Quantitative Response Of Runoff In Xilin River Basin To The Dual Effects Of Climate Change And Human Activities

Quantitatively analysing the impacts of climate change and human activities on runoff changes and the attribution analysis are of great significance to the sustainable management of water resources in the Xilin River Basin.The results of the study can provide a reference for basin water resources allocation.Based on the Xilin River Basin hydrological and meteorological data from 1968 to 2015,this paper uses Mann-Kendall non-parametric test method for trend analysis and other linear trend test methods for trend analysis.Mann-Kendall non-parametric test method and the double cumulative curve method are used for mutation analysis.The contribution of climate change and human activities to the impact of runoff was calculated using the double cumulative curve method,the cumulative rate change rate comparison method,and the elasticity analysis method.The study has reached following conclusions:(1)The results of trend analysis shows: During the period from 1968 to 2015,the average annual temperature in the Xilin River Basin showed an increasing trend,and increased rapidly in the 1990s;the average annual potential evaporation showed a significant upward trend;rainfall in the flood season accounts for 76% of the year,there is no significant change in precipitation;annual runoff shows a significant downward trend,after 2000,it is extremely obvious;runoff accounts for 53.25% and32.39% of the annual runoff in spring and summer,and the distribution of runoff shows a “double-peak” type.In April and August,the runoff were recharged by spring snowmelt and summer precipitation.Overall,the average temperature and potential evaporation in the Xilin River Basin showed an increasing trend,while annual precipitation and runoff show a decreasing trend.(2)The results of the mutation analysis showed that the temperature changed suddenly in 1988 and increased obviously after 1990;the potential evaporation abruptly changed in 1998,and the rate of change had increased significantly after the year of mutation;the runoff showed a significant decrease trend.The mutations occurred in 1984 and 2000.Based on this,1968-1984 was studied as the base period,1985-2000,and 2001-2015 were studied as the mutation period.(3)The quantitative response of runoff to climate change and human activities shows: The results from the comparison of empirical model double cumulative curve method and cumulant change rate method to calculate the effect of precipitation change on runoff are consistent.The elasticity analysis method used five methods,such as Turc-Pike,Ol?dekop and Budyko calculated similar results.In the period of1985 to 2000 and from 2001 to 2015,the contribution rate of human activities to runoff was 62% and 42%.The three methods reached the unanimous conclusion that the impact of human activities on runoff during the period from 1985 to 2000 was slightly greater than the period from 2001 to 2015.After 2000,the impact of human activities showed a slight downward trend.In addition,the elasticity analysis method and the cumulant change rate method have reached a consistent conclusion: the proportion of climate change and human activities on runoff during the period from2001 to 2015 is similar.(4)The analysis of attribution showed: compared with the period of 1968-1984,the runoff increased by 28.84% from 1985 to 2000,the precipitation increased by2.58%,the potential evaporation decreased by 0.01%,and the impact on the runoff was not significant.Despite the slowing population growth,the phenomenon ofoverloaded grazing is serious,and water conservancy projects have weakened the impoundment function of the underlying surface,affecting the runoff rule to a certain extent.The runoff decreased 42.4% from 2001 to 2015.The abrupt change point was obvious.At this stage,the proportion of climate change and human activities on runoff was similar.Since the 21 st century,the temperature increased significantly,the precipitation decreased by 6.37%,and the potential evaporation increased 5.88%,combined with the rapid development of the secondary and tertiary industries,led to the massive exploitation and consumption of surface groundwater volume,the runoff decreased under the combined effects of human activities and climate change.