Hydrological Evolution And Its Driving Factors In Jinghe River Basin

Under the combined influence of climate change and human activities,the complexity of the hydrological process in the basin has increased significantly.Quantitative analysis of the impact of the two factors on the hydrological process of the basin and further revealing the law of hydrological evolution in the basin are of great significance to the development of basin water resources planning and management.In this paper,the hydrometeorological evolution law and hydrological change driving factors of the Jinghe River Basin are studied from multiple perspectives such as runoff-sediment-sunshine duration-potential evapotranspiration,and the SWAT model is combined to predict the future runoff of the basin.The main conclusions are as follows:(1)The multi-year average precipitation and relative humidity in the Jinghe River Basin are 517.9 mm and 63.09%,respectively,and the spatial changes gradually decrease from south to north;the multi-year average potential evapotranspiration and sunshine duration are 953.99 mm and 6.49 h,respectively,and the spatial changes are from southwest to southwest while the northeast gradually increases;the multi-year average temperature is 7.88 ℃,and the spatial variation gradually decreases from southeast to northwest;the multi-year average wind speed is 2.19 m/s,and the spatial variation conforms to the law of small southeast and large northwest.The annual average precipitation and potential evapotranspiration in the basin showed an insignificant increase trend,and the annual average temperature showed a significant increase trend;the annual average wind speed and relative humidity showed a significant decrease trend,and the sunshine duration showed an insignificant decrease trend.(2)The land-use area of Jinghe River Basin before 2010 is: cultivated land > grassland >woodland > urban and rural industrial and mining residential land > water area.After 2010,the grassland area exceeds that of cultivated land.On the whole,land use is manifested in the decrease of cultivated land and water area,and the increase of grassland,woodland,and urban and rural industrial and mining residential land.This is mainly affected by the policies of returning farmland to forests and rebuilding beautiful mountains and rivers in the northwest.(3)The water and sediment in Jinghe River Basin came from above Yangjiaping Station and Yuluoping Station respectively,presenting a "heterogeneous" phenomenon.The multi-year average runoff depth and sand sediment modulus were 35.23 mm and 4545 t/(km2·a),respectively,showing a significant decreasing trend.The runoff and sediment had abrupt changes in 1996 and 1997,respectively.After the abrupt changes,the runoff depth and the sand sediment decreased by 17.83 mm and 3623 t/(km2·a),respectively.Runoff changes mainly exist in the main periods of characteristic time scales of 15 a,41 a and 58 a,with the average change periods of 10 years,27 years and 34 years respectively.Sediment change mainly exists in the main periods of 16 a,26 a and 56 a characteristic time scale,and the average change period is10 years,17 years and 34 years,respectively.(4)In recent years,human activities are the main reason for the reduction of runoff and sediment transport.Based on Budyko hypothesis and SWAT model analysis,it is found that the contribution rate of human activities to the reduction of runoff is as high as 90%.Based on the analysis of the separation and evaluation method,it is found that the contribution rate of human activities to the reduction of sediment transport reached 96.48%.(5)Under the scenarios of RCP 2.6,RCP 4.5 and RCP 6.0,the annual runoff of the basin will increase in the future,with 0.006 m~3/s,0.672 m~3/s and 1.135 m~3/s,respectively.Under the scenario of RCP 8.5,the annual runoff of the basin will show an insignificant increase trend in the future,which is 0.1025 m~3/s.There is a strong correlation between future meteorological changes and watershed runoff changes.Under the scenario of RCP 4.5,the multi-year average precipitation is reduced by 43.5 mm compared with the base period,and the watershed multiyear average runoff decreases by 27.30 %.The future land use changes are beneficial to runoff,and the annual average runoff has increased by more than 1 % under different scenarios.