Impacts Of Drought On A Water Supply Reservoir Under Environmental Change In Luanhe River Basin

With the impact of global climate change,social and economic development and human activities,the problem of drought disaster under environmental change is becoming increasingly prominent,and the water supply shortage of Panjiakou reservoir in the water supply system of Luanhe River diversion turns into more and more serious.Aiming at Luanhe water supply system(Panjiakou reservoir),this paper constructs a water supply risk analysis model to analyze the response degree of water supply risk of Panjiakou reservoir to drought events,and studies the actual effect of Tianjin water diversion project in the middle route of South-to-North Water Transfer Project on reducing water supply risk by using nonstationarity time series stochastic simulation technology.The results provide basic theoretical support for drought risk response.The main research contents and results are as follows:(1)Monthly runoff stochastic simulation method based on Copula function is used to simulate the monthly runoff series in 1956-1979 and 1980-2016 respectively.The random runoff series of 1000 years are generated respectively.Through the analysis of mean,standard deviation,coefficient of skewness and lag-1 serial correlation coefficient,it can be found the statistical properties of the original sequence are well preserved by the simulated sequence.(2)Risk analysis model of Panjiakou reservoir is constructed based on seven water supply risk analysis indicators(time-based reliability,volume-based reliability,resilience,vulnerability,relative vulnerability,drought risk index and sustainability index).Combined with the water demand and behavior simulation of the reservoir,the water supply risk of Panjiakou reservoir in 1956-1979 and 1980-2016 are calculated by simulation analysis.It is found that the water supply analysis model is reliable and the nonstationarity seriously affects the water supply safety of Panjiakou reservoir.(3)Importance sampling,the trend of Copula function parameter and perturbation coefficient are used with the method of generating stochastic simulated runoff series,the monthly runoff stochastic simulation series which can reflect the trend of future drought development is generated,and the impact of drought on water supply risk under environmental chang is analyzed.The results show that with the development of drought,the risk of water supply continues to increase,which seriously affects the water supply safety of the water supply system.(4)The nonstationarity stochastic simulation method based on mixed distribution model and simulated annealing algorithm is used to simulate the runoff series in 1956-2016.The water supply risk of Panjiakou reservoir in 1956-2016 is calculated by using the stochastic simulation results.The water supply risk of Tianjin diversion project in the middle route of South-to-North Water Transfer Project to Panjiakou reservoir is also analyzed.The results show that the Tianjin water diversion project in the middle route of the South-to-North Water Transfer Project effectively reduces the water supply risk of Panjiakou reservoir and significantly alleviates the water supply pressure.