Trisotca Reservoir is a "high gorge flat lake" formed after the Trisoteska Dam, the main project of the Trisoteska Hydropower Station, was completed and put into operation.
The Three Gorges Reservoir is located at the eastern end of the Three Gorges Dam in Sandouping City, Yichang City, Hubei Province, and the main stream of the Yangtze River as the lake basin. After the dam has a normal storage depth of 175 meters, the river can flow back more than 600 kilometers west to Chongqing, forming an average water level. It is the largest artificial lake on the mainland, with a width of about 1.8 kilometers and a total area of 1084 square meters. km, with a total storage capacity of 39.3 billion cubic meters.
The highest dam height of the Three Gorges Dam is 185 meters, and the maximum dam height is 181 meters. The normal water level during non-flood periods is 175 meters, and the lowest water level is 155 meters. Every year before the flood season, the water level must drop to 145 meters. Flood control limits the water level, releasing 22.15 billion cubic meters of flood control reservoir capacity, and reducing the peak flood of the Yangtze River.
As the world's largest hydropower project, the Three Gorges Project integrates comprehensive benefits such as flood control, power generation, shipping, irrigation, tourism and aquaculture. However, in the face of flood control, everything else has to be sidelined, from 175 meters to 145 meters. The 30-meter drop in water level can release 22.15 billion cubic meters of flood storage space during the rainy season, and flood control is the core function of the Three Gorges Project.
However, from November 1997, when the Yangtze River was dammed, to June 2003, when the Three Gorges Project was dammed for the first time, the water level in front of the dam reached 135 meters. With the increase of the dam height of the Three Gorges Dam in recent years and the strengthening of the ecological environment of the Yangtze River Basin, the protection of the Yangtze River Basin has increased, making it a paradise for many freshwater fish and other organisms to grow and reproduce freely.
People often ask themselves the question that the Three Gorges Dam has been storing water for almost 20 years. How big are the fish in such a large artificial tank? To understand this problem, we first need to figure out how many fish are in the Yangtze River.
What fish are in the Yangtze River?
With a total length of 6,387 kilometers, the Yangtze River is the longest river on the mainland and the third longest river in the world. Its length and average annual flow are second only to the Nile in Africa and the Amazon in South America.
As the river with the largest volume and widest basin on the mainland, the Yangtze River stretches for thousands of miles from the snow-capped mountains, across plateaus and through canyons. It is rich not only in water energy, but also in fish.
According to preliminary statistics, the Yangtze River has risen and has raised 424 species of fish, including 183 endemic species. It is not only the habitat and breeding ground of the four main fish species of mainland bluefish, grass carp, white-eyed fish and bigeye, but also the habitat and breeding ground of Chinese sturgeon, and a paradise for rare fish such as mullet and Yangtze paddlefish. Sturgeon (declared extinct on December 23, 2019) (note that the white dolphin is a small freshwater whale endemic to the continent, not a fish).
In recent years, in order to protect the fishery resources and biodiversity of the Yangtze River, the mainland has officially imposed a 10-year fishing ban on the main stream and important tributaries of the Yangtze River since January 1 this year. The ten-year fishing moratorium on the Yangtze River is important to improve the gene pool of wild fish and other species. It is important to increase the number of unique species.
The Three Gorges Reservoir is located on the main stream of the Yangtze River and is also a protected area where fishing is prohibited.
How big are the fish in the Three Gorges Reservoir?
Sichuan fishermen have a saying: "
The saying "a thousand wax seed cats, all cats, yellow species is not serious" refers to the three "peculiarities" of the Yangtze River. "Larzi" refers to the Chinese sturgeon and the "elephant" yellow waxy fish. Refers to the white sturgeon with a dry mouth and nose in the Yangtze River, and the "yellow card" refers to "mullet".
From this fisherman's words, we can clearly see that the Yangtze oarsmen are the largest, followed by the Chinese sturgeon.
The Yangtze paddlefish is also known as the Chinese swordfish. It used to be the largest freshwater fish on the continent, reaching a maximum body length of 7.5 meters. However, on December 23, 2019, such a semi-anadromous fish was discovered. Officially declared extinct, this means that the largest fish in the Yangtze River is now the Chinese sturgeon, with a maximum length of 5 meters and a weight of around 600 kilograms.
However, Chinese sturgeon is a migratory fish in the ocean and rivers, and its sexual maturity is late (males mature in the earliest 8 years, females in 14 years). The larvae feed on the shallow waters of the Yellow, East and South China Seas. Then it migrated more than 3,000 kilometers to the Yibin section of the upper reaches of the Yangtze River to spawn and reproduce. After laying their eggs, they go down the river again. Chinese sturgeon has been a migratory bird throughout its life, migrating along rivers between the outer seas of China and the southwestern continent. The shallow sea is rich in food and can meet its energy needs, while the upper reaches of the Yangtze River have more gravel and good water quality, which is conducive to spawning and reproduction.
However, the construction of Gezhouba directly interrupted the normal migration life path of the "Yangtze River King Fish" Chinese sturgeon, resulting in the loss of its main spawning grounds. Due to the difficulty of adapting to the new spawning environment in the middle and lower reaches of the river in a short period of time, it is difficult for Chinese sturgeon to adapt to the new spawning environment. The wild population of Chinese sturgeon, which has lost its "freedom to go to sea", is on the verge of extinction.
In addition, the successive construction of Gezhou Dam and Three Gorges Dam directly blocked the migration of Chinese sturgeon. As a result, the number of Chinese sturgeon upstream of the dam is small, and if any, it is mostly farmed and released. In 2017, a fisherman in Zhongxian (Three Gorges Reservoir Area) in Chongqing accidentally caught an adult Chinese sturgeon that was suspected to be wild, about 1.8 meters long and weighing about 120 kilograms. The fish was then released by the fisheries department.
In addition to these rare fish, the Three Gorges Reservoir is home to many large, common fish. Among the "four major fish", salted fish and blackhead fish are eligible to become "Yangtze River monsters". It is understood that someone once caught a 400-kilogram blue fish weighing 400 kilograms in the Shilu River, a tributary of the Yangtze River in the Yunyang Longgang Scenic Area of Chongqing. In fact, not to mention the Three Gorges pile with a water area of 1,084 square kilometers and a maximum depth of more than 100 meters, there are many lakes in the middle and lower reaches of the Yangtze River in the mainland that have records of catching "water monsters". For example, a fish weighing 100 pounds caught in the Jinniu Lake Reservoir in Nanjing. large herring weighing 212 kg; The Nanyang Yahekou Reservoir (upper reaches of the Bai River, tributaries of the Han River, and tributaries of the Yangtze River) also caught a large blue fish weighing 132 kilograms.
Loch Ness is the third largest freshwater lake in the UK, with a length of 39 km, a width of only 2.4 km at its widest point and an average depth of 200 metres. However, reports of the Loch Ness Monster have occurred repeatedly. It can be seen that there are still many problems in the Three Gorges Reservoir. Big fish exist.
Advantages and disadvantages of the Three Gorges Dam
As we all know, the mainland is the country with the most obvious monsoon climate in the world, and most of the Yangtze River basin is located in the monsoon climate zone south of the Qinling Huaihe River line and east of the Qinghai-Tibet Plateau (south of the 800 mm rainfall limit). Not only that, the annual runoff is as high as about 960 billion cubic meters, and the seasonal and interannual changes are large. About 70% of precipitation is concentrated in summer. Every year when the rainy season comes, especially the plum blossom season, Hubei, Hunan, Jiangxi, Anhui and other middle and lower reaches of the Yangtze River, Jiangsu and other places will face huge flood control pressure.
According to statistics, before the construction of the Three Gorges Dam, the middle and lower reaches of the Yangtze River flooded to varying degrees every year. On average, large-scale floods occur once every decade, seriously affecting the lives and property of coastal people. A huge threat is coming.
In order to reduce the occurrence of floods and make full use of the abundant water resources of the Yangtze River, the mainland finally built the Three Gorges Water Conservancy Hub Project of the Century Project in Sandouping, Yichang City, which controlled the area of 1 million square kilometers of the river basin, and after full demonstration by the expert group, covered 56% of the area of the Yangtze River basin, greatly optimizing the optimal layout of the Yangtze River water resources.
The construction of the Three Gorges Dam not only plays a central role in flood control, storing water and reducing flood peaks during the flood season, but also storing water in the rainy season and discharging water in the dry season to meet water demand. Downstream shipping, irrigation and water supply resources.
Of course, as the main project of the Three Gorges Hydropower Station, the world's largest hydropower station today, the Three Gorges Dam has installed 32 hydropower stations with a total power generation capacity of 700,000 kilowatts. With an annual power generation capacity of nearly 100 billion kWh, it is the largest hydroelectric power plant in central China. Hubei, Henan and Hunan, Jiangxi, Anhui, Jiangsu, Shanghai and Zhejiang in East China, Chongqing in Southwest China and Guangdong in South China have provided high-quality clean electricity, making great contributions to the mainland's energy conservation and emission reduction work. Although the completion of the Three Gorges Dam has created huge social and economic benefits, it is undeniable that the Three Gorges Dam also has many drawbacks. That's why many biologists have so far expressed concern about the dam during the demonstration phase. The dam directly divides the continuous river ecosystem of the main stream of the Yangtze River in two, destroying the habitat of migratory and semi-migratory fish, baiji dolphins and other animals, and is extremely harmful to the breeding populations of Chinese sturgeon and baiji dolphins.
However, the depletion of fish and other resources in the Yangtze River is not entirely caused by the Three Gorges Dam. The culprits are unreasonable human activities, overfishing (electric fish), water pollution, etc.
Thankfully, the mainland has now artificially bred rare fish in the Yangtze River, increasing their populations through artificial release. In addition, a 10-year fishing ban on the Yangtze River has been imposed. During this ban, most fish are able to reproduce. In 2-3 generations, I believe that in 10 years, the fish resources of the entire Yangtze River basin, including the Three Gorges Reservoir, will increase significantly, and there will be more and more large fish in it.