An Integrated Approach For Modeling The Climatedriven Streamflow In The Typical Basins In The Southern Slopes Of Tianshan Mountains Based On Downscaling The Earth Data Products

With the global warming,the water supply situation in the inland river basin in the arid region of northwest China has become more and more severe in the past 20 years.Since the headwater basin of the inland river in the arid area of northwestern China is located in a high-altitude mountainous region,and there are few meteorological observation sites,it is difficult to apply highly-precise distributed hydrological models and other models based on the physical mechanism of runoff generation to evaluate climate change and its impact on runoff.Therefore,it is necessary to develop a comprehensive model based on Earth data products to quantitatively assess the impact of climate change on runoff.Simulating and predicting the runoff in mountainous areas is of great significance to the sustainable development of the inland river basin in the northwest and the protection of the ecological environment.This study takes the Kumarak River and Toshgan River in the Kaidu River,the southern slope of the Tianshan Mountains,as typical study area,develops a downscaling method based on the Earth data products,tests climate change trends,builds an artificial neural network,and links weights,develops a comprehensive model to quantitatively evaluate the contribution of temperature and precipitation to runoff in mountainous areas.Research indicates:(1)Based on the downscaling the Earth data products,it is possible to effectively reconstruct the climate change characteristics of the data scarcity basin.Among the many reanalyzed data,the MERA temperature data and the China ground rainfall monthly value grid dataset have the best simulation accuracy for temperature and precipitation in mountainous areas on the southern slope of the Tianshan Mountains with the highest spatial resolution.Based on DEM,reanalysis data,and down-scale methods for measured data of earth data such as site data,we can reveal the spatial-temporal characteristics and trends of climatic changes in data-free watersheds.(2)The comprehensive model can be applied to mountainous basins lacking actual stations in the Inland River Basin of the arid region of northwestern China.The comprehensive model based on downscaling of the Earth’s data products,artificial neural network and weighted connection method can effectively reveal the climate change characteristics of the basin and its contribution to runoff.(3)The Kaidu River and Aksu head water showed warming and humidification in the past 30 years.The spatial distribution of the average and slope(rate of change)of the annual average temperature and annual precipitation of the downscaled reanalyzed data reveals the temporal and spatial characteristics of temperature and precipitation.The EEMD decomposition reveals the periodic and multi-scale variation characteristics of climatic-runoff changes in typical catchments on the southern slope of the Tianshan Mountains.The results of EEMD decomposition show that the temperature and precipitation of the Kaidu River and the Aksu River’s headwater show seasonal changes of 3 months.The runoff flux on the interdecadal scale is influenced by both temperature and precipitation factors.Judging from the last decadal trend,the temperature’s slow rising in the recent 10 years of the Kaidu and Aksu rivers’headwater areas are temporary and will continue to rise in the future,while the runoff from the Kaidu and Aksu rivers will continue to increase over the next decade.With the increase of temperature,it shows a tendency to continue to increase.(4)Based on the quantitative study of BPANN artificial neural network and weighted connection method,the contribution of temperature and precipitation changes to runoff can be effectively evaluated.The contribution of temperature and precipitation to the runoff of the Kaidu River was 44.21±2.08%and 55.79±2.08%respectively,the contribution to the runoff of the Kumarak River was 60.09±8.90%and 39.91±8.90%respectively,and the contribution to the runoff of the Toshkent River was 45.75±8.53%and 54.25±8.53%respectively.The Kumarak River Basin was mainly affected by the temperature,while the Kaidu River and the Toshkent River Basin were more affected by precipitation.(5)Based on the RCC4.5 scenario of the CMIP5 models,in the next 30 years,the temperature and runoff in the typical basins on the southern slope of the Tianshan Mountains will both increase,and the precipitation will show a downward trend.From2016 to 2050,the annual average temperature of the Kaidu River showed an increasing trend at a rate of 0.4°C per 10 years.The average annual temperature of the Kumarak River and the Toshkent River Basin also showed a significant increase,with an increase rate of 0.3°C/10 years.The annual precipitation in the Kaidu River decreases at a rate of 2.1 mm per 10 years,and the annual precipitation in the Kumarak and Toshkent Rivers also shows a downward trend.The rate of decline is 9.2 mm per 10 years and5.0 mm per 10 years respectively.The annual runoff of the Kaidu River showed a significant increase at a speed of 0.4×10~8 m~3/10 years,and the annual runoff of the Kumarak River and Toshkent Rivers also showed an increasing trend,with an increase rate of 3.5×10~8 m~3/10 years and 1.0×10~8 m~3/10 years respectively.The increase trend is significant.