Uncertainty Analysis Of The Impact Of Climate Change On Rainwater Harvesting Capacity In The Beijing-tianjin-hebei Region

The Beijing-Tianjin-Hebei region is an area frequent with extremely heavy rainfall in China,and it is also with serious water shortage.In order to alleviate water shortage and other urban water problems,it is necessary to strengthen the harvesting and utilization of rainwater.However,climate change has a great impact on rainfall,which will lead to great changes in the spatial and temporal distribution of rainfall in the future,which will have an uncertain impact on the rainwater harvesting capacity.It may be difficult to achieve the expected effect in the future if only historical data are used to determine the scale of rainwater harvesting facilities.Therefore,it is necessary to refer to the predicted results of rainfall changes to explore the uncertainties of rainwater harvesting capacity.In this paper,eight CMIP5 climate models were selected to evaluate the simulation ability of each model by comparing the historical data of meteorological stations in the Beijing-Tianjin-Hebei region and the six can simulate well.The spatial and temporal characteristics of future rainfall in the Beijing-Tianjin-Hebei region under RCP4.5 and RCP8.5 scenarios were analyzed after linear downscaling.By calculating the design rainfall,the possible changes of the rainwater harvesting capacity in the future can be judged,so as to determine the uncertainty of the impact of two different climate change scenarios on the rainwater harvesting capacity.The main conclusions as follows.(1)According to the historical rainfall data of each station,the spatio-temporal scale of the models was evaluated,and six models including ACCESS1-3,CNRM-CM5,GFDL-ESM2 M,IPSL-CM5A-MR,MRI-ESM-LR,and NORESM1-M were selected for future rainfall prediction research.(2)According to the prediction results of different RCP scenarios at each station,the predicted rainfall is generally larger than the historical annual average rainfall,and the predicted results of each model under the RCP8.5 scenario are large.In terms of the proportion of rainfall above 50 mm in the annual total rainfall,most of the models under the RCP4.5 scenario predicted a slightly increasing trend year by year in the future,while most of the models under the RCP8.5 scenario predicted a decreasing trend in the future.(3)According to the predicted data,the design rainfall range of the whole region is10.3mm~27.1mm,showing an increasing distribution trend from northwest to southeast.The predicted design rainfall in the future is generally lower than the historical value,and the change of design rainfall in each city under the RCP8.5scenario is greater than that under RCP4.5.Under the two scenarios,the uncertainty of the design rainfall at the Botou is the largest,with a range of 15.3mm under RCP4.5 and 14.1mm under RCP8.5.The least one is Zhangbei,with a range of2.7mm under RCP4.5 and 3.5mm under RCP8.5.(4)For the entire region,more rainwater can be collected under the RCP8.5 scenario than under the RCP4.5 scenario,but the changes greatly,and the future rainwater harvesting capacity with the RCP8.5 scenario is more uncertain.Under the scenario of RCP4.5,the uncertainty of the annual average rainwater harvesting capacity in Xingtai is the largest,with a range of 298.0mm,the least one is Zunhua,with a range of 27.5mm.Under the scenario of RCP8.5,the uncertainty of the annual average rainwater collection capacity of each city is large,and the largest is Raoyang,with a range of 359.0mm.The least is Zhangbei,with a range of 10.3mm.