Multi-objective optimization of the coastal groundwater abstraction for striking the balance among conflicts of resource-environment-economy in Longkou City, China.

Rational coastal groundwater planning is of great significance to freshwater supply for sustainable social-economic development, and to environmental protection in case of seawater intrusion (SI). Quantifying the relation among groundwater quality, quantity, and the related social-economic benefits in a coastal region with intense spatio-temporal variation in groundwater abstraction is helpful to the restoration of the coastal aquifer, and the practical policymaking. However, due to the comprehensive reality involving interdisciplinary principles, it is usually difficult to integrate all the main attributes of groundwater resources into a mono-policymaking process, which might lead to biased decisions, producing a series of adverse impacts on the environment and the social economy. This study thereby develops a combined simulation-optimization model (S-O model) in the coastal part of Longkou City, China, for striking the balance among the three main attributes of groundwater, i.e., the groundwater quantity, groundwater quality or its environmental function, and its related economic yield involving the agricultural and industrial sectors. It is seen that the industrial sector contributed over 80% of the economic yield by consuming over 10% of the total groundwater resource, and the massive agricultural use of groundwater was mainly responsible for the SI. The results of the multi-objective optimization provided practical alternative schemes for groundwater abstraction in terms of maximizing economic yield and minimizing SI. Moreover, the decision discrepancy caused by partial management only considering the groundwater quantity and quality would lower the water use efficiency, and then cause unacceptable economic losses for the enterprises and the government. Our research highlights that the interdisciplinary management of groundwater resources based on the S-O model could significantly improve practicability in groundwater policymaking, and provides a typical reference for the other developing regions facing difficulty in groundwater management during coastal urban planning and economic transformation.