The controversial sluice gate between Poyang Lake and the Yangtze River is to feature two additional holes to aid passage of the endangered Yangtze finless porpoise, according to its latest environmental impact assessment (EIA).
Moreover, for a one-year period every five years, the 3km-long sluice gate will be fully opened to re-establish water flow between the river and lake.
The level of Poyang, China’s largest freshwater lake, tends to be low in winter and high in summer once the rains have swelled the Yangtze. Last year, however, a prolonged heat wave and drought across much of the Yangtze Basin pushed the levels to summer lows not seen in decades.
According to the EIA, the 23-metre-high gate will help cope with such extreme weather: “The project can alleviate the impact of drought and extremely low water levels in the Poyang Lake area and the lower reaches of the Yangtze.”
Poyang is vital for the Yangtze finless porpoise. About half of the 1,000 remaining porpoises live in the lake, according to Xinhua News. Keeping it connected to the Yangtze is crucial for the genetic diversity of the species.
In the previous EIA, the sluice gate was to include four rather than six circular holes, 60 metres in width, that can be opened and closed with gates. But WWF believes the conclusion that these gates can allow “finless porpoises to pass freely” has not been scientifically demonstrated.
When the previous EIA was proposed, Zhou Jianjun, a professor at Tsinghua University’s Department of Water Conservancy, pointed out that “Once the gates are fully open, with the water passing through, it is impossible to control the water level anymore”.
As well as increasing the number of holes to six, the latest EIA states that no new large cross-lake engineering projects and wharfs will be planned within 30km up or downstream of the sluice gate.
Construction of the gate has been on the cards for nearly two decades. It has been postponed several times due to environmental concerns.
Read China Dialogue’s 2021 report on the Poyang Lake sluice gate.