Quantitative Assessment And Driving Mechanism Of The Contribution Of Climate Change And Human Activities To Runoff And Sediment Varialility In Dongting Lake Basin

The river network of Dongting lake is dense,the rivers and lakes are interlaced and the system is complex.Under the influence of climate change and human activities,the change of runoff and sediment is significant.The article is based on the measured data of 10 hydrological controlled stations in Dongting lake from 1951 to 2015 and the monthly precipitation data from 1961 to 2015 in Dongting lake and its surrounding meteorological stations to analyzed the change characteristics of runoff and sediment by using linear trend method,M-K nonparametric test,5a Moving T-test and wavelet analysis.And on this basis,based on the runoff and sediment,annual precipitation and monthly precipitation variance of each watershed,based on the empirical model of precipitation-runoff(sediment)multivariate regression,the contribution rate of climate change and human activities to the change of water and sediment in Dongting lake basin was quantitatively evaluated,and the driving mechanism of water and sediment variation in Dongting lake was revealed,which provided some guidance for the economic development,water resources exploitation and management.This paper mainly obtains the following conclusions:(1)In the view of interdecadal variation,in the whole Dongting lake,the changes of runoff and sediment in the three outlets basin are more severe than that of the four rivers basin,among which the changes of runoff and sediment in the Ouchi outlet are the most severe and the range is the largest,and the changes of water and sediment in the four rivers basin and Chenglingji are stable and close to each other,the change distributions is more uniform.(2)According to the results of M-K test in Dongting Lake,there were no abrupt changes in the runoff of the four rivers in Hunan Province,and the change was not significant.And the abrupt change points of sediment in Xiangjiang River,Zishui River and Yuanshui River were close to that in the vicinity of 1996,and the Lishui River occurred in 1992.The water and sand in the Chenglingji River and three outlets of Jingjiang river are all mutated,The year of runoff mutation in Songzi outlet,Taiping outlet is 1985,Ouchi outlet is 1975,and the year of sediment mutation in Songzi outlet,Taiping outlet and Ouchi outlet is 1995,1997,1988,the year of runoff and sediment mutation in Chengjingji is 1971,1982,abrupt year of runoff and sediment discharge is inconsistent.The sequence of runoff and sediment in Dongting Lake area shows the periodicity of different scales.The periodicity of water and sediment in the four watersheds of Hunan Province is consistent.The variation period of runoff and sediment in Songzi outlet is close to Taiping outlet,but it is quite different from Ouchi outlet.The runoff and sediment discharge of Chenglingji have the periodic variation of 33a and 23 a,respectively.(3)The contribution rate of precipitation to runoff variation in Xiangjiang River,Zishui River and Yuanjiang River basin is 77.11%,60.71%,54.48%respectively,and the contribution rate of human activities to runoff change is 22.89%,39.29%and 45.52%respectively.In the 1961-2015 years,the contribution rate of the three outlets in Jingjiang River and the Chenglingji river to the decrease of runoff was 22.74%,17.08%,5.80%and 7.67%respectively,and the contribution rate of human activities to the decrease of runoff was 77.26%,82.92%,94.2%,92.33%.The contribution rate of precipitation to sediment in four rivers of Hunan province was 0.87%,7.82%,3.60%and 3.31%respectively,and the contribution rate of human activities to the change of sediment was 99.13%,92.18%,96.4%,96.69%respectively.The contribution rate of the three outlets in Jingjiang River and the Chenglingji to the decrease of sediment was 3.69%,0.52%,8.38%and 4.85%respectively,and the contribution rate of human activities to the decrease of sediment was 96.31%,99.48%,91.62%,95.15%respectively.Except for the runoff of the four water basins,the influence of water and sediment on water and sediment in Dongting Lake is much greater than that on water and sediment caused by climate change.(4)The influencing factors of runoff and sediment in Dongting Lake are mainly divided into two aspects:climate change and human activities.Among them,there is a slight increase trend in the precipitation,mainly in the average year,the interannual change is relatively small,and the precipitation is alternately abundant and dry.The increase of water consumption in various industries,such as domestic water use and industrial water use,the construction of water conservancy facilities and the implementation of soil and water conservation projects all affect the evolution of water and sediment in Dongting Lake.