To enhance water exchange and alleviate eutrophication in Lake Taihu, China, four different routes of Yangtze River Water Diversion have been implemented or planned by transporting water from Yangtze River to flush pollutants out of Lake Taihu. The Route One (original) and Route Two (improved) Yangtze River Diversion have been put into practice now, improving the water exchange in Meiliang Bay and most of the eastern lake regions. However, the two routes did not significantly enhance water exchange in the western lake regions (e.g., Zhushan Bay, Northwest and Southwest Zone), known as the heavily polluted areas in Lake Taihu. Hence, the third and fourth routes of Yangtze River Diversion are put forward now to overcome this deficiency. Due to the shallowness and largeness of Lake Taihu, it is quite complex to set the optimal transferred inflow rate for each single route or the combination of routes to maximize the benefit for improving lake‘s water exchange with a minimum economical cost and environmental impact. In order to understand that, the appropriate transferred inflow rate and environmental impacts of different water transfer routes on both Lake Taihu (―receiver‖) and Yangtze River (―donator‖) were assessed using the concept of water age and particle tracking based on a three-dimensional Environmental Fluid Dynamic Code model (EFDC). The results showed that the appropriate transferred flow rates of each route were quite different when considering making most of a single route or the combination routes. The optimal flow rates depended on the priorities of interest targets, such as lowest economical cost, maximal environmental improvement for specific lake regions or the entire lake. In general, two typical optimal combinations of all the water transfer routes were obtained to improve the water exchange for most of the lake regions in the algae bloom season and non-algae bloom season. In algae bloom season, the optimal combination was that the inflow rates from Route one, three and four were about 80, 100 and 20 m3/s, while the outflow rates for Route two was about 70 m3/s. This solution focused on the eutrophication areas and prevented algae blooming. WA in Meiliang Bay, Zhushan Bay, Northwest Zone and Southwest Zone were about 99, 7, 96 and 235 days. In non-algae bloom season, the better solution was that the inflow rates from Route one, three and four were about 90, 70 and 20 m3/s , respectively, while the transferred water flow out through Route two was 40 m3/s. This combination could cover all the lake regions (97.8%) to enhance water exchange rates. Additionally, both the single route and the combination routes had slight impacts on the hydrodynamic process of Yangtze River. The findings of this paper could help local government and other decision-makers to operate the water transfer projects well.
EFDC inter-basin water transfer multi-objective optimization method particle tracking water age
Yiping Li Chunyan Tang Chao Wang Wei Tian Lei Hua Janet Lau Zhongbo Yu Kumud Acharya
Key Laboratory of Integrated Regulation and Resources Development of Shallow Lakes of Ministry of Ed Hydrology and Water Resources Investigation Bureau of Jiangsu Province, Nanjing 210029, China College of Environment, Hohai University, Nanjing, 210098, China;Zhejiang Institute of Hydraulics & Chemical and Process Engineering, University of Western Australia, Perth, 6009, Australia Department of Geoscience, University of Nevada, Las Vegas, NV 89119, USA Desert Research Institute, Las Vegas, NV 89119, USA