Abstract: Except from Poyang Lake and Dongting Lake, river-communicating lakes in the middle and lower reaches of the Yangtze River connect with the Yangtze River by culverts and sluices in general. The water quality of such lakes is inferior on account of the weak water exchange capacity, especially in dry season. Taking Huayang river-lake group as an example, we studied the feasibility of ecological operation and specific plans in non-flood period via data analysis, field investigation and numerical simulation. Results reveal that the concentrations of TN and TP decrease with the rising of water level; but such tendency attenuates when water level exceeds a certain value (13.5 m). The annual mean water level of lake group in late September is higher than the current controlled water level in non-flood period, indicating that it is feasible to use Huayang and Yangwan sluices for ecological regulation in non-flood period. In line with the current dispatching mode, the relation between rivers and lakes, the flood control security and the water environment improvement as well as the simulated results, we obtained the specific plan of ecological operation for Huayang river-lake group in non-flood season: using Yangwan sluice and Huayang sluice to control the water level in the lake area at 13 m in October-December,12.5 m in January-February,and 11.8 m in March-April.

Key words: river-communicating lake, relationship between rivers and lakes, non-flood period, ecological operation scheme, water quality parameters, numerical simulation, time of drainage