Coastal Groundwater Management: Seawater Intrusion Prevention, Artificial Recharge, and Climate Adaptation

Problem definition : Most of the world’s population relies on coastal aquifers for freshwater supplies. Groundwater is experiencing substantial overdrafts and facing ever-mounting freshwater demand. Existing groundwater management strategies are myopic and fail to coordinate production and the operation of protection approaches, including seawater intrusion barriers (SWIBs) and managed aquifer recharge (MAR). Motivated by the urgency of sustainable groundwater management, we investigate how to optimize the joint operations of groundwater production, protection (by injecting fresh water through SWIBs), and replenishment (via MAR). Methodology/results : We model a central planner’s decision on groundwater production, freshwater injection quantities, and artificial replenishment using stochastic dynamic models and identify that the optimal groundwater management policies follow a threshold-type structure. We find that SWIBs and MAR are strategic complements, except in cases with very high groundwater levels, when they turn into strategic substitutes. When the penalty for low groundwater levels decreases, the planner should use SWIBs more aggressively if groundwater levels are low and more conservatively if they are high. A similar pattern holds when natural recharge becomes more abundant, assuming that the natural recharge quantity has no impact on the purchasing cost of imported water. Moreover, we calibrate our model using real data sets in Orange County, California and find that the joint operations of SWIBs and MAR expand groundwater operational flexibility. In contrast, employing SWIBs alone comes at the expense of a lower groundwater level. Managerial implications : Our analysis offers strategic guidance on when to use SWIBs and MAR as complements or substitutes based on groundwater levels. It highlights the value of their joint operation in stabilizing groundwater, especially amid worsening droughts.