Impact Of Climate Change On Surface Runoff In The Upper Reaches Of The Datong River

Climate warming will speed up the rate of hydrological cycle,and has an important effect on precipitation-evaporation-runoff processes,and then cause a series of changes in hydrological process.Datong River is located in the important ecological function area of water conservation of Qilian Mountains,and it is also an important water source in the northeast of Qinghai Province and the western of Gansu Province,it has a very important status in the social and economic development of Qinghai and Gansu Province.The upper reaches of river runoff is the key area of river formation and development,under the background of clear climate change,the runoff evolution law of the upper reaches of Datong River is great significance for the adjust of water resources in the middle and lower reaches of the study area.At the same time,the study on the quantitative impact of hydrological factors in the upper reaches of Datong River can provide important scientific basis for the ecological environment protection of Qilian Mountain.Based on this,each study is based on the historical observation data of the upper reaches of the Datong River from 1960 to 2016,by trend analysis,MK test and wavelet analysis,meteorological and hydrological change characteristics and evolution law.On the basis of constructing the SWAT model of Datong River,the runoff of 2031?2100 is predicted by the CMIP6 climate model.The results of this study are as follows:(1)The average temperature in the upper reaches of the Datong River increased at a rate of 0.35?/10a(P<0.01)from 1960 to 2016,and the temperature increased significantly,with the fastest warming in winter.According to the MK test,the average temperature has a warming mutation at the end of last century,and there are three periodic oscillations of 6a,13a and 25a scales.From the spatial point of view,it shows the distribution characteristic of"high in southeast and low in northwest".Precipitation increased at a rate of 11.12mm/10a(P<0.01),and the proportion of average precipitation in the four seasons to annual precipitation was 17.12%,63.17%,18.61%and 1.1%respectively.The precipitation in the study area is mainly concentrated in summer,and the increase of precipitation in summer promotes the process of climate warming and humidity.(2)The main recharge source of runoff in the upper reaches of the Datong River is precipitation,and the annual average runoff is distributed unevenly and unimodally.The annual runoff is mainly distributed from May to October,accounting for 87.29%of the annual runoff.From 1960 to 2016,it increased at a rate of 0.5 billion m~3/10 a(P<0.1).(3)Based on the basic data of the study area,the SWAT model in the upper reaches of the Datong River is successfully constructed and divided into 39 sub-basins.After calibration and verification,the determination coefficient,Nash coefficient and Percentage deviation(PBIAS)all met the requirements of the model,which were 0.81,0.79 and-0.8%respectively in the rate period,and 0.81,0.75 and 15.8%respectively in the validation period.The results show that the SWAT model has good applicability in the upper reaches of Datong River.(4)Future simulated runoff data show that climate change will have a significant impact on the runoff in the upper reaches of Datong River basin.During2031 to 2100,the runoff increases at a rate of 50 million m~3/10a under SSP1-2.6scenarios,increases at a rate of 18 million m~3/10a under SSP5-8.5 scenarios,remains basically the same under SSP2-4.5 scenarios,and decreases at 0.55 billion m~3/10a under SSP3-7.0 scenarios.The average runoff in SSP1-2.6,SSP2-4.5 and SSP5-8.5scenarios from 2031 to 2100 is 0.64,2.18 and 2.47 billion m~3 higher than that in1960?2016,respectively,and the average runoff under SSP3-7.0 scenarios is 4.74billion m~3 lower than that under SSP3-7.0 scenarios.