Mississippi v. Tennessee: States fight over rights to groundwater

Millions rely on interstate groundwater for municipal, agricultural, or industrial uses.  The Supreme Court has never determined how to allot it.

On October 4, 2021, the U.S. Supreme Court heard oral arguments in Mississippi v. Tennessee, S. Ct. Orig. No. 143, an interstate fight over the groundwater in the Sparta-Memphis Aquifer.  That aquifer underlies Mississippi, Tennessee, and five other states.  It is the primary source of municipal water for the City of Memphis.  Over the years, Memphis has withdrawn about 187 million gallons of water from the aquifer daily to supply its 250,000 residents.

Mississippi filed suit in 2007, alleging that those withdrawals amounted to a theft of its water.  As relief, Mississippi sought $615 million of damages, as well as injunctive relief and a declaration “establishing Mississippi’s sovereign right, title, and exclusive interest in the groundwater” underlying its land.  The district court dismissed Mississippi’s 2007 suit, the appeals court affirmed, and the Supreme Court denied review. 

Then, after several years of unsuccessful negotiation between the parties, Mississippi filed the present action seeking essentially the same relief as it had in 2007.  This time, it filed directly to the Supreme Court, invoking the court’s original jurisdiction over disputes between states.  See U.S. Const. art. III, § 2.  In 2015, the court accepted review and appointed a special master to oversee initial fact finding in the case.

Like the district court, the special master recommended dismissal because Mississippi had alleged the wrong cause of action.  He found that the Sparta-Memphis Aquifer is an interstate resource subject to equitable apportionment, the doctrine that the Supreme Court has traditionally applied to resolve disputes over interstate waterbodies.  See e.g. State of Kansas v. State of Colorado, 206 U.S. 46 (1907).  Equitable apportionment divides shares of the waterbody between states according to principles of fairness.  In interstate-water disputes that lack a governing compact, equitable apportionment is the exclusive remedy.  But the Supreme Court has never determined if equitable apportionment is also the exclusive remedy in such interstate disputes over groundwater. 

We predict that the Court will adopt the special master’s recommendation and hold that equitable apportionment is also the exclusive remedy for such interstate-groundwater disputes.  At oral arguments, the justices were skeptical of Mississippi’s claim, pressing its attorney on the implications of his argument.  If the Court accepts Mississippi’s argument, that could encourage similar lawsuits across the country between neighboring states who allege thefts of the groundwater underlying their land.  That could also threaten water users’ entitlements to withdraw groundwater if their groundwater migrated from beneath another state’s land.

The Court will likely issue an opinion within the next months.  We will continue to monitor this case closely and provide updates.  Please contact us with your questions regarding groundwater.