Mississippi initiated an original action against Tennessee concerning the City of Memphis's groundwater pumping from the Middle Claiborne Aquifer, claiming it unlawfully siphons water from Mississippi and constitutes a tortious taking. Mississippi explicitly rejected the notion of seeking an equitable apportionment remedy, asserting that the principle of equal rights to shared water resources does not apply to this case. The appointed Special Master found that the aquifer is an interstate resource and that equitable apportionment is the sole judicial remedy available. Consequently, the Special Master recommended dismissing Mississippi's complaint but allowing an amendment. Mississippi contested the dismissal recommendation, while Tennessee opposed granting leave to amend.
The Supreme Court held that the Middle Claiborne Aquifer's waters are subject to equitable apportionment, dismissing Mississippi's complaint without leave to amend. The Court reaffirmed that equitable apportionment seeks a fair distribution of shared water resources among States, applicable to interstate rivers, streams, and groundwater affecting surface water flow. Although the Court had not previously ruled on equitable apportionment for aquifers, it found the circumstances of the Middle Claiborne Aquifer sufficiently analogous to warrant the same treatment. The Court noted that the aquifer's multistate nature and the natural flow of water between States justified the application of equitable apportionment, dismissing Mississippi's argument regarding the flow rate of the aquifer.
Tennessee's groundwater pumping has created a cone of depression affecting the aquifer beneath northern Mississippi, leading to reduced groundwater storage and pressure in that area. The Court affirms that equitable apportionment applies to the Middle Claiborne Aquifer, rejecting Mississippi's claim of exclusive sovereign ownership over the water. The Court emphasizes that no state can control interstate waters solely within its borders, as established in prior cases. The decision clarifies that while the origin of a water resource may inform equitable apportionment, it does not exempt the resource from this doctrine. The Court dismisses Mississippi's exceptions and the bill of complaint, noting that Mississippi has not sought to amend its complaint to include equitable apportionment. Tennessee's objections to granting leave for such an amendment are upheld. The case is dismissed, with the opinion delivered by Chief Justice Roberts for a unanimous Court.
Mississippi has initiated a legal case against Tennessee, claiming that Tennessee's groundwater extraction from the Middle Claiborne Aquifer has resulted in the loss of hundreds of billions of gallons of water that originally lay beneath Mississippi. The state is seeking at least $615 million in damages, alongside declaratory and injunctive relief. The Court permitted Mississippi to file its complaint and appointed a Special Master to oversee the proceedings. The Special Master has recommended dismissing Mississippi's complaint with leave to amend, to which both states have filed exceptions.
The Middle Claiborne Aquifer spans multiple states, including Mississippi and Tennessee, and supports significant groundwater extraction activities. The Memphis Light, Gas and Water Division (MLGW) pumps approximately 120 million gallons daily from the aquifer using over 160 wells, contributing to a regional cone of depression that affects both Memphis and nearby DeSoto County, Mississippi. Mississippi alleges that MLGW's pumping has significantly altered the natural groundwater flow, hastening the transfer of water from beneath Mississippi to Tennessee, a process that naturally occurs at a much slower rate of 30 to 60 feet per year. Mississippi acknowledges that some groundwater naturally migrates across the state line but contends that the extent of MLGW's pumping has accelerated this flow, enabling Memphis to extract water that could have remained under Mississippi for thousands of years. Prior to the current litigation, Mississippi had previously sued Memphis and MLGW in 2005, alleging wrongful appropriation of groundwater.
The District Court dismissed Mississippi's suit against Tennessee for failing to join Tennessee as an indispensable party, a decision affirmed by the Fifth Circuit. Both courts centered their rulings on the doctrine of equitable apportionment, which governs rights to disputed interstate water resources. Traditionally, this doctrine applies to interstate water disputes unless overridden by statutory provisions or prior agreements. The Fifth Circuit recognized interstate aquifers as subject to equitable apportionment, equating them to interstate rivers and dismissing the significance of their underground location. Consequently, the courts agreed that Tennessee’s inclusion was necessary for the adjudication of Mississippi’s claims regarding the aquifer's rights.
Mississippi attempted to pursue a writ of certiorari and sought to file a bill of complaint against Tennessee and others, claiming over $1 billion for the alleged taking of its water, as well as equitable apportionment. The Supreme Court denied both requests. In 2014, Mississippi renewed its attempt to file a complaint, alleging that Memphis Light, Gas and Water (MLGW) improperly extracted groundwater from Mississippi, resulting in significant drawdown effects in the state. Mississippi asserts a claim of absolute ownership over the groundwater beneath its surface, arguing that Tennessee’s actions constitute a tortious taking. The state seeks at least $615 million in damages and explicitly disclaims the applicability of equitable apportionment, contesting the notion of equal rights to the resource in this case. The Supreme Court granted leave for Mississippi to file its complaint and appointed Judge Eugene E. Siler, Jr. as Special Master to oversee the matter.
After extensive motions, discovery, and hearings, the Special Master recommended dismissing Mississippi's complaint regarding the Middle Claiborne Aquifer but allowed leave to amend. He identified the aquifer as an interstate water resource, affirming that Tennessee’s pumping impacts Mississippi’s groundwater and that prior to this, there was a natural flow between the two states, which Mississippi concedes. The Special Master concluded that equitable apportionment is the suitable remedy, as it is the established federal common-law principle for interstate water disputes. Since Mississippi's complaint did not request equitable apportionment, the Special Master suggested dismissal but offered the option for Mississippi to file an amended complaint, which has not yet occurred.
Both states filed exceptions to the report, with Mississippi contesting the dismissal and arguing against the Special Master’s equitable apportionment finding, while Tennessee objected solely to the recommendation for leave to amend. An independent review of the record led to the dismissal of Mississippi’s complaint without granting leave to amend.
Equitable apportionment aims for fair distribution of shared water resources among states, asserting equal rights for reasonable usage. Historically, the doctrine has been applied to rivers, streams, and even fish migration but has not been previously addressed regarding interstate aquifers. The court recognized the need to analyze whether applying equitable apportionment to the aquifer is sufficiently similar to past applications. Ultimately, it found that the Middle Claiborne Aquifer qualifies for such treatment due to its multistate nature.
Mississippi acknowledges that the groundwater in question is located in a geologic formation that spans two states. Central to Mississippi's lawsuit is the claim that Tennessee is extracting water that originated in Mississippi. Evidence indicates that both Memphis and northwest Mississippi draw from the same aquifer, the Middle Claiborne Aquifer, which is recognized as a single hydrogeological unit that allows for natural water flow between states. Mississippi argues that the aquifer's slow natural flow distinguishes it from interstate rivers and streams; however, the volume of water flowing—over 35 million gallons a day—supports the application of equitable apportionment principles, even if the flow rate is minimal.
Tennessee’s water extraction has created a cone of depression affecting groundwater levels in northern Mississippi, which Mississippi claims has diminished its groundwater resources. Such interstate impacts are consistent with past equitable apportionment cases. The court holds that the waters of the Middle Claiborne Aquifer are indeed subject to equitable apportionment.
Mississippi further claims sovereign ownership over the groundwater beneath its surface, suggesting that equitable apportionment should not apply. However, the court clarifies that while states have jurisdiction over lands and waters within their borders, this does not equate to exclusive ownership of interstate waters. The principle established in prior cases is that shared water resources require mutual respect among states, preventing upstream states from entirely cutting off water supply to downstream states. Mississippi's reliance on Tarrant Regional Water Dist. v. Herrmann is misplaced, as that case specifically addressed the interpretation of an interstate compact rather than general principles of water rights.
Equitable apportionment was not considered because the affected States negotiated a compact defining their rights to the resource. The Tarrant case's principle, which prohibits one State from entering another to extract water without agreement, is not applicable here, as Tennessee's wells are vertical and do not cross the border. Tennessee's groundwater pumping occurs within its territory, regardless of the water's prior location in Mississippi. The origin of interstate resources may inform equitable apportionment but does not exclude the resource from it. The waters of the Middle Claiborne Aquifer are subject to equitable apportionment principles.
The Special Master recommended dismissing Mississippi’s suit but suggested allowing an amended complaint for equitable apportionment. However, the Court refrains from deciding on this, as Mississippi has not requested such leave and previously disavowed equitable apportionment in its pleadings. The case is based on tort law principles, focusing on the aquifer's physical properties and Tennessee's actions, rather than the broader considerations required for equitable apportionment, such as existing uses and impacts on other States.
If Mississippi were to seek amendment, it would need to demonstrate substantial injury, a requirement it has not addressed. Consequently, Mississippi's exceptions to the Special Master’s report are overruled, Tennessee's exceptions are sustained, and the case is dismissed.
