Analysis Of Evolution Of Hydrological Regime In Ganjiang River Basin And Its Response To Future Climate Change

Runoff is the key driving factor of the river ecosystem,which is caused by climate change and human activities.There are many reservoirs in Ganjiang River Basin.Under the situation of global warming,it is bound to affect the hydrological regime of Ganjiang River.This study takes Ganjiang River Basin as the study area.Dongbei station is a typical section in the upper reaches of Ganjiang River,Ji'an station is a typical section in the middle reaches of Ganjiang River,and waizhou station is a typical section in the lower reaches of Ganjiang River.The change of historical meteorological and hydrological data in Ganjiang River Basin is analyzed by statistical method.Based on the abrupt change time of Ganjiang River runoff,IHA\RVA method is used to evaluate the overall hydrological regime change of Ganjiang River Basin.The WEP model of Ganjiang River Basin is constructed.Based on five global climate models,the climate factors with the best simulation effect in Ganjiang River Basin are integrated and input into the constructed WEP model to predict the runoff process and hydrological situation changes under different discharge scenarios in Ganjiang River Basin in the future.The results show that:(1)The annual and flood season precipitation in Ganjiang River Basin increased from 1992 to 2016,but it did not reach a significant level.The change of annual runoff at Dongbei and Waizhou Stations was the same as that of the annual precipitation in Ganjiang River Basin.The runoff of Dongbei Station in flood season decreased from 1986 to 2016,and the runoff of Waizhou Station in flood season decreased from 2008 to 2016.It showed that precipitation had a great influence on annual runoff,and human activities made the annual runoff distribution process more uniform.(2)The abrupt changes of runoff in flood season at three hydrological stations in Ganjiang River Basin occurred in 1991,and reached 0.01 significant level.(3)There were five hydrological indicators of Dongbei Station which had reached height change.Four hydrological indicators of Ji'an Station had reached high change degree.Waizhou Station did not reach the high change indicator.The hydrological regime of the upper and middle reaches of Ganjiang River has changed greatly,while the hydrological regime of the lower reaches had changed little.(4)The distributed hydrological model WEP constructed can well simulate the runoff of ganjiang river basin.The Nash efficiency coefficients of the three hydrologic stations in the fixed and verified stages were all about 0.9,with a relative error of about 5% and a correlation coefficient of more than 0.95.(5)After model optimization,the mean value of each climate factor of the five models is selected as the meteorological input data.which meets the input requirements of future estimated climate data.(6)RCP2.6,RCP4.5 and RCP8.5 were used as low,medium and high emission scenarios respectively.In the future,the precipitation and runoff of Ganjiang River Basin will increase in non flood season,decrease in non flood season and distribute more evenly in the year under the low emission scenario.Under the condition of medium emission,the trend of increase is in flood season and decrease is in non flood season,and the monthly average maximum value increases greatly,and the distribution is more concentrated in the year.High emissions have an increasing trend in both the flood season and the non-flood season.In the future,the water quantity of Ganjiang River Basin will be more resilient under the condition of low emission,and it will be more prone to drought and flood disasters if it is discharged in the medium level,and flood disasters if it is discharged in the high level.(7)In the future,the hydrological situation of Dongbei station will change the most under three discharge modes.In the medium scenario,the hydrological situation of Ji'an station will change more than that of waizhou station.In the other two discharge scenarios,the hydrological situation of Ji'an station and waizhou station will change more similar.In the low emission scenario,the change of three hydrological stations is the smallest,and in the middle and high emission scenario,the change of three hydrological stations is larger.In the future,the changes of hydrological situation index mainly focus on the minimum discharge index,discharge pulse index and discharge rise and fall index.