Evaluation And Comparison Of Water Conservation Functions In Songjiang And Baihe Small Watershedss

Among different ecosystem service functions,water conservation function is one of the most important service functions.In recent years,scholars have conducted a lot of research on forest-scale water conservation functions from analytical methods,hydrological processes and quantification of water conservation.However,there are relatively few comprehensive analyses of water conservation functions at the watershed scale.Different scholars lack a unified method for research and analysis of water conservation functions,and the credibility and accuracy of their research results also vary due to different methods.In terms of watershed water conservation function,changes in land use and climate will have an impact on the hydrological cycle process in the watershed,thereby changing the watershed water conservation function.Based on the SWAT distributed hydrological model,this study takes the Songjiang and Baihe small watersheds as research areas,simulates the hydrological cycle in the watershed,quantifies and calculates the annual water conservation in different periods of the area,and comparatively analyzes the causes of the differences in water conservation functions of the two watersheds.In order to analyze the impact of land use change,temperature and precipitation on the water conservation function of the basin,different simulation scenarios were set up to quantify and analyze its impact on the changes of water conservation function in different periods.Research indicates:1.The SWAT model has a good simulation effect on the hydrological cycle processes in the two watersheds,and the relative error of the simulation results is less than 10%.The average annual water conservation in Songjiang small watershed from1999 to 2018 was 308mm,the average annual water conservation was 3.84×10~8m~3,on the other hand,the average annual water conservation in Baihe small watershed from1999 to 2018 was 468mm,and the average annual water conservation was1.82×10~8m~3.There is a significant correlation between precipitation and water conservation in different years.The spatial distribution of water conservation is related to altitude,and the water conservation function in high-altitude areas is significantly higher than that in low-altitude areas.2.There were no significant changes in land use patterns in the two small watersheds from 1999 to 2018.The forest area in these two watersheds accounted for more than 85%of the entire watershed.In the analysis of the land use change simulation scenario,it is concluded that the land use type of the forest land type has an important regulating effect on the water conservation function of the river basin.From the conversion of land type simulation of forest land type to other types,the average water conservation in each stage of the two watersheds tends to increase,but the increase trend is not obvious in the simulation of other types of land converted to forest land.3.The average summer temperature in Antu County during the 1989-201830-year period tends to rise slowly.The average temperature in summer and the average temperature in other seasons have no significant changes,while the annual precipitation shows a significant upward trend.In the analysis of the climate change simulation scenario,it is concluded that the decrease in precipitation and the increase in temperature have a significant effect on the change of water conservation,and the increase in temperature will cause the actual evapotranspiration in the basin to increase significantly.The forest land in the watershed has a certain regulating effect on the reduction of precipitation and the impact of temperature rise.4.Under the same climatic background,the water conservation function of the Songjiang small watershed is significantly lower than that of the Baihe small watershed.The average annual water conservation in the 20 years from 1999 to 2018differs by 160mm.The annual average evapotranspiration of Songjiang small watershed is 50mm higher than that of Baihe small watershed.The differences in altitude,slope and aspect in the Songjiang small watershed have significant effects on the water conservation function in the watershed.