| In the context of global climate change and increased human activities,extreme climate events such as drought are more frequent.Drought disasters are closely related to people's lives.They are extremely harmful to social economy,ecological environment and agricultural production,and are a major environmental issue currently facing mankind.Agriculture is one of the sensitive industries affected by drought.Every year,due to serious agricultural economic losses due to drought,it is of great significance to grasp the spatial and temporal distribution and occurrence of agricultural drought and achieve scientific early warning and assessment.Therefore,in this study,taking above the Bengbu gate in the Huaihe River Basin(BHR)as research area,the effective coefficient method to calculate the effective precipitation,P-M formula combined with crop coefficient calculation of water demand,and analysis of the temporal and spatial characteristics of water supply and demand in the growing stage of summer maize.Secondly based on precipitation probability quantile and the optimal probability distribution model to set the precipitation threshold value of drought disaster during the critical period of summer maize growth.Then the spatial and temporal distribution characteristics of summer maize drought is analyzed using the CWDI,and the probability of different degree of drought in different stages of summer maize is discussed.Finally,the drought warning and assessment system for summer maize in the upper reaches of Huaihe River is constructed.The main research contents include:(1)Analysis on the characteristics of water supply and demand of summer maize in the area above Bengbu in the Huaihe River Basin: Spatio-temporal distribution characteristics of effective precipitation,water requirement and water deficit are analyzed by GIS spatial analysis and trend analysis.The results show that all the maize growing stages in the study area are generally characterized by water deficit and a high degree of water deficit in the northern part of the study area.The spatial distribution characteristics of the integrated effective precipitation and water requirement,high value area,but also the high value of water shortage area.Summer maize growth period and the growth period of water demand show a significant reduction trend,but the effective precipitation and water deficit no significant change trend.(2)Threshold of drought-induced precipitation during the critical period of summer maize growth in the area above the Bengbu Sluice in the Huaihe River: The threshold of drought-induced precipitation during the critical period of summer maize growth is determined by the probability quantile method and the optimal probability distribution model.The results show that there was significant difference in the optimal probability distribution model of precipitation during the critical period of summer maize growth and water stress in each site.Based on the obtained precipitation threshold of drought disaster at all levels of the site,and by using the Tyson polygon method,precipitation threshold of drought disaster during the critical period of water in summer maize growth in the BHR are: mild drought: 73?R<91mm,moderate drought: 54?R<73mm,severe drought: 37?R<54mm,extreme drought: R<37mm,respectively.(3)Spatial and temporal characteristics of summer maize drought above the Bengbu Sluice in the Huaihe River,China: Based on the drought index of summer maize,the CWDI is used to analyze the spatial and temporal characteristics of summer maize by GIS spatial analysis and trend analysis method and maize at different stages of the different levels of drought probability of occurrence.The results show that the water deficit of summer maize is the most serious during the early growing stage,the degree of aridification was lower in the middle growing stage,and the degree of aridification tended to be serious with the advancing stage.The change trend of CWDI in the growth period of summer maize in the past 55 years is not obvious,with the fluctuation mainly.In each growth stage of summer maize,the probability of drought in sowing – seeding and tasseling – milking stage was the highest,and the probability of different degrees of drought in each growth stage of summer maize except the probability of severe drought in sowing – seeding stage was in 30~50% and the remaining stages are roughly in 0~20% range.(4)The drought warning and assessment system for summer maize in the upper reaches of the Huaihe River Basin: based on the Microsoft Visual Studio.NET integrated development environment,the C# development language and the ArcEngine secondary development technology are combined with the SQL Server 2008 database to initially develop the early warning and assessment system for summer maize drought,which mainly includes four functional modules:(1)Information query management.(2)Drought threshold early warning.(3)Drought emergency response.(4)Drought analysis and assessment. |
PDF Full Text Request