The Texas v. New Mexico Rio Grande water dispute was a Supreme Court case in which Texas accused New Mexico of allowing groundwater pumping that siphoned off river water Texas was entitled to under the Rio Grande Compact of 1938. Texas filed suit in 2013. The case produced a landmark 5–4 ruling in 2024 rejecting a settlement the two states had reached without federal consent, and it ended in 2026 when the Supreme Court approved a new agreement requiring New Mexico to reduce pumping in the Lower Rio Grande by 18,200 acre-feet within ten years.1Justia. Texas v New Mexico, 602 US ___ (2024)
What Texas Accused New Mexico of Doing
The compact measures surface water. It requires New Mexico to deliver a set amount of Rio Grande flow to Elephant Butte Reservoir, roughly 125 miles north of El Paso, based on how much water enters the system upstream.2National Park Service. New Mexico – Elephant Butte Dam and Spillway Once the water is released from the reservoir, it flows south through the federal Rio Grande Project to farmers in southern New Mexico and Texas.
Hydrology doesn’t respect the surface-water framing. Aquifers in the Mesilla and Rincon valleys of southern New Mexico are hydraulically connected to the river, so pumping from a well near the Rio Grande draws down the surface flow. Texas’s argument was straightforward: New Mexico met its delivery obligation to Elephant Butte on paper, then let farmers and municipalities south of the dam pull groundwater that intercepted the same water before it could reach Texas. The effect was the same as diverting the river itself, but because the compact’s accounting measures deliveries at upstream gauging stations, the pumping went undetected in the compact’s ledger for decades.
New Mexico’s response was that the compact says nothing about groundwater and that regulating wells falls within state sovereignty. That tension, between what the compact says and what the water actually does, is what kept the case alive for more than a decade.
Why the Federal Government Was a Party
The United States intervened as a full party with two independent interests.
The 1906 Treaty with Mexico
A 1906 convention obligates the United States to deliver 60,000 acre-feet of Rio Grande water annually to Mexico at the head works of the Acequia Madre above Ciudad Juárez.3International Boundary and Water Commission. Convention Between the United States and Mexico Equitable Distribution of the Waters of the Rio Grande That water comes from the same supply the compact divides. Pumping in southern New Mexico that shrinks the flow reaching El Paso threatens the federal government’s ability to meet the treaty.
The Rio Grande Project
The Bureau of Reclamation operates the Rio Grande Project, which delivers irrigation water to about 178,000 acres split roughly 60 percent in New Mexico and 40 percent in Texas.4Bureau of Reclamation. Rio Grande Project The Bureau contracts with the Elephant Butte Irrigation District in New Mexico and the El Paso County Water Improvement District No. 1 in Texas. A 2008 Operating Agreement governs annual allocations and accounts for losses from groundwater diversions on both sides. Because the United States runs the project, the federal government argued that New Mexico’s unchecked pumping interfered with its own operations.
The 2024 Supreme Court Decision
After years of proceedings before a Special Master, Texas and New Mexico negotiated a proposed settlement and asked the Court to enter it as a consent decree. The Special Master recommended approval. The federal government objected, arguing the deal failed to protect its treaty obligation and its Rio Grande Project interests. On June 21, 2024, the Court sided with the federal government in a 5–4 decision and refused to enter the decree.1Justia. Texas v New Mexico, 602 US ___ (2024)
Justice Jackson wrote for the majority, joined by Chief Justice Roberts and Justices Sotomayor, Kagan, and Kavanaugh. The Court held that a consent decree in an original jurisdiction case cannot be entered over the objection of a party whose legal interests would be affected. Because the United States had intervened as a full party, Texas and New Mexico could not settle around it. The opinion emphasized that the proposed decree would cut the federal government off from remedies it was entitled to pursue.
The Dissent
Justice Gorsuch dissented, joined by Justices Thomas, Alito, and Barrett. He accused the majority of allowing the federal government to “prolong this original jurisdiction dispute” against the wishes of both states, called the ruling “inconsistent with how original jurisdiction cases normally proceed,” and described it as “a serious assault on the power of States to govern, as they always have, the water rights of users in their jurisdictions.” The dissent noted that the federal complaint had sought only to stop excessive groundwater pumping, which the proposed settlement addressed, and argued the United States could pursue any remaining claims elsewhere without blocking a state-to-state deal.
The 2026 Settlement
After the 2024 ruling, the parties returned to negotiations with the federal government now fully at the table. Special Master Judge D. Brooks Smith of the Third Circuit oversaw the process and endorsed a new agreement. Under the revised deal, New Mexico agreed to reduce groundwater pumping in the Lower Rio Grande by 18,200 acre-feet within ten years. The Supreme Court approved the settlement in 2026, closing the case after more than a decade of litigation.
What the Compact Actually Requires
The 1938 Rio Grande Compact, signed by Colorado, New Mexico, and Texas and ratified by Congress, apportions the waters of the Rio Grande above Fort Quitman, Texas. Its stated purpose is “effecting an equitable apportionment of such waters” and removing “all causes of present and future controversy” over those flows.5Council of State Governments. Rio Grande Compact
Rather than assigning fixed quantities, the compact uses a sliding scale. Colorado delivers water to the New Mexico state line. New Mexico delivers water to Elephant Butte Reservoir, with the required amount tied to how much flow is measured upstream at the Otowi Bridge gauging station near San Ildefonso. Shortfalls create debits against the state; surpluses create credits. A Rio Grande Compact Commission, with one representative from each state and a nonvoting federal chair, oversees the accounting.
What the compact does not do, and what drove the entire dispute, is regulate groundwater. Its ledger stops at surface deliveries.
What the Case Changed
Disputes between states go directly to the Supreme Court under Article III, Section 2 of the Constitution, and Congress has made that jurisdiction exclusive for state-versus-state cases.6Office of the Law Revision Counsel. 28 USC 1251 – Original Jurisdiction The Court appoints a Special Master to take evidence and issue recommendations. The process is slow: Texas filed in 2013 and the case did not close until 2026.
The 2024 decision is the case’s lasting contribution to interstate water law. It establishes that when the federal government intervenes as a party in an original jurisdiction dispute, two states cannot settle around it. For any future compact fight involving federal reclamation projects or international treaty water, the practical lesson is that federal consent has to be built into the deal from the start.