Drought Characteristics And Drought Disaster Risk Analysis In Yulin

Drought disasters have a high frequency,a long duration and a wide range of disasters.Therefore,risk assessment is of great significance to water resources management and disaster prevention.Yulin of Shaanxi province is an arid and semi-arid area,with less precipitation,strong evaporation,dry climate and fragile ecological environment.Based on the monthly precipitation data from 1971-2015 45 a of 12 meteorological stations in Yulin,the paper compares the univariate drought frequency with the bivariate drought frequency based on the connected drought runs and Copula function,and makes a comparative analysis with the historical drought to optimize the frequency calculation method suitable for Yulin.Based on meteorological data,basic geographic information data and social economic data,the selection of yulin to,the risk of disaster-causing factors,the vulnerability of disaster-prone environment,the exposure of disaster-bearing bodies and disaster recovery capability of four factors of 12 evaluation indexes,the Entropy method is adopted to define the weight of 12 evaluation indexs and the four big factor indexs,the drought disaster risk evaluation of yulin.The main conclusions are as follows:(1)The monthly precipitation data series of Yulin was obtained by using Thiessen polygon method,and the standardized precipitation index of the scale from 1 month to 6 months and 12 months scale was calculated.Compared with the historical drought,SPI-4 index was the most suitable for the drought monitoring of Yulin,and the monitoring effect was better,followed by SPI-3 index.(2)The temporal and spatial variation trend and period of annual and seasonal drought intensity in Yulin were analyzed by means of linear trend rate method,5-year sliding average method,M-K trend test method,wavelet analysis et al.From 1971 to 2015,the annual drought intensity of Yulin showed an insignificant decreasing trend.The annual drought intensity of most meteorological stations in Yulin showed an insignificant decreasing trend,that of Jiaxian station showed a significant decreasing trend,and that of Suide station and Qingjian station showed an insignificant increasing trend.The drought intensity of Yulin in spring,summer,autumn and winter showed an insignificant decreasing trend.Using wavelet analysis,it is found that the drought change period of Yulin is between 0?9a.(3)Calculated and counted the traditional univariate drought frequency and the bivariate drought frequency based on connected drought runs and Copula function,compared the calculation results of the two methods,and the bivariate method based on connected drought runs was closer to the historical drought events.(4)Calculate and analyze the risk of disaster-causing factors,the vulnerability of disasterprone environment,the exposure of disaster-bearing bodies,disaster recovery capability and comprehensive drought disaster risk of 12 counties in Yulin.Jingbian county,Yuyang district and Shenmu county are low drought disaster risk areas,Dingbian county,Hengshan county,Zizhou county,Qingjian county,Jia county and Fugu county are medium drought disaster risk areas,Mizhi county and Suide county are second high drought disaster risk areas,Wubao county is high drought disaster risk area.