An optimal control analysis for baseflow externalities in an interconnected lake-aquifer system

Groundwater resources play a vital role in regional growth and development. From a sustainability viewpoint, it is, however, imperative to ensure that groundwater extractions do not lead to deleterious environmental consequences. The interconnections between groundwater in the aquifers and surface water bodies are increasingly being recognized in recent times and groundwater discharges to surface water bodies are critical to maintain water levels and water quality during summer months and periods of drought. Excessive groundwater withdrawals can cause water levels in streams and lakes to drop below unacceptable levels. This phenomenon is referred to as baseflow externality in this study. The primary goal of this investigation was to develop a mathematical model useful to assess policy options pertaining to groundwater withdrawals considering baseflow externalities. The model was used to evaluate five wide-ranging policy options that emphasize economic gains and ecological impacts to different levels. The weak sustainability policy option represents a reasonable compromise and identifies groundwater pumping that maximizes economic benefits while maintaining acceptable water levels in an interconnected lake. However, the implementation success of this approach hinges on achieving consensus among stakeholders and the ability to find reliable additional water supplies at the end of the planning period. The developed model can be a useful tool for facilitating stakeholder discussions that foster participatory groundwater management.