Hydrological Response Of The Upper Qiantang River In The Context Of Climate And Land Utilization Change Based On SWAT Model

In recent years,the global influence of climate,land use changes and other comprehensive factors,the terrestrial hydrological cycle continues to change significantly,and the hydrological processes show non-stationary characteristics.The upper reaches of the Qiantang River is one of the demonstration areas for the practice of the Two Mountains Theory,which is proposed by General Secretary Xi Jinping to live in harmony with nature,protect ecological resources and give full play to the concept of the important value of ecological resources.With the gradual increase in population,urban planning and construction and yearly changes in climate,how to reasonably develop and utilize surface water resources in the area,protect ecological water resources and practice the core concept of the Two Mountains Theory has become a thorny issue nowadays.Based on this,a distributed hydrological model(SWAT model)is constructed in the upper reaches of the Qiantang River,and the optimal parameters are obtained through rate setting and validation,so that the constructed SWAT model has localized characteristics in the study area.The optimal parameter SWAT model was applied to simulate the runoff of different climate and land use change scenarios,and the response of hydrological runoff processes to climate and land use change in the study area was quantitatively analyzed.The main findings are as follows.(1)Precipitation and temperature in the region show a fluctuating upward trend during 2008-2018,and the abrupt change in precipitation was obtained by the abrupt change test in 2010,and the abrupt change in temperature occurred in 2015,and it showed different trends seen in different years.(2)The runoff volume in the region increased from 2008 to 2018,and the mutability test showed that the mutation year was 2010 and the change trend of runoff volume was different between years,and the runoff volume was unevenly distributed within the year.(3)Land use in the region from 2005 to 2018,the magnitude of change in each type of land is relatively small,specifically the arable land,forest land area slightly reduced,construction land area increased,grass and water area changes are not obvious;single land use type dynamic changes in the region is more obvious,comprehensive land use dynamic attitude first reduced and then increased.(4)The coefficient of determination R2 and Nash coefficient NS of Quzhou hydrological station in the rate period(2010-2013)and validation period(2015-2018)are 0.96,0.96(rate period)and 0.91,0.90(validation),respectively,and the coefficient of determination R2 of Kaihua hydrological station in the rate period(2008-2013)and validation period(2015-2018)and Nash coefficients NS are 0.95,0.92(rate period)and 0.94,0.89(validation),respectively,and the results are within the reliability range and have high accuracy,indicating that the constructed SWAT model has good applicability in the study area.(5)The response of hydrological runoff in the study area to temperature change is weak under the condition of constant land use,and the response to precipitation change is strong.It is assumed that the main climatic factor affecting the change of hydrological runoff process in the study area in the future is precipitation.(6)The hydrological runoff process in the study area under the condition of constant climate,although the land use change has an impact on the runoff,but did not lead to significant changes in the runoff in the study area,indicating that the response of the hydrological runoff process in the study area to the land use change is weak,not as strong as the response of climate change.