| Lakes are large water bodies of the land, which are both important for the regional and global area, cause lakes are both vital to the ecosystem and economy. Due to the global climate change and human activities, many lakes are shrinking, and the severe situation they faced,the study of lakes are becoming one of the research focus. Dongting lake is the second fresh water in China, with the function of reservation flood in the middle and lower Yangtze River, and it is important to the surrounding area’s socioeconomic development. Over the past decades,the changing climate and anthropogenic activity have changed the hydrographic feature in Dongting lake.Therefore, in long time series of water and sediment data based, on Dongting Lake water and sediment evolution characteristics of water and sediment are attributed to the contribution rate of separation, to develop under the new situation of Dongting Lake water resources reasonable development and utilization and protection measures of resource and environment, and optimize the water conservancy project scheduling scheme has very important significance.This study to 1951-2014 years of Dongting Lake 10 important hydrological station monthly average runoff and monthly average sediment sediment as well as the region and surrounding areas 19 important meteorological station 50 years of yearly rainfall data based, by variation coefficient ratio, Mann Kendall trend and mutation test method,moving t test, Morlet wavelet and cumulative variation of slope rate comparison method, from the multi time scale and spatial analysis of the sediment in Dongting lake evolution characteristics. On this basis, the separation and quantitation of the respective contribution to precipitation and water conservancy project as the symbol of the wave climate and human activities of sediment in Dongting lake evolution rate. The main results are as follows:(1) Under the background of competition in the global climatefluctuation and human activities, reducing in Dongting Lake area to Lake area, Jingnan three flow for a long time and into the lake shunt sediment gradually reduce; large reservoirs in the upper reaches of the Yangtze River water conservancy engineering activities in succession, the four main rivers in Hunan Province Group operation sign changes in the environment, changing the Dongting Lake water and sediment and water sediment transport process.(2) Dongting Lake Sediment Distribution in time and space, from April to September is the runoff and sediment peak, into the Lake flood years average runoff accounted for many years into the lake of annual runoff of 79.96%, for many years into the lake average sediment sand for the total quantity of 92.02%; Nan Jing three, of the four rivers in Hunan Province and Chenglingji runoff interannual variability of absolute ratio reached 11.87, 2.58, 3.53, while the input the interannual variation of sediment yield absolute ratio reached 184.7, 24.58 and 7.57; three accounted for Dongting Lake runoff into the lake 31.78%, four water accounted for 68.22%, and lost sediment three accounted for 81% of the total lake, four water only 19 percent.(3) The annual runoff and sediment load shows a significant decrease. The inlet and outlet runoff jump point are 1977 and 1975,the sediment jump point are 1978 and 1970; The period of outlet is consistent with inlet runoff, they both have the period of 4 year, and 9 year, and 25 year, and 32 year; The period of inlet sediment are 4 year, and 10 year,and 24 year, while the outlet’s period are 6 year,12 year, and 26 year.(4) Compared with the baseline period 1960-1966, 1967-1973 years1974 to 1980 years, 1981-2014 years rainfall of Dongting Lake diameter flow changes in the contribution rate of 11.28%, 6.83%, 0.84%,respectively, human activities of runoff flow changes in the contribution rate respectively 88.72%, 93.17% and 99.16%, indicating that with the water conservancy project for signs of human activity impact on runoff into the lake to reduce the maximum. |
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