This Note demonstrates that the Court’s surface water equitable apportionment doctrine, which primarily protects established uses, is insufficient to protect interstate groundwater resources. Protecting established uses of an overused aquifer ensures further depletion. Instead of relying on its surface water doctrine, the Court should create a new equitable apportionment doctrine for groundwater that uses proportional sustainable yield as its guiding beacon. Proportional sustainable yield allows each state to use the amount of groundwater that it contributes to the aquifer each year.
In addition, Congress and federal agencies should step in to incentivize interstate groundwater compacts by offering to fund groundwater-related projects, but only after the relevant states successfully negotiate a sustainable groundwater compact. Since the problem of aquifer depletion becomes more insidious with each passing year, prompt action must be taken to bring groundwater use into balance with the rate of aquifer recharge.