Study On Runoff Variation And Response To Land Use Change Of Shichuan River Basin

Shichuan River plays an irreplaceable role in economic development of the Wei River basin.With the economic growth,the demand for water resources in the Shichuan River basin is increasing greatly.However,the surface water resources in this basin are insufficient,and the main stream of Shichuan River is facing serious drought for years.The living and production of urban and rural residents mainly rely on groundwater,causing a decrease in the groundwater level year by year.Under the influence of climate and human activities,surface runoff in the basin has changed significantly.Analyzing the characteristics and revealing the law of the runoff change can provide a reliable basis for planning and managing water resources in the basin.Relying on the water conservancy science and technology project of Shaanxi Province,this paper carries out a study on the law of runoff change and the response of land use change in the Shichuan River basin.Based on hydrological and meteorological data,land use data,soil data,population,GDP,and surface water resource extraction in the basin,this paper analyzes the driving force factors of runoff change and response mechanism and studies the runoff simulation and land use response,with the SWAT hydrological model of the Shichuan River basin.The main conclusions are as follows:(1)Mann-Kendall trend test,linear regression,moving average,and cumulative anomaly methods are used to analyze runoff and reveal the law of runoff change.The analysis results show that the surface runoff of the Shichuan River basin has an obvious downward trend since1986,with a change process of first increasing,decreasing,and then increasing.The runoff of this basin is unevenly distributed mainly from July to October,and the largest in August.Complex Morlet wavelet transform applies to the study on the periodic characteristics of the basin runoff.The study demonstrates that the surface runoff has the characteristics of 9-14 a and17-25 a.Based on the two periods,it is predicted that the surface runoff will continue to rise in the short term in the future.(2)Mann-Kendall trend test,linear regression,moving average,and other methods are adopted to analyze the rainfall,evaporation,temperature,and humidity in the basin according to the measured data of 8 meteorological stations in and around the basin.The analysis results show that the mean annual rainfall and relative humidity in the basin are 586 mm and 61.4%,respectively,indicating decreases by 1.7mm/a and 0.08%/a.The annual mean temperature and evaporation in the basin are 11.9℃ and 1132 mm,respectively,showing increases by 0.04℃/a and 2.9mm/a.(3)The land use area of the Shichuan River basin,from 1980 to 2020,was cultivated land >forest land > grassland > urban and rural construction land > water area.On the whole,the forest land,grassland,and water area remained stable,while the cultivated land decreased and the construction land increased,which was mainly affected by the adjustment of industrial structure in the Shichuan River basin.In this basin,the GDP,population,and surface water resource utilization increased in different degrees,especially the GDP was growing rapidly.The population of the basin has experienced a rapid growth and then a slight decrease.By 2020,the population in the basin was about 1,789,200.The annual average utilization of surface water resources in the basin was 81,002,200 cubic meters,showing an overall increasing trend.(4)The gray correlation analysis method is used to analyze 8 main factors affecting the runoff.The results show that urban construction area,rainfall,and surface water utilization are important factors affecting the runoff.The principal component regression method of SPSS is used to study the main driving factors of runoff change in the Shichuan River basin.The study results show that the contribution rate of human factors to the runoff is 58.3%,and that of climate factors is 41.7%.It can be seen that human activities are the dominant factor affecting surface runoff in the Shichuan River basin,and the influence of meteorological factors on surface runoff cannot be ignored.(5)SWAT hydrological model of the Shichuan River basin is constructed to study runoff simulation under extreme land use change scenarios.The results show that the model has good effect on runoff simulation in this basin and has good applicability.In the Shichuan River basin,the increases of cultivated land and construction land area can promote the runoff,while the increases of forest land and grassland area can reduce the runoff.