Is it reasonable to build sluice (or dam) in Poyang Lake? After it is built, what will be the impacts on water regulation, migratory bird habitats and food chains, aquatic life migration and water environment quality? On January 16, 2021, the Research Department of CBCGDF invited two academicians of the Chinese Academy of Engineering and many experts and scholars in ecology, biodiversity protection, wetland, water conservancy, and other stakeholders to join the “Seminar on Poyang Lake Water Control Project” both online and offline. The following is the views shared by Jianqiao Han, an associate researcher of Institute of Soil and Water Conservation, Ministry of Water Resources and Chinese Academy of Sciences.

Whether a Sluice is Key to Solving Drought in Poyang Lake
Drought of Poyang Lake is the basic starting point of sluice construction. First of all, we need to have a scientific understanding of the impact of the Three Gorges Dam on Poyang Lake. According to the observation data, after the operation of the Three Gorges Dam, the low water level of Hankou hydrological station decreased by more than 1m at the same flow rate. This change is bound to increase the outflow of Poyang Lake under the same flow rate of the mainstream. In addition, the Three Gorges Dam stores clear water and discharges muddy water, and during the impoundment period, reduce main stream flow and water level. 

However, is the water level drop in the main stream of the Yangtze River only caused by the operation of the Three Gorges Dam? Whether the law of the river itself is working as well? Before the impoundment of the Three Gorges Dam, the channel is in the state of alternation of erosion and deposition; since the impoundment, the low water level of Luoshan Hydrological Station in the upper stream changed little, however, the water level of Hankou station in the lower stream declined, which is not in line with the general characteristics of downstream-wise erosion of the reservoir, why? Besides, the average annual runoff of Yichang hydrological station is about half of that of Hankou hydrological station, that is to say, the Three Gorges Dam can only regulate and store the runoff process above Yichang hydrological station. How much effect does it have on Poyang? Before the definite reason is confirmed, the reason for the water level drop in the main stream of the Yangtze River cannot be entirely attributed to the influence of the Three Gorges Dam. The Three Gorges Dam will affect the water level of the main stream of the Yangtze River, but its degree needs to be evaluated scientifically.

Secondly, the effects of watershed hydroperiod and human activities at lake regions on drought need to be understood scientifically. From the main stream of the Yangtze River, in recent 20 years, the runoff is about 10% less than before, which may be related to the hydroperiod. What's the situation inside Poyang Lake? In recent years, with the development of economy and society, what about industrial and agricultural water? Does the decline of groundwater cause the decline of water level in the lake area?
There should have been a lot of arguments about these reasons, which can be made public to locate the cause of the drought in Poyang Lake, then the demand for sluice construction would be clearer and there would be more understanding in society.

We need to weigh the pros and cons to assess whether to build sluice from the perspective of sustainability
Whether to build a water conservancy project depends on whether it can achieve the goal of "invigorating the interests and eliminating the disadvantages". Besides, we have to consider our needs in terms of time, because human needs are changing, which also directly affects the necessity of the water conservancy project. Since the last century, in order to produce more food, fertilizer is widely used in cultivated land. Now, the harm of soil hardening and area source pollution is serious, so we started to develop other technologies to improve the soil fertility. Fertilizers solved the problem of our survival at some stage in the past. So, whether it is necessary to build a sluice must start from our needs, and also consider the future development.

After being built, the sluice can maintain the water level of Poyang Lake, but at the same time, it will destroy the ecological environment. The reason for the differences lies in our different starting points. If the advantages of building sluice far outweigh the disadvantages, and the future ecological damage is controllable, then why not give full play to the advantages of water conservancy projects? If the advantages are not obvious or can be replaced by other ways, and the ecological environment will change irreversibly, then we will eventually become the victim of one's own evil deeds. All in all, as for whether to build the gate or not should be based on the basis of systematically revealing the causes of drought in Poyang Lake, considering both advantages and disadvantages. The sustainable development of engineering and ecology is the key to choose whether to do the engineering or not.

Translator/Wang Lei

Original Chinese article:

https://mp.weixin.qq.com/s/NQ1TuqSr-cot_5QhagP57w

Contribution

https://www.paypal.me/CBCGDFChina

http://www.cbcgdf.org/English/ConfirmDonaTion/0.html