Co-Authors: Bennett L. Bearden and Caleb T. Anderson
Introduction
The year 2021 will serve as a landmark moment for interstate water disputes and the application of the doctrine of equitable apportionment. During 2021, the Supreme Court of the United States (Court) ruled on two distinct interstate disputes: Florida v. Georgia and Mississippi v. Tennessee. The Florida v. Georgia case was an extended water availability dispute over allocations in the Apalachicola-Chattahoochee-Flint (ACF) River Basin. The dispute arose from a Florida claim that Georgia was using more than its fair share of water from the ACF Basin, resulting in low flows in the Apalachicola River that damaged the river ecosystem and Florida’s downstream oyster fisheries. The Court found that Florida failed to provide clear and convincing evidence that Georgia’s water usage “played more than a trivial role in the collapse of Florida’s oyster fisheries” and that mismanagement of artificial oyster habitats by Florida contributed to the ecological harm. The Court dismissed the case.
The year 2021 also saw the first ruling by the Court on an interstate groundwater dispute in Mississippi v. Tennessee. At issue in this case was the use of water from the Middle Claiborne aquifer (known locally as the Memphis Sand aquifer), which underlies several states including Mississippi and Tennessee. Mississippi claimed that groundwater extraction by the city of Memphis produced a cone of depression that extended into Mississippi, resulting in theft of a valuable state resource—Mississippi’s groundwater—across a state boundary. Because Mississippi framed the issue as a violation of state sovereignty instead of the allocation of an interstate resource, the state viewed equitable apportionment as inappropriate and requested monetary damages instead. The special master appointed to the case disagreed and recommended that the Court grant Mississippi leave to amend its complaint to include a request for equitable apportionment.
Throughout oral arguments, the justices asked if Mississippi would like to argue for equitable apportionment of the Middle Claiborne aquifer. Mississippi reiterated its view that equitable apportionment was irrelevant because the dispute was about a violation of state sovereignty. In its opinion, the Court unanimously concluded that the aquifer was subject to equitable apportionment, reasoning that the aquifer’s “multistate character,” with water flowing naturally between states, meant that apportioning the aquifer would be sufficiently similar to past applications of the equitable apportionment doctrine. The Court found that it did not matter that some of the water being pumped in Tennessee was previously located in Mississippi. Lastly, the Court chose to dismiss Mississippi’s complaint without granting leave to request equitable apportionment because Mississippi had already explicitly rejected apportionment as a remedy.
Issues in these two distinct cases, on either end of the water resources spectrum, produced similar thoughts espoused by the justices during analyses of the disputes. As interstate water availability increasingly becomes an issue due to a changing climate and resource demands, litigation between states becomes more frequent and the decisions handed down by the Court in these two cases provide insight into how interstate water disputes will be resolved in the future. Therefore, understanding the doctrine of equitable apportionment is key in state water resources management and water policy analysis.
The Doctrine of Equitable Apportionment
The equitable apportionment doctrine has been fashioned by the Court over decades of deliberations. Equitable apportionment was first articulated in Kansas v. Colorado as a conflict of laws doctrine designed to address a situation in which differing legal regimes fostered the over-appropriation of an interstate stream. The doctrine falls under the Court’s original and exclusive jurisdiction, which means that all equitable apportionment cases must be filed directly with the Supreme Court instead of starting off in a lower federal court. Many equitable apportionment cases restate a requirement of “ripeness”: for a state to be able to sue, the alleged invasion of its water rights must be threatened, of serious magnitude, and proved by clear and convincing evidence. This is a higher standard of proof than the standard applied to a request for an injunction in a lawsuit between private parties.
The Court considers a wide variety of factors in making an equitable apportionment determination. Three of the most important factors are a comparison of harms and benefits, feasible measures to improve water-use efficiency and enhance water supplies, and the protection of existing water-dependent economies. All three of these factors played a role in the 1982 case Colorado v. New Mexico. The Court required Colorado to show that its water needs could not be satisfied by implementing efficiency and enhancement measures elsewhere. The Court explained that it generally preferred to protect existing economies because “[t]he harm that may result from disrupting established uses is typically certain and immediate, whereas the potential benefits from a proposed diversion may be speculative and remote.” Colorado v. New Mexico also introduced the Court’s “burden-shifting” rule. Once New Mexico had met its burden of proof by showing that Colorado’s proposed diversion would cause serious injury to New Mexico, the burden of proof shifted to Colorado to show that the diversion was permissible under equitable apportionment principles.
The doctrine was extended beyond the context of surface waters in the 1983 decision Idaho ex rel. Evans v. Oregon, in which the Court found that interstate runs of anadromous fish could be equitably apportioned. However, the Court ultimately declined to apportion the fish runs in question due to a lack of ripeness.
Policy Implications for Future Disputes
Equitable apportionment’s policy implications are relevant to a diverse collection of water resources issues, including Waters of the United States (WOTUS), the potential application of the Endangered Species Act, and groundwater covered under the Safe Drinking Water Act, which underscores the necessity of understanding the conjunctive relationship between surface water, groundwater, and the environment at the intersection of hydrology, habitat, and policy. This understanding potentially can provide great benefit to the resolution of interstate water disputes. For example, how would you approach a scenario involving dewatering of a shallow interstate aquifer that directly recharges a water of the United States containing an endangered or threatened species? The Endangered Species Act has proven over the years to be a robust challenge in cases where the habitat requirements of a listed species outweighed the needs of the defendant, as demonstrated in the well-known 1978 “snail darter case,” Tennessee Valley Authority v. Hill.
The WOTUS Rule is a constantly evolving concept that changes with the political wind, with the most recent change coming in response to the Court’s decision in Sackett v. EPA in 2023. The Court’s ruling in County of Maui v. Hawaii Wildlife Fund demonstrated knowledge of wastewater contamination of a conjunctive groundwater–surface water system. The majority of these issues have been intrastate, involving lower federal courts, but what if they were interstate problems and reached the Supreme Court? Should all parties consider that the Court has applied, or suggested, equitable apportionment in similar cases? A solution to rule them all, so to speak.
When considering that equitable apportionment could be employed by the Court to resolve any dispute centered on interstate natural waters connected to the surrounding environment, a crucial question for future rulings is “what is acceptable loss?” Climate change models predict that water resources will be stressed by a variety of conditions and conjunctively stressed by growing water demands from the public supply and agricultural sectors. At what point in an environmental or water quality dispute will the acceptable loss to an individual water user be outweighed by acceptable loss to the public sector? Establishing levels of acceptable loss may help to mitigate decisions arising from the application of equitable apportionment.
Although the Supreme Court tends to employ equitable apportionment reluctantly, the outcomes of Florida v. Georgia and Mississippi v. Tennessee have renewed the doctrine’s relevance to the water resources profession. As the nature and intensity of environmental stressors and water-use demands change over time, it is increasingly important for anyone working in the field to understand how the country’s highest court might intervene in interstate water disputes and what the outcomes might look like.
Greg Guthrie is the director of Science Programs and the director of the Groundwater Assessment and Ecosystems Investigations Programs at the Geological Survey of Alabama. He is a board member of AWRA, the president-elect of the Alabama chapter of AWRA, and a registered professional geologist.
Bennett Bearden is deputy attorney general, chief of staff, and assistant state geologist at the Geological Survey of Alabama. He is a lawyer licensed in Alabama and Washington, D.C., and is admitted to the Bar of the U.S. District Court-Northern District of Alabama, U.S. Court of Appeals for the Eleventh Circuit, and U.S. Supreme Court. He is a fellow in the American Bar Foundation and was the founding director (2013–2018) of the Water Policy and Law Institute at The University of Alabama. Bennett is an affiliate (water policy analyst) with the Alabama Water Institute at The University of Alabama, where he serves as adjunct professor of water policy and law.
Caleb Anderson is a third-year J.D. candidate at The University of Alabama School of Law. He is a law clerk and research assistant at the Geological Survey of Alabama and an articles editor for the Alabama Law Review. He received his M.S. in Biology from The University of Alabama and his B.S. in Marine Science from the University of South Carolina.
This article was reprinted with permission from the May/June 2024 issue of the American Water Resources Association IMPACT magazine.