Future Climate Change On Runoff And Uncertainty In Shanmei Reservoir Basin

In the past hundred years,greenhouse gas emissions increased significantly,and the global average temperature has been increasing.The impact of climate change on human beings cannot be ignored.Water cycle as an important part of climate system,its response to climate change affects human life all the times.In recent years,flood and drought happens frequently,causing many people lost their families and giving huge threaten to our social.So,giving more researches to hydrological response study in future climate is particularly important for disaster prevention and mitigation and rational planning of water resources.At present,the study of hydrological response to future climate change is mainly based on the combination of climate model and hydrological model.At the same time,when research the impact of climate change on the hydrological water resources,there exist different sources in uncertainty.Among them,the future climate factor is an important input of hydrological response,and its accuracy plays a crucial role in hydrological process as well as climate change research.Only by quantifying the uncertainty of future climate factor's prediction can we make wise decisions on river basin water resources management and planning.In this study,the Shanmei Reservoir Basin is taken as the study area,choose 5 GCMs in CMIP5(GFDL-ESM2 M ?Had GEM2-ES?IPSL-CM5A-LR?MIROC?Noer ESM1-M),and combining four typical concentration paths(RCP2.6,RCP4.5,RCP6.0 and RCP8.5)to obtain meteorological data from 2020-2099,then coupling HSPF water model to obtain future runoff in the study area.Besides,using IHA(Indicators of Hydrological Alteration)to analyze the changes of hydrological situation in annual streamflow,monthly streamflow,annual extreme streamflow,low pulse count,low pulse duration,high pulse count and high pulse count,rise rate,fall rate and number of reversals.Finally,the uncertainty of hydrological effects caused by GCMs and RCPs was quantified.The results show as follow:(1)The MME(the multi-model ensemble)predicts that monthly precipitation is mainly increasing from April to May and September to November,while mainly decreasing from January to March,June to August and December.As far as the different period in future,the near term precipitation fluctuation is the biggest,the medium term is second,the long term fluctuation is the least.The monthly maximum and minimum temperature showed an increasing trend as a whole,and the closer it was to the longer term,the more significant it was.(2)The average annual streamflow mainly increases in the future.RCP2.6 has the largest annual streamflow while RCP8.5 has the smallest annual streamflow.When comes to average annual streamflow in GCMs,different term has different changing trends.The uncertainty of long term streamflow is bigger than recent term and medium term.The probability of the drought and flood is about48%?61%.(3)Streamflow is decreasing in January and December,and increasing in March to June and September to October.Besides,the increment rate is more than 20%from April to May.February,July to August and November has different change direction.(4)1-day and 3-day annual minimum flows are increasing,but 7-day annual minimum flows has different change direction.Comparing to extreme annual minimum streamflow,extreme annual maximum streamflow has bigger uncertainty.Under the scenario of RCPs,1-day annual minimum flows is decreasing,while 7-day annual minimum flows and 3-day annual minimum flows are mainly increasing.Under the scenario of GCMs,extreme annual maximum streamflow has different change direction,and bigger uncertainty.(5)The frequency of high and low pulses is decreasing,and duration of high and low pulses is increasing.(6)Streamflow variability(rise rate,fall rate and number of reversals)is declining in future,and drop more than 20%,and different terms don't have huge distinction.(7)Different RCPs and GCMs has huge hydrological response under climate change,especially in annual streamflow and extreme streamflow.At the same time,except for extreme annual maximum streamflow,for the most hydrological characteristic,GCMs has bigger uncertainty in streamflow than RCPs.