Analysis Of Runoff Evolution Characteristics And Driving Factors In Yongding River Basin

Yongding River system is a large tributary of Haihe River Basin and an important recharge water source for Beijing-Tianjin-Hebei urban agglomeration.Since the 20th century,the Yongding River basin has been faced with the shortage of natural water resources,and the water cycle has changed significantly.Scientific assessment of the response of climate change and human activities to the hydrothermal coupling process is extremely important for water resources planning and management.Therefore,selected the Yongding River as the research area,based on the long time series hydrometeorological data and remote sensing data,the spatiotemporal evolution of hydrometeorological elements and land use/cover is analyzed.The sensitivity and contribution rate of climate change and human activities to natural runoff in Sanggan River and Yanghe River Basin are quantified according to the Budyko assumed.The main conclusions are as follows:Using a variety of statistical methods,The evolution characteristics of runoff and rainfall,temperature and evaporation in Yongding River basin over 60 years were studied.There was a significant decline in runoff from 1957 to 2017,Decreasing rates of 155 million,101 million,298 million and 220 million m3/10a were found in the Shixiali,Xiangshuipu,Guanting Reservoir and Lugou Bridge,respectively In 1969 and1983.The main cycle of change is 28 years and 32 years respectively.The mean temperature showed a significant upward trend from 1957 to 2018a,the rate of increase is 0.3?/10a,pan evaporation decreased significantly by-48.88mm/10a.The main influencing factors of“evaporation paradox”are the falling net radiation and average wind speed.Average annual precipitation and potential evapotranspiration showed no significant decrease,the whole basin has a trend of warm drying.The mutation analysis found,Temperature and evaporation were significant in 1990 and 1975 years abrupt.Selection of the fourth issue of remote sensing data from 1980 to 2015 for analysis of land use changes,cultivated land of 43%,decrease of 991.49km~2over 30years.Continuous reduction in water area 77.13km~2;grassland increase 191.35 km~2,area of urban and rural areas,industrial and mining areas and residential land increased935.28km~2;due to vegetation afforestation,conversion of farmland to forests and other soil and water treatment,a significant increase in the Yongding River Basin Normalized Vegetation Index(NDVI)over the period 1982-2019a,change rate 0.02/10a.In space,the vegetation cover of Guanting Gorge is high,NDVI between 0.351?0.457,minimum vegetation cover in the above Cetian Reservoir areas,NDVI value is between0.205?0.327.The overall performance is a gradual increase in values from the northwest to the southeast.According to the complementary relationship method of Budyko hypothesis,the influence of climate and human activities on runoff change can be accurately divided.In general,the contribution rate of rainfall,potential evaporation and underlying surface change to runoff reduction in Sanggan River basin is 54%,4%and 42%,respectively.Among them,rainfall is the main control factor of runoff from 1970 to 1983 years,and it becomes the main control factor of runoff after 1984a under the intense intervention of human activities.Rainfall,potential evapotranspiration and human activities contribute 18%,-10%and 9%respectively.Generally,human activities are the influencing factors that can not be ignored in the upper reaches of Yongding River.