| Human activities and climate change are important factors that affect the harmony of human and water and the sustainable development of economy and society.Therefore,it is extremely important to coordinate water resources and economic and social development,and to quantify the response laws and spatial distribution of water resources under human activities and climate change.The Jialing River Basin is an important water source for survival,production,living and ecology in the Chengdu-Chongqing region.Studying the response of climate change and land use change in the Jialing River Basin to blue-green water has important reference value for the water resources planning and management of the water source areas in the Chengdu-Chongqing region.This paper takes the Jialing River Basin as the research object,based on the daily meteorological data of 20meteorological stations from 1978 to 2020,and the measured monthly runoff data of 4hydrological stations over the years,to explore the trend of climate change and land use change.Evaluation tool(Soil and Water Assessment Tool,SWAT)model,selection coefficient of determination(Coefficient of Determination,R~2),Nash-Sutcliffe efficiency coefficient(Nash-Sutcliffe efficiency coefficient,NSE)and other evaluation model applicability parameters;The spatial and temporal distribution characteristics,and at the same time,the scenario setting method is used to establish a variety of response scenarios to simulate the impact of blue-green water volume under different land use/cover scenarios,climate change,crop rotation and fallow,different farming measures and future climate models.conclusion as below:(1)From 1980 to 2020,the temperature in the Jialing River Basin increased year by year,the rainfall showed a trend of first decrease and then increase,and the overall trend was upward;the area of cultivated land decreased by 2.39%,the area of forest land increased by 2.08%,the area of grassland decreased by 2.76%,and the area of construction land increased by 192.70%.The water area increased by 21.06%.(2)The SWAT model of the Jialing River Basin was established,generating 1838Hydrologic Response Units(HRUs)and 21 sub-basins,and using the SWAT Calibration and Uncertainty Programs for SWAT(SWAT-CUP)software The runoff was calibrated and verified,and the determination coefficient R~2of Beibei,Xiaoheba,Wusheng and Luoduxi hydrological stations in the regular and verification period were all greater than 0.7,and the Nash coefficient NSE was all greater than 0.7,indicating that the model was suitable for use.(3)The simulation results of the amount of blue-green water resources and their spatial distribution in the study basin from 1981 to 2020 show that the amount of precipitation and green water resources increased in time from 1981 to 2020,but the increase trend was not significant,and the amount of blue water resources was The decreasing trend is not significant.Spatially,the amount of blue-green water resources shows a spatial pattern of first decreasing and then increasing from upstream to downstream,with less in the west and more in the east.(4)Explore the impact of climate change and land use on blue-green water resources based on scenario settings and variable control,and further calculate the contribution rate of land use and climate change to blue-green water resources.The average contribution rate of climate change to green water resources is 141.54%,and the average contribution rate to blue water resources is 80.31%;the average contribution rate of land use change to green water resources is-51.26%,and the average contribution rate to blue water resources is-51.26%.The average contribution rate is 20.27%.The combined effect of climate change and land use change has a significant impact on the amount of blue water and green water resources in the Jialing River Basin.The impact of climate change on the amount of blue-green water resources is far greater than that of land use change on the amount of blue-green water resources..(5)Under a single land use change,the conversion of cultivated land to forest and grassland can increase the amount of green water resources in the study area and reduce the amount of blue water resources in the study area.The study area is mainly about the mutual transformation of three kinds of land use:cultivated land,forest land and grassland.Under a single land use change,cultivated land is transformed into forest and grassland.At this time,the increase of forest and grassland area can increase the amount of green water resources in the Jialing River Basin,and the increase of forest and grassland area can reduce the amount of blue water resources in the Jialing River Basin.(6)When the precipitation varies from(-20%P)to(+20%P)and the temperature varies from(T-3℃)to(T+3℃),there are 55 scenarios in which the precipitation remains unchanged and the temperature The average responses of changes to green/blue water resources under the above scenarios are 7.32 mm/℃and 6.79 mm/℃,respectively,and the average responses of constant temperature and precipitation changes to green/blue water resources under the above scenarios are 13.48 mm/10%P,60.47mm/10%P.(7)Contour tillage,strip tillage,crop residue tillage and returning farmland to forest can effectively improve the utilization efficiency of green water.Cultivation of crop residues increased the amount of green water resources by 1.39mm,and the measures of returning farmland to forests increased the amount of green water resources by 0.25mm.Crop rotation and no-tillage measures can also affect the conversion of blue-green water in the study area.Compared with no-tillage measures,crop rotation measures can increase the amount of blue water resources in the study area by 2.81mm.(8)Under the model of Representative Concentration Pathway 4.5(Representative Concentration Pathway 4.5,RCP4.5)and Typical Concentration Pathway 8.5(Representative Concentration Pathway 8.5,RCP8.5),the precipitation in the study area of RCP4.5 model will increase by 37 mm in the next 40 years;blue water The amount of resources increases by 5 mm,and the amount of green water resources increases by 32 mm;the precipitation in the RCP8.5 model study area will increase by 36 mm in the next 40years;the amount of blue water resources increases by 1 mm,and the amount of green water resources increases by 35 mm. |
