The U.S. Supreme Court found that Tennessee didn’t steal groundwater from Mississippi, in a dispute with wide-ranging implications for how states manage natural resources.
The justices in Mississippi v. Tennessee said in a unanimous decision that interstate groundwater is covered by equitable apportionment, which is the standard process by which water resources are shared.
It’s the high court’s first use of the equitable apportionment doctrine related to interstate groundwater.
Mississippi accused a Memphis utility of improperly pumping water out of an interstate aquifer spanning the region, claiming it wasn’t a “shared resource.” The dispute centered on whether the utility interfered with Mississippi’s authority over its land and waters.
Mississippi filed an original jurisdiction case—which goes straight to the high court— asking the justices to make Tennessee pay damages. A court-appointed special master in 2020 encouraged the high court to toss the case and give Mississippi a chance to rework its challenge into a request for equitable apportionment.
But Mississippi filed exceptions to the special master’s report, arguing that it ignored constitutional principles of state sovereignty and misinterpreted legal precedent. The state claimed equitable apportionment is appropriate only in cases dealing with interstate rivers and streams, not groundwater pumping.
The justices in October seemed skeptical that water underlying both states isn’t a shared resource over which disputes couldn’t be resolved using equitable apportionment.
The case is Mississippi v. Tennessee, U.S., No. 22O143, 11/22/21.
—With assistance from Ellen M. Gilmer.