A fish lift has been installed on the 1900 MW Huangdeng dam on the Lancang River in Yunnan Province, China. It is one of the latest attempts to help migratory fish species who, to spawn, must travel up a river increasingly obstructed by hydropower dams.
When the engineers working on the Huangdeng dam were faced with the task of constructing the first fish lift in China, they turned to scientists with the CGIAR Research Program on Water, Land and Ecosystems in the Greater Mekong to draw on their international experience and expertise. The lift, which was completed in August 2017, complements other efforts that try to mitigate the significant adverse impacts that hydropower dams are having on fish populations and biodiversity.
Managing inevitable trade-offs
The Lancang River springs from Mt. Guozong-mucha in Qinghai Province in China and runs for about 2,000 km before it meets the borders of Myanmar, Thailand and Laos. Here, the river becomes known as the Mekong River, flowing through the countries of the Lower Mekong Basin until it empties out in delta in Vietnam.
The hydropower potential of the Lancang is significant, with an estimated total hydropower capacity of 35.9 GW – about the same as the potential for the entire Lower Mekong Basin. Six hydropower projects have been developed on the middle and lower reaches of the Lancang so far, and seven projects are under construction on the upstream Yunnan reach. One of these is the 1900 MW Huangdeng, which is expected to be put into use in 2018.
“A number of endemic fish species migrate in the river reach where the Huangdeng Dam is located, and the dam will block their up-river journey,” explains Dr. Yu Xuezhong, Senior Hydro-Environmental Scientist at Ecofish Research Ltd. “Since the dam is very tall—203 meters—a fish lift is the most appropriate solution.”
Although the hydropower projects on the Lancang serve multiple purposes, including electricity generation, flood control, water supply, and navigation improvement, they also block fish migration and change their habitats from fast-flowing rivers to stagnant reservoirs. This means that biodiversity and fish populations have decreased.
Drawing on experience from the United States
The environmental impact assessment study completed on the Huangdeng dam recommended the installation of a fish lift. The dam developer, HydroLancang, retained the PowerChina Kunming to design the facility. In 2015, PowerChina Kunming turned to the scientists working on a project called Balancing River Health and Hydropower Requirements in the Lancang River Basin, led by Ecofish Research Ltd, to obtain advice on the design, operation, monitoring, and management of the lift.
“At that time, I believe something like this had never been built in China, and therefore neither the developer nor the engineers had a lot of knowledge of the components, criteria, and parameters of a successful fish lift,” said Dr. Yu.
That’s why, in late July 2015, he organized a study trip to visit six fish passage facilities in the United States with five engineers from PowerChina Kunming. They visited fish lifts at Conowingo Dam, Holtwood Dam, and Safe Harbor Dam.
Giving fish a lift: How it works
Following the trip, the research team made recommendations on how to improve the design of the fish lift.
“With this dam, the challenge is not so much its height, but rather how to attract the fish. We provided suggestions for where to place the fish trap and how to entice fish to swim into it, for example by simulating the natural flow of the river,” said Dr. Yu.
Recommendations adopted by the Chinese engineers include putting guiding nets at the entrance of the facility, revising the shape of the transport tank, and adding flow regulation within the structure.
To traverse the dam, fish are first guided into a holding pool and then lifted up the dam wall in a tank. With a conventional design, the fish would be released directly into the reservoir above, but the height of the Huangdeng dam creates a stagnant reservoir to which these fish species cannot adapt. Therefore, the fish tank is transported by ship to a tributary with an appropriate habitat, where the fish are then released. The same ship can also transport fish traveling the other way—from the headwaters and downstream.
This lift is one out of a number of mitigation measures put in place along the Lancang River, including artificial fish hatch-and-release programs for both endangered and endemic species. In a 2015 presentation, HydroLancang stated that more than 683,700 fish had been bred and released, and that fish elevators were are also planned for the Da Hua Qiao and Wu Nong Long dams.
Monitoring and assessment key to future improvements
The capacity of the recently installed fish lift at the Huangdeng dam has not yet been estimated, but a monitoring and assessment plan has been put in place to evaluate whether the lift is effective.
So far, monitoring and assessment of the various fish conservation measures along the Lancang River have been relatively poor, and the effect of hatch-and-release efforts is still to be documented.
Similarly, the effect of the fish lift remains to be seen. On the Conowingo dam, one of those visited in the United States, the number of American shad passing upstream reportedly peaked at 193,000 in 2001. HydroLancang considers fish passages to be a more efficient solution, but that is not a viable option at Huangdeng.
“Monitoring the effectiveness of the fish lift at Huangdeng is critical for improving the performance of the facility. Meanwhile, effective fish passages in other dam sites on the Lancang are also essential for the migratory fish—the single fish lift at Huangdeng cannot alone mitigate the adverse impacts of this cascade of dams,” cautions Dr. Yu.
Time will tell whether fish lifts could be a break-through solution for mitigating adverse impacts of hydropower dams on the Lancang River and elsewhere in the region. Let us know your thoughts on their potential in the comments below.