| Aims:Restricted by the "three red lines of water resources" and influenced by the increase of extreme weather,the available water in irrigated areas is decreasing year by year,and the uncertainty of water resources is also increasing,which makes the reasonable allocation of irrigation water resources increasingly difficult.Aiming at this problem,in this thesis,is located in the northwest arid areas of Wujiaqu irrigation district as an example,the study on irrigation water resources prediction and optimization deployment model,in order to Wujiaqu irrigation irrigation water resources reasonable allocation,as well as the sustainable development of social economy in the irrigation district to provide technical support,to alleviate the contradiction between supply and demand of irrigation water resources in arid areas of northwest to provide technical reference.Methods:Firstly,three different water resources prediction models were constructed based on empirical mode decomposition(EMD),variational mode decomposition(VMD),wavelet denoising(WDD)and weighted Markov chain.Then,the three prediction models were compared to determine the best water resources prediction model suitable for Wujiaqu irrigation district.Then,according to the predicted value of water resources,a multi-objective programming model was established under the condition that the available water amount was determined.Jensen crop water production function was introduced to reflect the crop yield and benefit in the irrigated area,GINI coefficient was introduced to reflect the fairness of water allocation results of the model,and the multi-objective optimization of irrigation water resources was carried out.Finally,considering the optimization deployment of the uncertainty of parameters and the amount of water available in the system,to reflect the uncertainty parameter range planning,with fuzzy Numbers reflect the uncertainty of the amount of water available,and add constraints of credibility,build the uncertain interval multi-objective programming model,to explore the optimal water allocation of irrigation district under uncertainty.Results:(1)By comparing the performance of EMD-MK,VMD-MK and EMD-WDD-MK water resource prediction models in the four evaluation indexes,it is concluded that EMD-WDD-MK model has the best performance in the validation period of 2019 and 2020.Therefore,it is determined that this model is the best water resource prediction model in Wujiaqu irrigation district.The surface water available in Wujiaqu irrigated area in 2021 predicted by this model is 1.21×108 m3.(2)Under the three Scenarios of emphasizing economic objectives,emphasizing both economic and social objectives,and emphasizing social objectives,the multi-objective optimization results are all within the range of single-objective optimization results,and the model achieves a balance under the mutual constraints of multiple objectives.The economic benefits of irrigated areas from Scenario 1 to Scenario 3 are 797 million yuan,844 million yuan and 883 million yuan respectively.With the increase of the weight of economic objectives,the economic benefits of irrigated areas gradually increase.GINI coefficient,which represents the fairness of water allocation,gradually increased from 0.39 in Scenario 1 to 0.46 in Scenario 3,and the fairness gradually decreased.Under the condition of equal economic and social goals,the economic benefit of cotton in irrigated area reached 844 million yuan,and the social goal was 0.43.(3)The results of the interval multi-objective programming model under uncertain conditions show that the groundwater usage in irrigated areas increases from[0,0]m3 to[3.03×107,3.16×107]m3 under the three typical level years of abundant,moderate and dry conditions.Due to the high cost of groundwater water,the economic benefits of irrigated areas increase from[800,822]down to[689,724]million yuan.By comparing the optimization results at the confidence level λ=0.9 and λ=0.5 of the three typical levels of abundant,smooth and low flow years,it is concluded that with the increasing degree of dissatisfaction of the model constraint conditions,the water allocation of the irrigated area gradually increases,and the economic benefits increase by[40,42]million yuan,[38,57]million yuan and[38,42]million yuan.Conclusion:(1)EMD-WDD-MK model has high accuracy in predicting the available water quantity in Wujiaqu irrigation district.(2)The multi-objective and interval multi-objective optimization models of irrigation water resources constructed in this thesis can provide a reasonable optimal water allocation scheme for the Wujiaqu irrigation district under the two conditions of the parameters and available water quantity being determined or uncertain,which has certain practical significance to alleviate the contradiction between supply and demand of irrigation water resources in the Wujiaqu irrigation district. |
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