Runoff And Sediment Change And Its Response To Human Activities In Lianshui In The Upper Reaches Of Ganjiang Basin

Changes of runoff and sediment and their responses to human activities in theLianshui River were systematically analyzed in this article with the method of mathematical statistics and wavelet analysis based on the measured data of rainfall,runoff and sediment transport from 1967 to 2016 in Lianshui River in the upper reaches of the Ganjiang River.The contribution of rainfall changing and human activities to the changes of water and sediment in Lianshuihe River was quantitatively analyzed with double accumulation curve method.The main findings are presented below:(1)Characteristics of runoff changes.There was an unevenly distribution of runoff during the year in the Lianshui River from 1967 to 2016,with a single peak distribution at the end of May,whose uneven coefficient was 0.91.The overall trend of annual runoff decline was weak.There were obvious stages of runoff changes:the normal period from1967 to 1983,the dry period from 1984 to 1991,the wet period from 1992 to 2002,the dry period from 2003 to 2014,and the wet period from 2015 to 2016;There was a certain periodicity with 28a,17a,and 7a cycles of annual runoff,of which the first main cycle was28a.(2)The characteristics of sediment transport.There was an unevenly distribution of the sediment transported amount of during the year in the Lianshui River from 1967 to 2016,which was a single peak curve with the maximum transport volume at the end of May;The average annual sediment transport is significant decrease in inter-annual sediment(p<0.01,Z_s=-0.46).There was a significant mutation point in the sediment transport sequence of Lianshui River in 2002.While was a plentiful sediment period from 1967 to 2002 and the less sediment period from 2003 to 2016,the first main cycle was 28a.(3)Characteristics of rainfall changes.there was an average annual rainfall of 1620.50mm in Lianshui River from 1967 to 2016 with a non-significant increase trend,there was uneven distribution of rainfall during the year with average multi-year episode in late May.There was an obvious period changes of rainfall:normal period from 1967 to 1983,dry period from 1984 to 1991,wet period from 1992 to 2002,dry period from 2003 to 2014,wet period from 2015 to 2016.From 1986 to 2008,there was a single peak distribution of erosive rainfall in April to August,and with the peak in June.(4)The contribution of rainfall and human activities to changes in runoff and sediment.From 1984 to 2002,the contribution of rainfall to the changes in runoff and sediment transport in the Lianshui River was-74.37%and-4.64%,respectively.The contribution of human activities to the changes in runoff and sediment transport was 174.39%and 104.64%.From 2003 to 2016,the contribution of rainfall to the changes in runoff and sediment transport in the Lianshui River was 13.86%and 3.52%,respectively.The contribution of human activities to the changes in runoff and sediment transport was 86.14%to runoff and96.48%,respectively.(5)The change of runoff in Lianshui River Basin mainly depends on the change of rainfall factors.Its characteristics are basically consistent with the rainfall,and there is no obvious trend.The change of sediment transport is mainly affected by human activities,besides the influence of rainfall factors.The impact is significantly reduced;human activities such as soil and water conservation measures are the main driving factors for the drastic reduction of sediment transport in the Lianshui Basin and the mutation.