Abstract:

Based on the annual runoff and sediment load data observed at four hydrological control station of Four Water basin (Xiang River, Zi River, Yuan River and Li River) in Hunan province from 1951 to 2011 of four representative gauging stations (Xiangtan, Taojiang, Taoyuan, Shimen), the Periodic regularity and characteristics of mutation of annual runoff and sediment changes fluxes into the Dongting Lake from Four water basin was analyzed using MannKendall trend test, moving average value, Wavelet analysis and double mass analysis. The results show that the annul changes of runoff and sediment was different in a great scope. ①The annual runoff of Four water basin has a plurality wave phenomena of rise and decline, but no significant change. And sediment discharge has certain fluctuation with the overall downward trend, and the downward trend is obvious. The annual runoff is highest in Xiang River(653.7×108 m3), intermediate in Zi River (2269×108 m3)and Yuan River (6362×108 m3), and lowest in Li River (1461×108 m3). The annual sediment is highest in Yuan River(1 003×104 t), intermediate in Xiang River (9389×104 t)and Li River (5299×104 t), and lowest in Zi River (2191×104 t).②The runoff and sediment of Xiangtan Station, Taojiang Station and Taoyuan Station have a primary period of 20-25 years. But the Runoff and sediment of Shimen Station of the first main period is not consistent. Annual runoff and sediment discharge cycles of Xiangtan, Taojiang and Taoyuan is more consistent. Among them, the runoff and sediment discharge in Xiangtan station of Xiangjiang River also has the second main cycle of seven years. And the annual runoff and sediment discharge of Taojiang also exist the periodical characteristics of seven years. The annual runoff and sediment discharge of Taoyuan station also has the main cycle of 14 years and 12 years respectively. But the annual runoff and sediment discharge of Shimen station in the first cycle is not consistent. The runoff has the main period of 2 years, and the sediment discharge has the main cycle of 13 years. Runoff and sediment discharge of Shimen in the second cycle change law is basicly consistent, which is about 3-5 years period. The cycle of the annual sediment discharge lag than the cycle annual runoff 2-3 years. ③The construction of water conservancy project is a major cause of sediment reduction