Research On Agricultural Drought Risk Analysis Method And Application

Natural disasters are inevitable natural phenomena of human beings,and their occurrence seriously affects social and economic development.Among many natural disasters,drought is the most widely affected natural disaster in the world.Under the background of global warming,global drought has a tendency of increasing.At present,drought disaster has more influence on social life and economic development than any other natural disaster,and has become an important unstable factor affecting world development and a bottleneck factor affecting sustainable development of national economy.The influencing factors of drought and water shortage are extremely complex and have strong uncertainties.Risk analysis is an effective technical tool to study the uncertainty system and has been widely used in the field of social science and economics.Aiming at the problems and deficiencies in the current agricultural drought risk research,this paper takes xi 'an as the research project area and summer corn as the research object to carry out the agricultural drought risk analysis method and application research.Major research achievements include:(1)Analysis of crop drought characteristicsBased on the analysis and understanding of agricultural drought concept and quantitative evaluation index,the drought characteristics and occurrence rules of representative crops were studied by means of information diffusion and fractal analysis technology.Based on the data of precipitation,temperature and crop yield per unit area over the years,the fractal rule of crop drought occurrence time was found,the occurrence time of drought was predicted and the degree of drought was estimated,which provided scientific basis for drought prevention and disaster reduction.The results show that the occurrence time of corn meteorological drought in xi 'an has fractal characteristics,and the degree of meteorological drought increases slowly;Corn trend yield increases as a whole,the rising trend is gradually gentle,basically in a stable state at present.(2)Characteristics analysis of drought and flood in crop growth period based on information diffusion and chaos theoryThe degree of drought and flood was evaluated with the data of precipitation and temperature.The severity of drought and flood in each growth period over the years of representative crops was calculated.By using the chaotic time series analysis and prediction method,the chaotic characteristics of the evolution of drought and flood were analyzed,and the occurrence of drought and flood on yield was predicted.With the help of information diffusion technology,the evolution rules of drought and flood in different growth stages of crops and the key factors affecting crop yield were explored.The results show that the chaos time series analysis model of maximum lyapunov index has certain accuracy in predicting the occurrence of drought and flood;Information diffusion technology can make sample data smooth and realize trend analysis well;Drought and flood appear alternately in each growing stage of corn in xi 'an city,which presents the form of fluctuation.The overall trend of the emergence~jointing and tasseling~maturity phases is slowly developing towards drought,while the whole trend of the remaining two growth stages was normal;The time series of drought and flood in corn is chaotic to some extent;The degree of drought and flood in stage jointing~tasseling affected the yield significantly more than that in other growth stages.(3)Agricultural drought risk simulation analysisAccording to the law that crops are sensitive to water deficit in different growth stages,a numerical model of the effect of water deficit on crop yield in different growth stages was established by using crop water production function.The mutation theory evaluation method was used to analyze the mutation effect of water deficit on crop yield in different growth stages,and to determine the factors that affected the mutation,so as to provide theoretical support for optimizing crop irrigation.The results showed that soil moisture content had a great influence on corn drought.The change of relative water shortage rate at the stage of emergence~jointing had an unstable effect on maize drought degree,which was easy to cause mutation.(4)Study on regional agricultural drought risk assessment systemThe Copula function is used to establish the joint distribution of rainfall in the adjacent growth stage,which can reflect the characteristics of drought in the crop growth stage more comprehensively.The analysis of drought resistance of relative yield of crops is helpful to reflect the actual drought resistance.The correlation curve of meteorological drought probability and agricultural drought risk coefficient constructed can be used to predict the probability of agricultural drought risk in the future.The four main contents studied in this paper are all innovative to some extent,and the main innovation points are as follows:(1)A new method for crop drought characteristics analysis based on information diffusion technology and fractal theory was established;(2)A method to analyze the characteristics of drought and flood in crop growth period by using information diffusion technology and chaos theory was proposed;(3)The function of mutation potential between water shortage rate and drought degree was constructed.(4)The copula function was used to construct the joint distribution of rainfall in different growth stages of crops,and a new agricultural drought assessment system was established based on the quantitative index of agricultural drought loss.