Impact Of Climate Change On Hydrological And Meteorological Elements In Oujiang Basin

In recent years,climate change has become a hot topic of society.It affects precipitation,evaporation and runoff,which play important roles in the hydrological cycle.Once these hydrological and meteorological elements have changed,the availability of water resources would change as well.Therefore,it's of great significance to study the impact of climate change on hydrological and meteorological elements for scientifically planning water resources.In this study,Oujiang Basin in Zhejiang Province was taken as the study area.The historical period is 1971-2000 while the future period is 2041-2070.Firstly,meteorology,hydrology and land use data were collected.Then,18 GCMs from CMIP5 were chosen,and the statistical downscaling method BCSD was used to downscale GCM data.DHSVM model was driven by the downscaled data to simulate the hydrological process of the basin.Finally,the impacts of climate change on hydrological and meteorological elements were evaluated.The main achievements of this study are as follows:(1)After downscaling,GCMs show good performance both in temperature and precipitation simulation.The performance of temperature downscaling is better than precipitation.The results show the applicability of BCSD method and 18 GCMS in the Oujiang River basin.(2)Under the future scenario,all maximum temperature,average temperature and minimum temperature will probably increase.The temperature under RCP8.5 scenario increase more than that under RCP4.5 scenario.Different GCM shows different changes in precipitation under future scenarios.From the perspective of ensemble,the order of increase in temperature is summer>autumn>spring>winter,and the increase in the southern basin is higher than that in the northern basin.The order of increase in precipitation is winter>spring>summer>autumn,and the increase in the southern basin is lower than that in the northern basin.Precipitation of GCM ensemble increases by 54.41mm and 54.06 mm respectively under RCP4.5 and RCP8.5.(3)There are 18 sensitive parameters of DHSVM model,such as rain LAI multiplier,lateral conductivity,soil porosity and minimum stomatal resistance.It was found that both daily runoff and monthly runoff simulations are quite consistent with the observed ones,and model performance on monthly runoff simulation is better than that on daily runoff.Nash-Sutcliffe efficiency coefficient and relative error are within acceptable limits,indicating DHSVM has its applicability in Oujiang Basin.(4)GCMs and their ensemble show increase in annual evapotranspiration.Evapotranspiration of GCM ensemble increases 92.63 mm and 86.16 mm respectively under RCP4.5 and RCP8.5,which are higher than the increase of annual precipitation.(5)The average annual runoff of GCM ensemble reduces under RCP4.5 and RCP8.5.The monthly average runoff of GCM ensemble is higher than the historical period in August and September,and lower than the historical period in other month.5%quantile flow Q5 and 95%quantile flow Q95 show decrease in most modes and scenarios when compared to historical period.The design flood is mostly lower than the historical period under different return periods.Only a few GCMs show increase.It indicates that the frequency and intensity of extreme flood will decrease in Oujiang River basin.