Research On The Variations Of Precipitation And Runoff,and Response To The Droug Ht/flood Events In Shaanxi Province

Drought and flood are antonyms,which are two extreme events.Water connect the two events.When water is extremely scarce,drought is formed.Water is excessively numerous and floods are formed.Shaanxi is located in the central region of' China.According to its geographical location,it is divided into three regions:Northern Shaanxi,Guanzhong and Southern Shaanxi.The rainfall in these three regions is gradually increasing from north to south.Studying the changes of rainfall and runoff and the characteristics of drought and flood in three typical areas of Shaanxi Province is of great signi:ficance in preventing and coping with frequent drought and flood events.This paper analyzes the characteristics of rainfall and runoff changes in Shaanxi Province with mathematical models,analyzes the causes and characteristics of drought events and the characteristics of extreme precipitation,puts forward countermeasures and solutions,and sets up the flood control and drought relief consultation system based on comprehensive platform,applies plans and solutions to reality.The specific results of the thesis are as f-ollows:(1)Using the moving average,accumulative departure and linear tendency estimation methods,this paper investigated the precipitation characteristics and the characteristics of typical annual rainstorm over the past 72 years in Northern Shaanxi and Yan'an.The results show that the precipitation in Yan'an is decreasing as a whole.The proportion of light and moderate rain is large,but precipitation tends to increase in flood season in recent years,Using linear fitting,smoothing t test,orderly clustering and the Mann-kendall method analyzes the changing trend and abrupt change of meteorological and hydrological elements such as precipitation and temperature in Guanzhong Xi'an during the recent 60 years.The results showed that the annual precipitation in Xi'an generally showed a decrease trend.The precipitation in flood season accounted for 58%of the annual precipitation.The distribution of precipitation in the year was uneven.The annual average temperature and extreme minimum temperature were on the rise.The trends of precipitation and precipitation days in southern Shaanxi-Foping during the recent 50 years were analyzed by using the methods of sliding average method,cumulative distance method and linear tendency estimation method.Using the sliding t-test and orderly clustering method analyzes the abrupt change of precipitation.The results show that the precipitation in Foping overall precipitation showed a decreasing trend in fluctuations.The decrease of precipitation is mainly caused by the decrease of precipitation in spring and autumn.The abrupt change point of annual precipitation occurred in the early 90s of last century.The annual total precipitation days,the number of light rainy days and the number of moderate rainy days all showed a decreasing trend.There was a significant positive correlation between heavy rain days above and the annual precipitation.(2)Taking the main stream of Weihe River and Jinghe River as the research object,using the moving average,accumulative departure and linear tendency estimation methods analyzes the trend of annual runoff.Using the smoothing t test,and orderly clustering methods analyze the abrupt runoff changes.The results show that the runoff in the Jinghe River Basin has shown a decreasing trend since the 1960s,and there are differences in the abrupt changes among different hydrological stations.Since the 1970s,the runoff in the Weihe River Basin has been decreasing,and the trend of annual runoff in each station is similar.The abrupt runoff changes occurred at the hydrological stations in the early 1970s and early 1990s,and there were differences in the abrut changes at different hydrological stations.Among them,the point mutations of Linjiacun village occurred in 1970 and 1990,and in Xianyang station in 1970 and 1990-1992,Lintong Station was between 1968 and 1990-1994,Huaxian Station was in 1968 and 1990.(3)The normalized precipitation index,such as precipitation anomaly percentage,relative humidity index,standardized precipitation index,soil relative humidity index,Palmer drought index and other single drought index,and integrated meteorological drought index were used as indicators of drought analysis to analyze the spatial and temporal evolution of drought frequency and intensity in Shaanxi Province.The results showed that the average drought intensity was the largest in the 1990s.The trend of drought intensity and the number of substations were basically the same.The frequency of light drought and moderate drought was higher,while the frequency of severe drought and special drought was lower.Light and dry,the ratio of middle and lower reaches of drought was decreasing weakly,and the ratio of special drought and severe drought was increasing.The drought area of Shaanxi had an expanding trend.In spring and winter,the drought range is expanding,and the decreasing range of summer and autumn droughts.At the same time,focusing on the analysis of northern Shaanxi,the results show that the main drought in the drought,drought intensity showed a certain decrease.(4)Taking the contribution of Id maximum precipitation,5d maximum precipitation and extreme precipitation to annual precipitation,annual extreme precipitation and extreme precipitation days as extreme precipitation index,taking Southern Shaanxi as an object,according to the daily rainfall data of 12 rainfall stations in the region,the extreme precipitation threshold of the annual time scale is defined by the percentile method,and the spatial and temporal distribution and trend change characteristics of the extreme precipitation events are analyzed.A digital flood control contingency plan is established for the extreme precipitation events to form a county-Township-Village three emergency warning methods to deal with varying degrees of extreme precipitation events.(5)On the basis of the integrated platform,the application system of flood control and drought-resisting business was constructed based on component library + knowledge map +theme database mode to realize the flood control and drought relief emergency response plan electronicization and form data integration service,water and rain information service,video consultation service,rainfall and runoff feature analysis services,real-time early warning services,emergency response services and other six applications,to achieve rainfall and runoff analysis,drought and flood response integration,the theory applied to reality.