Colorado River

Beyond the Haze: A UC Dust Report on the Causes, Impacts, and Future of Dust Storms in California

University of California, San Diego (UC San Diego) | December 5th, 2024

This report is intended to be a comprehensive summary of the current state of knowledge of dust storms in California, including where dust storms occur, the features cont

This report is intended to be a comprehensive summary of the current state of knowledge of dust storms in California, including where dust storms occur, the features contributing to their geographic distribution, factors driving historical and likely future changes in dust, the impact dust storms have on human health, the economy, and environment of the state, and an assessment of what is needed to mitigate or adapt to those impacts. The purpose of this report is to be a resource to the public, community-based organizations, state agencies, and policy makers on dust storms in California. The information here is intended to help guide future adaptation and mitigation efforts and identify critical gaps in understanding that impede those efforts.

Biological Condition of Non-Perennial Streams and Spring-Fed Oases in the Colorado River Basin Region

California State Water Resources Control Board (SWRCB) | August 22nd, 2014

The Colorado River Basin Regional Water Board conducted bioassessment sampling at high-quality (i.e., “reference”) streams in their region during 2013-2015. The purpo

The Colorado River Basin Regional Water Board conducted bioassessment sampling at high-quality (i.e., “reference”) streams in their region during 2013-2015. The purpose of the study was to characterize the biological condition of these streams, which had never been done before, and to expand ongoing research as to whether existing biological indices, developed primarily for perennial streams, apply in nonperennial streams. The latter are usually excluded from bioassessment surveys, but make up the majority of stream length in the most arid parts of the state like the Colorado River Basin, leaving stream condition assessments in such regions largely incomplete. The indices evaluated were the California Stream Condition Index (CSCI) based on benthic macroinvertebrates and the first to have statewide applicability in perennial streams, and the D18 and S2 indices for diatoms and soft algae, respectively, developed for use in perennial streams of southern coastal California. Sixteen sites were sampled during the 3-year period, and data loggers that measure water depth were deployed for 2 of the 3 years to characterize the hydrologic regime at each site. Most sites were nonperennial, but a few were spring-fed perennial oases. Fourteen of the sites passed formal reference screening criteria developed by statewide programs. The CSCI and S2 indices had generally good applicability in the region, with most samples from reference sites indicated either good or fair (i.e., non-degraded) biological condition. The mean CSCI score at regional reference sites was slightly lower than the statewide mean (i.e., 0.90 vs. 1.0, respectively), but the difference could be an artifact of a relatively small regional data set. The fact that CSCI and S2 performed as well as they did in a region, and in a set of stream types, largely excluded from their development indicates that the indices can be used in nonperennial streams (and spring-fed oases) in the Colorado River Basin as long as certain minimum flow conditions are met, such as sustained flow for several weeks prior to sampling and sufficient wetted width to employ existing protocols developed for perennial streams. By contrast, the D18 index did not perform well in the region. A majority of samples from reference sites indicated poor or very poor biological condition when condition thresholds based on statewide data sets were used, but even when more relaxed thresholds based on just south coast reference sites were applied, the number of reference sites in good or fair condition was still much lower than expected. This was not a result of regional reference sites being of low quality, but was most likely an artifact of applying the index to a set a stream types unintended for its use. Development of statewide algal indices is underway, which may improve the performance of diatom indices in the southern desert.

Boulder Canyon Project Agreement: Requesting Apportionment of California’s Share of the Waters of the Colorado River among the Applicants in the State

U.S. Bureau of Reclamation (USBR) | August 18th, 1931

Breathing Hazard: Air Pollution in the Salton Sea Region

Pacific Institute | August 14th, 2025

The Salton Sea, California’s largest lake, has shrunk by more than 70 square miles (19%) in the past 30 years. Colorado River water irrigates more than half a million a

The Salton Sea, California’s largest lake, has shrunk by more than 70 square miles (19%) in the past 30 years. Colorado River water irrigates more than half a million acres of productive farmland in the Imperial and Coachella valleys, in southeastern California (Figure ES-1). Runoff from these fields sustains the lake but has decreased by almost 20% since the 1990s (Figure ES-2) as a result of agreements transferring water out of the region. Continuing efforts to protect Lake Mead and Lake Powell have incentivized farmers to further reduce their use of Colorado River water, accelerating the decline of the Salton Sea and exposing additional lakebed (known as “playa”). More playa means more dust in an area already suffering from bad air quality and some of the highest respiratory hospitalization rates in the state. Expected additional water use reductions will accelerate the Salton Sea’s decline and increase the amount of playa exposed, affecting the health of the 560,000 people in the region.

Building water resilience in the face of cascading wildfire risks

American Association for the Advancement of Science (AAAS) | September 15th, 2023

Bulletin 118 - California's Groundwater Update 2013

California Department of Water Resources (DWR) | April 15th, 2015

California’s Groundwater Update 2013 compiles and analyzes readily available groundwater information to characterize California’s groundwater basins, aquifers, and we

California’s Groundwater Update 2013 compiles and analyzes readily available groundwater information to characterize California’s groundwater basins, aquifers, and well infrastructure. It also presents data and analysis related to groundwater monitoring efforts, aquifer conditions in response to extraction, groundwater management practices, and conjunctive management programs. It expands and enhances baseline groundwater information on a regional scale, identifies challenges associated with sustainable groundwater management, and helps guide implementation of diverse resource management strategies. The set of data, information, and analysis developed can help local and regional groundwater managers, as well as individual well owners, better understand California’s hidden and commonly misunderstood resource. This Bulletin has been uploaded in the following separate files reflecting hydrologic regions and appendices. Chapter One / Introduction  Chapter Two / State-wide Update  Chapter Three / North Coast Chapter Four / San Francisco Bay Chapter Five / Central Coast Chapter Six / South Coast  Chapter Seven / Sacramento River Chapter Eight / San Joaquin River Chapter Nine / Tulare Lake Chapter Ten / North Lahontan Chapter Eleven / South Lahontan Chapter Twelve / Colorado River Appendix A: Methods and Assumptions Appendix B: CASGEM Basin Prioritization Appendix C: Groundwater Use Data 2010-2015 Appendix D: Conjunctive Management Survey Appendix E: Change in Groundwater in Storage Appendix F: Subsidence

Bulletin 118: California's Groundwater Update 2020 (draft)

California Department of Water Resources (DWR) | March 1st, 2021

Groundwater is a precious and limited resource that is used in meeting the needs of California’s large and small urban areas, rural groundwater users, irrigated agricul

Groundwater is a precious and limited resource that is used in meeting the needs of California’s large and small urban areas, rural groundwater users, irrigated agriculture, and the environment. Since the last California’s Groundwater (CalGW) Update in 2003, there has been significant changes to land use, water use, water application practices, and water allocations. In addition, the effects of climate change have affected California’s reliance on groundwater. It is expected that there will be additional changes in land use, water use, adjustments in water allocations, and that climate change will continue to affect the environment, thus elevating the importance of the reporting in CalGW Updates.  According to the last comprehensive report, California’s Groundwater Update 2003 (CalGW Update 2003), California’s reliance on groundwater was approximately 30 percent during a wet-to-average precipitation water year and approximately 40 percent during dry periods. Since then, the percentage of groundwater reliance has increased to between 30 and 40 percent during above normal to-wet years and to as much as 58 percent during dry periods (California Department of Water Resources 2018).

Bulletin 17-00, Dams within Jurisdiction of the State of California

California Department of Water Resources (DWR) | July 31st, 2000

Bulletin 17-65, Dams within Jurisdiction of the State of California

California Department of Water Resources (DWR) | August 31st, 1965

Bulletin 17-71, Dams within Jurisdiction of the State of California

California Department of Water Resources (DWR) | October 29th, 1971