Pecos River Basin

The Pecos River Basin extends over much of southeastern New Mexico.  Beginning at an elevation of over 12,000 feet, the Pecos watershed extends from the north-central Sangre de Cristo Mountains and continues south and east encompassing approximately 25,000 square miles before reaching the New Mexico-Texas state line at an elevation of approximately 3,000 feet.

The Pecos River provides water for beneficial use in both New Mexico and Texas.  In New Mexico, the river has provided surface water for irrigation in the Carlsbad area since the late 1800s, and irrigated agriculture continues to be the dominant beneficial use of Pecos River water.  Competing New Mexico demands for limited Pecos River supplies present an ongoing water-management challenge in the basin. 

New Mexico also is required to deliver a portion of the Pecos River’s water to the state of Texas, but it took decades to develop accounting protocols that could be agreed upon by both states.  After failed attempts to reach agreement starting in the 1920s, New Mexico and Texas agreed in 1948 to the Pecos River Compact which was signed into Federal law by President Truman in 1949. 

Although the Compact was intended to remove causes of “present and future controversies”, it did not and in 1974 Texas filed a complaint against New Mexico in the U.S. Supreme Court alleging chronic under-delivery of water in violation of the Compact.  The Court found for Texas and fined New Mexico $14 million, and also stated that New Mexico must never again underdeliver water.  The lawsuit resulted in a 1988 Amended Decree that appointed a federal River Master to perform all Compact accounting in accordance with updated water accounting methodology contained in the River Master Manual.  New Mexico’s failure to comply with the terms of the Compact and Decree could ultimately result in Federal intervention, whereby the state could lose its authority over water management in the basin.

To ensure protection of New Mexico water-right owners and compliance with the Pecos River Compact, state and federal stakeholders in New Mexico entered into the 2003 Pecos Settlement Agreement that implemented water-management strategies to better protect New Mexico’s interests in the lower Pecos River. 

Under the Pecos Settlement Agreement, the ISC Pecos Bureau operates and maintains two augmentation well fields and pipelines, in Lake Arthur and Seven Rivers, to provide additional water to the Pecos River under specified conditions.  The ISC Pecos Bureau has an extensive groundwater monitoring network around its Seven Rivers well field and pipeline.  Groundwater-elevation and water-quality data from ISC’s monitoring network are presented on the Technical Data and Resources page; this page also includes links to various technical articles and reports.Pecos Basin.png

The ISC Pecos Basin Bureau is also actively involved with Environmental Management Issues on the river; specifically, partnering with other water management entities to ensure compliance with the Biological Opinion for the Pecos bluntnose shiner, a threatened species under the federal Endangered Species Act. 

Additional information for the Pecos Bureau is provided on the sidebar to the left or using the embedded links above.