| As one of the major natural disasters, drought has the biggest impact on agricultural production, agricultural drought have threatened to food security and sustainable development of economic society of our country, even to the extent that become an important factor affecting social stability. So, it has important theoretical and practical significance that carry out the study actively on agricultural drought risk and the corresponding countermeasures.According to the comprehensive analysis of current situation and development trend of agricultureal drought risk analysis study and existing problems, the analysis of the concept and the meaning and characteristics of agricultural drought risk, Qucun irrigation district of Puyang at downstream of the Yellow River taken as study region, the paper established the evaluation index system of agricultural drought through analyzed the concept of drought; discussed the characteristics and variation of regional agricultural drought, and evaluated the agricultural drought vulnerability of irrigation district which we studied starting from the inner mechanism; constructed the model of agricultural drought risk evaluation which with more rational and comprehensive,studied the agricultural drought risk management and corresponding countermeasures. The main results and conclusions are obtained as follows:(1) Based on the summary of various definitions and related concepts of drought, the paper pointed out that the core of drought is abnormal under certain conditions of water deficit, while agricultural drought is a phenomenon that crop's production reduction even extremely due to abnormal water stress under certain conditions,and put forward clearly that climate change and human activities are two factors which driving agricultural drought. After summated different meanings about risk at home and abroad, classed the risk and proposed the main study system on agriculture drought risk.(2) Combining with the actual situation of study area, we established the comprehensive evaluation index system of drought was established, and the drought condition of the irrigation district comprehensively was evaluated by applicating variable fuzzy evaluation model. The results showed: the drought level of the study region falled between moderate and serious, slightly to the serious,and the assessment results were consistent with the actual situation in study region. Selected summer corn as the research object, evaluated the agricultural drought grade by using the improved Palmer drought severity model and the corp water stress index(CWSI), the results showed that the evaluation results of two method were consistent with the actual situation of crop drought in the irrigation district, but Palmer drought severity model was more suitable for drought evaluation of study region.(3) Selecting the rainfall data of Qucun irrigation district, using the average monthly rainfall as threshold,and applying the run-length theory, the paper selected drought duration(LS), drought intensity(LD) and intensity peak(FZ) for drought variables, With the help of Frank, Clayton, Gumbel-Houggard and Ali-Mikhail-Haq copula functions, we constructed joint distribution of two dimensional drought characteristics of LS—LD,LS—FZ and LD—FZ, and joint distribution of three-dimensional drought characteristics by the pair-copula decomposition of LS—LD—FZ, studied on the drought characteristics of study region. Using maximum likelihood estimate,results showed that the pair-copula functions constructed with Frank, Clayton and Gumbel reflect the empirical probability numerical of joint distribution of two-dimensional and three-dimensional weel,and can be used in simulating and analyzing the joint properties of drought.(4) According to the mechanism of agricultural drought vulnerability,and taking various influence factors into account under comprehensive consideration from the natural, social and econom icaspects, this paper selected twelve vulnerability index of the agricultural drought and established the agricultural drought vulnerability evaluation index system, then analyzed and evaluated the agricultural drought vulnerability degree using fuzzy comprehensive evaluation method based on entropy, The results showed that the comprehensive evaluation index system established is reasonable, can characterize the influence factors of regional drought vulnerability comprehensively,the evaluation method used can weight the index objectively, avoid the influence of subjective factors effectively, and reflect the role of each index truly,the evaluation result was objective and reliable, consistent with the actual situation of the study region, and could provide reference for local governments to take targeted countermeasures to against drought effectively.(5) Based on water production function, the paper established the static,dynamic and comprehensive assessment model of agricultural drought risk, which not only could objectively quantify agricultural drought severity and drought disaster, accurately provide the loss information, but also could complete the risk assessment of agricultural drought under different time scales according to the rainfall situation; the method for constructing distribution function of regional drought degree based on the Maximum-Entropy principle, could improve the randomness of previous drought degree probability distribution function determination,overcome the existing shortcomings in the current drought degree study,and provided a new idea to study agricultural drought degree quantitatively for the area where lacked of information relatively.(6) The paper pointed out that risk management is a scientific way and the development direction of drought disaster management based on summarizing advanced management experience of drought both at home and abroad, and studied agriculture drought countermeasures of irrigation district from several aspects such as the establishment of drought monitoring system, the strength of water conservancy infrastructure construction, the promotion of new technology of water saving irrigation, the strength of optimal allocation of water resources,the implementation of drought disaster risk management, and the implementation of risk control strategy,et al.Finally, a summary is made and a few work which need to be further studied are listed. |
PDF Full Text Request