Mississippi v. Tennessee

Aquifers are subject to remedy from the courts under equitable apportionment.

Mississippi brought suit against Tennessee for tortious taking of groundwater from an aquifer which lies under both states. A Special Master was appointed who recommended the Court dismiss the complaint but grant Mississippi leave to amend; Mississippi challenged the recommendation to dismiss, and Tennessee objected to the recommendation to grant Mississippi leave to amend. Equitable apportionment is a doctrine meant to produce fair allocation of a water source shared between states. The Court ruled in this case that the doctrine applies to interstate aquifers as well because aquifers have a “multistate character” and actions of one state will affect other states which rely on the water. Because the aquifer is an interstate water source, equitable apportionment “stands alone as the federal common law principle for disputes over interstate water.” The waters of the aquifer are subject to remedy under equitable apportionment, Mississippi’s complaint is DISMISSED without leave to amend.