By Roderick E. Walston

In Mississippi v. Tennessee, ___U.S.___, Case No. 143 Original (Nov. 22, 2021), the U.S. Supreme Court unanimously held that in a dispute among states over groundwater in an interstate aquifer, the Supreme Court must apportion the groundwater between the states under the Court’s doctrine of equitable apportionment, and one state cannot claim an ownership interest in the groundwater that would impair the rights of other states. Therefore, Mississippi cannot sue Tennessee under a tort theory for damages and prospective relief for Tennessee’s pumping of groundwater from an aquifer underlying both states, but must pursue its claim in an original Supreme Court action seeking equitable apportionment of the groundwater. The Supreme Court’s decision is the first to hold that the doctrine of equitable apportionment that has often been applied to interstate disputes over surface waters also applies to interstate disputes over groundwater.

This article will describe the facts of Mississippi v. Tennessee; the Supreme Court’s original jurisdiction over interstate water disputes; the doctrine of equitable apportionment that the Supreme Court has fashioned in resolving such disputes; the Court’s decision and analysis in Mississippi; and will then provide a brief comment on state ownership of water.

Facts of the Case: Mississippi v. Tennessee

In Mississippi v. Tennessee, the City of Memphis, a city in Tennessee located near Tennessee’s border with Mississippi, pumped groundwater from a vast interstate aquifer, the Middle Claiborne Aquifer, that underlies both states. The aquifer underlies many other states in the Mississippi River Basin as well—Alabama, Arkansas, Illinois, Kentucky, Louisiana and Missouri. Although Memphis pumped the groundwater from wells located in Memphis, the pumping of the groundwater creates a “cone of depression,” which is reduced water pressure at the site of the wells, and which has the effect of drawing groundwater from other locations, including from Mississippi. Thus, Memphis’ pumping of groundwater from its wells causes groundwater in Mississippi to migrate to Memphis, reducing groundwater in Mississippi.

Mississippi filed a motion in the Supreme Court for leave to file a complaint against Tennessee and Memphis under the Court’s original jurisdiction. Mississippi based its complaint on a tort theory. Specifically, Mississippi claimed that it “owned” the groundwater beneath its surface, and that Memphis’ pumping of groundwater caused migration of Mississippi’s groundwater to Tennessee, as a result of which Memphis was extracting hundreds of billions of groundwater “owned” by Mississippi. Mississippi sought at least $615 million in damages as well as declaratory and injunctive relief. Mississippi argued that the doctrine of equitable apportionment—which the Supreme Court traditionally applies in resolving interstate water disputes—did not apply because Mississippi “owned” the groundwater that was being taken by Memphis.

The U.S. Supreme Court’s Original Jurisdiction

Under Article III of the U.S. Constitution, the Supreme Court has original jurisdiction over certain types of actions, meaning that such actions can be brought directly in the Supreme Court and need not be brought in the lower courts. U.S. Const., Art. III, § 2, Cl. 2. The Judiciary Act of 1789 (Act) implements Article III by specifically defining the Supreme Court’s original jurisdiction. Under the Act, the Supreme Court has original jurisdiction over actions brought by the United States and a state against each other, and actions brought by a state against the citizen of another state. 28 U.S.C. § 1251(b).

In one important class of cases, however, the Supreme Court’s jurisdiction is not only original but also exclusive, meaning that the Supreme Court alone can hear the dispute. Under the Judiciary Act of 1789, the Supreme Court has original and exclusive jurisdiction over disputes between states. 28 U.S.C. § 1251(a). Thus, a state can only bring an action against another state in the Supreme Court, and no other court has jurisdiction to hear the case. The Supreme Court’s original and exclusive jurisdiction applies only to disputes between states, and not where a subdivision of a state, such as a city or county, attempts to bring an action on behalf of the state. Illinois v. City of Milwaukee, 406 U.S. 91 (1972).

Although the Supreme Court has original and exclusive jurisdiction over interstate disputes, the Court does not necessarily hear a dispute simply because it is between states. Instead, the Court exercises its exclusive jurisdiction only if the states are asserting truly sovereign interests, and are not attempting to litigate private interests that might be litigated through the normal judicial process. Pennsylvania v. New Jersey, 426 U.S. 660, 666 (1976). The Court’s exclusive jurisdiction is reserved for disputes of “seriousness and dignity,” and that might be a casus belli if the states were truly sovereign. Texas v. New Mexico, 462 U.S. 554, 571 n. 18 (1983); Illinois v. City of Milwaukee, 406 U.S. 91, 93 (1972). The Court exercises its exclusive jurisdiction only if it is “appropriate” to do so. Ohio v. Wyandotte Corp., 401 U.S. 493 (1971). The Court’s original jurisdiction does not allow it to be become enmeshed in “intramural disputes” between private citizens within the states, and is not a substitute for a class action, in which members of a class collectively join to protect their common interests. New Jersey v. New York, 345 U.S. 369, 373 (1953).

Since the Supreme Court has discretion in deciding whether to hear an original jurisdiction action, the plaintiff—whether the United States or a state—cannot simply file a complaint in the Court, as in a district court proceeding. Instead, the plaintiff must file a motion in the Supreme Court for leave to file a bill of complaint, and the Court then decides whether to grant the motion and hear the case. The Court may decline to hear a case if it does not truly involve a dispute between the states.

For example, in United States v. Nevada and California, 412 U.S. 534 (1973), the United States sought to file a complaint under the Supreme Court’s original jurisdiction in what the United States described as a dispute among the United States, Nevada and California over water rights in the Truckee River, an interstate river that flows from California to Nevada and terminates at Pyramid Lake in Nevada. The United States’ sought additional water rights for the Pyramid Lake Indian Tribe beyond those awarded to the Tribe in a 1944 judicial decree. The Supreme Court denied the United State’ motion to file the complaint, ruling that the dispute was between the United States and Nevada over water rights in Nevada and did not involve California, and that the United States could bring an action against Nevada in a Nevada federal district court in the normal judicial process. The United States then brought its action in the district court, and the action ultimately reached the Supreme Court, which ruled that the United States was barred by res judicata from seeking additional water rights for the Tribe. Nevada v. United States, 463 U.S. 110 (1983).

The Supreme Court has great flexibility in fashioning rules governing original jurisdiction actions. The Court may consider the Federal Rules of Civil Procedure as a guide, but is not bound by the federal rules. Supreme Court Rule 17.2. In one notable case, California brought an original action in the Supreme Court against Texas and other states that had imposed an embargo on fruits and vegetables grown in California. (The states had imposed the embargo because of the Mediterranean fruit fly infestation in California.) California argued that the states’ embargo imposed an unreasonable burden on interstate commerce and thus violated the Constitution’s Commerce Clause. The Supreme Court issued a temporary restraining order (TRO) prohibiting the states from imposing their embargo, even though the Court does not have specific authority to issue a TRO and apparently had never issued a TRO before. California v. Texas, et al., 450 U.S. 977 (1981).

The Supreme Court’s original jurisdiction to resolve disagreements among states was considered one of the most innovative concepts of the American Constitution. Benjamin Franklin was the first to propose—in 1775, before the Declaration of Independence was signed—that the federal government should have the power to resolve disputes among the colonies. Indeed, the Articles of Confederation, which preceded the Constitution, provided for the creation of a special court with power to resolve interstate disputes, and a special court resolved a boundary dispute between Pennsylvania and Connecticut, as a result of which the City of Scranton is located in Pennsylvania today.

The Doctrine of Equitable Apportionment

The Supreme Court reviews many kinds of interstate disputes under its original jurisdiction, such as disputes over interstate boundaries, Oklahoma v. Texas, 258 U.S. 574, 581, 598 (1922), interstate air and water pollution, Georgia v. Tennessee Copper Co., 206 U.S. 230 (1907), and state tax or regulatory schemes that allegedly discriminate against citizens of other states, Maryland v. Louisiana, 451 U.S. 725 (1981). Probably the most significant interstate disputes that the Court reviews, however, are those over water rights in interstate waters. Under its original jurisdiction, the Supreme Court has resolved several interstate water rights disputes. E.g., Colorado v. Kansas, 320 U.S. 383 (1943) (Arkansas River); New Jersey v. New York, 283 U.S. 336 (1931) (Delaware River); Nebraska v. Wyoming, 325 U.S. 589 (1945) (North Platte River).

In resolving interstate water rights disputes, the Supreme Court necessarily fashions federal common law, because federal statutes generally do not apply and the Court cannot properly apply the law of any state. Although the Supreme Court has expressed reluctance to fashion federal common law—stating that federal courts, unlike state courts, are not general common law courts—the Court has nonetheless held that federal courts may develop federal common law where “Congress has not spoken” or there is “significant conflict between some federal policy or interest and the use of state law.” Milwaukee v. Illinois, 451 U.S. 304, 312-313 (1981).

The federal common law that the Supreme Court has fashioned in resolving interstate water rights disputes is the doctrine of equitable apportionment. Under this doctrine, the Court considers all relevant facts and attempts to reach a result that is fair and equitable to all states. Nebraska v. Wyoming, 325 U.S. 589 (1945); New Jersey v. New York, 283 U.S. at 342-343; Kansas v. Colorado, 206 U.S. 46 (1907). The Court is not bound by the priority of water rights in the different states, although the Court may consider such priority of rights if the states recognize the same principles of water law, such as the doctrine of prior appropriation. Nebraska, 325 U.S. at 618. But the Court must consider other equitable factors as well, such as physical and climatic conditions, the extent of established uses, water uses and efficiencies, the availability of alternatives, return flows, availability of storage water, and the costs and benefits to the states. Id. at 618; Wyoming v. Colorado, 259 U.S. 419, 470 (1922).

The Supreme Court’s equitable apportionment of interstate waters limits the amount of water available to water users within each state. The Court has held that the rights of all water users in a state cannot exceed the state’s equitable apportionment. Hinderlider v. La Plata River & Cherry Creek Ditch Co., 304 U.S. 92, 102 (1938). Thus, even though a water user may have a right to use water under state law, the water user may not have the right to use the water if this causes the state to exceed its equitable apportionment. As the Supreme Court has stated, equitable apportionment is not dependent on or bound by existing legal rights to the resource being apportioned. Idaho ex rel. Evans v. Oregon, 462 U.S. 1017, 1025 (1983).

One of the most important interstate water dispute that the Supreme Court has addressed under its original jurisdiction—and certainly the most important to California—was the dispute between Arizona and California over the Colorado River. Arizona v. California, 373 U.S. 546 (1963). In the early twentieth century, southern California was taking increasing amounts of water from the Colorado River to meet its growing needs, and Arizona claimed that California was taking more than its fair share and depriving Arizona of water necessary to meet its anticipated future needs. Arizona brought an original action against California in the Supreme Court, and the Court, after a lengthy adjudication, issued a decree that apportioned Colorado River water among the Lower Basin states of Arizona, California and Nevada. More precisely, the Court did not apportion the water itself, but instead held that Congress—in passing the Boulder Canyon Project Act of 1928, which authorized construction of the Hoover Dam on the Colorado River—had effectively apportioned the water among the states. Under the congressional apportionment, the Court ruled, California was entitled to 4.4 million acre-feet of Colorado River water each year, Arizona 2.8 million acre-feet, and Nevada 300,000 acre-feet. Although California received the largest share of water, California’s share was less than it claimed, and the Supreme Court decree has generally been regarded as limiting California’s right to take Colorado River water to meet its growth needs.

The Supreme Court’s Decision

In Mississippi v. Tennessee, the Supreme Court, in a unanimous decision written by Chief Justice John Roberts, rejected Mississippi’s claim that it owned the groundwater in the portion of the interstate aquifer lying within its borders, and therefore could assert a tort claim against Tennessee for pumping groundwater from the aquifer, and held instead that the states’ shares of the groundwater must be apportioned between the states under equitable apportionment principles established by the Court in resolving interstate water disputes.

As the Court noted, the Court first established the equitable apportionment doctrine in an interstate dispute between Kansas and Colorado over water rights in the Arkansas River. Kansas v. Colorado, 206 U.S. 46 (1907). In Kansas, the Court held that all states have equal sovereignty over their waters, with the right to determine their water laws. The Court also held, however, that when one state attempts to allocate an interstate water resource for its own benefit but to the detriment of other states, the laws of neither state can properly apply to the controversy, nor can the courts of either state properly adjudicate the controversy. Rather, the Court held, the Supreme Court has sole jurisdiction to adjudicate the controversy, and has fashioned a federal common law doctrine—the doctrine of equitable apportionment—that allocates a fair and equitable share of the waters to each state. The Court in Mississippi noted that it had applied equitable apportionment in resolving many interstate water disputes, such as Nebraska v. Wyoming, 325 U.S. 589 (1945), Colorado v. New Mexico, 459 U.S. 176 (1982), and Wyoming v. Colorado, 259 U.S. 419 (1922).

The Mississippi Court also noted that it applied equitable apportionment in resolving a dispute between Oregon and Idaho over anadromous fish in the Columbia-Snake River system. Idaho ex rel. Evans v. Oregon, 462 U.S. 1017, 1018-1019, 1024 (1983). Thus, while equitable apportionment generally applies to interstate disputes over water, the same principle also applies to interstate disputes over fishery resources in the water. And while equitable apportionment generally protects the right of a downstream state to a fair share of interstate waters, Evans held that equitable apportionment also protects the right of an upstream state to a fair share of a fishery resource in the waters (although Evans rejected Idaho’s claim that it had been denied a fair share of the fishery resource under the facts of the case). Thus, equitable apportionment is a flexible doctrine that applies to any interstate water dispute, whether the dispute is over water rights or fish and whether the beneficiary is an upstream state or downstream state.

Applying Equitable Apportionment Doctrine to an Interstate Dispute over Groundwater

The Mississippi Court acknowledged, however, that the Court had never applied the equitable apportionment doctrine in resolving an interstate dispute over groundwater. Thus, the issue raised in Mississippi was one of first impression.

Resolving the dispute, the Court held that equitable apportionment applies to the Middle Claiborne Aquifer because the dispute over the aquifer is “sufficiently similar” to past interstate water disputes in which equitable apportionment has been applied. Slip Op. 7. The Court held that the Middle Claiborne Aquifer was of a “multistate character,” in that the aquifer underlies both Mississippi and Tennessee and thus groundwater pumping in both states is from the “same aquifer.” Id. at 8. The Court also held that water in the Middle Claiborne Aquifer “flows naturally” between the states, and that the Court’s equitable apportionment decisions have concerned water that flows between the states. Id. Although acknowledging that the flow of the water within the aquifer may be “extremely slow”—as much as an inch or two per day—the Court held that the speed of the flow does not place the aquifer beyond equitable apportionment. Id. Most importantly, the Court held that pumping of groundwater from the aquifer in Tennessee affects groundwater in the aquifer in Mississippi, in that pumping in Tennessee creates a cone of depression that reduces groundwater storage and pressure in Mississippi. Id. The Court concluded that the doctrine of equitable apportionment applies to the interstate aquifer.

The Court rejected Mississippi’s claim that equitable apportionment does not apply because it owns all groundwater beneath its surface. Id. at 9. Although the Court acknowledged that a state has “full jurisdiction over the lands within its borders, including the beds of streams and other waters,” the Court held that such jurisdiction does not confer “unfettered ownership or control of flowing interstate waters themselves.” Id. (citations and internal quote marks omitted). When a water resource is shared between different states, the Court held, each state has “an interest which should be respected by the other.” Id. at 9-10. As the Court stated, Mississippi’s argument would allow an upstream state to completely cut off the flow of groundwater to a downstream state, contrary to the Court’s equitable apportionment jurisprudence. Id. at 10.

The Court also rejected the Special Master’s recommendation that the Court should allow Mississippi to amend its complaint to seek equitable apportionment, because, the Court stated, Mississippi has not sought to amend its complaint to seek equitable apportionment and the Court cannot assume that Mississippi would do so. Slip Op. 11. As the Court stated, Mississippi sought relief under tort principles, and it cannot be assumed that Mississippi would seek equitable apportionment, which would be based on a broader range of evidence and might require joinder of the other states that rely on the Middle Claiborne Aquifer. Id. The Court did not, however, specifically preclude Mississippi from filing a motion for leave to file a complaint seeking equitable apportionment. If Mississippi were to file such a motion, the Court presumably would consider the motion based on the Court’s established equitable apportionment principles.

It is telling that the Court spoke unanimously in holding that Mississippi could not pursue its tort claim against Tennessee under the Court’s original jurisdiction, and that there were no dissenting or even concurring opinions. Not a single justice supported Mississippi’s ownership claim as applied to the interstate aquifer. Although the Court’s decisions in the modern era are often fragmented and divided, it is salutary that at least with respect to an interstate dispute over an aquifer, the Court has spoken with one voice.

Conclusion and Implications: State Ownership of Water

Mississippi’s claim that it “owns” the groundwater in its portion of the interstate aquifer—which was the predicate for its claim that Tennessee was liable in tort for taking groundwater from the aquifer—is not without foundation. The Supreme Court has long held that under the equal footing doctrine—which holds that all states are admitted to statehood on an equal footing with other states—the states acquire sovereign title and ownership of navigable waters and underlying lands upon their admission to statehood. PPL Montana v. Montana, 565 U.S. 576, 589-593 (2012); Shively v. Bowlby, 152 U.S. 1, 13, 14 (1894); Martin v. Waddell, 41 U.S. 367, 410 (1842). The Court relied on this principle in its seminal decision establishing the public trust doctrine, which held that the states, having acquired title and ownership of navigable waters and lands, hold the water and lands in trust for the public’s common use. Illinois Central R.R. Co. v. Illinois, 146 U.S. 387 (1892). The Court has also held that, under the Tenth Amendment of the Constitution, the states have the right to adopt laws governing water rights—such as the appropriation doctrine and the riparian doctrine—and that Congress cannot enforce either rule upon any state. Kansas v. Colorado, 206 U.S. 46, 93 (1907). Additionally, the Court has held that Congress has generally deferred to state water laws by enactments such as the Desert Land Act of 1877, which provides for disposition of the public lands in the western states, California Oregon Power Co. v. Beaver Portland Cement Co., 295 U.S. 142, 163-164 (1935), and the Reclamation Act of 1902, which authorizes federal water projects in the western states, California v. United States, 438 U.S. 645 (1978).

Thus, the states have sovereign ownership interests in their waters under both constitutional and statutory principles, with authority to regulate and control water rights in the waters. The states’ sovereignty over water is a bedrock principle of the federalism that underlies our constitutional order. PPL Montana, 565 U.S. at 551. Since the states have ownership interests in their surface waters, they logically have the same interests in groundwater beneath the surface.

Under the Supremacy Clause of the Constitution, the states’ sovereignty over water, however broad, is subject to Congress’ paramount powers under the Constitution, particularly Congress’ power to regulate navigable waters under the Commerce Clause. United States v. Rio Grande Dam & Irrig. Co., 174 U.S. 690, 703 (1899); Martin, 41 U.S. at 410. Indeed, the states’ sovereignty over water is subject is subject to Commerce Clause limitations even when Congress does not act; under the dormant Commerce Clause, a state cannot impose an unreasonable burden on interstate commerce even absent congressional action. United States Haulers Ass’n, Inc. v. Oneida-Herkimer Solid Waste Management Authority, 550 U.S. 330, 337 (2007). In Sporhase v. Nebraska, 458 U.S. 941, 953-954 (1982), the Supreme Court applied the dormant Commerce Clause in holding that groundwater is an article of interstate commerce, and thus Nebraska could not impose an unreasonable burden on interstate commerce by preventing the transfer of groundwater from Nebraska to another state.

The states’ sovereignty over water is also subject to a principle of federal common law—the doctrine of equitable apportionment—that applies to interstate disputes over interstate waters. As the Supreme Court has held, interstate waters are a common resource that must be shared equally by the states, and the states’ shares of the waters must be apportioned under the Court’s equitable principles. Kansas v. Colorado, 206 U.S. 46, 85-96 (1907); Wyoming v. Colorado, 259 U.S. 419, 466 (1922). Plainly the laws of a single state cannot properly apply to the controversy; otherwise, one state, such as an upstream state, could wholly allocate interstate waters for its own use and deprive other states, such as downstream states, of their own rights to use the waters. This equitable principle limits the state’s authority to allocate interstate water to its own users, because the amount of water that the state allocates among its users cannot exceed the amount of the state’s equitable share of the waters. Hinderlider v. La Plata River & Cherry Creek Ditch Co., 304 U.S. 92, 102 (1938).

The Supreme Court in Mississippi held that the doctrine of equitable apportionment that applies to interstate disputes over surface waters also applies to interstate disputes over groundwater. The states have common rights and interests in both types of waters, and thus the same principle of equity that applies to surface waters logically applies to groundwater. A contrary result would create an anomaly in federal law, in that a different rule would apply to disputes over surface water and groundwater, even though the states have common rights and interests in both types of water; federal law frowns on anomalies, particularly those created by the Supreme Court’s own common law, which the Court itself can correct. Mississippi should have recognized the logic and force of equitable apportionment at the outset rather than pursuing an ill-conceived claim that it could assert a tort claim against Tennessee because it wholly owned the portion of an interstate aquifer located beneath its surface. Even so, the Supreme Court did not preclude Mississippi from pursuing equitable apportionment under the Court’s original jurisdiction, and thus Mississippi presumably has the right to pursue such a claim if it decides to do so.

It is significant that the Supreme Court in Mississippi did not suggest that the states do not have ownership of water within their borders, and held instead that the states do not have “unfettered” and “exclusive” ownership of interstate waters that would preclude other states from having equitable shares of the waters. Slip Op. 9. Thus, the Court did not adopt the view, expressed in its earlier decision in Sporhase v. Nebraska, that the theory of state “ownership” of water is a “fiction.” Sporhase, 458 U.S. at 951. Contrary to the Sporhase statement, the Supreme Court has long held that under the equal footing doctrine the states acquire sovereign “title” and “ownership” of navigable waters and lands upon their admission to statehood, a principle established under the Constitution itself and not Congress’ statutes. E.g., PPL Montana, 565 U.S. at 589-593, 603. The Court applied this principle in establishing the public trust principle that the states hold the waters and lands in trust for the public’s common use. Illinois Central, 146 U.S. at 435, 452. Thus, state ownership of water is not a “fiction.” Rather, the states acquire an ownership interest in water under the equal footing doctrine, but, under the principle of federal supremacy, the states’ ownership interest is subject to Congress’ paramount power to regulate navigable waters under the Commerce Clause, and subject to the federal common law rule that interstate waters must be equitably apportioned among the states.

In sum, while Mississippi rejected Mississippi’s claim that it owned the groundwater in an interstate aquifer and could assert a tort claim against Tennessee for pumping groundwater from the aquifer, Mississippi did not suggest that states do not have an ownership interest in groundwater, or other waters, within their borders. Rather, Mississippi held that regardless of a state’s ownership interest in groundwater, an interstate dispute over groundwater must be resolved under the principle of equitable apportionment that applies to other interstate disputes over water.

Roderick E. Walston, Esq has litigated—and is litigating—many of the nation’s most significant water rights cases, and has garnered impactful, precedent-setting victories at both the U.S. Supreme Court and the California Supreme Court. Rod is now of counsel in Best Best & Krieger, LLP’s Environmental & Natural Resources practice group. During his career, Rod has litigated many of California’s most important natural resources and environmental cases, particularly at the appellate level.

Rod has argued original jurisdiction cases in the Supreme Court, including some mentioned in this article. He has served as Deputy Solicitor and Acting Solicitor of the U.S. Department of the Interior, and as Chief Assistant Attorney General (and head of the Public Rights Division) and Deputy Attorney General of the State of California.