Mississippi v. Tennessee


Can the state of Mississippi obtain damages or injunctive relief without an equitable apportionment of groundwater from the Middle Claiborne Aquifer, which Mississippi claims was stolen by the state of Tennessee through Tennessee’s pumping operations in Shelby County?

Oral argument: 
October 4, 2021
Court below: 
Original Jurisdiction

This case asks the Supreme Court to determine if groundwater should be classified as an interstate resource and fall within federal common law equitable apportionment jurisprudence. The Special Master determined that the Middle Claiborne Aquifer is an interstate resource and that the Supreme Court should allow Mississippi to amend its complaint to include an equitable apportionment claim. Mississippi disputes the Special Master’s conclusions and argues that groundwater naturally flows from its territorial boundaries. Mississippi asserts that Tennessee's underground pumping violates Mississippi’s territorial sovereignty by disrupting the groundwater’s natural flow within Mississippi’s borders. Tennessee argues that the Special Master is correct in identifying the aquifer as an interstate resource, but that the Supreme Court should not allow Mississippi to amend its complaint because any amendment would create additional costly and time-consuming litigation. The outcome of this case has serious implications for interstate water rights and the apportionment of belowground natural resources.

Questions as Framed for the Court by the Parties 

(1) Whether the Court will grant Mississippi leave to file an original action to seek relief from respondents’ use of a pumping operation to take approximately 252 billion gallons of high-quality groundwater; (2) whether Mississippi has sole sovereign authority over and control of groundwater naturally stored within its borders, including in sandstone within Mississippi’s borders; and (3) whether Mississippi is entitled to damages, injunctive, and other equitable relief for the Mississippi intrastate groundwater intentionally and forcibly taken by respondents.


The Middle Claiborne Aquifer is a “hydrogeological unit” that extends through Tennessee, Kentucky, Louisiana, Mississippi, and Alabama and consists of the “Sparta Sand” in the South and the “Memphis Sand” in the North. Report of the Special Master, Eugene E. Siler, Jr. at 15. Groundwater flows into the aquifer through a process called “recharging” and flows out through a process called “discharging.” Id. at 12. Since 1985, Memphis Light, Gas & Water Division (“MLGW”) has been pumping groundwater from the Middle Claiborne Aquifer in Shelby County, Tennessee. Brief of Mississippi, in Support of Mississippi’s Motion for Leave to File Bill of Complaint at 7, 10.

In 2005, Mississippi sued The City of Memphis (“Memphis”) and MLGW in the United States District Court for the Northern District of Mississippi. Id. at 3. Mississippi claimed that MLGW “forcibly siphoned” more than 252 billion gallons of its water from the Middle Claiborne Aquifer. Id. at 9. Mississippi thus contended that it was entitled to damages and injunctive relief Id. at 21, 25.

The District Court dismissed the case for “failure to join a necessary party” under Rule 19 of the Federal Rules of Civil Procedure, reasoning that because the dispute was over “interstate waters,” the proper remedy was “equitable apportionment.” Report of the Special Master, at 2–3. In the absence of a compact between states, the Court uses the federal common law doctrine of equitable apportionment to designate each state’s right to use the interstate body of water. Id. at 27. Because any equitable apportionment would determine Tennessee’s right to use the aquifer, Tennessee was a necessary party, thus making the case one between two states over which the Supreme Court has “original and exclusive jurisdiction.” Id. at 3. Mississippi appealed the dismissal, which was upheld by the Fifth Circuit in 2009. Id. The Supreme Court in 2010 denied Mississippi’s petition for certiorari and denied, without prejudice, its motion for leave to file a bill of complaint. Id. at 4.

In 2014, Mississippi again filed a motion for leave to file a bill of complaint. Id. at 1. Despite opposition from Tennessee, Memphis, and MLGW, the Supreme Court granted Mississippi’s motion and appointed a Special Master to preside over the initial proceedings. Id. at 4, 6. In his report, the Special Master agreed that equitable apportionment was the proper remedy in this case. Id. at 27. Given that Mississippi expressly disclaimed equitable apportionment as a remedy in its complaint, the Special Master recommended that the Supreme Court dismiss the complaint and allow Mississippi to file an amended complaint based on the theory of equitable apportionment. Id. at 6, 32.



Mississippi argues that the Special Master overlooked the crucial legal issue—state sovereignty over local groundwater—when he categorized this groundwater dispute as falling under the Supreme Court’s equitable apportionment jurisprudence. Brief for Petitioner on Exceptions to the Report of the Special Master, State of Mississippi (“Mississippi”), at 18. Mississippi disputes the Special Master’s classification of the aquifer as an interstate resource that Tennessee can access. Id. at 19. Mississippi asserts that the groundwater comes from the “soils of Mississippi” and, unlike an interstate river, is under Mississippi’s exclusive control. Id. at 18.

Mississippi emphasizes that the Supreme Court’s federal common law equitable apportionment jurisprudence should not apply to underground natural resources, like aquifers, because such resources would remain undisturbed within the state’s territorial boundaries if neighboring states did not interfere. Id. at 26. Finally, Mississippi highlights that the Supreme Court has never applied equitable apportionment beyond interstate disputes over aboveground bodies of water like streams and rivers. Id. at 28.

Tennessee argues that the Special Master correctly categorized the groundwater as an interstate resource. Reply of Respondent to Exceptions of Plaintiff to the Report of the Special Master, State of Tennessee (“Tennessee”) et al. at 23. Tennessee also contends that equitable apportionment is the correct remedy, and there is no persuasive reason for the Supreme Court to use a different analytical framework. Id. Tennessee highlights the real-world impracticability of distinguishing groundwater from surface water because water constantly flows above and below the soil surface. Id. at 24–25. Tennessee also emphasizes that dynamic groundwater flow patterns make it hard to determine when the groundwater crosses a state boundary. Id. Tennessee further points out that underground water pumps cause “cones of depression” in the soil, further frustrating any kind of determination of when the water crosses “political boundaries.” Id.

Tennessee argues that Mississippi’s state sovereignty approach would upend well-settled interstate water jurisprudence that protects states from being sued by neighboring states for lawfully using interstate water sources. Id. at 25–26. Finally, Tennessee contends that because the geology behind aquifer pumping makes “cones of depression” in the soil inevitable, Mississippi’s state sovereignty approach would prevent states from using resources close to their territorial borders because of the threat of a lawsuit from a neighboring state. Id.


Mississippi explains that it did not argue for equitable apportionment in its complaint as it claims that the Supreme Court should decide this case on state sovereignty grounds. Plaintiff’s Reply to the Defendants’ Exception to the Report of the Special Master Mississippi, at 4–5. Mississippi, however, maintains that if the Supreme Court rejects its sovereignty claim, then the Court providing the correct standard warrants allowing Mississippi to amend its complaint. Id. at 5. Mississippi contends that the Special Master’s recommendation to allow Mississippi to amend its complaint would not enlarge the scope of the litigation Id. at 4.

Mississippi also notes that Tennessee has regularly argued for equitable apportionment and therefore an amended complaint would not unreasonably expand the proceedings. Id. at 5–6. Mississippi stresses that Tennessee’s argument that Mississippi cannot meet the threshold injury standard for equitable apportionment is premature because Mississippi did not present an equitable apportionment remedy in the evidentiary hearing before the Special Master. Id. at 7. Mississippi argues that it would not be skirting procedural rules because any amended complaint would still be subject to federal pleading requirements. Id. at 8. Mississippi also points out that Tennessee would have the opportunity to argue against the potential equitable apportionment claim. Id. at 8. Finally, Mississippi argues that to deny it the chance to argue for equitable apportionment in the future would be inappropriate at this stage of the litigation. Id. at 9.

Tennessee argues that the Supreme Court should reject the Special Master’s recommendation to allow Mississippi the opportunity to amend its complaint and include an equitable apportionment claim. Exception in Part of Defendants Tennessee, Memphis & MLGW, Tennessee at 15. Tennessee also argues that this action hinged on Mississippi’s disavowal of any claim of equitable apportionment and that the amendment standard for federal pleadings prohibits states from asserting previously disavowed claims. Id. at 16–17. Tennessee further contends that Mississippi has never made the threshold injury showing required for equitable apportionment claims. Id. at 17. Tennessee notes that Mississippi’s main argument is that its exclusive rights to the groundwater free the state from having to meet the threshold injury requirement. Id. at 17-18.

Tennessee highlights that the aquifer at issue extends beneath parts of eight different states: (1) Missouri (2) Kentucky (3) Tennessee (4) Arkansas (5) Louisiana (6) Mississippi, (7) Alabama and (8) Illinois and stresses that these states would be interested in how the Supreme Court apportions the Middle Claiborne Aquifer. Id. at 3, 18. Tennessee warns that any amendment to Mississippi’s complaint would affect the legal interests of other states, thus possibly adding additional parties and complexities to the litigation. Id. at 19. Tennessee also emphasizes that allowing an amendment at this stage would prejudice Tennessee because the amended complaint would lead to more costly and time-consuming litigation and would give Mississippi an unfair opportunity to prolong this fifteen-year litigation. Id. Tennessee lastly labels Mississippi’s failure to include an equitable apportionment claim in its original pleading as a strategic move that allowed the state to pursue common law tort claims and seek a “financial windfall” of more than 615 million dollars in damages. Id. at 25.


Mississippi asserts that Tennessee’s preclusion argument is meritless. Sub-Reply of Petitioner in Support of its Exceptions to the Report of the Special Master, Mississippi at 17. Mississippi argues that neither the federal district court nor the Fifth Circuit had the jurisdiction to determine Mississippi’s rights in this litigation because Article III, Section II of the United States Constitution grants “original and exclusive jurisdiction” over interstate lawsuits to the Supreme Court. Id. at 18. Mississippi further argues that neither of the lower courts had the authority to determine that equitable apportionment was the only remedy available to Mississippi and contends the only issue within the lower courts’ power to decide was whether Tennessee was a “necessary and indispensable party” within the meaning of Rule 19 of the Federal Rules of Civil Procedure. Id. Mississippi highlights that the lower federal courts declined to make any rights determinations about the groundwater because the Supreme Court had not decided how the aquifer should be divided and stresses that the portion of the federal district court’s opinion about equitable apportionment is not binding because the court did not have the authority to decide the issue. Id.

Tennessee argues that Mississippi already fully and fairly litigated its main contention of its exclusive rights to the aquifer in the Fifth Circuit. Reply of Respondent to Exceptions of Plaintiff to the Report of the Special Master at 35. Tennessee contends that because Mississippi’s claims before the Supreme Court rely on the same property-rights theories Mississippi argued and lost in the Fifth Circuit, Mississippi’s claims are legally barred. Id. at 34–35. Tennessee also emphasizes that the Supreme Court’s original jurisdiction over this controversy does not negate the fact that Mississippi lost on its central issue in the Fifth Circuit. Id. at 36. Tennessee further argues that the Supreme Court would be properly exercising its original jurisdiction by applying issue preclusion because Mississippi should not be allowed to relitigate issues and that Mississippi’s bid to relitigate offends the core principles behind issue preclusion, including conserving judicial resources and encouraging parties to rely on judicial decisions. Id. at 37-38. Tennessee argues that it relied on the Fifth Circuit’s holding that Tennessee cannot be sued by Mississippi for pumping water from the aquifer unless the Supreme Court applied equitable apportionment and stresses that, in reliance on the Fifth Circuit’s holding, it continued to access the groundwater to meet crucial state water needs. Id.



Mississippi argues that an equitable apportionment of the water in its territory infringes on its sovereignty as a State. Brief of Mississippi, in Support of Exceptions to Report of the Special Master at 27. In support of its position, Mississippi points to the historical importance of states’ rights through United States history. Id. at 40. Mississippi further argues that it has a strong interest in sovereignty over its groundwater because, unlike the surface water in rivers and streams that flows between states, groundwater remains confined in the aquifer. Id. at 28, 30.

A group of law professors (“Law Professors”), in support of Tennessee, counter that groundwater should be treated differently than land because it is a “precious national resource” in high demand, especially given the state of climate change. Brief of Amici Curiae Law Professors, in Support of Defendants at 16. The Law Professors contend that by allowing Mississippi to assert “unilateral claims of ownership” of the water in the Aquifer, the Court would disincentivize future cooperation among States that have competing claims to water, increasing the competition for an already strained resource. Id. at 16, 18. In addition, the United States (“US”), in support of overruling Mississippi’s exceptions to the report of the Special Master, contends that equitable apportionment is the correct remedy to deal with control of interstate resources such as the Middle Claiborne Aquifer. Brief of Amicus Curiae the United States, in Support of Overruling Mississippi’s Exceptions to the Report of the Special Master at 19. The US asserts that equitable apportionment respects the “equal sovereignty of the States” by allowing a state the beneficial use of resources within its own borders without depriving another state of resources. Id. at 19–21.

The International Law Committee of the New York City Bar Association, (“ILCNYCBA”), in support of neither party, argues that the court should treat the states as sovereign entities and thus should draw on International Law – which when dealing with “transboundary water” calls for “equitable and reasonable” utilization – to settle the dispute. Brief of Amicus Curiae ILCNYCBA, in Support of Neither Party at 17–18.


Mississippi maintains that the “equal footing doctrine” provides support for its theory of territorial sovereignty. Brief of Mississippi, in Support of Mississippi’s Motion for Leave to File Bill of Complaint at 17. Mississippi argues that as a condition of its admission to the Union in 1817, it was given sovereignty over the “land within its borders, including the beds of streams and other waters.” Id. at 3, 17. Thus, Mississippi contends that it should be entitled to the entirety of the groundwater beneath its state borders. Id. at 19.

The States of Colorado, Idaho, Nebraska, North Carolina, North Dakota, Oregon, South Dakota, and Wyoming (“Colorado, et al.”), in support of Tennessee, counsel against allowing claims for damages or injunction without an equitable apportionment, because it could topple economies that are built on the predictability of municipal water administration. Brief of Amici Curiae Colorado et al., in Support of Tennessee at 11–12. Similarly, Law Professors, in support of Tennessee, argue that the “public nuisance” doctrine, which involves balancing shared interests and harms, is more appropriate in the present case than the equitable apportionment doctrine, which assumes that “the entire resource is available for division and allocation.” Brief of Amici Curiae Law Professors at 19.


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