Changes of Beach and Genetic Analysis in the Dongting Lake Wetland during the Initial Running of the Three Gorges Project

Data sets of beach wetlands area in the Dongting Lake were extracted using MODIS imagery from 2000 to 2010. The data sets were compared with the observed water-level of the Chenglingji. And the changes of beach wetlands area and their emergence time were analyzed. The results indicated that after the initial running of the Three Gorges Project, the beach wetlands area of the Dongting Lake increased 71.0 km 2 , 87.7 km 2 , 103.5 km 2 , 118.5 km 2 , 132.5 km 2 at the Chenglingji water level of 24 m, 25 m, 26 m, 27 m and 28 m respectively. And the emergence time of the beach wetlands prolonged 19 d, 27 d, 25 d, 11 d and 8 d, respectively. In conclusion, it is resulted from multi-factors, including reduction of runoff from the Three Channels (Songzi, Ouhe, Taiping) and the Four Branches (Xiang River, Zi River, Yuan River and Li River), reduction of rainfall, etc., which contributed to the reduction of beach wetlands area and prolonging their emergence time of the Dongting Lake. The impoundment of the Three Gorges Project from September to October would further aggravate the emergence trend of beach wetlands.