The Status of Tribal Water Rights in the Colorado River Basin

Water and Tribes Initiative | April 9th, 2021

There are 30 federally recognized tribes in the Colorado River Basin. Twenty two of these tribes have recognized rights to use 3.2 million-acre feet (maf) of Colorado Riv

There are 30 federally recognized tribes in the Colorado River Basin. Twenty two of these tribes have recognized rights to use 3.2 million-acre feet (maf) of Colorado River system water annually, or approximately 22 to 26 percent of the Basin’s average annual water supply. In addition, 12 of the tribes have unresolved water rights claims, which will likely increase the overall volume of tribal water rights in the Basin. Under the Upper Colorado River Basin Compact and the U.S. Supreme Court’s decree in Arizona v. California, all tribal water uses are counted against the apportionments made to the states. Tribes’ rights are generally senior to state law-based water rights.

The twenty-first century Colorado River hot drought and implications for the future

American Geophysical Union (AGU) | February 17th, 2017

Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906–1999 average, the worst 15-year drought on record. At least one-sixth to one-half (averag

Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906–1999 average, the worst 15-year drought on record. At least one-sixth to one-half (average at one-third) of this loss is due to unprecedented temperatures (0.9°C above the 1906–1999 average), confirming model-based analysis that continued warming will likely further reduce flows. Whereas it is virtually certain that warming will continue with additional emissions of greenhouse gases to the atmosphere, there has been no observed trend toward greater precipitation in the Colorado Basin, nor are climate models in agreement that there should be a trend. Moreover, there is a significant risk of decadal and multidecadal drought in the coming century, indicating that any increase in mean precipitation will likely be offset during periods of prolonged drought. Recently published estimates of Colorado River flow sensitivity to temperature combined with a large number of recent climate model-based temperature projections indicate that continued business-as-usual warming will drive temperature-induced declines in river flow, conservatively −20% by midcentury and −35% by end-century, with support for losses exceeding −30% at midcentury and −55% at end-century. Precipitation increases may moderate these declines somewhat, but to date no such increases are evident and there is no model agreement on future precipitation changes. These results, combined with the increasing likelihood of prolonged drought in the river basin, suggest that future climate change impacts on the Colorado River flows will be much more serious than currently assumed, especially if substantial reductions in greenhouse gas emissions do not occur.

The twenty‐first century Colorado River hot drought and implications for the future

American Geophysical Union (AGU) | February 17th, 2017

Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906–1999 average, the worst 15‐year drought on record. At least one‐sixth to one‐half (

Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906–1999 average, the worst 15‐year drought on record. At least one‐sixth to one‐half (average at one‐third) of this loss is due to unprecedented temperatures (0.9°C above the 1906–1999 average), confirming model‐based analysis that continued warming will likely further reduce flows. Whereas it is virtually certain that warming will continue with additional emissions of greenhouse gases to the atmosphere, there has been no observed trend toward greater precipitation in the Colorado Basin, nor are climate models in agreement that there should be a trend. Moreover, there is a significant risk of decadal and multidecadal drought in the coming century, indicating that any increase in mean precipitation will likely be offset during periods of prolonged drought. Recently published estimates of Colorado River flow sensitivity to temperature combined with a large number of recent climate model‐based temperature projections indicate that continued business‐as‐usual warming will drive temperature‐induced declines in river flow, conservatively −20% by midcentury and −35% by end‐century, with support for losses exceeding −30% at midcentury and −55% at end‐century. Precipitation increases may moderate these declines somewhat, but to date no such increases are evident and there is no model agreement on future precipitation changes. These results, combined with the increasing likelihood of prolonged drought in the river basin, suggest that future climate change impacts on the Colorado River flows will be much more serious than currently assumed, especially if substantial reductions in greenhouse gas emissions do not occur.

Torres Martinez Tribe Salton Sea Oral Testimony

Salton Sea Authority | September 24th, 2020

 Chairman and Ranking Member, I sincerely appreciate the opportunity to testify today. I am the Tribal Council Chairman of the Torres Martinez Desert Cahuilla (Tribe) an

 Chairman and Ranking Member, I sincerely appreciate the opportunity to testify today. I am the Tribal Council Chairman of the Torres Martinez Desert Cahuilla (Tribe) and a director on the Salton Sea Authority (SSA). I offer this testimony on behalf of both the Tribe and SSA.  I want to begin by thanking Congressman Ruiz (D-Calif.) and Congressman Vargas (D-Calif.) for their hard work to place this issue squarely before the Committee today. The Tribe and SSA view this hearing as a very important beginning of a more robust Congressional effort to drive federal action at the Salton Sea. 

Tribal Water Study: An Overview

Water and Tribes Initiative | October 28th, 2019

The purpose of this policy brief is to provide an overview of the Colorado River Basin Ten Tribes Partnership Tribal Water Study (Study), a unique review of the water rig

The purpose of this policy brief is to provide an overview of the Colorado River Basin Ten Tribes Partnership Tribal Water Study (Study), a unique review of the water rights, water uses, and future plans of the member tribes of the Colorado River Basin Tribes Partnership (Ten Tribes Partnership). The information in this policy brief is taken directly from the Study. In the foreword to the Study, Bureau of Reclamation (Reclamation) Commissioner Brenda Burman states that Reclamation and the Ten Tribes Partnership collaborated to document current water use and potential future water development to better facilitate planning and decision-making throughout the Colorado River Basin (Basin). The Study strengthens a Department of the Interior commitment to address water issues facing tribes and recognizes that the Colorado River is an essential foundation for the physical, economic, and cultural sustenance of tribes in the Basin. The Study also explores ways to provide a wide range of benefits to both Partnership Tribes and other water users. The mutual trust and understanding forged during the Study will prove to be critical as the Basin collaboratively addresses the significant challenges ahead. The Ten Tribes Partnership, in its foreword, stated that in addition to producing technical information, the Tribes had other goals. First, they wanted to better understand how, at present, the Study’s water use scenarios fit into the overall scheme of Colorado River Basin management. Second, they wanted to know how future development of tribal water resources will affect other water users who are now using water to which a tribe may hold legal title, but which the title-holding tribe has not yet developed for its own use. Finally, they wanted to assess--to the extent present information allows -- the role future development of tribal water rights will have on Basin operations. The Ten Tribes Partnership hopes the Study resolves some uncertainty about how tribes perceive the future for their water uses, and establishes a baseline of information for discussions and development of relationships among tribes, states, federal government, water managers, and water users throughout the Basin.

U.S.-Mexican Water Sharing: Background and Recent Developments

Congressional Research Service (CRS) | March 2nd, 2017

The United States and Mexico share the waters of the Colorado River and Rio Grande pursuant to binational agreements. Increasing water demands and reduced supplies derivi

The United States and Mexico share the waters of the Colorado River and Rio Grande pursuant to binational agreements. Increasing water demands and reduced supplies deriving from drought and air temperatures increase the challenges and significance of reliable water sharing. The International Boundary and Water Commission (IBWC) is charged with addressing issues that arise during application of binational water treaties. The IBWC is a binational entity with a U.S. Section that operates under foreign policy guidance from the U.S. Department of State. Under the binational 1944 Water Treaty, disputes and new developments can be resolved through agreed-upon interpretations of the treaty, called minutes. Mexican-U.S. relations generally grew closer during the George W. Bush and Obama Administrations. Water sharing was addressed through IBWC technical meetings and bilateral talks between government officials; these meetings and talks were the primary forum for addressing treaty compliance and frustrations of water users in Texas with Mexico’s water delivery regime. Treaty minutes were used to enhance bilateral cooperation and provide flexibility in how treaty compliance was accomplished. It remains uncertain what principles will guide and what mechanisms will be used during the Trump Administration to address water conflicts and what role enhanced cooperation (e.g., measures similar to recent binational efforts in the Colorado River basin) may play in U.S.-Mexican water sharing.

Understanding Uncertainties in Future Colorado River Streamflow

American Meteorological Society (AMS) | January 1st, 2014

The Colorado River is the primary water source for more than 30 million people in the United States and Mexico. Recent studies that project streamf low changes in the Col

The Colorado River is the primary water source for more than 30 million people in the United States and Mexico. Recent studies that project streamf low changes in the Colorado River all project annual declines, but the magnitude of the projected decreases range from less than 10% to 45% by the mid-twenty-first century. To understand these differences, we address the questions the management community has raised: Why is there such a wide range of projections of impacts of future climate change on Colorado River streamflow, and how should this uncertainty be interpreted? We identify four major sources of disparities among studies that arise from both methodological and model differences. In order of importance, these are differences in 1) the global climate models (GCMs) and emission scenarios used; 2) the ability of land surface and atmospheric models to simulate properly the high-elevation runoff source areas; 3) the sensitivities of land surface hydrology models to precipitation and temperature changes; and 4) the methods used to statistically downscale GCM scenarios. In accounting for these differences, there is substantial evidence across studies that future Colorado River streamflow will be reduced under the current trajectories of anthropogenic greenhouse gas emissions because of a combination of strong temperature-induced runoff curtailment and reduced annual precipitation. Reconstructions of preinstrumental streamflows provide additional insights; the greatest risk to Colorado River streamf lows is a multidecadal drought, like that observed in paleoreconstructions, exacerbated by a steady reduction in flows due to climate change. This could result in decades of sustained streamflows much lower than have been observed in the ~100 years of instrumental record.

Upper Colorado River Basin Compact, 1948

U.S. Bureau of Reclamation (USBR) | October 11th, 1948

Upper Division States Alternative for Post-2026 Operations of Lake Powell and Lake Mead

Colorado Department of Natural Resources (DNR) | March 5th, 2024

Utah's Land, Water and Air 2022 Report to the Governor

Utah State University | November 30th, 2022