Confirming expectations, the Supreme Court on Monday unanimously denied Mississippi’s claim that Tennessee is stealing its groundwater. If Mississippi wants to pursue its groundwater battle with Tennessee, it will have to file a new complaint with the court asking for an equitable apportionment of the Middle Claiborne Aquifer, which lies beneath Mississippi, Tennessee, and other states.
Defying everyone else’s agreement that equitable apportionment was its only cause of action, Mississippi argued before the Supreme Court that Tennessee had invaded Mississippi’s sovereign territory by allowing the Memphis Light, Gas and Water Division to pump so much water from the aquifer that it created a cone of depression that extended across the state line and caused groundwater that naturally would have remained under Mississippi to flow into Tennessee. For this state-level version of a trespass, Mississippi sought over $600 million in damages.
During oral argument, some of the justices expressed discomfort with the potential breadth of the equitable apportionment doctrine if they applied it to groundwater, envisioning a proverbial flood of interstate original-jurisdiction litigation about aquifers. Nevertheless, they determined that their longstanding remedy for natural resource disputes among states was Mississippi’s only option. Equitable-apportionment law seeks to balance the states’ sovereign interests in water by delineating how exactly the two states will share an interstate waterway.
“[W]e hold that the waters of the Middle Claiborne Aquifer are subject to the judicial remedy of equitable apportionment,” Chief Justice John Roberts wrote in the unanimous opinion in Mississippi v. Tennessee.
Whether Mississippi will actually be entitled to equitable apportionment, however, is highly debatable. As the court confirmed last year in Florida v. Georgia, the complaining state has a heavy burden of demonstrating that the other state’s water use is causing the complaining state significant injury. Facts as developed so far indicate that Mississippi will be unable to meet that burden.