Dynamic simulation for comprehensive water resources policies to improve water-use efficiency in coastal city.

Coastal cities play an important role in regional economic development and sustainable development strategies of water resources and their ecological environment. As a typical coastal city in Hebei Province, Qinhuangdao city is facing severe problems, such as water shortages and water environment deterioration, while social and economic development continues. Based on input-output analysis, we established a dynamic optimization model among Qinhuangdao city's socioeconomic development, water resources and water environment. The 2013-2030 simulation after introducing comprehensive water resources policies of regional development, examines the regional socioeconomic development, optimizes the water resources supply structure and improves the water environment under the optimal scenario, and evaluates policy feasibility through cost-benefit analysis (CBA). The simulation results suggest that under the optimal scenario, the water-use efficiency (WE) of Qinhuangdao is improved by 59.14% and the proportion of reclaimed water and desalinated seawater in the water supply structure is increased by 13.70%. In addition, it has achieved an average annual gross regional production (GRP) growth rate of 6.36% and an average annual chemical oxygen demand (COD) emission rate of 17.95%. Moreover, the net present value (NPV) of the projects under the optimal scenario is 1.534 billion Chinese yuan (CNY), which means that the policy is economically feasible. Our research is helpful to improve the WE, optimize the water supply structure and protect the hydrogeological environment in coastal cities with water shortages and can provide a reference for Qinhuangdao city and other similar coastal cities to realize the rational utilization of water resources and regional sustainable development.