Coupling Characteristic Between Agriculture And Extreme Precipitation In Loess Plateau Of Northern Weihe Area

The research on the characteristic frequency of precipitation is a great significance for guiding regional agricultural planning,water conservancy project designs,and drought and flood control.Droughts and floods occurred in northern Weihe Loess Plateau,affecting growing and yield of winter wheat in the area.Based on the daily precipitation data of 29 meteorological stations from 1981 to 2012,this study is to address the analysis of three different frequencies of annual precipitation at 5%,50%,and 95%,and to determine the amount of rainfall excess and water shortage during seven growth stages of winter wheat at 5%,10%,and 20% frequencies,respectively.Pearson type III curve was selected for this study to analyze the distribution frequency of annual rainfall and rainfall amount following seven growth stages of winter wheat crop in 29 stations of Northern Weihe Loess plateau.As a result of our study,annual precipitation is gradually increasing from southwest to northeast of Northern Weihe loess plateau.The highest amount of annual precipitation occurred in the Baoji area and the lowest precipitation covered by the northwest area of Northern Weihe loess plateau.Moreover,the amount of rainfall of seven growth stages indicates that excessive rainfall occurs not only in the first stage(sowing to tillering)and seventh stage(flowering to ripening)but also in second stage(tillering to wintering).In the seventh stage,a large amount of excessive rainfall occurred in Changwu,Bin,Qianyang,Fengxiang,Baojiqu,and Baojixian.Moreover,water shortage is distributed in the third stage(from wintering to greening),the fourth stage(from greening to jointing),the fifth stage(from jointing to heading),and the sixth stage(from heading to flowering).Furthermore,the worst water shortages occurred in Hancheng,Heyang,Chengcheng,Pucheng,Dali,Tongchuan,and Fuping in the fourth stage(greening to jointing stage).Even though we study the crop water requirement under extreme rainfall conditions,the amount of rainwater still supply inadequate in some parts of the winter wheat growth stage.Therefore,this study provides main clues for the next step to study the irrigation water needs of winter wheat crops and to reduce agricultural risks in 29 counties in the northern loess plateau and other regions.