Research On Multi-factor Optimization Of Agricultural Water Resources Allocation

Developing the high-efficiency and water-saving agriculture is a strategic choic for agricultural sustainable development,and rational allocation of agricultural water-land resources is an important way in improving the efficiency of agricultural resources utilization.On the basis of analysis for pattern of crop water requirements and process of agricultural water resources allocation,as well as consideration of response of multiple factors and uncertainty,it is of important significance for enhancing agricultural water efficiency and guaranteeing sustainable economy development to carry out optimal allocation research for agricultural water resources and evaluate various strategies and their effects under different scenarios.In this paper,aimed for rational water resources utilization,methods and models for optimal agricultural water resources allocation in irrigation areas are delved based on multi-factor coordition and uncertainty programming.Takind irrigation areas in Minqin country as example,the contents and conclusions include as follows.(1)The water resources for irrigation area is optimized considering meteorological factor.Gray correlation analysis and linear correlation analysis are adopted to calculate the relationship between ET0 and different meteorological factors.The results show that the negative linear correlation between ET0 and mean relative moisture is closest.Then a linear fractional programming integrated with meteorogical driven factor for optimal water resources allocation is established.A case study of Hongyashan irrigation area,Minqin is conducted and results show that the agrigultual water production(AWP)is[1.02,1.10]kg/m3,and under scenario RHU is[1.04,1.12]kg/m3,when monthly mean relative moisture equals annual mean relative moisture.When mean relative moisture is reduced and increased by 10%,AWP will be[1.02,1.10]and[1.05,1.13]kg/m3 respectively.(2)A decomposition-coordination optimization model for water-land resources allocation considering allocation process coordination factor is established.Based on decomposition-coordination theory and deficit irrigation theory,a optimization model for water-land resources allocation is generated,which reflects allocation process.The mdoel is solved by genetic algorithm.A case study of wheat and maize in Hongyashan,Minqin shows that the in scenario where crop evapotranspiration and effective rainfall are least,the available water will be 500 million m3,the AWP and water benefit per unit can reach biggest,2.79 kg/m3and 6.79 ?/m3,the allocation water for wheat and maize are 227.7 and 299.8 million m3,and the plant area for both types of crops are 6758 and 7732 ha.(3)A two-stage interval programming for optimal irrigation water allocation considers water deficit penalty.Firstly,in order to minimize water resources regulation cost of multiple irrigation areas and multiple water sources,interval number is introduced to reflect the uncertainty of system and the water resources are optimally allocated among different irrigation areas.Then,takeing the results of first model as inputs,an irrigation scheduling optimization model is developed based on water production function of whole crop growth period.The model is applied in Hongyashan,Changning and Huanhe irrigation areas of Minqin.The optimal water resources allocation targets are:surface water 21.9 million m3,groundwater 64.47 million m3 for Hongyashan;groundwater 18.02 million m3 for Huanhe and groundwater 7.18 million m3 for Changning.Meawhile,there are water deficts to some extent under different flow levels in irrigation areas.Then,optimal water allocation targets and optimal water allocation are taken respectively as available water resources and crop water allocation are determined by optimization model.The results show that the irrigation quota is less in high flow level than in middle and low flow level and larger in Huanhe and Changning than in Hongyashan when available water is fixed.Due to the fact that the crop with higher net benefit will be allocated first,the allocated water of maize and cotton is closer to crop water demand targets.(4)Optimizaiton model for agricultural water resources allocation based on multi-factor coordination.Aimed at efficient water reouseces utilization and improving agricultural water production,fuzzy optimization theory,fractional programming and multi-dimentional regulation theory is integrated to generate optimal regulation system of water resources allocation in irrigation areas.Taking Hongyashan,Minqin as example,the results show that the comprehensive benefit index of commercial crop is larger than grain crop.For grain crop,when the ratios of transferred water and minimum crop water requiremets are 1.5 and 0.8 respectively,the order degree entropy is least,the coordination degree is highest and the allocation strategy is optimum.