| In recent years,the impact of climate change and human activities on the hydrological cycle has become increasingly evident,particularly in arid and semi-arid regions,and therefore active research on the evolution and response of runoff under changing conditions is necessary for the efficient allocation and use of regional water resources.In response to the major development strategy of "ecological protection and quality development of the Yellow River Basin",this study takes the Gansu section of the Weihe River Basin,the first major tributary of the Yellow River Basin,as the target,and analyses the evolution of hydro-meteorological elements and land use changes in the study area.On the basis of this,the runoff at the Weihe River Beidao hydrological station was simulated using the SWAT model,and the response of runoff to climate change and land use change was further analysed by setting different scenarios,and the CA-Markov model was used to predict the future land rationale and make runoff predictions based on this:(1)The evolution characteristics of hydro-meteorological elements of the Weihe River basin in Gansu were analysed.The runoff series of the Weihe River basin in Gansu showed an overall decreasing trend,with a significant downward trend and a sudden change concentrated in the mid to late eighties.Precipitation shows an overall decreasing trend,mean annual temperature shows a significant increasing trend and potential evapotranspiration shows an increasing trend in the last 40 years,with abrupt changes in both mean temperature and potential evapotranspiration occurring in 1994.There is a synchronization between the runoff cycle and the precipitation cycle,a correlation between mean temperature and potential evapotranspiration,and many links between hydro-meteorological elements.(2)The characteristics of land use change in Weihe River basin in Gansu are clarified.In the past 40 years,the area of arable land in the Weihe River Basin in Gansu has been decreasing,the area of forest and grass has been increasing,and the quality of forest and grass has improved significantly.Land use changes are mainly concentrated in the interchange between arable land,forest land and grassland,especially between arable land and grassland.Human activities have greatly influenced land use changes in the Gansu section of the Weihe River basin,mainly due to the promotion of soil and water conservation measures and accelerated urbanization.(3)The applicability of the SWAT model in Weihe River basin in Gansu was investigated.The SWAT model was constructed with a minimum catchment area of80,000 ha,generating 25 subbasins and 293 hydrological response units.The results of the parameter sensitivity analysis showed that the SCS runoff curve basin runoff process is the most sensitive parameter;the monthly runoff SWAT parameters were rate determined using 2008-2013 as the rate period and 2014-2017 as the validation period The results of the runoff simulation in the Gansu section of the Weihe River basin can be used in the next study.The contribution analysis shows that runoff changes are mainly influenced by human activities.(4)The mechanism of runoff evolution in the Weihe River basin in Gansu under changing environments is revealed and runoff changes are predicted under future land use scenarios.Compared to temperature changes,runoff changes are more sensitive than precipitation changes.Temperature is negatively correlated with runoff,while precipitation is significantly positively correlated with runoff;a 10% change in precipitation causes a change in runoff of between 16% and 18%,while a 0.5°C change in temperature causes a change in runoff of less than 1%;an increase in forested areas reduces surface runoff,and an increase in forested areas has a more prominent effect on the reduction of runoff.The rates of change in runoff due to conversion to cropland,conversion to woodland and conversion to grassland are 1.65%,-2.18% and-1.51%respectively,while keeping watershed and construction land unchanged;the CAMarkov model applies well in the simulation of land use scenarios,and in the predicted land use data for 2050,the change in construction land increases significantly by Nearly 80%,based on this land use data future runoff is predicted to increase by 2.50%,mainly due to the increase in built-up land. |
