Attribution Analysis For Runoff Change In The Qingliu River Catchment Of Anhui Province

Climate change and human activities are the two driving factors for the change of runoff in the basin.Moreover,contributions of the driving factors to runoff change may vary over time.Studying the contribution of each driving factor to the runoff change and its interannual variation can not only help identify the causes of runoff evolution,but also provide scientific support for water resources management.This study takes the Qingliu River Cathment in Anhui Province as the research object to analyze the changes of hydro-meteorological elements and the temporal and spatial evolution characteristics of land use.The results showed that the annual average runoff and precipitation increased insignificantly in the Qingliu River Cathment from 1960 to 2012.The abrupt change point of runoff occurred in 1984 identified by the MannKenall method.Temperature showed a significant increase trend(0.02?/a)and pan evaporation showed a significant downward trend(2.01mm/a).Cultivated land and forest dominated land use in the study area.During 1960-2012,areas with land use changes accounted for 28.1%,where mainly refer to conversions from forest and cultivated land to construction land.The elastic coefficient method and the SWAT model method were used to quantify the impacts of climate change and human activities on runoff on different time scales.According to the results of the elastic coefficient method,both climate change and human activities increase runoff,with relative contributions of 97.27% and 2.76% on the annual scale,respectively.The results of the SWAT model method showed that the contributions of climate change and human activities to runoff change are 95.36% and 4.46% on the annual scale,respectively.The findings are consistent with the results of the elastic coefficient method.Climate change has a positive impact on runoff in January,March,July and August,and land use change is the mainly positive factor to runoff change in other months.On the dry and wet season scale,climate change increases runoff in the dry and wet seasons,and human activities increase runoff in the dry season and reduce runoff in the wet season.In order to reveal how the attribution of runoff changes vary over time,an interannual attribution analysis method for runoff variation was proposed based on the continuous land use classification algorithm and the SWAT model,aiming to quantitatively distinguish the impact of each driving factor(climate change,land use change,other human activity factors)on runoff change during 1989-2012.The results showed that the contributions of different driving factors to runoff changes vary over time.Climate change dominated runoff changes in most years during 1989 and 2012.Human activities were the main driving factors of runoff changes in 2005 and 2007.Land use changes lead to increased runoff,and its contribution to runoff change is relatively small.After 2004,other human activity factors have an increased impact on runoff with an average contribution of-16.13 %.Finally,the future climate hypothesis scenario method was applied to study the change of runoff in the future climate scenarios.The results showed that runoff will increase 1.51%,3.1%,and 18.29% by 2020,2050,and 2100,respectively.The results of this study provide a scientific basis for understanding how and why watershed runoff changes and would benefit decision makers on regional water resources management and sustainable development in a changing environment.