| Agriculture is China’s primary industry and an important basis for supporting industry,service industry and other industries.It transports the original means of production for economic and social operation.The balance between supply and demand of agricultural water determines the stable operation of economy and society.Heilongjiang Province is an important grain production base in China,but the distribution of water resources does not match the pattern of grain productivity,resulting in low efficiency of water resources utilization.In recent years,in order to increase grain output,Heilongjiang Province has been developing and planting continuously and intensively,which has seriously affected the sustainable development of local agriculture.Based on the scientific evaluation and analysis of the main evaluation index of economic production and effective utilization of water resources-irrigation water use efficiency,the regulation strategy of irrigation water use for the optimization of agricultural planting structure in irrigation area can effectively realize the optimal allocation of water resources and sustainable agriculture on the basis of high agricultural crop output and high economic return.In order to promote the efficient utilization of water resources and the sustainable development of agricultural economy,this study takes 24 large and medium-sized typical irrigation districts in Heilongjiang Province as the research object,deeply analyzes the connotation of irrigation water use efficiency,carries out relevant research on irrigation water use efficiency,explores the optimal evaluation model of irrigation water use efficiency,analyzes its driving mechanism,and preliminarily explores its adaptive regulation strategy.On this basis,15 irrigation districts are selected to further carry out the optimization research of agricultural planting structure under the constraint of irrigation water use efficiency,and determine the optimal pattern of agricultural planting structure in the irrigation district.It has laid a theoretical foundation for the steady and balanced development of agriculture in the whole province.The main conclusions of this study are as follows:(1)Based on the in-depth analysis of the connotation of irrigation water use efficiency in irrigation districts,fully considering many factors affecting irrigation water use efficiency,combined with the actual situation of irrigation districts in Heilongjiang Province,the indexes that may affect irrigation water use efficiency in irrigation districts are selected from the five dimensions of nature,ecology,management,technology and economy,and a primary index data set containing48 evaluation indexes of irrigation water use efficiency is established.In order to avoid the problem of information duplication and redundancy among the primary evaluation indexes,the index screening method based on cumulative information contribution rate-R Clustering-grey correlation advantage analysis-coefficient of variation analysis was adopted.A total of 20evaluation indexes were selected and finally passed 40.67%of the indicators reflect 90.33%of the original information,making the information of the preferred evaluation index more concise and clear.On this basis,the previous research results and the indexes optimized by entropy method are compared and analyzed to ensure that the evaluation index system constructed in this paper is reasonable and reliable.(2)In order to obtain more accurate evaluation results of irrigation water use efficiency,BP neural network and ELM model are used to evaluate the irrigation water use efficiency of irrigation area,and CSA and SMO algorithm are introduced to optimize the ELM model.Four evaluation models,BP,ELM,CSA-ELM and SMO-ELM,are established to evaluate the irrigation water use efficiency in the irrigation districts.The spatial variation characteristics of irrigation water use efficiency in the irrigation districts are analyzed respectively,and the optimal evaluation results are determined through the performance of the model and the stability of the evaluation results of each model.The results show that the evaluation results of the four models are slightly different,but the spatial variation characteristics still show the same change law,and show certain regional differences.The irrigation water use efficiency of the irrigation areas in the east of the study area is better than that in the middle and West;Grade IV～V irrigation districts with higher evaluation grade are mostly distributed in the east of the study area,and most of grade I～II irrigation districts with lower evaluation grade are close to the main stream of Songhua River.In order to further evaluate the advantages and disadvantages of these four evaluation methods,by comparing the determination coefficient R~2,MSE,MAPE,Accuracy of BP,ELM,CSA-ELM and SMO-ELM models,SMO-ELM models are 0.9999,4.33×10-10,0.00039 and 99.8%,far better than the other three models,which is much better than the other three models.It is verified that smo-elm model has the optimal rationality and superiority.Through the complexity theory analysis,it is verified that the evaluation result of smo-elm model has the optimal stability.Finally,the evaluation result of SMO-ELM model is the optimal evaluation result.(3)Based on the evaluation results of SMO-ELM model,the Pearson correlation coefficient method is used to identify the main driving factors causing the difference of irrigation water use efficiency in irrigation districts,analyze its driving mechanism,and still explore the adaptive regulation strategy.In addition,in order to test the accuracy of Pearson correlation coefficient method in identifying key driving factors,principal component analysis method and Pearson correlation coefficient method are selected for comparative analysis.The results show that the water use coefficient of canal system is the main driving factor causing its spatial differentiation,and the Pearson correlation coefficient is 0.788,accounting for 12.164%;The average buried depth of underground level is the least important driving factor,and the Pearson correlation coefficient is0.044,accounting for 0.679%。Water utilization coefficient of canal system,evaporation capacity,output capacity of agricultural commodities,soaking quota and proportion of rice sowing area are the most important driving factors affecting irrigation water use efficiency.Natural dimension,management dimension and technical dimension have a great impact on irrigation water use efficiency,while ecological dimension and economic dimension have a relatively small impact on irrigation water use efficiency.The key driving factors identified by principal component analysis verify the reliability of Pearson correlation coefficient method.Combined with the key driving factors,this paper puts forward targeted control strategies such as strengthening project construction and optimizing and adjusting planting structure,so as to effectively improve the efficiency of irrigation water use in irrigation districts.(4)Considering the key driving factors of irrigation water use efficiency in irrigation districts,the optimization model of planting structure in irrigation area under the constraint of irrigation water use efficiency is constructed,MOEA/D algorithm is used to solve the multi-objective function of social and economic benefits,ecological benefits and water resources benefits.The results show that:When the planting area of rice,corn and soybean is adjusted to 115275.8 hm~2,28598.7 hm~2and 19249.6 hm~2 in 2025,the social and economic benefits,ecological benefits(measurement)and water resources benefits are 0.6688×10~4yuan/hm~2,0.2826 and 0.9280 kg/m~3 respectively,which is greatly improved compared with the current year;When the planting area of rice,corn and soybean is adjusted to 113548.8 hm~2,27063.1 hm~2 and 17518.3 hm~2 in 2030,the social and economic benefits,ecological benefits and water resources benefits are 0.7493×10~4yuan/hm~2,0.2971 and 0.9582kg/m~3 respectively,which is greatly improved compared with the current year;When the planting area of rice,corn and soybean is adjusted to 111012.3 hm~2,26165.6 hm~2 and 20952.2 hm~2 in 2035,the social and economic benefits,ecological benefits and water resources benefits are 0.7861×10~4yuan/hm~2,0.3189 and 0.9707 kg/m~3 respectively,which is greatly improved compared with the current year;Comparing the planting structure optimization scheme with the national and local government policies,the rationality and necessity of the agricultural planting structure optimization scheme in the irrigation districts are verified. |
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