Peak Groundwater: Aquifer‐Scale Limits to Groundwater Withdrawals

Abstract “ Peak Groundwater ” is the maximum withdrawal rate of groundwater from an aquifer system that precedes a decline in withdrawals resulting from aquifer depletion. This paper traces generalizable phases in groundwater‐withdrawal regimes in individual aquifer systems and their associated impacts on eco‐ and geosystem services. The concept seeks to address common misunderstandings of fundamental concepts in hydrogeology, which have practical consequences for the management of groundwater systems that sustain these services. The Peak Groundwater concept highlights the critical need to acknowledge the nested character of transient groundwater flow systems and the effects of groundwater withdrawals beyond the aquifer boundary. Importantly, estimations of sustainable groundwater withdrawals need to consider indirect human‐environmental risks of withdrawals, such as surface water depletion and land subsidence. Estimating acceptable steady‐state limits for future groundwater withdrawals presents an “optimization challenge.” Solving this optimization challenge, estimating sustainable withdrawals for balanced groundwater budgets, is rooted in societal priorities and demands high‐quality simulation models and monitoring tools and practices such as 4D monitoring systems that are complementary in type and scale. Recognition and prediction of Peak Groundwater can guide groundwater managers on how to operate within sustainable limits of abstraction. Proactive adaptive groundwater management can prevent Peak Groundwater and associated decline in withdrawal capacities.