Exploring the synthetic optimal policies for solving problems of agricultural water use with a dynamic optimization simulation model.

Agriculture, a strategic industry that secures the country and stabilizes society, has invariably been valued by China to feed its 1.4 billion people. However, the long-term extensive development of agriculture has led to a series of water problems such as groundwater overexploitation, water shortages, and water pollution in some areas of China, resulting in great pressure on the ecological environment and social economy. In this paper, we constructed a dynamic optimization simulation model based on the input–output (I–O) approach within the horizon of 2012–2025 to explore the synthetic optimal policies for achieving both socioeconomic development, and water resources and water environment protection in a node city on the middle route of the South-to-North Water Transfer Project, Handan. Six scenarios based on various synthetic policies were adopted. The simulation results show that during the simulation period, the maximum development of the social economy can be achieved under the premise of achieving the specific objectives of water resources and water environment protection in a comprehensive scenario. In addition, the water environment improved: the annual chemical oxygen demand (COD) emissions reduced by 7.5%, 10.3%, 5.0%, and 5.9% in pig farming, cattle farming, chicken farming, and households, respectively. Furthermore, the water supply–demand structure was optimized. The water demand of wheat planting and groundwater extraction decreased at an annual rate of 9.1% and 7.7%, respectively. The supply of reclaimed water increased at an annual rate of 9.2%. The model adapted in the paper can simulate and evaluate the impact of all the feasible synthetic policies on the economy, water resources, and water environment, and provide targeted, scientific recommendations for solving the agricultural water use problems in other regions. [ABSTRACT FROM AUTHOR]