Click the link to access the report on the University of Colorado website (Eric Kuhn,1 Anne Castle,2 Carlos de la Parra,3 John Fleck,4 Jack Schmidt,5 Kathryn Sorensen,6 Katherine Tara7). Here’s the abstract:
March 26, 2026
Since 1945, the United States and Mexico have managed common interests on their two largest shared rivers systems, the Colorado and the Rio Bravo/Rio Grande, under the terms of the 1944 international treaty that was designed from the beginning with tools to adapt to changing hydrologic and societal conditions.
A recent emergency agreement on the Rio Bravo/Rio Grande illustrates what is possible, and with old river management rules on the Colorado both within the United States and between the United States and Mexico about to expire, we are at a moment of opportunity for meaningful change.
The core problem on the Colorado River, which we address in the analysis that follows, arose from decisions made in the first half of the 20th century to allocate fixed volumes of water. As usage patterns and hydrology change in the 21st century, fixed volumes no longer work. A shift to a percentage-based split between the United States and Mexico on the Colorado River, based on the river’s actual natural flow, would provide a solid foundation for the two countries’ joint management of the Colorado in the decades to come.
1 Retired General Manager, Colorado River Water Conservation District.
2 Senior Fellow, Getches-Wilkinson Center, University of Colorado Law School; former US Commissioner, Upper Colorado River Commission; former Assistant Secretary for Water and Science, US Dept. of the Interior.
3 Founder and Managing Partner, Centro Luken de Estrategias en Agua y Medio Ambiente, Tijuana, Mexico.
4 Writer in Residence, Utton Transboundary Resources Center, University of New Mexico.
5 Director, Center for Colorado River Studies, Utah State University; former Chief, Grand Canyon Monitoring and Research Center.
6 Director of Research, Kyl Center for Water Policy, Arizona State University; former Director, Phoenix Water Services.
7 Staff Attorney, Utton Transboundary Resources Center, University of New Mexico.
Author note
This paper is intended to supplement and complement a series of related papers written in the last year by the authors (or subset of the authors) addressing the critical problems facing the Colorado River Basin, including:
• Eric Kuhn, Anne Castle, & John Fleck, Royce Tipton and the Hydrology of the 1944 Treaty with Mexico, (May 2025). Available at: Kuhn-et-al-2025-Royce-Tipton-Mexico-Hydrology.pdf.
• Anne Castle, John Fleck, Jack Schmidt, Kathryn Sorensen, and Katherine Tara, Essential Pillars for the Post-2026 Colorado River Guidelines, (April 2025). Available at: 2025-04-25 Principles.
• Jack Schmidt, Anne Castle, Eric Kuhn, John Fleck, Kathryn Sorensen, and Katherine Tara, Analysis of Colorado River Basin Storage Suggests Need for Immediate Action, (September 2025).
• Kathryn Sorensen, Sarah Porter, Anne Castle, John Fleck, Eric Kuhn, Jack Schmidt, and Katherine Tara, Consideration for Assigned Water after Expiration of the 2007 Guidelines
(January 2026). Available at: https://issuu.com/asuwattscollege/docs/full_considerations_for_assigned_water_.