lower reaches of the Jingjiang reach 22 were conducive to the release of more floods waters. The cross-sectional geometry shows that the shape of the channel above bankfull was not significantly changed (Fig.  6 ). Dongting Lake and Poyang Lake are downstream of the middle and lower reaches of the Yangtze River, and variations in the lake volume will also affect the main channel flood level. Therefore, when analysing the factors causing the increasing flood level at the same discharge in the main stream of the Yangtze River, we must consider the relationship between the river and lakes, human activities, beach vegetation above the bankfull channel and controls in the watershed.

Erosion and deposition changes in the channels of the Yichang–Hukou reach.

The Influence of River and Lake Diversion

Net siltation occurred in the Dongting Lake region from 1960 to 2006, but the overall balance shifted to scouring from 2007–2015. In the Poyang Lake region, there was alternating siltation and scouring from 1960 to 1999, but from 2000 to 2015, there was a tendency for increased scouring (Fig.  7 ). Both lakes receive sediment scoured from upstream rivers 15 , 32 . Before construction of the TGR, the siltation and flooding capacity in the Dongting Lake area decreased, and the flood discharge capacity of the main stream increased, but this did not lead to higher flood levels at the same discharge. Sedimentation of the Luoshan–Hankou reach was the main cause of flood level elevation at the same discharge 15 , 32 . After construction of the TGR, the trend towards increasing erosion in the Dongting Lake and Poyang Lake was reduced, the area flooded during the flood season was reduced 33 , and the storage volume of the lakes was somewhat increased, reducing the contribution of the lakes to floods and reducing the pressure on flood-control measures along the main stream. Flow rates at the entrances to the river control the influence of the lakes on flooding in the main stream and determine whether flooding in the middle and lower reaches of the river is comprised of upstream flood water or a combination of lake water and upstream flood water. However, the flow rate is not the main determinant of fixed flow-rate flood water levels.

Sedimentation in Dongting Lake and Poyang Lake.

Sedimentation in Dongting Lake and Poyang Lake can be expressed as follows:

Effect of beach vegetation

Beach vegetation can help prevent erosion of riverbanks and maintain river bed stability 34 . It also increases flow resistance and thereby decreases the speed of the flow, which increases the water level and affects flood prevention to a certain extent 35 . The Mississippi River in the United States flooded in 2011. Flow rates during that flood were lower than those in the floods of 1928 and 1973 3 . Lush vegetation at higher elevations in the flood plain (corresponding to high beach areas) caused backwater that further increased the flood water level 4 . This led to localized “medium flood flow rate, high flood water level” conditions. Figure  8 shows the number of days per year that the flow rate exceeded 30,000 m 3 /s in 2009–2015 and in 2016 after water was stored in the TGR compared to that in 2003–2008. Over the 2009–2015 period, the number decreased slightly overall, but in 2016, it increased considerably at Luoshan and further downstream (Fig.  8 ). Flooding occurred in the lower reaches of Luoshan and in the middle reaches of the Yangtze River in 2016, and water inundated the floodplain for a longer period of time. Prior to this, the number of days of flooding was low, and the vegetation on the beach was relatively lush, which increased the river flood capacity to flood level. In the Zhicheng – Chenglingji River section, due to the combined effects of peak cutting by the TGR and diversions to Dongting Lake, the floodplain rarely flooded, and thus Jingjiang reach flood control security was guaranteed. In 2016, the flow rate in the Hankou – Jiujiang reach was high, due to flows from the Daoshui, Jushui, Bahe, and Xishui tributaries. These tributaries caused the flow rate in the main stream to rise by as much as 24,800 m 3 /s (measured on June 30, 2016, as the difference between the flow rates at Jiujiang and Hankou stations). This partially explains why the flood water level at Hankou was high in 2016. The channel-boundary node protruding from river bank of the Wuhan–Jiujiang reach is a hindrance to flooding 36 , and when the Wuhan–Jiujiang reach discharge is ≥50,000 m 3 /s, the Tianjiazhen node blocks the discharge of upstream flooding for 2 to 3 days 37 , which also leads to a high flood level capacity, and is one of the reasons for the high flood level of this section.

The regulatory effect of the TGR and the change in the number of days of flooding.

Influence of shoreline control, waterway management, and other human activities

The Jingjiang reach is a major flood control region in the middle reaches of the Yangtze River and is regarded by many to be the most dangerous part of the Yangtze, as river bank collapses occur occasionally 22 . There are ports, wharves, bridges, and scenic works all along the banks of the middle and lower reaches of the Yangtze River, and these occupy portions of the flood control zone and narrow the flood channel. After the floods of 1998, the water conservancy department strengthened and improved the prevention and control embankments on the middle and lower reaches of the Yangtze River, and the flood control capacity of the embankment was increased by 0.51–3.00 m (Table  3 ). The total number of embankment collapses in 2016 was only 0.51% of that in 1998 18 , and there was no greater risk (Table  4 ), indicating that embankment reinforcement and improvement can effectively reduce flooding.

The middle and lower reaches of the Yangtze River have always had the reputation of being a “golden waterway”. During the period from 2003 to 2015, the Yangtze River Waterway Bureau implemented a targeted waterway regulation project. For the sand and cobble river sections, the project goal was to protect the bottom of the river, to prevent the water level in the channel from dropping as a result of further erosion. For sandy river sections, the goal was mainly to protect the bank beaches and central beaches, and protection or adjustment works were carried out at the low beaches of the centre and sides of the Yangtze River and its tributaries. At the same time, to improve the boundary stability, shoreline reinforcement or revetment works were implemented, and the flood storage capacity was somewhat improved by the comprehensive engineering project. In a June 2015 report, the Changjiang River Scientific Research Institute (CRSRI) 38 showed that after remediation of 29 shipping obstructions, 10 sections of beach had a maximum hydraulic resistance of 5–12.2%, and 19 sections of beach had a hydraulic resistance of 0–5%. In seven sections of beach, maximum flood water levels were elevated by 5–12.4 cm, and in 22 sections of beach, maximum flood water levels were elevated by 1–5 cm. Single projects have limited impact on overall flood control, but the combined influence of all bridges and wharves has a significant impact on flood water levels and adversely affects flood control in the channel 39 , 40 .

Effect of river bed coarsening

A rougher river bed increases a river’s hydraulic resistance, and raises water levels. After water was stored in the TGR, the river bed downstream became rougher 23 , 24 . The median grain size (D 50 ) of the surface of the river bed between Yichang and Zhicheng increased by a factor of 48, i.e., from 0.638 mm in December 2003 to 30.4 mm in October 2010. Between Zhicheng and Dabujie, the D 50 value increased by a factor of 20. The roughness increased by 91%, 65%, 3%, and 2% in reaches below the TGD from Yichang to Zhicheng (distance to Yichang is approximately 61 km), from Zhicheng to Dabujie (61 km to 116.4 km), in the upper Jingjiang reach (116.4 km to 319 km), and from Chenglingji to Hukou (319 km), respectively (Table  5 ).

Mathematical model calculations 40 show the following: in the pebble and gravel Yichang–Dabujie reach of the river, after coarsening of the river bed, the water levels corresponding to Yichang flow rates of 5,000 m 3 /s, 10,000 m 3 /s, 23,000 m 3 /s, and 35,000 m 3 /s increased by an average of 1.57 m, 2.04 m, 2.7 m, and 3.3 m, respectively. These values are higher than the actual drop in the water level due to the increased channel depth corresponding to each flow rate increase. This explains how coarsening of the river bed effectively mitigated low water-level drops in this pebble and gravel section of the river. In the sandy reaches downstream from Dabujie, the average increases in the water level corresponding to Yichang flow rates of 5,000 m 3 /s, 10,000 m 3 /s, 23,000 m 3 /s, and 35,000 m 3 /s were 0.13 m, 0.11 m, 0.16 m, and 0.16 m, respectively. These increases were limited relative to the effects of undercutting.

Based on the above analysis, changes in the drought water-level for the same flow were as follows: before and after the impoundment of the TGR in the Yichang-Zhicheng and Upper Jinjiang Reach, river channel erosion was the main cause of the decreased drought water-level; in the Lower Jingjiang Reach, Chenglingji-Wuhan, and Wuhan-Hukou reach, river channel sedimentation before the impoundment developed into erosion after the impoundment, and because the decrease in water level caused by channel erosion was similar to that caused by channel coarsening, there was no obvious trend in the same-flow drought water level. The changes in the flood water-level under the same flow-rate were as follows: Before and after the abovementioned impoundment, the Yichang-Zhicheng and Upper Jingjiang Reach exhibited a continuous erosion trend; the Lower Jingjiang, Chenglingji-Wuhan, and Wuhan-Hukou Reach changed from sedimentation to erosion; and the trend in the flood water level under the same flow-rate was inconsistent with the channel erosion trend, which indicated that channel erosion was not the main reason for the increased flood water-level under the same flow-rate.

The confluence points of the Dongting and Poyang Lakes only influenced water levels close to the intersections and had a minor influence on the mainstream flood water-levels under the same flow-rate. Moreover, lake erosion improved the regulation of lakes and weakened the contribution of Lake Flood water to the mainstream runoff, thus helping to alleviate the flood control pressure of the Yangtze River mainstream. After the impoundment of the TGR, the duration of the flow rate exceeding the bankfull elevation downstream of the dam decreased, increasing the exposure time of the area above the bankfull channel and, in turn, allowing the shore vegetation to flourish. This resulted in an increased flood water-level under the same flow-rate due to the backwater effect.

However, this is not unique to the Yangtze River. The importance of this effect is illustrated by the Mississippi River floods in 2011. The combined effect of river channel erosion, waterway engineering, and river regime control engineering caused riverbed coarsening, which further accelerated the increase of the same-flow flood water-level. Substantial waterways, river regime control, and shoreline engineering were implemented in the middle and lower reaches of the Yangtze River, which significantly reducing the floodwater river width. Although the effects of individual projects are small, the combined effect of many can contribute towards the upward trend in the same-flow flood water-level.

Relationship between changes in low water levels and siltation and scouring of the channel

The predict show that after 40 years (2005–2045) of impoundment 13 , when the flow (Q) at Yichang Station 20,000 m 3 /s, the low-flow water level in the 700 km reach below the dam will have a decreasing trend. An examination of the depth of the channel in a 410 km section of the river downstream from the TGR in October 2014 showed an average undercutting of 1.50 m compared with October 2002. Further downstream, alternating siltation and scouring occurred at several locations during this same period (Fig.  9a ). On average, the low-flow water level in the 240 km downstream from the TGR was 1.10 m lower in the 2003–2014 period compared with 1981–2002; further downstream, the low-flow water levels rose on average when compared with the low-flow water level from 1981–2002. Undercutting was concentrated in the Yichang–Zhicheng reach and in the upper and lower sections of the Jingjiang reach, and low water level decreases mainly occurred in the Yichang–Zhicheng reach and the upper section of the Jingjiang reach (Fig.  9b ). In the immediate future, undercutting in the lower sections of the Jingjiang reach should be controlled to prevent low water levels from dropping.

Downstream thalweg and water level elevations before and after construction of the TGR. Note: ( a ) depths are from a selected number of cross-sections along the Yichang – Hukou river section, with a spacing of generally 200–500 m. The thalweg depth is the deepest point of the cross-section. In the case of multiple waterways, the main channel of the multiple waterways is selected; ( b ) water levels (98% highest water level) measured relative to the waterway datum during 1981–2002 and 2003–2014, and the difference in elevation between these periods.

Since water has been stored at the TGR, the depth of the waterway has been controlled mainly by erosion. To prevent adverse effects, such as shoreline collapse, beach and shoal atrophy, and reduction of flow in the main waterway during the dry season, the Yangtze Waterway Bureau carried out systematic waterway remediation work in the middle and lower reaches of the Yangtze from 2003 to 2015. As a result, the depth of the waterway increased by 0.50 to 0.60 m in the Yichang–Chenglingji, Chenglingji–Wuhan, Wuhan–Anqing, Anqing–Wuhu, and Wuhu–Nanjing reaches, from 2.9 m, 3.2 m, 4.0 m, 4.5 m, and 6.0 m (2003) to 3.5 m, 3.7 m, 4.5 m, 6.0 m, and 9.0 m (2015), respectively (Fig.  10 ). The width of the waterway also increased significantly. Thus, by 2015, the dimensions of the waterway had already increased to the target dimensions for 2020 41 , 42 .

Change in the depth and width of waterway from Shuifu to Yangtze Estuary. (Note: The water depth and width of the waterway are the values of the main waterway).

Impact of changing flood water levels on flood control conditions in the middle reaches of the Yangtze River

Wuhan is the key city for flood control in the middle reaches of the Yangtze River. Using Hankou Station as an example, during the period from 2003 to 2016, the flood control water level was exceeded in both 2010 and 2016. The highest water level in 2010 exceeded the flood control water level by 1 cm, while the water level exceeded the flood control water level by 107 cm on 7 July 2016; this is the 5 th highest water level since 1870. The discharge corresponding to the flood control water level in different years has recently been recalculated (Fig.  11 ), and the discharge at the flood control water level at Yichang Station, Luoshan Station, Hankou Station and Datong Station declined, whereby the flood-alarm discharge in 2016 compared with 1998 reduced by 8,800 m 3 /s, 8,400 m 3 /s, 5,600 m 3 /s and 2,600 m 3 /s, respectively. The discharge in 2016 also showed a decreasing trend compared with 2003. Jianli and Jiujiang stations were affected by the backwater effect at the outflow points of both Dongting and Poyang Lakes. The water-level and flow-relationship curve (Fig.  5 ) shows a wide flow-fluctuation range corresponding to flood control warning levels, and the statistical analysis shows that the minimum flow rate reached the flood control warning level (Fig.  11 ). On the other hand, the flow rate at Jianli station exceeded the minimum flood control warning level, showing an increasing trend, which indicates that the influence of Dongting Lake inflow on the mainstream water level weakened. This can be attributed to the combined effect of the Three Gorges Reservoir regulation and the increase in the lake basin capacity. The minimum flow at Jiujiang station also exceeded the flood control warning level due to the increasing trend. However, compared with Jianli station, the trend was relatively weak. Due to the large distance between the station and the TGR, the effect of reservoir regulation was relatively weak, but the increased lake basin capacity was beneficial in reducing the mainstream runoff. In the near-dam section at Yichang Station, due to the peak-cutting effect of the TGR, the discharge flow was drastically reduced, and the number of days exceeding the flood-control water level was also reduced. Before construction of the TGR, siltation of the Luoshan reach was the main reason for the increasing flood level 43 , 44 . However, due to river erosion in the Luoshan-Hankou reach after construction, there was an increase in vegetation and bed resistance and an obvious increase in water capacity, which was the main reason for the change in flood elevation at Luoshan Station, before and after construction of the TGR. A comparison of the periods 2003–2013 and 2000–2002 indicated that when the flow rate at Hankou Station was 50,000 m 3 /s, the corresponding increase in the water level was 0–1.0 m 17 . A comparison between 2016 and 2003 showedthat this elevation trend did not decrease, which is not conducive to flood control in Wuhan.

In July 2016, a major regional flood occurred in the middle and lower reaches of the Yangtze River. Through the use of the TGR and upper reaches of the cascade reservoirs, 22.7 billion m 3 of flood water was intercepted and stored. Consequently, the water levels in the Jingjiang reach, the Chenglingji area, and the lower reaches of Wuhan were reduced by 0.8–1.7 m, 0.7–1.3 m, and 0.2–0.4 m, respectively, and the length of the section was reduced decreased by 250 km, which effectively reduced the pressure on flood-control measures in the Chenglingji reach and Dongting Lake area in the middle reaches of the Yangtze River. Scenarios exceeding the alarm level in the Jingjiang reach and flood diversion to the Chenglingji area were avoided, the safety of the population of the Jingjiang reach was secured, and the integrity of the Yangtze River embankment was guaranteed.

Analysis of water level data from 38 rivers in the United States indicates that dam construction resulted in a reduction in the average annual flood peak discharge of 7.40% to 95.14% 45 . According to the TGR Dispatching Rules, the TGR will regulate small and medium floods 16 , which will effectively alleviate the flood risk in the Yichang–Luoshan River reach. After the flood control standard at the Jingjiang embankment is improved, pressure on flood-control measures on this river section will be greatly reduced. The combined regulating process of the TGD and its upstream cascade reservoirs can not only stop floods with a large flow rate, but also gradually stop floods with low and medium flow rates, resulting in a decrease in the peak value of the outflow during the flood season in the TGD. After a continuous long period, the large flood processes downstream of the TGD will be lost, and the flow process will tend to become uniform throughout the year. With no shaping of river channels due to periods of large flow rates, the flood capacity of the river channels will decrease 16 . Once severe floods occur, especially regional floods in the middle and lower reaches of the TGD due to integrated effects of Dongting Lake, Poyang Lake, Hanjiang River and other tributaries and local rainfall, these floods will be less regulated by the TGD. Without long-term shaping of flood river channels by large floods, the vegetation in the high beach areas will become lush, and silt will gradually accumulate, resulting in increases in integrated resistance of river channels, and the effective flood control capacity will be further reduced 16 .

After the impoundment of the TGR, floods similar to those in 1954 and 1998 did not occur in the middle and lower reaches of the Yangtze River. However, as the discharge corresponding to the flood-control water level reduces, a high flood discharge – high flood level gradually transforms into one of moderate flood discharge – high water level, which should raise concerns of increased flooding. For the near future, issues of flood control and disaster reduction are still highly significant along the Yangtze River, and flood control is still the primary task of development and protection in this area. We should continue strengthening the comprehensive Yangtze River flood control and disaster reduction system and its management, as well as speeding-up the transformation from flood control to flood management and other measures to address flood security issues.

Conclusions

Construction and operation of the TGP have been studied by many researchers. The effect of reservoir operation on the flood and low-flow water levels in the lower reaches and related issues have been the focus of the river management and waterway management departments. Through analysis of measured data from the reaches below the TGD over the period 1955–2016, the following conclusions have been drawn:

The low-flow water level at the same discharge in the reaches below the TGD declined, an effect also observed in downstream water levels of other large dams around the world. Due to the compensating effect of the reservoir during dry seasons, the discharge at low-flow water levels is increased and the lowest water level showed an increasing trend. At the channel scale, the decline in the low-flow water level in the reaches below the TGD is less than the undercutting value of the basic flow channel. Governed by the action of such a large-scale waterway regulation project, water depths in the reaches below the dam have been improved, and the proposed objective for 2020 has been achieved five years in advance.

The flood water level at the same discharge increased slightly in the channels below the TGD. The flood characteristics had a tendency to change from a high flood discharge-high flood level to a moderate discharge-high flood level, which is not conducive to flood safety. Peak cutting by the reservoir reduced the highest water levels downstream. For example, during the regional flood of July 2016, the flood height in the reaches below the dam (based on flood heights and flows prior to dam construction) was reduced by 1.7–0.2 m; but the relative magnitude of the reduction declined downstream. The scouring of Dongting Lake and Poyang Lake and the main channel erosion allowed for additional reduction of the flood water level at the same discharge. Increased vegetation, coarsening of the riverbed and human activities have led to increased flood levels at the same discharge in the reaches below the dam, although the flood level at the same discharge in this area was expected to decline.

In the future, the TGR and the upstream cascade reservoirs will adopt a joint dispatching method, and the sediment volume downstream of the dam will be kept at a low level. The continuous flooding and erosion of the river will tend to decrease the low-flow water level, and insufficient water depth in the waterway caused by the drop of the low-flow water level should be controlled and avoided. The joint dispatching of the TGR and the upper reach cascade reservoirs will play a more prominent role in reducing flood peaks, which will reduce pressure on flood control measures downstream of the dam. Nonetheless, the current elevation of flood water level at the same discharge should be a focus of concern.

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Acknowledgements

This study was funded by the National Key Research and Development Program of China (2016YFC0402106, 2016YFC0402305); the National Natural Science Foundation of China (51579123); and the Fundamental Research Funds for Central Welfare Research Institutes (TKS160103); Open Research Fund Program of State Key Laboratory of Water Resources and Hydropower Engineering Science (2016HLG02); Key Research and Development Program of Tianjin (16YFXT00280); and the Doctoral foundation of Northwest Agriculture and Forestry University (2452015337). The hydrological data for this study were provided by the Bureau of Hydrology, Changjiang Water Resources Commission, China and Yangtze River Waterway Bureau. The contributions of both other organizations and individuals involved are gratefully acknowledged.

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Yunping Yang, Mingjin Zhang, Wanli Liu & Yanhua Yang

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Y.P.Y. and J.Q.H. conceived the study and wrote the draft of the manuscript. M.J.Z. and L.L.Z. contributed to the improvement of the manuscript. Y.H.Y. prepared Figs 1–5. Y.P.Y. and W.L.L. prepared Figs 6–11 and Tables 1–5. All authors reviewed the manuscript.

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Yang, Y., Zhang, M., Zhu, L. et al. Influence of Large Reservoir Operation on Water-Levels and Flows in Reaches below Dam: Case Study of the Three Gorges Reservoir. Sci Rep 7 , 15640 (2017). https://doi.org/10.1038/s41598-017-15677-y

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March 25, 2008

12 min read

China's Three Gorges Dam: An Environmental Catastrophe?

Even the Chinese government suspects the massive dam may cause significant environmental damage

By Mara Hvistendahl

SHANGHAI—For over three decades the Chinese government dismissed warnings from scientists and environmentalists that its Three Gorges Dam —the world's largest—had the potential of becoming one of China's biggest environmental nightmares. But last fall, denial suddenly gave way to reluctant acceptance that the naysayers were right. Chinese officials staged a sudden about-face, acknowledging for the first time that the massive hydroelectric dam, sandwiched between breathtaking cliffs on the Yangtze River in central China, may be triggering landslides, altering entire ecosystems and causing other serious environmental problems—and, by extension, endangering the millions who live in its shadow.

Government officials have long defended the $24-billion project as a major source of renewable power for an energy-hungry nation and as a way to prevent floods downstream. When complete, the dam will generate 18,000 megawatts of power—eight times that of the U.S.'s Hoover Dam on the Colorado River. But in September, the government official in charge of the project admitted that Three Gorges held "hidden dangers" that could breed disaster. "We can't lower our guard," Wang Xiaofeng, who oversees the project for China's State Council, said during a meeting of Chinese scientists and government reps in Chongqing, an independent municipality of around 31 million abutting the dam. "We simply cannot sacrifice the environment in exchange for temporary economic gain."

The comments appeared to confirm what geologists, biologists and environmentalists had been warning about for years: building a massive hydropower dam in an area that is heavily populated, home to threatened animal and plant species, and crossed by geologic fault lines is a recipe for disaster.

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Among the damage wrought: "There's been a lot less rain, a lot more drought, and the potential for increased disease," says George Davis, a tropical medicine specialist at The George Washington University (G.W.) Medical Center in Washington, D.C., who has worked in the Yangtze River Basin and neighboring provinces for 24 years. "When it comes to environmental change, the implementation of the Three Gorges dam and reservoir is the great granddaddy of all changes."

Dam Quake When plans for the dam were first approved in 1992, human rights activists voiced concern about the people who would be forced to relocate to make room for it. Inhabited for several millennia, the Three Gorges region is now a major part of western China's development boom. To date, the government has ordered some 1.2 million people in two cities and 116 towns clustered on the banks of the Yangtze to be evacuated to other areas before construction, promising them plots of land and small stipends—in some cases as little as 50 yuan, or $7 a month—as compensation.

Chinese and foreign scientists, meanwhile, warned that the dam could endanger the area's remaining residents. Among their concerns: landslides caused by increased pressure on the surrounding land,  a rise in waterborne disease , and a decline in biodiversity. But their words fell on deaf ears. Harnessing the power of the Yangtze has been a goal since Nationalist leader Sun Yat-sen first proposed the idea in 1919. Mao Zedong, the father of China's communist revolution, rhapsodized the dam in a poem. The mega- project could not be realized in his lifetime, however, because the country's resources were exhausted by the economic failures of the Great Leap Forward in the late 1950s and then the social upheaval of the Cultural Revolution from the mid-1960s a to the early 1970s. Four decades later, the government resuscitated Mao's plans. The first of the Yangtze's famed gorges—a collection of steep bluffs at a bend in the river—was determined to be the perfect site.

In June 2003, nine years after construction began, the state-owned China Yangtze Three Gorges Development Corporation (CTGPC) filled the reservoir with 445 feet (135 meters) of water, the first of three increments in achieving the eventual depth of 575 feet (175 meters). The result is a narrow lake 410 miles (660 kilometers) long—60 miles (97 kilometers) longer than Lake Superior—and 3,600 feet (1,100 meters) wide, twice the width of the natural river channel. Scientists' early warnings came true just a month later, when around 700 million cubic feet (20 million cubic meters) of rock slid into the Qinggan River, just two miles (three kilometers) from where it flows into the Yangtze, spawning 65-foot (20-meter) waves that claimed the lives of 14 people. Despite the devastating results, the corporation three years later (in September 2006) raised the water level further—to 512 feet (156 meters). Since then, the area has experienced a series of problems, including dozens of landslides along one 20-mile (32-kilometer) stretch of riverbank. This past November, the ground gave out near the entrance to a railway tunnel in Badong County, near a tributary to the Three Gorges reservoir; 4,000 cubic yards (3,050 cubic meters) of earth and rock tumbled onto a highway. The landslide buried a bus, killing at least 30 people.

Fan Xiao, a geologist at the Bureau of Geological Exploration and Exploitation of Mineral Resources in Sichuan province, near several Yangtze tributaries, says the landslides are directly linked to filling the reservoir. Water first seeps into the loose soil at the base of the area's rocky cliffs, destabilizing the land and making it prone to slides. Then the reservoir water level fluctuates—engineers partially drain the reservoir in summer to accommodate flood waters and raise it again at the end of flood season to generate power—and the abrupt change in water pressure further disturbs the land. In a study published in the Chinese journal Tropical Geography in 2003, scholars at Guangzhou’s South China Normal University predicted that such tinkering with the water level could trigger activity in 283 landslide-prone areas.

That is apparently what happened to the 99 villagers of Miaohe, 10 miles (17 kilometers) upstream of the Yangtze, who saw the land behind their homes split into a 655-foot- (200-meter-) wide crack last year, soon after the reservoir water level was lowered for the summer floods. Officials evacuated them to a mountain tunnel where they camped for three months.

One of the greatest fears is that the dam may trigger severe earthquakes, because the reservoir sits on two major faults: the Jiuwanxi and the Zigui–Badong. According to Fan, changing the water level strains them. "When you alter the fault line's mechanical state," he says, "it can cause fault activity to intensify and induce earthquakes."

Many scientists believe this link between temblors and dams—called reservoir-induced seismicity—may have been what happened at California's Oroville Dam, in the foothills of the Sierra Nevada. The largest earthen dam in the U.S., it was constructed on an active fault line in the 1950s and filled in 1968. Seven years later, when the reservoir's water supply was restored to full capacity—after engineers lowered it 130 feet (40 meters) for maintenance—the area experienced an unusual series of earthquakes. U.S. Geological Survey seismologists subsequently found a strong link between the quakes and the refilling of the reservoir.

The Oroville area was sparsely populated, so little damage was done. But earthquakes have also been connected to past hydropower projects in China, where dams are often located in densely populated and seismically active river basins. Engineers in China blame dams for at least 19 earthquakes over the past five decades, ranging from small tremors to one near Guangdong province's Xinfengjiang Dam in 1962 that registered magnitude 6.1 on the Richter scale—severe enough to topple houses.

Surveys show that the Three Gorges region may be next. Chinese Academy of Engineering scholar Li Wangping reports on the CTGPC's Web site that the area registered 822 tremors in the seven months after the September 2006 reservoir-level increase. So far, none have been severe enough to cause serious damage. But by 2009, the dam's water level is set to be raised to its full 575-foot capacity and then lowered about 100 feet (30 meters) during flood season. That increase in water pressure, in water fluctuation and in land covered by the reservoir, Fan says, makes for a "very large possibility" that the situation will worsen.

Local news media report that whole villages of people relocated to make room for the dam will have to move a second time because of the landslides and tremors, indicating that officials failed to foresee the full magnitude of the dam's effects. Guangzhou's Southern Weekend late last year reported that villagers in Kaixian County were eager to move again, citing landslides, mudslides and ominous cracks that had appeared in the ground behind their homes. They also hoped that moving might resolve land allocation issues: Some said they received only half of the acreage they had been promised.

Water Displacement The dam is also taking a toll on China's animals and plants. The nation—which sprawls 3.7 million square miles (9.6 million square kilometers)—is home to 10 percent of the world's vascular plants (those with stems, roots and leaves) and biologists estimate that half of China's animal and plant species, including the beloved giant panda and the Chinese sturgeon, are found no where else in the world. The Three Gorges area alone accounts for 20 percent of Chinese seed plants—more than 6,000 species. Shennongjia, a nature reserve near the dam in Hubei province, is so undisturbed that it is famous for sightings of yeren, or "wild man"—the Chinese equivalent of "Big Foot"—as well as the only slightly more prosaic white monkey.

That biodiversity is threatened as the dam floods some habitats, reduces water flow to others, and alters weather patterns. Economic development has spurred deforestation and pollution in surrounding provinces in central China, endangering at least 57 plant species, including the Chinese dove tree and the dawn redwood. The reservoir created by Three Gorges dam threatens to flood the habitats of those species along with over 400 others, says Jianguo Liu, an ecologist at Michigan State University and guest professor at the Chinese Academy of Sciences who has done extensive work on biodiversity in China.

The dam further imperils delicate fish populations in the Yangtze. Downstream, near where the river empties into the East China Sea, the land around the Yangtze contains some of the densest clusters of human habitation in the world, and overfishing there has already endangered 25 of the river's 177 unique fish species. According to a 2003 letter to Science by Wuhan University ecologist Ping Xie, many of these fish evolved over time with the Yangtze flood plain. As the dam decreases flooding downstream, it will fragment the network of lakes around the middle as well as lower the Yangtze's water level, making it difficult for the fish to survive. The project has already contributed to the decline of the baiji dolphin , which is so rare that it is considered functionally extinct.

The reservoir could also break up land bridges into small islands, isolating clusters of animals and plants. In 1986, Venezuela's Raúl Leoni Dam flooded 1,660 square miles (4,300 square kilometers) of land, creating the vast Lake Guri, along with a scattering of nonsubmerged land. The nascent islands lost 75 percent of their biological species within 15 years, according to research published in Science.

To determine the true toll, the Three Gorges Dam is taking on animal and plant species, Liu says, long-term data is needed, so that decreases in population totals can be compared with natural species fluctuation. But he cautions that many of the dam's effects may not be immediately apparent. The project is altering reproduction patterns, meaning it may already be too late for some plants and animals. "In the short term, you see the species still there, but in the long term you could see [them] disappear," Liu says. It is here that State Council representative Wang's allusion to "hidden dangers" rings especially true.

Disease and Drought When officials unveiled plans for the dam, they touted its ability to prevent floods downstream. Now, the dam seems to be causing the opposite problem, spurring drought in central and eastern China. In January, the China Daily (the country's largest English-language newspaper) reported that the Yangtze had reached its lowest level in 142 years—stranding dozens of ships along the waterway in Hubei and Jiangxi provinces. An unnamed official with the Yangtze River Water Resources Commission blamed climate change, even as he acknowledged that the dam had reduced the flow volume of the river by 50 percent. To make matters worse, China is now plowing ahead with a controversial $62-billion scheme to transfer water from the Yangtze to northern China, which is even more parched, through a network of tunnels and canals to be completed by 2050.

Meanwhile, at the mouth of the Yangtze residents of Shanghai, China's largest city, are experiencing water shortages. The decreased flow of fresh water also means that saltwater from the East China Sea now creeps farther upstream. This, in turn, seems to be causing a rise in the number of jellyfish, which compete with river fish for food and consume their eggs and larvae, thereby threatening native populations that are already dwindling as a result of overfishing. In 2004, a year after the dam was partially filled, scientists noted a jellyfish species in the Yangtze that had previously only reached the South China Sea.

The effects of the dam's disturbance of whole ecosystems could reverberate for decades. G.W.'s Davis is part of a project researching the disease schistosomiasis (a.k.a. snail fever or swimmer's itch), a blood parasite transmitted to humans by snails; people can get it by swimming or wading in contaminated fresh water when infected snails release larvae that can penetrate the skin. (Symptoms include fever, appetite and weight loss, abdominal pain, bloody urine, muscle and joint pain, along with nausea, a persistent cough and diarrhea.) The snails used to breed on small flood plain islands where annual flooding prevented a population explosion. Now, the decreased flow downstream from the dam is allowing the snails to breed unchecked, which has already led to a spike in schistosomiasis cases in some areas.

According to Davis, such alterations could precipitate a rise in other microbial waterborne diseases as well. "Once you dramatically change the climate and change water patterns, as is now seen in the Three Gorges region," he says, "you change a lot of environmental variables. Almost all infectious diseases are up for grabs."

The official recognition of the dam's dangers suggests that the project's environmental and public health impacts are starting to sink in. Political analysts speculate that President Hu Jintao and Premier Wen Jiabao are eager to distance themselves from a project they inherited. Although halting plans at this point would be an admission of government error, the openness following the Chongqing meeting raised the hopes of worried scientists that officials would take action to minimize the project's environmental and public health fallout.

Government-funded institutions have been quietly assessing possible recourses. Officials say they've spent more than $1.6 billion on fortifying landslide-prone areas and will spend an additional $3.2 billion on water cleanup over the next three years. In January the CTGPC signed a memorandum of understanding with the Nature Conservancy allowing that organization to consult on species protection and river health in the dam area. China's Ministry of Health, meanwhile, is trying to control schistosomiasis infections with a combination of drugs and applications of molluscicides, pesticides that wipe out the disease's snail carriers.

But these measures may not be sufficient to avert disaster. In February China's State Environmental Protection Administration said reservoir water quality targets had not been reached despite a cleanup effort that had been underway since 2001. And fighting schistosomiasis requires a more holistic, multi-pronged approach—particularly now that ecosystems in the Three Gorges region have been altered. To ward off an outbreak, Davis says, the government would have to prevent the use of night soil as fertilizer, build cement irrigation ditches, and ensure area villagers access to clean water. So far, that hasn't happened.

Government Oversight In the wake of media reports about the government's concerns, officials began to backpedal. In a November 2007 interview with state news agency Xinhua , State Council's Wang claimed that "no major geological disasters or related casualties" had occurred since the reservoir's water level was raised in 2006; five days later, the earth in Badong crumbled and the railroad tunnel landslide wiped out the bus and its passengers.

Following a brief period of openness, discussion of the dam's environmental effects has once again become largely taboo in China. Government officials fear that continued free discussion of the project's ramifications could lead to civil unrest. One internationally published Chinese scientist working in the Yangtze Basin declined to comment publicly, noting, "This is a very sensitive topic…. I can't give hypotheses."

Despite the Three Gorges dam's growing list of problems, however, hydropower remains an integral—and ostensibly green—component of China's energy mix. China still draws 82 percent of energy from coal, but large dams are crucial to the country's climate change program, which aims to increase its proportion of electricity from renewable resources from the current 7.2 percent to 15 percent by 2020. Over one third of that will come from hydropower—more than from any other source. Twelve new dams are planned for the upper Yangtze alone.

The logistical and environmental hurdles involved in executing these dams underscore China's commitment to hydropower. The Yangtze's newest dams include several smaller projects that are necessary to alleviate sedimentation caused by the Three Gorges reservoir. In his 2007 report to the National People's Congress, Prime Minister Wen Jiabao said that China had relocated 22.9 million people to make room for its large hydroprojects.

China's original goal was to fill the reservoir to its maximum level by 2013. Despite all the trouble, that target was moved up to 2009, Fan says, to boost hydropower output by an additional 2.65 billion kilowatt-hours each year.

"For the economic interests and profit of the Three Gorges Project Development Corporation," he says, "that's very important. But the function of any river, including the Yangtze, is not only to produce power. At the very least, [a river] is also important for shipping, alleviating pollution, sustaining species and ecosystems, and maintaining a natural evolutionary balance."

"The Yangtze doesn't belong to the Three Gorges Project Development Corporation ," Fan adds. "It belongs to all of society."

Three Gorges Dam: Consequences of Hydropower in China

Kitty kwan december 15, 2016, submitted as coursework for ph240 , stanford university, fall 2016, introduction to hydropower.

Hydroelectric power has strong energy potential in terms of its output and sustainability. As population's increase and economies grow, there is a clear increase in worldwide energy demand. According to BP's Statistical Review of World Energy, worldwide primary energy consumption has increased from 10,940 to 13,147 million tonnes of oil equivalent, while hydroelectricity consumption has increased from 661.4 to 892.9 million tonnes of oil equivalent from 2005 to 2015. [1] While the primary energy space is still dominated by fossil fuels, hydroelectric energy production and use is becoming more popular. As it further develops, there are concerns over its environmental and social effects on neighboring areas. Hydropower is one of the most important renewable energy sources in electricity generation. As water is found naturally moving in many locations, energy can be extracted from its velocity and positioning to power machinery and generate electricity. Hydropower provides a significant amount of energy in the world, contributing approximately 15% of the global electricity production. [2] Global growth has been primarily concentrated in several key countries, top of which is China. China had 15GW deployed in 2012 and has a 5-year plan to have 284GW through 2015, hypothetically using 71% of its available hydroelectric power. [3]

Three Gorges Dam

Given the prominence of China in the hydropower space, it is fitting to explore the Three Gorges Dam as a case of a large-scale hydropower project with wide reaching impact. The Three Gorges Dam is the largest hydroelectric dam in the world, providing energy production, flood control, and navigation to China's Yangtze River area. In its full completion with 26 turbines, it has a full power capacity that exceeds 22,000 MWe. Intended to help reduce China's energy reliance on burning coal, the energy from Three Gorges Dam is able to replace around 50 million tons of coal that otherwise would have been burned. [4] Additionally, the Three Gorges Dam has the added benefit of flood control, a major problem of the Yangtze River Basin. The Three Gorges Dam additionally is able to divert water resources to northern China, where rainfall is in a shortage.

However, the Three Gorges Dam has also had many negative implications on the local ecology and relocation of people. Ecosystems have been destroyed through the process of blocking a massive river. Additionally, the process of its construction offsets many of the immediate benefits it poses to reducing the negative externalities of fossil fuels. An estimated 2 million people downstream of the dam were relocated, without acknowledgement of their loss of livelihood. This project has also greatly affected the farming and fishing communities. The river is fished out, and the Yangtze's four major species of carp are dwindling, as referenced in the figure. This is a result of increased traffic, pollution from construction, and various industrial wastes. [5]

Future Directions

The Three Gorges Dam in China has proven to be a controversial project for its added pros and cons to the Yangtze River landscape. As China propels and continues to lead hydropower generation and leverage its hydropower potential, it is very important for planners to maintain careful planning and design to work around the challenges. In particular, lessons from the Three Gorges Dam must be taken when considering the development of new dams, such as the Nu River Dam. This 13-cascade would leverage China's last undammed river, have immense power generating potential, but also face many similar ecological and social consequences. [6]

© Kitty Kwan. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

[1] " BP Statistical Review of World Energy 2015 ," British Petroleum, June 2016.

[2] C. S. Kaunda et al. , " Hydropower in the Context of Sustainable Energy Supply: A Review of Technologies and Challenges ," ISRN Renewable Energy 2012 , 730631 (2012).

[3] " World Energy Resources ," World Energy Council, 2013, Ch. 5.

[4] P. H. Gleick, "Three Gorges Dam Project, Yangtze River, China," in The World's Water, 2008-2009 , ed. by P. H. Gleick (Island Press, 2008), p. 139.

[5] R. Stone, "Three Gorges Dam: Into the Unknown," Science 321 , 628 (2008).

[6] P. H. Brown, D. Magee, and Y. Xu, "Socioeconomic Vulnerability in China's Hydropower Development," China Econ. Rev. 19 , 614 (2008).

Main page content

Three gorges dam conflict in china.

The construction of the world's largest dam on the world's third largest river (the Yangtze River) has displaced some 1.2 million people. The Three Gorges Dam has been one of the most controversial dam projects in the world for its social, environmental and economic impacts.

• Agricultural/Pastoral land
• Ecosystem stability

Conceptual Model

Conflict history.

China has embarked on numerous massive dam projects, including the Three Gorges Dam, the largest dam in the world. The displacement of millions of people and their loss of livelihood, combined with harsh environmental consequences, which threaten the extinction of fish species and geological instability, have caused local discontent and international criticism from environmental and human rights organisations, such as Human Rights Watch and International Probe. Contestation of the dam project and protests for greater compensation have remained non-violent, appearing mostly in scientific reports and in the form of petitions from civil society. The Three Gorges Dam was completed by 2006 and displaced more than 1.2 million people ( International Rivers, 2006 ). The dam was constructed not only to produce energy, but also to stop large-scale seasonal flooding. Moreover, hydropower also has environmental benefits compared to fossile fuels in particular and its extension can thus be construed as a reponse to increasing pressure from the international community for China to reduce its carbon footprint.

Environmental impacts

The environmental impacts of the dam were immediately apparent one month after opening, when landslides caused by increased water levels in the reservoir killed fourteen people ( International Rivers, 2006 ). Downstream erosion caused by irregular water flow also led to bursting river banks and flooding. In addition to landslides and floods, the dam sits atop two major fault lines causing hundreds of tremors. In 2011, Chinese authorities admitted the concerning scale of environmental side effects. Fish stocks diminished, threatening the endangered Chinese sturgeon and paddlefish and leading to the extinction of the baiji river dolphin ( International Rivers, 2008 ). Fish harvest downstream has decreased by up to 70% below 2002 yields, threatening the livelihoods of thousands ( Gleick, 2009 ). Water pollution has also been a major problem as the reservoir has submerged hundreds of factories, mines and waste dumps and urban run-off has led to algae blooms. This has exacerbated China's water shortage problem.

Civil society protests

Since the dam was commissioned in 1994, protestors have petitioned against the dam and resettlement. The Three Gorges Dam was designed as a symbol of Chinese engineering prowess and has high international visibility. Because of the attendant government intervention and censoring, localised protests have been less visible and difficult to follow  ( Qing, 2011 ; Guo, 2010 ). In 2001, Human Rights Watch reported on the arrest and trial of four farmers who protested against resettlement, although they were later acquitted. Again in 2009, protestors of displaced persons frustrated by corruption and insufficient compensation reportedly clashed with police forces ( Radio Australia, 2009 ). There have been no official reports of fatalities caused by protests against the dam.

The government has invested billions in resettlement and clean-up programs to mitigate displacement and geological insecurity and to clean up polluted drinking water. However, many have not been sufficiently compensated and many farmers have been given sloped arid land on the banks of the Yangtze, thus contributing to erosion, geological instability and pollution of the water.

Conflict resolution

The "environmental assessment storm”.

To address criticism from scientific and environmental circles, the Chinese central government State Administration of Environmental Protection board embarked on what is now referred to as the "environmental assessment storm” in 2005. This attempted to hold companies, including the state-owned Three Gorges Project Corporation, accountable for disregarding requirements set out by Environmental Impact Assessment Law ( Guo, 2010 ). However, fines introduced for violating these requirements remained low and arguably do not encourage compliance today ( International Rivers, 2006 ).

Other steps have been taken at the state level, such as the investment in water purification infrastructure to increase access to water otherwise limited by the dam. However, industries are still permitted to discharge their waste into the Yangtze, thus defeating the purpose of these measures. Other steps taken to reduce the environmental impact of the dam include a three-month fishing ban every spring to protect fish stocks. However, this targets commercial fish only and does not consider the overall ecological balance of the Yangtze ( Yang & Lu, 2014 ). Furthermore, the livelihoods of fishermen have not been regarded in this policy. Little has also been done regarding the lack of compensation for those displaced by the dam project, with corruption preventing many from receiving their designated amount and poor living conditions in resettlement communities forcing others to relocate ( Qing, 2011 ).

The main challenges in overcoming the conflict surrounding the Three Gorges Dam lie in the government and its bureaucratic structure. Management of the Three Gorges Dam is distributed in a multilayer and hierarchal model, with the State Council overseeing the project at the highest level. Nineteen state-level agencies with equal power manage the dam and its reservoir, thus making decision-making slow and conflict inevitable ( Yang & Lu, 2014 ) . To address the problems of the Three Gorges Dam in both environmental and social spheres, it has been suggested that management of the dam should be centralised in the Changjiang (Yangtze) Water Resources Commission (CWRC), a department within the Ministry of Water Resources. This would improve coordination, minimise conflicts and increase compliance with national level environmental laws ( Yang & Lu, 2014 ). It could also offer a platform for conflict resolution. Furthermore, greater public participation in the local government concerning the dam has been recommended and interregional cooperation along the Yangtze has also been encouraged to enhance the scope of addressing environmental sustainability ( Guo, 2010 ).

Resilience and Peace Building

Cooperation.

Furthermore, interregional cooperation along the Yangtze has also been encouraged to enhance the scope of addressing environmental sustainability.

Mediation & arbitration

The State Administration of Environmental Protection board attempted to hold the Three Gorges Project Corporation accountable for disregarding environmental laws. However, the fines that were introduced remained low and do not encourage compliance.

Compensation

Proper compensation for those displaced by the project must still be adequately regarded in governmental policies as many are still struggling to receive their designated amount and are living in poor conditions

Social inclusion & empowerment

Greater public participation in local decision making concerning the dam has been recommended.

Changes in constitutional balance of power

In order to improve coordination, minimise conflicts and increase compliance with national level environmental laws, it has been suggested that the management of the dam should be conferred to a state commission: the Changjiang Water Resources Commission (CWRC).

Environmental restoration & protection

The government has taken steps to reduce the environmental impact of the dam, such as investing in water purification infrastructure and implementing a three-month fishing ban. However, these measures do only address isolated issues and are therefore not completely effective.

Resources and Materials

• International Rivers (2006). Three Gorges Dam. A Model of the Past
• International Rivers (2008). Three Gorges Dam. The Cost of the River
• Radio Australia (2012).Thousands clash with police over China's Three Gorges Dam
• Gleick, H. (2009). The The Gorges Dam Project. Yangtze River, China
• Adams, P. (2008). Human rights abuses and the Three Gorges dam
• Yang, X. & Lu, X. (2014). Ten years of the Three Gorges Dam: a call for policy overhaul
• Guo, G. (2010). Environmental Security Concerns and the Three Gorges Reservoir Basin in China
• Qing, D. (2011). Dai Qing: On The Completion of the Three Gorges Project

Viterbi Conversations in Ethics

Ethical Analysis of The Three Gorges Project

The Three Gorges Project is the development of the largest hydroelectric dam in the world: the Three Gorges Dam. Since its conception, the project has remained the focus of controversy due to its long construction duration, significant social and economic impacts, and broad environmental implications. The ethicality of the dam’s construction will be determined through an examination of its impacts from a utilitarian perspective. 

About the Three Gorges Project

The Three Gorges Project (TGP) has a significant and far-reaching impact on China’s energy supply as well as the livelihood of many people throughout the region. Located in Yichang City, Hubei Province, China, the dam provides surrounding areas with power, flood control, and shipping facilitation [1]. 

The massive scale of the Three Gorges Project influenced the duration of its development process. After decades of exploration and research, construction began on December 14, 1994. Twelve years later, it entered the initial operation stage with a water level of 156 meters. In 2008, it began to carry out experimental water storage, and in 2010 it reached the target level of 175 meters. In July 2012, the TGP’s final generator unit was connected to the power grid. This marked the completion of the construction process and the beginning of formal operation [2]. At the time of writing this paper, the Three Gorges Hydropower Station is the largest hydropower station in the world and the largest engineering project ever constructed in China. The total size of the Three Gorges Dam is about 3335 meters long and 185 meters high, with an operational water level of 175 meters and a reservoir length of 2335 meters [1]. 

The most significant benefit of the TGP is its contribution to the power supply of several provinces. The Three Gorges Hydropower Station is located at the center of the national power grid. It optimizes the power supply between provinces while improving the security and economy of those on the grid. Electric power from the TGP has been exported to Hubei, Shanghai, Guangdong, Chongqing, and other provinces and municipalities under the Central Government [3]. In 2018, the annual power generation reached a record of 101.6 billion kWh [4]. The Three Gorges Hydropower Station has replaced many thermal power stations, reducing the annual combustion of standard coal by 35.28 million tons and thereby reducing coal emissions [5].

Another important task of the TGP is to reduce or prevent damage caused by flooding. The uneven distribution of rainfall in the basin of the Yangtze River has been the source of a high incidence of floods. Flooding on the Yangtze River is the result of high-speed water flow caused by a large amount of precipitation at the high elevation of the river’s upper course [6]. The location of the Three Gorges Dam enables it to control floods effectively in approximately one million square kilometers of the Yangtze River basin above the dam. It has formed a flood control system in the middle and lower course of the Yangtze River by serving as a storage and detention area for floods. 

The TGP also improved the shipping condition of the upper course of the Yangtze River. The channel from Chongqing to Yichang has massively improved; 139 rapids, 24 shoals, and 46 one-way channels from the dam site to Chongqing were eliminated with its construction. The main channel of the Three Gorges reservoir area has been upgraded from its Grade III pre-construction rating to its post-project rating of Grade I, and the annual shipping capacity has increased from 18 million tons to more than 100 million tons. After impoundment, the number of accidents, shipwrecks, and direct economic losses decreased by 72%, 65%, and 20%, respectively [7].

In conclusion, the TGP affects a large population due to its power supply, flood prevention functionality, and improved shipping conditions. Additionally, the establishment of the TGP has benefitted aquaculture, shipping, and tourism industries in the middle and lower reaches of the Yangtze River. The TGP has undoubtedly improved the living quality of the people in the Yangtze River basin.

Ethical Concerns

The TGP can be analyzed using a utilitarian ethics approach. Utilitarianism states that the most ethical choice is one that benefits the largest amount of people [8]; in other words, maximum gain for minimum pain. The development of the TGP benefitted most of the population in China, but people living upstream and the wildlife in the upper basin of the Yangtze River were affected negatively in the process.

Societal Impact

The mainstream of the Yangtze River basin passes through 11 provincial-level administrative regions such as Qinghai, Sichuan, Chongqing, and Jiangsu, all of which are home to dozens of ethnic groups. These groups have lived here for a significant amount of time and have formed unique living habits and cultural customs. These habits and customs are an essential part of Chinese culture and of great significance to China’s artistic development and progress. The TGP has resulted in the migration of millions of people that belong to these ethnic groups and has caused a cultural loss in the ancient towns in which these people lived.

A total of 1,256,500 people were relocated when their homes were submerged due to the rising water level directly caused by the construction of the TGP from 1994 to 2009. The impact caused by the TGP affected 19 administrative regions in Chongqing and Hubei province, covering 56,000 square kilometers of land [9]. Studies have shown that, like international or urbanization migrants, TGP immigrants often suffer from additional economic, social, cultural, and physical health difficulties due to resettlement [10]. 

Many of the TGP immigrants resettled to nearby towns or cities that were not affected by the construction of the TGP [10]. Even though they were compensated for the loss of their land, a lack of income following migration made the immigrants more vulnerable to financial hardship. Prior to relocation, TGP immigrants were largely reliant on agriculture for their survival and development. TGP immigrants were also more likely to encounter employment problems due to their skills differing from local employment demands. After the resettlement, immigrants with lower education levels and lack of relevant experience and skills found it difficult to adapt to the pace of urban life, and the difficulties in re-employment also caused unstable income. As a result, these immigrants have a high demand for financial aid such as low-interest loans and subsidies, prompting them to rely on help from the government.

The involuntary migration caused by the construction of the TGP became a social governance problem that restricted the overall development of affected regions. Resettling immigrant groups led to a series of economic and social issues such as social network reconstruction, residential space differentiation, and social welfare changes. Further, too much emphasis was placed on short-term resettlement relief policies rather than long-term planning. For example, there was investment in economic compensation but not enough in support programs that would offer skill training. As a result, many immigrants entered a life of poverty and became marginalized in their new residential area. The incumbrance of poverty combined with social adversities prompted immigrant-led protests and even escalated into conflicts between immigrants and residents. The irreversible and destructive nature of these conflicts on the social environment violated the project’s original intention.

The central government set up a development fund for both the enterprises and immigrants in the TGP-affected areas and established an official plan named “Master plan for follow-up work of the Three Gorges Project.” Since 2011, more than 1,800 projects have been arranged to help immigrants in the Three Gorges Reservoir area secure their livelihood and develop their economy, with a total of 29 billion RMB of special state subsidies approved [9]. Overall, the living standards of most TGP immigrants improved, reached, or even exceeded the average level in the settlement area. The infrastructure and many other public service facilities in towns and cities close to the TGP received a massive update due to the economic development brought by the TGP. Unfortunately, the effectiveness of the development fund was weakened by corruption within local governments in the towns and cities that accepted TGP immigrants. So far, nearly 240 officials from the Three Gorges Reservoir area in Chongqing have been investigated and punished for job infringement, embezzlement, and bribery [11]. 

Many new infrastructures were constructed after TGP immigrants moved in. Although the construction process was relatively fast, the industrial development in these towns and cities could not keep up. This caused many enterprises to go bankrupt, resulting in slow economic growth and an increased unemployment rate. Rural areas have also been affected by TGP-related economic development stagnation and decreased income for farmers. These economic issues can lead to social unrest as we saw during the “Wanzhou Incident” a few years ago, in which tens of thousands of people surrounded the Wanzhou City Hall.

Environmental Impact

As the mother river of China, the Yangtze River is of great value to regional ecological stability, economic development, and scientific research. It is considered an environmental and cultural treasure to China and the world. As an unprecedented water conservancy project, the TGP has an inevitable impact on the ecological environment of the Yangtze River Basin. However, environmental friendliness and resource protection should always be regarded as the ethical criteria of a project in the early planning, construction, and later resettlement. 

The construction of the TGP had a significant impact on ecology. Dams have large impacts on river health and the living quality of river organisms [12]. The construction of TGP had many effects on the river’s ecological system: It separated the natural living environment, disrupted the food chain of aquatic, half aquatic, and terrestrial organisms, destroyed vegetation and soil, caused water loss in the Three Gorges Valley region, and threatened the living conditions of some rare species [13]. Specifically, the spawning ground of the Chinese sturgeon became unreachable because of the dam. Since Chinese sturgeon only lay their eggs within these spawning grounds, the population of the Chinese sturgeon was greatly reduced [14]. The population of four Chinese food fish also decreased due to a change in water temperature and quality following the dam’s construction. Additionally, the impounding of the Three Gorges Reservoir separated fish populations between the Yangtze River and many mountain streams, resulting in loss of genetic diversity [13].

The impact of the TGP on the Yangtze River is different upstream of the dam than it is downstream. Upstream, the TGP slowed down the speed of water flow, reduced the river’s self-cleaning ability, and worsened the water quality. Downstream, the TGP reduced the amount of sand that the river carries, resulting in a lowered riverbed that affects lakes that are connected to the Yangtze River [15]. Dongting Lake is a large lake that is downstream of the TGP and is a natural flood basin of the Yangtze River [16]. The lowered riverbed reduced the amount of water that flows into Dongting Lake during the rainy season and increased the amount of water that flows out of the lake during the dry season. Combined, these effects led to a decrease in the size of Dongting Lake [15].

To reduce the impact on the environment, many environmentally friendly measures have been made in recent years. These measures include setting up nature reserves along the Yangtze River basin, restocking fish fry, and adjusting the downstream water flow to maintain the water level in lakes connected to the Yangtze River [13,14]. Since there are still unknown long-term effects on the environment caused by the TGP, additional efforts will need to be made to minimize the impact of future effects.

Economic Impact

The two main economic advantages of the TGP are electricity generation and shipping facilitation. The TGP has created significant economic and environmental benefits by generating clean energy to meet electricity needs. Clean energy production by the TGP hydro plant saves around 10 million tons of coal annually, promotes energy conservation, and reduces the emission of harmful gasses including carbon dioxide and sulfur dioxide. This electricity is then transmitted to industrial provinces that have a high electricity demand. The profit that the TGP earned in 2017 from selling its generated electricity reached 743 million U.S. dollars [17]. Counties located in the TGP reservoir area saw a 259% increase in their gross domestic product from 1996 to 2007 [14].

Ship locks on the TGP allow a 10,000-ton level freighter to reach Chongqing directly [18]. Thanks to the Three Gorges Project, the Yangtze River is now a powerful tool in coordinating economic development in regions along the river. However, the TGP ship locks have reached their designed capacity. Although the TGP ship locks allow direct shipping to Chongqing, it takes a long time for a fleet of 10,000-ton freighters to get to there. As a result, the dam became a bottleneck for Yangtze River shipping and is responsible for an increase in shipping time and cost. 

The benefits from the completion of the Three Gorges Project are enormous, but these benefits are a result of environmental and societal sacrifice. Despite these sacrifices, the Three Gorges Project satisfies the requirement of a utilitarian approach as it brings the most benefit to the largest number of people. The electricity generated by the TGP supplies many industrial provinces. As a result, these industrial provinces no longer need to build their own thermal power plants, thereby reducing the provinces’ pollution production. The TGP also prompted economic growth such as increased GDP in counties within the TGP reservoir area. An additional advantage of the TGP is the TGP’s flood control capabilities that benefit millions of people who live along the lower basin of the Yangtze River. However, all these benefits came with damage to the environment and the involuntary migration of 1,256,500 people. There are also unknown long-term impacts to the environment that researchers have yet to discover. Overall, the TGP can be considered a beneficial project for China, but the rights of the immigrants that suffered from the resettlement process deserve better consideration.

By Tianhua Lyu, Viterbi School of Engineering, University of Southern California

About the Author

At the time of writing this paper, Tianhua Lyu was an undergraduate senior in computer science. He is interested in motorcycles, machinery, and computer hardware. During the pandemic, he could usually be found either in front of his work desk or in the garage working on his motorcycle.

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Links for Further Reading

https://www.npr.org/series/17785161/china-s-three-gorges-assessing-the-impact

https://www.scientificamerican.com/article/how-do-dams-hurt-rivers/

https://www.bard.edu/cep/blog/?p=12930

Evaluating the hydrological effects of the Three Gorges Reservoir based on a large-scale coupled hydrological-hydrodynamic-dam operation model

• Research Articles
• Published: 02 May 2023
• Volume 33 , pages 999–1022, ( 2023 )

Cite this article

• Sidong Zeng 1 , 2 ,
• Xin Liu 1 , 2 ,
• Jun Xia 1 , 2 , 3 ,
• Hong Du 4 ,
• Minghao Chen 1 , 2 &
• Renyong Huang 5  

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Understanding the hydrological effects of the Three Gorges Dam operation in the entire reservoir area is significant to achieving optimal dam regulation. In this paper, a large-scale coupled hydrological-hydrodynamic-dam operation model is developed to comprehensively evaluate the hydrological effects of the river-type Three Gorges Reservoir. The results show that the coupled model is effective for hydrological, hydrodynamic regime and hydropower simulations in the reservoir area. Dam operation could have a notable positive effect on flood control and could reduce the maximum daily flood peak by up to 26.2%. It also contributes a large amount of hydropower, approximately 94.27 TWh/year, and a water supply increase for the downstream area of up to 22% during the dry season. In the flood season, the water level at Cuntan would increase under the condition that the water level of the dam is higher than approximately 158 m due to dam operation. In the dry season, attention should be paid to the low flow velocity near the dam in the reservoir area.

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Strategic Priority Research Program of the Chinese Academy of Sciences, No.XDA23040500; Youth Innovation Promotion Association, CAS, No.2021385; Central Guidance on Local Science and Technology Development Fund of Chongqing City, No.2021000069

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Sidong Zeng, Xin Liu, Jun Xia & Minghao Chen

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State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China

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Zeng, S., Liu, X., Xia, J. et al. Evaluating the hydrological effects of the Three Gorges Reservoir based on a large-scale coupled hydrological-hydrodynamic-dam operation model. J. Geogr. Sci. 33 , 999–1022 (2023). https://doi.org/10.1007/s11442-023-2117-7

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Received : 06 April 2022

Accepted : 01 December 2022

Published : 02 May 2023

Issue Date : May 2023

DOI : https://doi.org/10.1007/s11442-023-2117-7

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Case study: Three Gorges Dam

Introduction.

With the recent worldwide focus on renewable energy sources, Hydroelectric dams that control the flow of a river are being built faster than ever before. One of the prime examples of this, is the Three Gorges Dam – now the largest power station in the world.

The Three Gorges dam originally began construction in 1992 , on a chokepoint of the River Yangtze. Only being finished recently in 2012 , there are many benefits and disadvantages that have come with its construction.

Socio-economic

• The dam currently provides protection from 1 in a 100 year floods. This is vital in ensuring the livelihoods of people living in the nearby Dongting Lake Plains .
• The dam provides 18,200 MW of hydro-electric power. This is estimated to be about 10% of China’s total electricity needs.
• The dam has improved the Chinese inland shipping system. Areas of the valley that were once out of reach for ships are now becoming major ports of trade.
• Water supply for towns in the valley has also improved.

Environmental

• Reduced air pollution as HEP energy is mostly generated in a clean and safe manner.

Disadvantages

Socio-Economic

• At least 1.2 million people have been resettled due to controlled flooding when the dam was built. Whole towns have disappeared.
• Some people living in the valleys have had to move to steeper areas with poorer soils for agriculture.
• Cultural heritage has been destroyed as over 1700 sites of cultural importance have been submerged by flooding.
• Due to the dam blocking the flow of the river, sewage and industrial effluent have piled up in the reservoir.
• The famous Yangtze River Dolphin is now thought to be extinct due to loss of its habitat
• Such a large-scale dam has slightly increased earthquake risk in the area.

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Case Study on The Three Gorges Dam in China

Geography Coursework

The Three Gorges Dam

長江三峽大壩

Chris Stanley 11IRW

      Candidate Number 2527

25 th  January 2007

Introduction

The Three Gorges Dam project, presently being built on the Chinese  River Yangtze and it is know to be the world’s largest dam and one of the most controversial public works of modern times. The proposed 2.3km long by 185m tall, concrete hydroelectric dam is to cross the river around 400km west of the city of Wuhan. The dam will create a huge reservoir behind it 660km long stretching within the three gorges behind it and allow for the regulation of water west of the Dam.  The Three Gorges Project is speculated to be completed by 2008, one year ahead of previous predicted schedule.

                                                                                   Map of the River Yangtze

Damming the Yangtze River was first proposed in 1919 by the founder of the Republic of China in order to protect the river communities from the erratic flooding caused by the river that caused a huge amount of destruction and death; however the poor economic state of the country at the time delayed the process. A later communist leader Mao Zedong, in office from 1945-1976, was known to be the most prominent supporter of the project, although it was not until 1993 when the river was diverted and 1994 when construction began. Over the last 50 years, the economy of china has increased vastly in strength. Since 1952, the GDP has increased by around 280 times mainly due to the market based reforms since 1978 which include the privatisation of farming and entrance to the World Trade Organisation. With an increasing economic strength, the Chinese Communist government can afford huge public works such as the Three Gorges dam which they believe will benefit the economy further in the future.  Presently (2007) the structure of the dam is said to be completed although it will not be fully operational until 2008 when it will be able to generate electricity at full capacity.

The River Yangtze

The River Yangtze is the world’s third largest river which flows for a total of 6,211km from the Tibet in the West through China and ends in the East where it branches of as a delta into The Pacific Ocean. It has a drainage area that is 1.8 million square kilometres which is around 18% of Chinese Territory. Whilst transporting fertile silt the river often floods and causes much devastation due to flooding due to an influx in rain. Before the dam was built, the river was relied on heavily for fishing, transport and sustaining fertility of farmland among many other things. The river is said to support 230 million Chinese citizens and affect one in ten people on Earth in some way or another.

What Are the Effects of the Three Gorges Dam?

The construction of The Three Gorges Dam has sparked up some serious debate about the social and environmental costs of the project. Most of the issues have two sides to them, some benefiting different aspects and that do not.

Regulation of Water

         The two main rives of China often flood due to the vast, seasonal summer rains of China often causing disastrous effects. The Yangtze floods of 1998 were due to torrential rain in July caused water levels to rise downstream on the river at levels of up to 1.25m above danger level, threatening cities such as Wuhan. By the end of August the floods had killed in excess of 2,000 people, swept away around 3 million houses and destroyed 9 million hectares of crops. This disastrous flood was said to have affected one fifth of the Chinese population.

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According to a study on Chinese water management by the Tibet Justice Organisation, water shortages in China are such that over 60 million people do not get enough water for their daily needs. Figures show that in 1995, 400 of 595 Chinese cities had savvier water shortages and presently one in three rural inhabitants don’t have access to clean water whilst in the cities such as Beijing there is still a mere individual allowance of 66,000 gallons per year. 11.9% of the Chinese economy relies on agriculture, much of which is for growing rice for export which requires huge amounts of water; the Yangtze provides 66% of China’s rice.

The construction of the three gorges dam means that west of the dam on the Yangtze water can be regulated and controlled, preventing the event of freak flooding such as those in 1998 which will benefit all citizens east of the dam. However sceptics believe that the freak flooding on the Yangtze is predominantly due to the high levels of water entering the river from some of the seven hundred tributaries that are east of the dam meaning the regulation of the Yangtze at three gorges would be superfluous to preventing freak flooding although this is theory is not backed by any available figures. The regulation of water east of the three gorges dam will help prevent water shortages further east on the Yangtze in cities such as Wuhan, Nanjing and Shanghi.  As a part of the three gorges project a 600km canal is planned to be constructed from the three gorges reservoir to the city of Beijing in order to supply the city with 8 billion cubic meters of water a year preventing water shortages in the area. On the downside, if 22.5 billion cubic meter flood control capacity is exceeded that there is little to prevent overspill from causing disastrous effects in unprotected valleys surrounding The Three Gorges.

The Reservoir

By creating a dam, a lake is formed behind it. The lake behind the three gorges dam will flood 632 squared kilometres an area the size of Singapore including many villages and towns. An estimated 1.3 million people who live in the area that will be flooded by the lake will be displaced and be forced to relocate. The three gorges project allows for compensation of those that will loose their jobs, home and land as a result, however there have been complaints that these reparation payments have not reached those that it has be intended for due to corruption. The map on the following page indicates this loss of land to the reservoir.

River cruises on the Yangtze have become ever more popular through the scenic area of the Three Gorges as the Chinese tourism industry has grown in recent years. There are many luxury cruises that run up and down the Yangtze but many were suspended for a time around the construction of the dam. After completion of the dam these cruises will again be able to travel along the Yangtze by crossing through the ship locks beside the dam.

Many people criticize the dam because of the flooding of the three gorges area will mean that large part of this scenic area that attracts tourism will be destroyed. The dam itself is visually unappealing to say the least, which is said to decrease tourism in the immediate area, but there are steps being taken to make the critically acclaimed, World’s Largest Dam, into a tourist attraction. A viewing platform and bus rides along the dam are said to begin after all construction leaves the area completely.

Power & Electricity

In 1995 73.2% China’s energy consumption was Coal (as shown by the pie chart below). The hydroelectric power generators of The Three Gorges Dam are thought to be able to generate up to an estimated 18,000 megawatts per year allowing China to reduce its dependency on coal.  Not only will this cut CO 2  emissions (see Greenhouse Gas Emissions) but this will mean China will no longer have to rely as much on foreign imports of coal. This reduction in foreign imports for coal will reap huge benefits for the Chinese government and economy in the long term, despite the huge cost of the dam. The construction of the Three Gorges Dam will contribute to the 2010 target of 840GW per year power capacity of China which will help reduce and end the frequent generator “burn outs” and rolling “black-outs” that are experienced in China. The Generators began running at full capacity recently on October 26 th  2006.

Greenhouse Gas Emissions

Hydro Electric Power in any form saves coal, trees and other un-renewable recourses from being burned in order to create energy. The reaction of burning fossil fuels is: Fuel + Oxygen → Energy + Carbon Dioxide + Water. The Carbon Dioxide emitted by fossil fuel power stations such as the coal power stations in China contribute heavily to the Greenhouse Effect. China emits the second largest, after the USA, volume of greenhouse gasses in the world and will soon emit more than the USA.

On the other hand there is some worry about the natural greenhouse gasses such as methane that may be created as a result of flooding a huge area to become the three gorges reservoir. It is believed that a large amount of methane gas will be created as trees and plants rot in the reservoir. However, most people believe that the benefits of the Dam producing green energy far out-weigh the effect of Greenhouse gasses from the reservoir.

Vegetation & Wildlife

Many environmentalists think that the environmental impact of the dam could be devastating. As well as the flooding of some rare ancient trees many rare speciesmay be affected badly.

Many aquatic creatures of the Yangtze River are likely to be effected by the Dam, including many types of fish, the Yangtze dolphin, the Chinese Alligator to name a few. The construction the dam will affect these creatures due to several reasons. Firstly is the temperature of the river. The Yangtze River is not a particularly deep river and therefore it has relatively warm temperatures, but as the river rises and becomes a reservoir behind the Three Gorges Dam it will become very deep and a lot colder. This may cause many species to reduce in numbers or even die out completely.

The 632km that are to be flooded behind the Three Gorges Dam will destroy some of the areas finest scenery, including beautiful forests and breathtaking deep valleys.

The flooding of the reservoir will caused s 1.1million people will be required to relocate to less desirable places, however some riverside villages and towns will just be moved to higher ground in order to prevent their flooding when the lake completely filled. There is some debate to weather this is a good thing. One the one hand the Chinese government are putting money into the rebuilding and relocation of towns and villages that will perhaps make them a more desirable place to live in the future and more able to sustain economic development.

As the reservoir behind the three gorges dam is created the water will flood many towns and villages containing some of China’s most treasured historic sites for example. According to archaeologists, the reservoir will engulf around 1,200 historical sites, some dating back to over 50,000 years old and another presently 8,000 unexcavated sites. Some of the historic sites will be buried in a tomb of water and silt, whilst some will be moved and relocated, ensuring their protection. One historic site that will be relocated is the Zhang Fei Temple shown in the image on the right. Despite its ensured safety from the waters of the Yangtze many people are disappointed that it is to be moved to a less scenic and desirable place. A total of $37.5 million has been allocated by the Three Gorges project to protect Chinese history and culture. Like other large sums of money allocated for different areas of the project some of the money is expected to be lost due to corruption.

Silt & Fertility

Silt that is carried by the River Yangtze has caused the region around the river to be one of the most fertile regions in the whole of China. The dam will deny most places west of the dam any silt whatsoever which will cause the fertility of farmland west of the dam to decrease terribly. This will be a disadvantage to farmers west of the dam as it will mean their crops have a smaller yield, perhaps bringing an economic decline in the area. However, as previously mentioned, whilst preventing the flow of silt to the western farmers, they are also ensured protection from the flooding which causes clay to ruin their crops completely. The build up of silt behind the dam, in the reservoir can lead to the clear, clean lake becoming very murky. This can lead to an alteration in aquatic conditions which could affect many river creatures negatively. The build up of silt can also clog up the dam, preventing water from flowing through it easily, leading to a reduction in the efficiency of the hydroelectric power turbines. This could very well mean that the dam has a very short life span in terms of generating electricity and controlling water levels effectively although the designers do believe they have a method that may counter this effect.

Construction

It is said that The Three Gorges Dam will cost the Chinese government over $28 billion (USD). This money will be spent on the, 26 turbo generators, 26 million tonnes of concrete, 250,000 tonnes of steel, and a workforce over 40,000 strong, all required to construct the dam over the period many years. There is some debate on whether the workers will have good working conditions, although many workers are happy that the work is being brought to the area.

The construction requiring 40,000 labourers will provide a large amount of work in the area whilst the movement, relocation and reconstruction of town and historic sites that would be effected by the Three Gorgers Reservoir will also create jobs for a period of time during and after the construction of the dam allowing the area to prosper economically in the future. On the down side many factories are being forced to close due to the prospect of them being flooded by the rising waters of the Three Gorges Reservoir. It is intended that those that loose their job to the reservoir are to receive compensation.

Those working on the dams’ construction will eventually loose their livelihoods when the project is completed whilst it is likely that they will find jobs in the ongoing relocation and improvements in the area that will continue for many more years after the dam is completed. As the towns and cities increase in terms of economic activity due to the modern design of the new towns and cities new opportunity and economic expansion is due for the future of China.

After researching the effects of building the Three Gorges Dam I have been made to think of many positives, such as economic advantage and the prevention of devastating floods, and many negatives, such as the ecological and environmental disaster that the dam may cause.

It is clear that after tabulating a conflict matrix on the effects of The Three Gorges Dam on different people there were more agreements than disagreements within groups of people. This suggests that the construction of The Three Gorges Dam predominantly creates agreements between different groups. There are some major disagreements in the project such as the power companies. This new source of cheap energy will cause the price of power in China to go down, impairing the profit of power companies. I think that problems such as there can be easily solved by regulation. In this case the price of electricity should be regulated so that it does not negatively effect the power companies too much.

I think in total the population that benefit from the dam far exceeds the population affected negatively by it and in the big picture China will benefit economically from projects such as these and that the utilisation of their renewable energy sources will help China continue become one of the worlds’ strongest economies.

In my opinion I think that the main problem with the construction is the environmental impact of the dam that could perhaps be devastating. However I think the ‘green energy’ that it will create will far outweigh this effect. Despite this, I feel that if the reservoir becomes polluted, I do not think that the project will be much of a success in all fields. The key to the success of this project is to manage the water in the reservoir correctly in order to prevent it becoming a cesspool of human and industrial waste which would conflict with the tourism industry and with those living on the high ground west of the Dam.  China as a country has the money to prevent this happen, but whether this money is allocated towards environmental protection or lost in the widespread corruption of the project.

Sources & Bibliography

• Wikipedia.org
• BBC News Online – 20 th  May 2006
• Washington Post Online
• International Rivers Network  (IRN.org)
• European Space Agency – China 1998 Flooding (ESA.int)
• ImperialTours.net – Yangtze River & the Three Gorges Tour.
• Energy Information Administration (EIA.doe.gov)
• Discovery Channel Online
• Tibet Justice Organisation – “Hydro Logic: Water for human development”

                                        - An Analysis of China’s Water Management and Politics.

Document Details

• Word Count 2951
• Level AS and A Level
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