This week, the U.S. Supreme Court put an end to thirteen years of original jurisdiction litigation between the States of Texas, New Mexico, Colorado, and the United States by entering the negotiated Compact Decree Supporting the Rio Grande Compact (Decree) that protects Texas’ interests in surface water from the Lower Rio Grande. The State of Texas was represented in the matter by Stuart Somach, Theresa Barfield, and Sarah Klahn of Somach Simmons & Dunn, in partnership with the Texas Office of the Attorney General.
The case Texas v. New Mexico, Original Action No. 141, was filed by Texas in 2013 alleging that New Mexico has, contrary to the purpose and intent of the 1938 Rio Grande Compact (Compact), allowed and authorized Rio Grande Project (Project) water intended for use in Texas to be intercepted and used in New Mexico. In its complaint, Texas asserted that New Mexico was improperly reducing the quantity of surface water available to Texas from the Lower Rio Grande by increasing groundwater pumping from aquifers that are hydrologically connected to the stream system and impacting surface water flows. Parties to the litigation also included the State of Colorado as a signatory to the Compact, and the United States (who intervened against New Mexico, and against whom New Mexico alleged counterclaims).
In recent years, following lengthy discovery between the parties and a partial evidentiary trial before the Special Master appointed by the Supreme Court, the focus of the litigation shifted to negotiating a mutually beneficial settlement between the States of Texas, New Mexico, and Colorado, and the federal government. Various amici, including two districts that receive water from the Project, were closely involved in the negotiations.
The Decree approved by the Supreme Court this week was entered by the parties in August 2025. Says Stuart Somach, “We appreciate the diligent work and cooperation by all parties and the Mediator in reaching this Decree, which vindicates Texas’ concerns regarding the depletion of surface water supplies via groundwater pumping.”
The Decree is organized into three main components, which combine to resolve the parties’ primary concerns and establish a clear path forward.
First, New Mexico agreed to reduce depletions in the Lower Rio Grande by 18,200 acre-feet per year within ten years of the effective date of May 26, 2026. Half of that commitment must be met by May 26, 2031. Depletions may be reduced by permanently retiring irrigated farmland and the groundwater rights associated with that land, with calculations set forth to determine the exact amount of depletion achieved. New Mexico is required to prepare annual reports documenting its retirement of groundwater rights and irrigated land.
Second, the parties agreed to certain Enforceable Hydrologic Conditions applicable to the Project and aquifer storage loss, with New Mexico committing to take all reasonable action to achieve stable or gaining aquifer levels under certain hydrologic conditions. The Decree also sets forth procedures to monitor groundwater levels and to initiate consultation on aquifer storage losses.
Third, New Mexico agreed to adopt a Lower Rio Grande Water Management Plan establishing a plan to manage and administer water in the Lower Rio Grande, which must include actions to satisfy and maintain its depletion reduction obligation, to achieve stable or gaining aquifer levels in certain conditions, and to limit depletions from domestic wells, among others. New Mexico retains discretion, however, as to the details of these actions.
Ultimately, the Decree serves to clarify measurement of Compact apportionments and is a lasting solution to a complex and longstanding dispute over the division of Rio Grande water. The Decree is consistent with and achieves the ultimate goal of the Compact by ensuring that Texas and New Mexico both receive and can use their respective apportionments of the waters of the Rio Grande.
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