Mississippi College

Law Review

Mississippi v. Tennessee: The Fight for Sovereign Groundwater

By: Cindy Denley

Water is the driving force behind all life, including lawsuits.  For example, in June 2014, Mississippi filed an original action in the United States Supreme Court against Tennessee, the City of Memphis, and Memphis Light, Gas & Water for allegedly stealing groundwater underneath Mississippi for its municipal supply.  Although the water is in Mississippi, it connects to a much larger aquifer system spanning at least eight states.

Mississippi’s claims seem easy enough – they claim that Tennessee has stolen and continues to steal its water.  Typically, a state resolves surface-water issues in one of two ways.  First, the injured state could request equitable apportionment of the resource from the Supreme Court.  This doctrine, developed to apportion surface-level streams, recognizes that neighboring states have real and substantial interests in interstate waters.  Notably, this Court has extended this doctrine to apply to other shared natural resources like fish.  A state will seek reconciliation and apportionment from the Court when affected by another state’s use but must demonstrate that the actions harm them by clear and convincing evidence. 

Second, a state can enter a congressionally approved interstate compact that allocates water rights.  However, Mississippi sought to distinguish its stolen groundwater from standard surface-water remedies and advanced a territorial property rights theory.

Instead of relying on the equitable apportionment doctrine or an interstate compact, Mississippi claimed it owned all the groundwater that would have remained under Mississippi.  Accordingly, they sought an injunction, monetary damages, and a declaratory judgment “establishing Mississippi’s sovereign right, title and exclusive interest in the groundwater stored naturally in the Sparta Sand formation,” or restitution based on claims of trespass, conversion, and tortious interference with protected interests in personal property.

Interstate Groundwater?

Mississippi v. Tennessee hinges on whether the groundwater is an interstate resource that falls within the federal common law equitable apportionment jurisprudence normally applicable to surface water.  Mississippi acknowledged that the aquifer extends across multiple states but claimed that because Tennessee could only access the groundwater by pumping it out of Mississippi, they have “sole authority” over the water located within its borders.  As a result, the groundwater “is neither interstate water nor a naturally shared resource,” and equitable apportionment cannot apply.

The Supreme Court appointed a Special Master to oversee the case, and he recommended the Supreme Court deem the groundwater an interstate resource after a lengthy evidentiary hearing. He found that the aquifer is a “continuous, interconnected hydrogeological unit beneath several states.”  Furthermore, the groundwater flows across the border and is connected to interstate surface water.  Because the water is an interstate resource, the Special Master rejected Mississippi’s “sole authority” argument stressing that the Court has never allowed one state’s sovereignty to incorporate an entire interstate resource.  Therefore, the Special Master recommended that the Supreme Court dismiss Mississippi’s complaint with leave to amend because the complaint failed to request the proper relief – an apportionment of the aquifer among the overlying states.

Oral Arguments

Unhappy with the Special Master’s decision, Mississippi and Tennessee both requested exceptions, and oral arguments took place before the Supreme Court on October 4, 2021.  Arguing for Mississippi, Mississippi Deputy Solicitor General emphasized the extraterritorial effect of Tennessee’s pumping and the invasion of their sovereign territory.  Additionally, Mississippi argued that the equitable apportionment doctrine was inappropriate and urged the Court to apply the principle only when the groundwater connects to disputed surface water.

Tennessee argued that because Mississippi was not injured, the Court should dismiss the case. Lastly, on behalf of the United States, the assistant to the U.S. solicitor general argued that equitable apportionment should be extended to interstate groundwater just as it applies to interstate surface water.

The Supreme Court challenged Mississippi’s novel claim that it holds sole authority over the water in the aquifer during oral arguments. The justices appeared eager to analogize the groundwater-sharing question to surface water management. However, some justices showed concern regarding the potential breadth of the equitable apportionment doctrine, specifically focusing on how the Supreme Court may have an increasing role in interstate disputes over natural resources. The Supreme Court’s line of questioning signifies a simple dismissal. Still, if the justices decide to participate in the state sovereignty issues and their concerns about the scope of equitable apportionment, the decision will change how states manage disputes over interstate natural resources.


The outcome of this case is significant as most states have underground, yet connecting, aquifers.  If the United States Supreme Court finds that a body of groundwater found in Mississippi is an interstate resource, it will set a precedent that will require states to either seek apportionment of groundwater or negotiate their rights through interstate compacts when conflicts occur. Apportioning groundwater will likely be difficult due to the nature of the resource, making it difficult to prioritize uses, likely negatively impacting water sources for urban and industrial areas.  However, if the Supreme Court sides with Mississippi, the ruling could redefine how the law views groundwater resources between multiple states.