Response Of Runoff To Climate Change In Runoff Producing Area Of Manasi River Basin

Object:Most inland river basins in Northwest China belong to mountain basin system structure.Water resources originate from mountain areas,and are utilized and operated in oasis areas,and dissipated in desert areas.Because the runoff is formed in high altitude runoff producing area,there is a lack of long-term monitoring data in this area.Runoff simulation and Hydrological Prediction in runoff producing area become one of the important directions of hydrological and water resources research.Manas River Basin is located in the south of Junggar Basin in Xinjiang Uygur Autonomous Region,which originates from the northern foot of Tianshan Mountain.Its runoff is a mixture of glacier snow and precipitation.It is a typical arid inland river basin in Northwest China.In recent years,under the background of global warming,the runoff of Manas River Basin,which is dominated by glacial snow melt water,has changed significantly,and the research on the response mechanism of runoff in Manas River basin to climate change is not perfect.Therefore,watershed runoff simulation under climate change is of great significance for regional water resources management.Methods:Based on the analysis of the general situation of Manas River Basin,this study analyzes the meteorological law of the north slope of Tianshan mountain where Manas River Basin is located,integrates the domestic and foreign open meteorological data sets and interprets the TRMM satellite precipitation data,and finally constructs the Manas River Basin meteorological data set to drive the SWAT(Soil and Water Assessment Tool)model of runoff producing area.Through sensitivity analysis and parameter adjustment of SWAT Model in Manas River basin runoff producing area,the SWAT model of Manas River basin runoff producing area is constructed.Finally,four climate change scenarios of Had GEM2-ES model in CMIP 5(Coupled Model Intercomparison Project Phase 5)are combined,the trend of climate change and runoff evolution in Manas River Basin was simulated under different climate change scenarios.The main conclusions are as follows:Results:(1)The annual average temperature and precipitation of 15 meteorological stations on the northern slope of Tianshan Mountain,where Manas River Basin is located,are compared with the altitude of the meteorological station,and the linear regression equation of the annual average temperature,annual average precipitation and elevation of the northern slope of Tianshan Mountain is constructed.The results show that:in the area of 200 m to 4500 m above sea level,the average annual precipitation increases by 190.7 mm for every 1 km increase;in the area of 4500 m to 5500 m,the precipitation decreases in the same gradient for every 1 km increase;In the northern slope of Tianshan Mountains,the average annual temperature decreases by 5.2°C with the increase of 1 km.(2)Based on the interpretation and interpolation of daily grid data set(0.5°×0.5°)of surface precipitation in China,TRMM satellite precipitation data set,CMADS meteorological data set and CRU meteorological data set,the meteorological data set of Manas River Basin is constructed according to the regional climate change characteristics of the northern slope of Tianshan Mountains.The results show that:from 1961 to 2015,the annual average precipitation and average temperature increased significantly.The annual average precipitation growth rate of Manas River basin runoff producing area was 2.63 mm/a,and the annual average temperature growth rate was 0.015?/a.(3)Based on the meteorological data set of Manas River Basin,combined with the underlying surface and hydrological data of Manas River Basin,the SWAT hydrological model of Manas River Basin was constructed.The results show that the calibration period(1981-1999):NSE=0.86,R~2=0.87,PBIAS=13.75;During the validation period(2000-2015),NSE=0.75,R~2=0.77,PBIAS=-11.78.After adjusting the parameters,all the parameters are in a reasonable range,and the accuracy of SWAT model of Manas River basin runoff producing area meets the requirements.(4)Four main climate change scenarios(RCP 2.6,4.5,6.0,8.5)of Had GEM2-ES model in CMIP 5 were selected to drive SWAT Model in Manas River Basin.The results show that the total annual water resources of Manas River Basin from 2020 to 2099 under four climate change scenarios of RCP 2.6,4.5,6.0 and 8.5are respectively 14.21×10~8 m~3,13.56×10~8 m~3,13.09×10~8 m~3and 13.44×10~8 m~3.Conclusion:The historical climate change in Manas River Basin is closer to the RCP 8.5 scenario.Under the same climate change scenario,the uncertainty and hydrological extreme value of runoff in Manas River Basin will be further enhanced.