Evaluation of the agricultural water resource carrying capacity and optimization of a planting-raising structure

The serious shortage of water resources and the progressive deterioration of downstream water environments restrict development of the agricultural economy. It is necessary to study the optimization method of water allocation from the perspective of sustainable development, considering the real situation of agricultural production and water quality. First, an improved principal component analysis that considers the importance of indicators to the principal components is performed to select evaluation indicators, and the entropy weight method is modified to stably and sensitively determine the weight of the evaluation indicators. Moreover, Dempster-Shafer evidence theory is proposed to obtain the comprehensive weight of the evaluation indicators, taking into account both subjective and objective factors. Second, the model to optimize the planting-raising structure and regulate water quantity and quality is established by combining the evaluation of agricultural water resource carrying capacity (AWRCC). A method of water allocation based on the characteristics of water requirement of crops and livestock is put forward, which can not only avoid imbalanced water supply, but also reduce the dimensions of the model. Finally, our proposed method of optimal allocation of agricultural water resources is applied to the Yang River Basin. The evaluation results show that the AWRCC of the subareas fall between the saturated and the transition state during the years included in this study. The optimization results show that the monthly concentration of ammonia nitrogen and chemical oxygen demand can meet the requirement of water quality of less than 1 mg/L and 20 mg/L, respectively. Meanwhile, economic benefits are increased, and the AWRCC is improved. In conclusion, the proposed method and model can provide a valuable tool to evaluate and promote the coordination between the agricultural economy, water quality safety, and sustainable development of local agricultural water resources.