The depletion of groundwater resources is a widespread phenomenon that can jeopardize both water and food security by making groundwater less accessible, degrading water quality, reducing surface water flow, and compromising the buffering capacity provided by groundwater reserves (Aeschbach-Hertig & Gleeson, 2012). There is abundant documentation of the severity and extent of groundwater depletion, especially in intensively cultivated areas (Bierkens & Wada, 2019;Gleeson et al., 2012). However, undesirable depletion occurs despite knowledge of the problem among water users and despite evidence that effective management and cooperation can reduce the adverse effects of exploitation (Madani & Dinar, 2012b;Ostrom, 1990).Here we address some basic questions about the physical and economic aspects of long-term groundwater depletion. What controls pumping decisions in an unconfined aquifer with multiple wells operated by different users? Can cooperation among the aquifer users increase the benefits and reduce the adverse impacts of pumping? What are the revenue and environmental implications of well yield limitations and regulatory constraints? How are the effects of pumping distributed between storage depletion and reductions in aquifer outflow? These research questions address groundwater depletion issues that are long-standing but have largely remained unresolved, at least in any quantitative sense. Quantitative answers to these questions can provide useful insight about how depletion occurs and how it might be reduced.In order to address our research questions, we need to consider the economically driven pumping decisions made by the agents who use the aquifer (e.g., farmers or irrigation districts) as well as physical processes and policies that may constrain these decisions. One way to include decision-making is to treat pumping rates as time-dependent variables (rather than inputs) that agents continually adjust to maximize particular objectives. This perspective naturally leads to an optimal control formulation of the decision problem. Solutions to this problem describe the pumping and storage histories that can be expected for particular aquifers and management strategies. The optimization process is constrained by physical groundwater flow constraints and by well yield and regulatory constraints that may limit pumping.The constraints required in this decision-driven approach to depletion analysis need to consider local conditions at the well scale, which guide pumping decisions, as well as conditions at larger aquifer scales where the economic and environmental impacts of agent decisions are felt. Consequently, the relevant spatial scales for our