Effect of groundwater quality on sustainability of groundwater resource: A case study in the North China Plain

- We develop a reactive transport model for nitrogen species in the North China Plain.
- Groundwater overexploitation heightens nitrogen pollution in the cone of depression.
- We build a groundwater quality optimization model to improve sustainability in NCP.
- A parallel genetic algorithm can enhance efficiency of groundwater optimizations.
- Groundwater pumping strategy by optimization lightens nitrate contamination in NCP.

The North China Plain (NCP) is one of the most severe water shortage areas in China. Due to the scarcity of surface water in the NCP, groundwater system is seriously over-exploited and use of nitrogen fertilizers is greatly increasing year by year to improve soil fertility and crop production, causing a variety of environmental issues in the processes of abstracting groundwater. Considering that previous research was limited on approaches to assess sustainability of groundwater through flow modeling and water level decline, this study focuses on addressing the implications of groundwater contaminant for water resource sustainability in the central part of NCP. Based on the previously developed groundwater flow model, a reaction modular code for the reactive transport in three-dimensional aquifers (RT3D) is developed for simulating the reactive process of nitrogen species transport in groundwater system. The management optimization model coupled with the nitrogen reactive transport model under consideration of water quality constraints is then conducted to quantify and improve the sustainability of groundwater utilization in the study area. Thus, the optimal pumping well locations and pumping rates that lead to the maximum total yield or the minimum total management costs subjecting to a series of groundwater level constraints are obtained from the optimization models. Compared with the optimization model without water quality constraints, this study could provide a more useful tool for developing cost-effective strategies for sustainable management of groundwater resource in the NCP, and greatly improve groundwater management level and water quality.