The State Water Project Delivery Capability Report 2023 Addendum - Impacts of Subsidence

California Department of Water Resources (DWR) | May 7th, 2025

The purpose of this addendum is to show how ongoing subsidence effects on the California Aqueduct will impact operation of the State Water Project (SWP). The addendum pro

The purpose of this addendum is to show how ongoing subsidence effects on the California Aqueduct will impact operation of the State Water Project (SWP). The addendum provides information to SWP water users about a potential range of water delivery impacts over the next 20 years if no corrective action is taken to address the subsidence effects. However, the California Department of Water Resources (DWR) is committed to restore the conveyance capacity of the California Aqueduct and has an engineering plan for near-term fixes. DWR is also working with its partners to secure additional funding sources for this work. DWR is confident that the California Aqueduct capacity will be restored and the SWP will not see the impacts outlined in this addendum. Thus, long-term water supply planning activities by water users should rely on the potential future SWP allocation results presented in the 2023 Delivery Capability Report (DCR 2023) released in 2024.

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.

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

Utilization of Waters of the Colorado and Tijuana Rivers and of the Rio Grande: Treaty Between the United States of America and Mexico

U.S. Government Publishing Office (GPO) | November 14th, 1945

Water Allocation, Use, and Regulation in California

California Department of Water Resources (DWR) | October 30th, 2014

In California, water use and supplies are controlled and managed under an intricate system of common law principles, constitutional provisions, State and federal statutes

In California, water use and supplies are controlled and managed under an intricate system of common law principles, constitutional provisions, State and federal statutes, court decisions, and contracts or agreements. All of these components constitute the institutional framework for the protection of public interests and their balance with private claims in California’s water allocation and management.

What will it take to stabilize the Colorado River?

American Association for the Advancement of Science (AAAS) | July 21st, 2022

The Colorado River supplies water to more than 40 million inhabitants in the southwestern United States and northwestern Mexico. A basin-wide water supply crisis is occur

The Colorado River supplies water to more than 40 million inhabitants in the southwestern United States and northwestern Mexico. A basin-wide water supply crisis is occurring because of decreased watershed runoff caused by a warming climate and legal and water management policies that allow systematic overuse. By the end of 2022, combined storage in Lake Powell and Lake Mead, the two largest reservoirs in the United States, will have declined from 95% full in 2000 to approximately 25% full. If this “Millennium Drought” persists, then stabilizing reservoir levels to avoid severe outcomes will require reducing water use to match diminished runoff. With a process underway to renegotiate interstate and international agreements on consumptive uses of the river, we describe a promising new management approach based on combined storage of both reservoirs, rather than just Lake Mead as currently used, to trigger consumptive use reductions to the Lower Basin and Mexico.