Research on change of the outflow of Dongting Lake during the refill period of the Three Gorges Reservoir

Based on the one- and two-dimensional coupled hydrodynamics model of the Yangtze River and Dongting Lake,the hydrological processes of the Dongting Lake area before and after the impoundment of the Three Gorges Reservoir were simulated. Quantitative analysis was carried out for the response relationship between the impoundment of the Three Gorges Reservoir and the outflowing water volume of Dongting Lake. The results indicate that the inflowing water volume of Dongting Lake from the three outlets along Jingjiang was reduced due to the impoundment of the Three Gorges Reservoir during the water storagerefill period. This also changed the variation speed of the Dongting lake storage capacity. Compared to the original conditions,the outflowing water volume of Dongting Lake was significantly reduced from September to October in each typical year,with greater reduction in October than in September,while the change in November was not distinct. The water volume change of the three outlets along Jingjiang from September to October was the dominant factor for the outflowing water volume variation of Dongting Lake,with the change of the lake storage capacity being the dominant factor in November. Through multiple regression analysis,the response relationship between the impoundment of the Three Gorges Reservoir,the outflowing water volume of the Dongting Lake,and the change of lake storage capacity was constructed. Under the conditions of constant lake storage capacity,the reduction of the outflowing water volume of Dongting Lake was about 23% of the impoundment of the Three Gorges Reservoir.