The water level of Qiandao Lake in Zhejiang Province has skyrocketed due to flooding, so it has to rely on flood discharge to maintain this torrent.
However, for Qiandao Lake, every flood discharge will face huge losses.
According to the local fishing company, Qiandao Lake was released from nine holes on July 8, 2020, and the direct economic loss on that day exceeded hundreds of millions of yuan. First of all, when the 9 holes are fully open, the direct flow of the flood discharge reaches 8,000 cubic meters per second, and we all know that the water intake place of the well-known bottled water "Nongfu Spring" in the mainland is Qiandao Lake.
The net content of each bottle of water is 550 ml, then, in the process of this second, 14 million bottles of water will be lost, which is 28 million according to the calculation of the market price of 2 yuan per bottle. And once the Qiandao Lake has to open the flood gate and discharge the flood through 9 holes, it proves that the water level of the entire Qiandao Lake will not stop until it is controllable.
In addition, every time the gate is opened in Qiandao Lake, it will also cause a large loss of organic fish in the lake, such as the 9-hole flood discharge in 2020, which caused the loss of as many as 1 million catties of silver carp in Qiandao Lake, and if the silver carp in Qiandao Lake is calculated at market price, the economic loss caused by the flood discharge alone has reached 68 million. In addition to silver carp, there are many other fish species that have lost immeasurable amounts.
Although the flood discharge will cause such a large loss to the economy of Qiandao Lake, once it is to be discharged, it is a strong proof that the entire dam will be subjected to a huge impact due to the increased rainfall. If the flood is not discharged, not only will the dam be in danger, but the soaring water level will even cause flooding in the surrounding residential areas.
Qiandao Lake, as a well-known super-large artificial lake in the mainland, was built in 1955 and took 5 years to complete. Because there are 1078 islands in the whole lake, it is named "Thousand Island Lake".
The total area of Qiandao Lake has reached 590 square kilometers, with a maximum depth of more than 100 meters, an average water depth of 30.44 meters, a total water storage of 17.8 billion cubic meters, and a warning water level of 106.5 meters.
The water quality of the reservoir area of Qiandao Lake has reached the national class I water, and it is one of the reservoirs with the best water quality in the country.
Superior water quality, complex reservoir structure, and good climate and environment have also brought rich biological resources to Qiandao Lake. It is understood that there are 83 species of fish in the Qiandao Lake area. In addition to the four major fish species (blue, grass, silver carp, bighead carp), carp, crucian carp and other common fish species, there are also precious fish species such as catfish, mandarin fish, eel, etc., which are the main fishery economic output of Qiandao Lake. In addition, Qiandao Lake can produce more than 3,000 tons of organic fish every year.
The loss of fish resources caused by a flood discharge in Qiandao Lake is as high as one million catties, which is equivalent to one-sixth of the annual output of Qiandao Lake.
那么，为何泄洪会造成如此多鱼类的损失
Many people will wonder why so many fish are lost every time the floodgates are opened.
Actually, this is still very easy to explain. Because, no matter what kind of water it is, most of the hiding places that fish will choose are either areas with complex underwater structures, or places where the water is relatively deep and the water surface is relatively wide.
In a reservoir, the location of the dam is often an area with a large water surface and a deep water level. Naturally, this attracts a lot of fish.
And, for many fish, they go with the current. In addition, once the reservoir is opened, it will cause a very large flow of water in the instantaneous process, so these fish near the dam will not react in time at this moment, and will eventually be carried into the gate by the huge flow of water and washed downstream.
At the same time, in the process of opening the sluice gate to drain the water, many fish will follow the current in groups. Even if the situation is found to be wrong, the huge turbulent water will be beyond the strength of these fish themselves, so they will eventually be swept away by the current.
In addition to the loss of fish in the reservoir area, there is another reason why the flood discharge will also cause fish loss.
I don't know if you have noticed, but every time the water rises, or floods, it eventually causes the fields to be flooded, the rural towns to be flooded, and there will be a lot of fish in the water.
These fish are flooded because of the low water level and the abundance of food. In addition, the water level has skyrocketed, and the water level of some tributaries has increased as a result. As a result, some fish swim upstream.
Eventually, after the water recedes, some of the fish will run aground, or stay in these tributaries, or in ditches, or ponds. This part of the churn is also very important.
Finally, there is another situation where floods cause damage to fish.
In fact, this part of the disaster was the least damaged.
Every time there is a flood, a lot of sewage will be washed out due to the rapid current, and the environmental pollution of the inundated area will be added. Therefore, especially in the upstream part of the reservoir area, a large number of fish will be inhaled by sewage, causing bacterial infections and eventually sudden diseases. Then there is the turbidity of the water, the sediment content in the water is large, and the melting oxygen of the water becomes low. Therefore, it will cause the gills of the fish to filter without urgency, not enough oxygen, and suffocation due to lack of oxygen.
结语
Although, a flood discharge from Qiandao Lake will cause huge losses as a result. However, if it remains within the controllable range, it will bring unimaginable disasters to the villages and towns upstream. The water level is very high, and the upstream will eventually become waterlogged as a result. And once towns are flooded and farmland is flooded, the economic damage caused by this is also incalculable. In addition, the reasonable discharge of flood water from Qiandao Lake can better ensure that these losses are minimized. Therefore, for the flood discharge of Qiandao Lake, although it will cause its own losses, it can save greater benefits.
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