Impact Of Climate Change On Hydrology And Water Resources In Typical River Basins In Zhejiang Province

The world has developed rapidly since industrial revolution and growing greenhouse gas emissions make the earth become warmer.Climate change has become a common challenge for all mankind.The latest report of IPCC shows that climate change is mainly caused by human activity.Climate chang has greatly affected global hydrological cycleleading to increased frequency and intensity of extreme meteorological disasters.Study on the impact analysis of climate change on water resource and hydrology can provide useful advice for policy makers of water resource management.GCMs are one of the most important tools for climate change research,but there is always resolution gap between GCMs and study area scales.Downscaling method is often used for impact analysis purpose.Compared to dynamic downscaling,statistical downscaling method is more flexible and easy to realize.Statistical downscaling method is usually used to downscale the precipitation and temperature from GCMs to drive the hydrology model.Huge uncertainty can be found from GCMs and the ensemble method is a useful method to reduce the uncertainty.The main study area of this thesis is Zhejiang Province and the baseline period is set as 1971-2000.The first work of this thesis is to evaluate the historical simulations of CMIP5 GCMs for six key climatic variables in Zhejiang Province.18 GCMs from CMIP5 are evaluated on their creditability of simulating regional climate change in the province.Simple graphical approaches and three evaluation indices are used to determine the simulation performance of six key climatic variables during the baseline period.The results show that most GCMs can simulate the temperature,precipitation and solar radiation well,but few GCMs can reproduce the observed wind and relative humulity.BCC-CSM1-1 and BNU-ESM are the best GCMs for climate change studies in Zhejiang Province.The second part of the thesis is to calculate the ensemble changes of temperature and precipitation from CMIP5 models over Zhejiang Province.Changes of precipitation and temperature between 1971-2000 and 2071-2100 in the province are analyzed based on 18 GCMs from CMIP5.Bayesian Model Averaging method is used to obtain ensemble of future climate changes under different scenarios.The results show that different GCMs have varyi ng outputs under the same RCPs.Large amount of uncertainty can be found.Results from IPSL-CM5A-LR,MIROC5,CNRM-CM5,CSIRO-Mk3-6-0,GFDL-ESM2G,GFDL-ESM2M,GISS-E2-H,GISS-E2-R,BCC-CSM1-1 and BNU-ESM show that the future precipitation will probably decrease by less than 25%under RCP2.6 and RCP4.5 in the study area,while CanESM2 and MPI-ESM-LR show that the precipitation may increase by less than 10%.BCC-CSM1-1,CSIRO-Mk3-6-0,GFDL-CM3,GFDL-ESM2G,GFDL-ESM2M,GISS-E2-H,GISS-E2-R,IPSL-CM5A-LR,MIROC5 and MRI-CGCM3 indicate that the precipitation of future will probably decrease under RCP6.0.BCC-CSM1-1,BNU-ESM,CNRM-CM5,GFDL-CM3,MRI-CGCM3,GISS-E2-H,GISS-E2-R and IPSL-CM5A-LR claim that precipitation of future will probably decrease under RCP8.5.CanESM2,GFDL-ESM2G,GFDL-ESM2M,MPI-ESM-LRand CSIRO-Mk3-6-0 have different coclusions.The monthly precipitation increases in most conditions.The minimum temperature changes varys from 1.3 to 2.4?,while the maximum temperature change varys from 0.8 to 4.1??Hadgem2_ES under RCP8.5 is chosen to evaluate the impact of climae change on water resource in Qiantang River Basin.The multi-site statistical downscaling method,GIST is used.The results show that GIST can well simulate the future precipitation with reasonable spatial correlations among sites.The GR4J hydrological model is used with GIST to project the future flow of Jinhua River Basin.Several low flow indices are calculated and the results show that there may be more water resources during the dry season in the future in Jinhua River Basin under RCP8.5.The last part of the thesis is to assess the impact of climate change on future flow of Lanjiang Basin,one of the tributaries of Qiantang River Basin.Ten GCMs from CMIP5 are chosen to calculate the future flow under four RCPs based on the results of the first part of evaluation work.LARS-WG and LARS-WGPP are used to simulate the future precipitation with spatial correlations.The future flow is generated by SWAT model.The results show thar generated precipitation with spatial correlations can provide better inputs for hydrological modeling.The generated data from LARS-WGPP are used to drive the SWAT to simulate the future flow under four RCPs in Lanjiang Basin.The results show that the future flow of Lanjiang may increase,especially in summer and autumn.Howerver,water shortage can be found in winter and spring under RCP8.5.There may be more extreme flows in the future period in Lanjiang Basin.