May 05, 2021

Special Master’s report sets stage for Supreme Court to rule in longstanding dispute between states over groundwater in aquifer

Wilson Buntin and Sohnia Hong

Water is a precious resource and, with any precious resource, disputes are bound to arise. The U.S. Supreme Court has settled disputes in the past between states over the allocation of rights to surface waters. Never, until now, in the case of State of Mississippi v. State of Tennessee, City of Memphis, Tennessee, and Memphis Light, Gas, & Water Division, No. 143 Original, has the Court been confronted squarely with a dispute between states over rights to groundwater contained in an aquifer.

The prior litigation

In 2005, the State of Mississippi filed suit against the City of Memphis and its utility Memphis Light, Gas and Water (MLGW) alleging that MLGW’s pumping of water from wells in Tennessee near the border with Mississippi had resulted in the unlawful taking of groundwater from Mississippi. Tennessee was not named as a party. This case percolated through the courts and wound up in the U.S. Court of Appeals for the Fifth Circuit. See Hood ex rel. Mississippi v. City of Memphis, Tenn., 570 F.3d 625 (5th Cir. 2009), cert. denied 559 U.S. 904 (2010). The Fifth Circuit affirmed the district court’s finding that the aquifer in dispute was an interstate body of water and must be allocated before one state may sue an entity for invading its share. See id. at 630. The court held that “[a]llocation of an interstate water source is accomplished through a compact approved by Congress or an equitable apportionment.” Id. (citation omitted). Because Tennessee’s presence in the lawsuit was deemed necessary, the court ruled that joinder of Tennessee in the matter would remove the district court’s subject matter jurisdiction because such a dispute between states was in the Supreme Court’s original jurisdiction. See id. at 632. In 2010, the Supreme Court denied Mississippi’s petition for writ of certiorari in this case and denied without prejudice a motion filed by Mississippi seeking permission to file a bill of complaint against Tennessee, the City of Memphis, and MLGW.

The present case

The present litigation began in 2014 when Mississippi sought leave from the Supreme Court to file a bill of complaint against the City of Memphis, MLGW, and the State of Tennessee (collectively Tennessee Defendants). Mississippi’s complaint was based on various tort-law theories and alleged that the City of Memphis was unlawfully taking groundwater that Mississippi owned through MLGW’s pumping operations located near the border with Mississippi and that this activity was sanctioned by the State of Tennessee. Mississippi asserted that it was not seeking an equitable apportionment of the aquifer. Mississippi sought injunctive relief as well as hundreds of millions of dollars of damages for past unlawful withdrawals of groundwater. The Tennessee Defendants opposed the motion for leave to file a bill of complaint.

In 2015, the Supreme Court granted Mississippi’s motion, Mississippi v. Tennessee., No. 143, Original, *1, 2015 WL 2473469 (June 27, 2015), and appointed Special Master Eugene E. Siler, Jr., a Senior Judge on the U.S. Court of Appeals for the Sixth Circuit, to preside over the case. The Special Master determined that there needed to be an evidentiary hearing to answer the factual question of whether the aquifer in dispute is an interstate resource. In May 2019, the parties presented the testimony of five experts in the field of hydrogeology. The parties presented closing arguments in February 2020.

The Special Master’s report

On November 5, 2020, the Special Master issued his report to the Supreme Court. The Special Master recommended the dismissal of Mississippi’s Bill of Complaint with leave to file an amended complaint based on equitable apportionment. Report of Special Master (Rep.) at 32. Equitable apportionment is the federal common law doctrine that the Supreme Court has relied upon in the past to adjudicate disputes between states over interstate surface water resources. The Supreme Court has never applied this doctrine in a case involving only groundwater.

The Special Master concluded that the aquifer in dispute was an interstate resource for four key reasons. First, the Special Master concluded that the scope of the aquifer in dispute was the large, regional aquifer underlying several states referred to by the U.S. Geological Service as the Middle Claiborne Aquifer and not smaller subunits of the aquifer as Mississippi had argued. Rep. at 15–21. Second, the Special Master reasoned that the undisputed fact that pumping in Tennessee affects groundwater flow in the aquifer in Mississippi proved that the aquifer was an “interconnected hydrogeological unit” that crosses the Mississippi-Tennessee border. Rep. at 21. Third, the Special Master found that the evidence of interstate flow of groundwater under pre-pumping natural conditions between Mississippi and Tennessee showed the aquifer to be an “interconnected hydrogeological unit.” Rep. at 24–25. Fourth, the Special Master found that there was evidence in the record that the aquifer connects with an interstate surface water, the Wolf River, and therefore should be considered an interstate resource. Rep. at 25.

The Special Master rejected Mississippi’s argument that equitable apportionment should not apply in this case and that the Supreme Court should instead fashion a new rule for groundwater. Rep. at 27. The Special Master found that the difference between groundwater and surface water not “legally meaningful.” Rep. at 27–28. The Special Master stated that there was a “clear line” of Supreme Court precedent, holding that equitable apportionment applies when a state reaches into the territory of another state through “agency of natural laws.” Rep. at 28 (citations omitted). The Special Master found that the Tennessee Defendants’ pumping was affecting the flow of groundwater in Mississippi. Rep. at 28. For these reasons, the Special Master concluded that “equitable apportionment applies to aquifers.” Id. Finally, the Special Master rejected other arguments advanced by Mississippi based on state sovereignty and state tort law claims finding them fully displaced by the federal law of equitable apportionment. Rep. at 28–31.

Next steps

On December 7, 2020, the Supreme Court received the Special Master’s report and ordered it filed with the Clerk’s Office of the Supreme Court. The parties have an opportunity to file exceptions to the report before the Supreme Court considers the matter. The briefing schedule is as follows: exceptions were due February 22, 2021; replies were due April 23, 2021; and sur-replies are due June 7, 2021. It is expected the briefs will be distributed for discussion on June 24, 2021, at the Supreme Court’s final conference of this term. The parties anticipate that oral argument will be scheduled for this fall after the Court’s 2021 Term begins in October.


Wilson Buntin and Sohnia Hong


Wilson Buntin and Sohnia Hong are senior assistant attorneys general in the Tennessee Attorney General’s Office. This article reflects the opinions of the authors and not necessarily those of the Tennessee Attorney General’s Office.