Study On Optimal Allocation Of Agricultural Water Resources In Irrigation District Under Uncertainty

Water resources is the foundation of human survival and development.In recent years,with the development of economy and the acceleration of urbanization,water shortage caused by water pollution and the contradiction between water supply and demand has become increasingly prominent.Therefore,it is important to improve the utilization rate of water resources,and promote the balance between supply and demand of water resources,and improve the rationality of water resources allocation.Agriculture is the largest sector and the irrigation area was the main individual of water resources utilization of the agricultural sector.The rational and optimized allocation of irrigated water resources could promote the efficient and effectively release the pressure of water system.However,previous optimization models and methods are limited in practical application.The main reason is that there are many uncertain factors in optimal allocation of agricultural water system which lead to the risk of water allocation process.Previous studies haven't considered the uncertainty and risk of system comprehensively,which makes the difference between results of model and actual situation.In this paper,the uncertainties,complexity and risk of irrigation water system are considered.The optimal allocation model is established with multiple uncertainty analysis methods.Firstly,the uncertainty of water in Mudanjiang irrigation area is analyzed,including the uncertainty of rainfall level,the uncertainty of water supply and the crop water demand.According to the irrigation practical situation,the rainfall level conforms to a certain probability distribution.Based on the two-stage stochastic programming model,the probability distribution function is used to solve the uncertainty of rainfall level.The change of water supply and crop water demand is expressed in discrete interval.In view of the characteristics of risk in water allocation model,a robust optimization method is added.The risk decision is introduced into the model,and the robust coefficient is used to express the attitude of the decision maker to the risk.The system risk was successfully reflected in the model,which overcomes the lack of uncontrollable system risk.Coupled with the above processing methods,an interval-parameter two-stage robust stochastic programming model is constructed.The model is applied to Mudanjiang irrigation area in Sanjiang plain to provide a solution for water resource allocation.The model takes the minimum cost as the objective function.It was applied to the rational allocation of multi-water(surface and groundwater)and multi-crops(corn,soybean and rice)in the irrigated area.We can obtain that:(1)the optimal allocation and shortage of water,the optimal target allocation water with multi-water,multi-crops and different robustness coefficients;(2)according to the robustness coefficients,the decision-makers can compare solutions with different risk degrees,weigh the economy and stability of solutions,and choose the optimal solution.The resolute showed that:(1)compared with the traditional interval-parameter two-stage stochastic programming model,the interval-parameter two-stage robust stochastic programming model can not only effectively solve the stochastic problems and interval problems under uncertain conditions,but also capture the risk problems generated in the planning process with the addition of robust optimization method.The model avoids the high-risk state of the optimization results,makes up for the defects of the model and enhances the stability of the system;(2)with the increase of the robustness coefficient,the system stability is enhanced.But with the increasing of system cost,system economic was reduced.The feasibility of the model results is enhanced with the increase of the robustness coefficient with different water levels.The cost of water,the stability and risk of the system are fully balanced,which makes the allocation scheme more practical and flexible.In a word,the robust optimization method is a supplement and improvement to the traditional ITSP,and the improved model is more suitable for the practical situation of optimal allocation of irrigation water.With the addition of robust optimization method,the feasibility of the model solution and the stability of the system are enhance.At the same time,the optimization results are given in an interval manner,which can provide sufficient space for decision makers.It also can provide technical support for the rational allocation of agricultural water resources and promote the sustainable and common development of resources,environment,economy and society.