◎ Wu Chunxin Science and Technology Daily reporter Liu Zhiwei correspondent Fu Jing Qin Jianbin
In June, the Jinsha River, clear water and blue sky, fish soar shallow bottom.
Standing on the observation deck of Jinsha Dam, you can only see the majestic dam holding a bay of clear water, and a waterway like a "U" trough on the left bank meanders out, overturning the dam to connect up and down, forming an ecological corridor that continues life.
This is the first fish passage in the main stream of the Yangtze River, and the Fish of the Yangtze River have a special line to go home.
"Since it was put into use, the effect of passing fish has been good, and the monitoring data shows that the average number of fish per month is more than 3600." Zhu Shihong, deputy director of the Navigation and Fish Design Department of the Yangtze River Design Institute Hub Institute, said that he was very pleased to see the works he designed and outline the ecological picture of "fish leaping into the golden sand".
The great protection of the Yangtze River, starting from the source of design, can draw the ecological blueprint to the end.
It can be "vetoed" by one vote
Most of the fish in the Yangtze River have the habit of migrating to spawn. In recent years, with the acceleration of the cascade development process of the Jinsha River and Yalong River in the upper reaches of the Yangtze River, the natural river channel has been intercepted by the dam and the migration channel has been blocked, which has affected the reproduction and balance of aquatic species to a certain extent.
A few years ago, Niu Xinqiang, an academician of the Chinese Academy of Engineering and president of the Yangtze River Design Institute, talked about "the tears of fish", a group of fish could not find a passage against the current, struggling to cross the dam and crash into the concrete dam body. This begs the question: how can water conservancy projects coexist in harmony with ecology?
This is also a major problem for China's environmental protection department to include a "one-vote veto" at the beginning of the planning of water conservancy and hydropower projects.
"In 2011, when Jinsha Hydropower stood in the pre-feasibility study and demonstration stage, we considered the fish problem, which is also the top priority of the EIA." Yan Shuanghong, chief engineer of jinsha hydropower station design and deputy chief engineer of the Yangtze River Design Institute, said that for this reason, their first special study focused on how to fish.
As early as the early 1980s, the problem of passing fish attracted the attention of relevant experts. After the completion of the Gezhouba Hydropower Station, the expert team conducted a fish test on the turbine and came to the conclusion that "fish under 50 centimeters can pass normally".
This conclusion solves the problem of downward passage of upstream fish, and the downstream backtracking is still "stuck neck".
Since then, nets have been used to catch fish, fish lifts and other means, and gradually used in hydropower stations.
Zhu Shihong introduced that the net has caught fish and the fish lifter, which has broken the barrier of fish migration to a certain extent, but there are some flaws. For example, too much manual intervention leads to resource depletion and the inability to meet the needs of all migratory fish.
Is it possible to break through the obstacles once and for all through one means and let all the fish swim all the way?
After consulting a large number of materials and going to hunan Yangtang hydropower station and Guangxi Changzhou water conservancy hub to learn about fish facilities, Zhu Shihong came up with the idea of laying a fish passage around the shoreline of the dam.
Countless calculations, collisions and demonstrations, Zhu Shihong and the design team cooperated with the Yangtze River Water Resources Protection Science Research Institute to complete the "Special Report on The Evaluation of Aquatic Ecological Impacts of Jinsha River Jinsha Hydropower Station".
Subsequently, Yan Shuanghong led the team to Beijing to make a special report to the environmental protection department. It was quickly approved and requested: "In the next stage, we will deepen the experimental study of the hydraulic model of the fish road and optimize the design scheme of the fish road." This means that the "one-vote veto" of jinsha hydropower station has successfully passed the trial, and it also means that the first fish passage in the main stream of the Yangtze River is about to come out.
The innovative force smooths the Fish Migration Road of the Yangtze River
The dam axis of Jinsha Hydropower Station is nearly 400 meters, and the fish road is like a jade belt, winding along the downstream left bank dam line for nearly 200 meters, passing through the dam, and nearly 300 meters upstream, which is the exit of the fish road.
In order to reduce the occupation of river shoreline resources, the fish road ends are folded three times to meet the needs of fish swimming and climbing.
How do fish pinpoint the entrance to the fish tunnel downstream of the dam that is no more than 1 meter wide? Zhu Shihong said that this is the key to the success or failure of the design of the fish road.
"Fish have a natural ability to find a suitable flow field and move around the area." Zhu Shihong recalled that before the plan was approved, the team began hydraulic research with the researchers of the Academy of Science and Technology, simulating various flow fields with water mechanics models to find out the most suitable flow rate for fish to swim.
For more than a year, they studied 63 species of fish collected in the Jinsha hydropower station and finally came up with a flow rate of 0.3 to 1 meter per second. Accordingly, combined with river potential, dam obstruction and other factors, three fish channel inlets were designed in the lower left bank to cover the swimming characteristics of most fish.
The fish road was built, and it was also necessary to ensure that the fish "should pass through". In order to help a small number of "lost" fish find their way home, Zhu Shihong's team used their brains in the fish replenishment canal parallel to the direction of the dam.
Zhu Shihong introduced that if the fish collection canal is relatively wide, the water replenishment inlet is perpendicular to the canal body, which will cause only a small flow rate at the outlet, and most of the water flow in the canal has not formed a special flow field, and the effect of guiding the fish into the canal is not large. After repeated trial and demonstration, the team innovatively proposed that the water replenishment outlet be tilted to the direction of the fish swimming, and the overall flow rate in the canal was driven by controlling the water replenishment flow rate to form a flow field that the fish liked.
This greatly expanded the scope of fish collection, enhanced the effect of fish collection, and also obtained a national patent. This is just one of the highlights of the Golden Sands Fish Road.
At present, in similar international and domestic buildings, fish tunnels generally pass through the dam through hidden culverts, resulting in no light in the culverts, resulting in stagnation of the expelled fish. To this end, the design team used the method of slotting around the dam and making better use of the natural light environment to meet the light repellent characteristics of different fish.
The head of Jinsha Hydropower Station is more than 20 meters high, how to design the fish road as short as possible under the premise of meeting the migration conditions of the fish?
In five years, Zhu Shihong's team has undergone countless experiments to set various slopes across the fish pond on the physical model to observe the ability of fish to gram. In the end, the fish road was optimized from 1755 meters to 1486 meters, which alone reduced the investment of the fish road construction by one-fifth for the owner.
At the same time, a vertical seam performance partition and more than 380 vertical seam performance partitions were installed at a distance of 3.5 meters in the fish road, imitating the natural river flow pattern. "Fishway imports and exports are close to 1 to 1 excess fish, which verifies the scientific nature of the design." Zhu Shihong said that the success rate of fish crossing the dam has been greatly improved.
Equipping migratory fish with "hospital" and "delivery room"
"Look, this is Iwahara carp, this is a spring water fish, and it is lining up to pass the exit." On June 25, on the fish monitoring screen, the fish gracefully crossed, and Zhu Shihong carefully identified the type of fish. Suddenly, he raised his voice: "Round mouth copper fish, a round mouth copper fish!" ”
It turned out that the round-mouth copper fish, commonly known as the Fat Tuo, is a rare fish living in the Yangtze River and is rarely seen.
"Next, we will further upgrade the fish road, strengthen the landscape design, and better present the beauty of the fish leaping sands." Yan Shuanghong was full of expectations.
Yan Shuanghong said that the passage through the fish is equivalent to setting up a "Queqiao Bridge" for the fish, and in order to better reproduce, it is also necessary to support the appropriate "hospital" and "delivery room".
In 2015, breeding and stocking and spawning site planning were added to the hydropower plant design.
After on-site investigation, Yan Shuanghong's team found that the breeding and stocking station of the eighth cascade Guanyinyan Hydropower Station in the middle reaches of the Jinsha River is only more than 20 kilometers away from the Jinsha Hydropower Station, covering the water area and meeting the ecological needs of the two cascades, and the "hospital" has landed.
In 2017, the Jinsha Hydropower Station intercepted the flow, and the above-mentioned breeding and stocking station undertook the release task of the Jinsha Hydropower Station, cultivating and releasing nearly 200,000 fish fry every year.
In the future, the tenth cascade Yinjiang Hydropower Station downstream of Jinsha Hydropower Station will also join the release plan, and the release station will become the first "hospital" shared by three power stations in the country.
Artificial intervention is one of the breeding methods of migratory fish, and more fish are still naturally reproducing after migration. Therefore, Yan Shuanghong's team began to look for a suitable "delivery room" after the fish road was put into operation.
In the next step, they will further purify the water quality through constructed wetlands and create a comfortable "delivery room" for the fish.
The pictures in this article are provided by the respondents
Editor: Zhang Qiqi
Review: Julie