Attribution Analysis Of Runoff Changes In The Shiyang River Basin

In the context of global warming and increased human activity,the spatial and temporal characteristics of runoff have changed significantly over the past decades.These changes are directly affecting the allocation,development,management and utilization of water resources in the basin.In response to this challenge,quantifying the effects of climate change and human activities on runoff can better understand the process of hydrological circulation,which is of great significance to the scientific and rational utilization and sustainable development of regional water resources.Therefore,this paper quantified the impacts of climate change and human activities on runoff in the upper reaches and its tributaries,middle and lower reaches of Shiyang River Basin(SRB)from 1961 to 2018 based on the Improved Double Mass Curve method(IDMC),which will lay a foundation for the formulation of policies for water resource management and comprehensive management in the basin and regional sustainable development in the future.The results show that:(1)The variation characteristics of runoff at different time scales: On the interannual scale,the runoff from the mountains in the upper reaches of Shiyang River Basin(USRB)showed a slight increasing trend,among the tributaries,the Xida and Dongda River which located at the west of basin showed a significant increase trend,the Gulang and Dajing River which located at the east of basin showed a significant decrease trend,and the other rivers showed no obvious change trend.In the middle and lower reaches,the runoff showed a decreasing trend.On the seasonal scale,the runoff from the mountains in the USRB decreased in spring and summer,increased in autumn and winter,and increased significantly in winter.All tributaries showed an increasing trend in winter,but the other seasonal trends were not completely consistent.In spring,summer and autumn,runoff in the middle and lower reaches of SRB showed a trend of overall decrease,and in some parts,it first decreased and then increased,and in winter,it significantly decreased.The uneven degree of distribution in the upper reaches of SRB is greater than that in the middle and lower reaches of Shiyang River Basin,and the change trend is that the former not decrease significantly,but the latter increase significantly.(2)The variation characteristics of climate change and human activities: On climate change,the precipitation in the upper and middle reaches of the SRB has not increased significantly since 1961.Among the tributaries,the other sub-basins also show no significant increasing trend except Gulanghe River Basin and Dajing River Basin.Also,the increasing rate of the five sub-basins in the west is lower than that of the three sub-basins in the east.The temperature and Potential evapotranspiration showed a significant increasing trend.On human activities,the population of the upper reaches and the middle and lower reaches increased rapidly before the 20 th century,and then stabilized.GDP exploded after the early 20 th century.The area of effective irrigation in the USRB increased rapidly from 1990 s to 2000 s,and then decreased and became stable,while in the middle and lower reaches of SRB it fluctuated and increased after the 1990 s.(3)IDMC quantitative assessment results show that climate change and human activities contributed 181.45% and-81.45% to runoff change in the upper reaches,respectively,and-28.45% and 128.54% to runoff change in the middle and lower reaches of Shiyang River Basin,respectively.Among the tributaries of the upper reaches of Shiyang River Basin,the Xida River,Donghe River,Xiying River and Zamu River in the west of the basin are less affected by human activities,while the Jinta River,Huangyang River,Gulang River and Dajing River in the east of the basin are more affected by human activities.By comparing the calculated results of IDMC and DMC method,it is found that the results of the Jinta River basin before the improvement are not consistent with the actual situation,and the value of the other tributaries are somewhat different,which is related to the fact that the unimproved method only considers precipitation.In contrast,the IDMC method is more perfect,and it is more reasonable and accurate to comprehensively consider the combined effects of precipitation and evaporation in climate factors on runoff.Through the analysis of effective precipitation,land use change,population,GDP,effective irrigated area and CRSC,it is found that that the runoff variation in the upstream runoff producing area is mainly affected by climate change,and there is a great difference between the east and the west of each tributary.The runoff dissipation area in the middle and lower reaches is mainly affected by human activities.(4)The influence of human activities on the hydrological process in the tributaries of the USRB is vary greatly.In the future management process,the specific situation of each tributary should be fully considered,and the land resources should be rationally and optimally allocated,so as to further improve the water conservation capacity of the ecosystem.The middle and lower reaches should continue to strengthen people's awareness of water saving in the process of future social and economic development,improve the utilization rate of water resources,and ensure the coordinated and sustainable development of social economy and ecological environment of the whole basin.