In June, the Jinsha River, clear water and blue sky, Yuxiang shallow bottom.
Standing on the observation deck of the dam of Jinsha Hydropower Station, you can see the towering dam embraces a bay with clear water, and a waterway shaped like a "U" groove on the left bank winds out, connecting the upper and lower dams, forming an ecological corridor that continues life Tao.
This is the first fish passage in the main stream of the Yangtze River, and the Yangtze River fish has a "special line" to go home.
"Since it was put into use, the fishing effect has been good. Monitoring data shows that the average monthly fishing volume is more than 3,600." On July 2, Zhu Shihong, deputy director of the General Aviation and Fishing Design Department of the Yangtze River Design Institute, said, watching his design. His work outlines the ecological picture of the fish leaping over the sands, which is very gratifying.
The great protection of the Yangtze River starts from the design source to draw the ecological blueprint to the end.
Break through the obstacles and let all the fish swim all the way
Most of the fish in the Yangtze River have the habit of migrating and spawning.
In recent years, with the accelerated development of the Jinsha River and Yalong River in the upper reaches of the Yangtze River, natural rivers have been intercepted by dams and migratory channels have been blocked, which has affected the reproduction and ecological balance of aquatic species to a certain extent.
A few years ago, Niu Xinqiang, an academician of the Chinese Academy of Engineering and dean of the Yangtze River Design Institute, talked about "the tears of fish."
This begs a question: How to coordinate the development of water conservancy projects with the ecological environment?
"In 2011, during the research and demonstration stage of Jinsha Hydropower Station, we considered the problem of fish passing." said Yan Shuanghong, chief engineer of Jinsha Hydropower Station design and deputy chief engineer of Yangtze River Design Institute. For this reason, their first special study focused on how to live. fish.
As early as the early 1980s, the problem of fishing caught the attention of relevant experts.
After the completion of the Gezhouba Hydropower Station, a team of experts conducted a water turbine fish test and concluded that "fish below 50 cm can pass normally".
This conclusion solves the problem of upstream fish passing downwards, but the downstream backtracking problem remains unsolved.
Since then, fishing nets and fish lifters have been gradually used in hydropower stations.
Zhu Shihong introduced that nets have caught fish and fish lifters have broken the barriers to fish migration to a certain extent, but there are some flaws.
For example, excessive manual intervention caused resource depletion and could not meet the needs of all migratory fish.
Can a means be used to break through the obstacles once and for all, so that all the fish can swim all the way?
After consulting a lot of information and going to Hunan Yangtang Hydropower Station and Guangxi Changzhou Water Control Project to learn about fish facilities, Zhu Shihong came up with the idea of arranging fish passages around the dam's shoreline.
After countless calculations, collisions and demonstrations, Zhu Shihong and his design team cooperated with the Yangtze River Water Resources Protection Research Institute to complete the "Special Report on Hydroecological Impact Assessment of Jinsha Hydropower Station on the Jinsha River."
Subsequently, Yan Shuanghong led a team to Beijing to make a special report to the environmental protection department, and was quickly approved and asked them: "Deepen the fishway hydraulic model experimental research in the next stage, and optimize the fishway design plan."
The first fish passage on the mainstream of the Yangtze River is ready to emerge.
Scientific design to ensure that the fish "should be overwhelmed"
The axis of the dam of Jinsha Hydropower Station is nearly 400 meters, and the fishway is like a jade belt, winding along the left bank dam line for nearly 200 meters, passing through the dam, and reaching the exit of the fishway nearly 300 meters upstream.
In order to reduce the occupation of river shoreline resources, the two ends of the fish channel are folded and rounded three times to meet the needs of the fish to swim and climb.
How can the fish accurately find the entrance to the fishway downstream of the dam that is less than 1 meter wide?
Zhu Shihong said that this is the key to the success or failure of the fishway design.
"Fish have a natural ability to find a flow field that suits them, and to move in the area." Zhu Shihong recalled that before the plan was approved, the team and the long-term scientific research staff began hydraulic research together, and hydraulic models simulated various flow fields. , To find out the most suitable flow rate for the fish to swim.
For more than a year, they studied 63 kinds of fish collected in the river section of the Jinsha Hydropower Station, and finally got the flow velocity data of 0.3 meters per second to 1 meter per second.
Based on this, combined with various factors such as river regime and dam water blocking, three fishway entrances were designed on the lower left bank to cover the swimming characteristics of most fish.
Once the fishway is built, it is also necessary to make sure that the fish "should pass through."
In order to help the few "lost" fish find the right way, Zhu Shihong's team used their brains in the fish-collecting channel parallel to the direction of the dam.
Zhu Shihong introduced that if the fish-gathering channel is relatively wide and the water replenishment port is perpendicular to the channel body, it will cause only a small flow rate at the water outlet, and most of the water flow in the channel does not form a special flow field, which has little effect in guiding fish into it.
Through trial and error, the team innovatively proposed that the water replenishment port should be tilted toward the fish's swimming direction, and the overall flow velocity in the channel can be driven by controlling the water replenishment flow rate to form a flow field that the fish like.
This move greatly expanded the scope of fish collection, enhanced the effect of fish collection, and also won a national patent.
At present, in similar buildings both at home and abroad, fish passages generally pass through the dam through a hidden culvert, resulting in no light in the culvert, causing the phototaxis to stagnate.
To this end, the design team adopted the method of slotting around the dam to better use the natural light environment to meet the phototaxis characteristics of different fishes.
The head of the Jinsha Hydropower Station is more than 20 meters high. How to design the fishway as short as possible while meeting the conditions for fish migration?
In 5 years, Zhu Shihong's team has undergone countless experiments and set the fish pond to various slopes on the physical model to observe the fish's ability to overcome the current.
In the end, the fish pass was optimized from the 1755 meters proposed in the research stage to 1486 meters. This alone saved one-fifth of the investment in the construction of the fish pass.
At the same time, a vertical slit efficiency partition is installed every 3.5 meters in the fishway, and there are more than 380 vertical slit efficiency partitions to imitate the natural river flow pattern.
"The fish pass import and export are close to the 1 to 1 fish passing volume, which proves the scientificity of the design." Zhu Shihong said that the success rate of the fish passing the dam has been greatly improved.
Upgrade files and equip "hospitals" and "delivery rooms" for migratory fish
"Look, this is Iwabara carp, and this is a spring fish. It is queuing for the exit." On June 25, Zhu Shihong carefully identified the type of fish through the fish monitoring screen.
Suddenly, he raised his tone: "Round-mouthed bronze fish, a round-mouthed bronze fish!"
It turns out that the common name of the round mouth copperfish is Feituo, which is a rare fish that lives in the Yangtze River and is usually rarely seen.
"Next, we will further upgrade the fishway, strengthen the landscape design, and better present the beauty of the fish leap into the golden sands." Yan Shuanghong said that crossing the fish channel is equivalent to setting up a "magpie bridge" for the fish, in order to better To multiply, a suitable "hospital" and "delivery room" are needed.
In 2015, in the design plan of the hydropower station, the planning of multiplication and release and spawning field was added.
After on-site investigation, the Yan Shuanghong team found that 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. It covers the water area and can meet the ecological needs of the two cascades, and the "hospital" is here.
In 2017, the Jinsha Hydropower Station closed the river, and the above-mentioned multiplication and release station took on the release task of the Jinsha Hydropower Station, cultivating and releasing nearly 200,000 fry every year.
In the future, the tenth cascade Yinjiang Hydropower Station downstream of the Jinsha Hydropower Station will also join the discharge plan. At this point, the discharge station will become the country's first "hospital" shared by the three power stations.
Artificial intervention only assists the reproduction of migratory fish, and more fish will still reproduce naturally after migration.
As a result, Yan Shuanghong's team started to find a suitable "delivery room" for Yuer after the Yudao was put into operation.
In the next step, they will use constructed wetlands to further purify the water quality and create a comfortable "delivery room" for the fish.
◎Our reporter Liu Zhiwei and Wu Chunxin
Correspondent Fu Jing Qin Jianbin