Runoff Evolution Regularity And Attribution Analysis In Zijiang Watershed

Global climate change and the intensification of human activities are the major environmental problems faced by human society,the dual effects of climate change and human activities,and the alternation and frequent occurrence of flood and drought disasters in the basin,which poses a major threat to the development of social economy and water security.In this paper,the temporal and spatial evolution characteristics of the long series hydrological elements and meteorological elements in the Zi River basin are analyzed,and the effects of climatic fluctuations and man-made factors on runoff are quantitatively analyzed by using different statistical methods and hydrological model methods.The main conclusions are as follows:(1)The annual runoff of hydrological stations in Zi River watershed was analyzed by linear regression method and trend test method:The annual runoff of Luo Jia Miao,Lengshuijiang,Dabuxi and Taojiang 4 hydrologic stations showed a decreasing trend in the fluctuation,and the rate was 8.2*106m3/a,8.1*106m3/a,0.59*106m3/a,1.2*106m3/a.The trend of annual runoff in four hydrologic stations was changed by MK Test and slide T-test,and the mutation was found in 1987 and 2002,and 1987-2001 years as variant period I,2002-2014 year as variant period II.The precipitation decreased gradually from 60s to 80s.However,the precipitation increased significantly by 90s,and the change of precipitation was stable in 21st century,but it still showed a decreasing trend over the years.The precipitation changed in 1987.The annual mean temperature is rising,the rise is 0.14?/10a,and the overall fluctuation is rising after the mutation in 1997.The trend of the annual fluctuation of latent evapotranspiration is much the same as that of the temperature,and the potential evapotranspiration sequence was changed in 1968 and 2002 by Slip T test.(2)The contribution rate of precipitation and human activity is calculated by using the cumulative slope change rate comparison method and the double cumulative curve method respectively.The results show that:Except for Luo Jiamiao station,the influence of human activities is obvious,its contribution is outside 70%-72.9%,I(1987-2001)in variant period,the influence of precipitation on watershed runoff is greater than the contribution rate of human activities;In the variant period II(2002-2014),The contribution rate of human activities has greatly increased and gradually become the main driving factor of runoff change.Using the grey relational model,the comprehensive correlation degree between the Zi River watershed and 8 factors in the 1989?2001 year is ranked as precipitation>evapotranspiration>gdp>effective farmland irrigation area>temperature>Reservoir dam Tangku capacity>population>large livestock head number.The comprehensive correlation between the zijiang diameter flow and 8 factors in the 2002?2014year is ranked as the temperature>Population>large livestock head>rainfall>effective irrigation area>evapotranspiration>reservoir dam capacity>GDP.Therefore,the change of runoff in the 2001?1989 is mainly affected by meteorological factors,and the influence of human activities on runoff is less.In the 2002?2014,the influence of meteorological elements on runoff was greatly reduced,while human factors became the dominant factor.(3)Establish the distributed SWAT hydrological model of Zi River basin and set up the model from upstream to downstream to lower,and then reduce the model error and improve the precision.Compared with the 1980?1986 years,runoff in the 1987?2001 year,the runoff caused by climate change increased by 5.35 billion m3,climate change on the change in the contribution rate of runoff accounted for 78%;the contribution rate of land use to runoff change accounted for 6.5%;the contribution rate of human activities to runoff change accounted for 15.5%?In the2002?2013 year,the runoff caused by climate change increased by 1.516 billion m3,the effect from 78%was reduced to 49.3%,land use induced runoff decreased by 249 million m3,human activities reduced the runoff by 1.308 billion m3,and the contribution rate of runoff amounted to 42.6%.In a comprehensive sense,the change of runoff in the Zi River Basin is more from the influence of human activities(including the construction of reservoirs,urbanization,artificial water consumption and other comprehensive factors).