Colorado River

Salinity Trends in a Groundwater System Supplemented by 50 Years of Imported Colorado River Water

American Chemical Society (ACS) | September 21st, 2023

The Indio subbasin of the Coachella Valley is a desert area of southern California where a growing population depends primarily on groundwater for drinking and agricultur

The Indio subbasin of the Coachella Valley is a desert area of southern California where a growing population depends primarily on groundwater for drinking and agricultural uses. The aquifer system has been supplemented with Colorado River water through managed recharge and widespread irrigation since the mid-20th century. We use a combination of geochemical modeling and trend analysis to identify changes in total dissolved solids through time, elucidate the sources of dissolved solids, and quantify the extent of contributions from those sources throughout the Indio subbasin. We conclude that recharged Colorado River water is the primary source and driver of increasing salinity, particularly in areas immediately downgradient from the recharge locations and in the eastern part of the subbasin away from the recharge ponds due to irrigation using imported water. Other contributions of dissolved solids to groundwater resources include geothermal waters, wastewater effluent, and agricultural return flow, although their effects are more localized. This study presents a broadly applicable framework for identifying sources of dissolved solids in groundwater wells and salinity trends at a regional scale in a large data set.

Salton Sea Exceedances of California’s Air-Quality Standards Highlight Governance Gaps and Monitoring Needs

University of California, Los Angeles (UCLA) | September 4th, 2025

The Salton Sea region is known for its poor air-quality, which is often linked to dust and contributes to alarmingly high rates of respiratory problems among residents. H

The Salton Sea region is known for its poor air-quality, which is often linked to dust and contributes to alarmingly high rates of respiratory problems among residents. However, air-quality issues extend beyond dust. Residents also face the distressing reality of frequent hydrogen sulfide (H2S) emissions. Depending on individual experiences, these emissions can range from uncomfortable to severely suffocating. To gauge the severity of these concerns, the Salton Sea Environmental Timeseries (SSET), a community-based research group, recently installed two hydrogen sulfide monitors in the area. Their data indicates that H₂S emissions consistently exceed the California Air Resources Board state standard of 30 parts per billion (ppb), with 243 hours above this threshold recorded between May and September 2024 alone. Existing government air-quality monitors, located north of the Salton Sea, primarily detect H₂S only when winds blow from the southeast, whereas SSET data show elevated emissions occur regardless of wind direction. This highlights a critical gap in the current government monitoring network, which fails to capture the full scope of H₂S pollution. As more data highlight connections between water and air-quality, it is crucial to monitor air-quality in all its aspects, not just those related to dust. The Salton Sea region has a predominantly low-income Latinx, immigrant, and Indigenous population across two California counties. The persistent issue of hydrogen sulfide pollution serves as a clear example of environmental injustice. For over two decades, the state and federal governments have been legally obligated to restore the Salton Sea—meeting that obligation today means pairing public health action with robust monitoring.

Salton Sea Fisheries Long-term Monitoring Sampling Report: Summer 2017

California Natural Resources Agency (CNRA) | July 13th, 2017

In early 2016, historic indices of tilapia abundance at the Salton Sea appeared to have reversed: tilapia fry were no longer observed in places where fish were regularly

In early 2016, historic indices of tilapia abundance at the Salton Sea appeared to have reversed: tilapia fry were no longer observed in places where fish were regularly visible in the past, piscivorous bird numbers at the lake were severely reduced, anglers were only catching a small fraction of past numbers of fish, and only a few small fish kills were observed. As observations of these conditions continued in early 2017, the question of whether the tilapia population was still viable was the impetus for the California Department of Fish and Wildlife (CDFW) to re-initiate gillnetting efforts.

Salton Sea Management Program and Community Needs

California Natural Resources Agency (CNRA) | January 31st, 2024

In the Southeastern corner of the state, straddling Imperial and Riverside counties, the Salton Sea (the Sea) is California’s largest inland lake and home to many Calif

In the Southeastern corner of the state, straddling Imperial and Riverside counties, the Salton Sea (the Sea) is California’s largest inland lake and home to many California Native American tribes and communities. Once a resort destination, the Sea has since become a growing environmental issue. The Sea has been shrinking, largely due to water transfers out of Imperial Valley that reduce inflows to the Sea. Drought and changes to Colorado River water availability exacerbate this trend. Although it continues to provide a vital stop along the Pacific Flyway for migratory birds, the water has become increasingly saline. As the Sea shrinks, it exposes the lakebed that has the potential to release dust, contributing to worsening air quality in a region already struggling with poor air quality from high wind events, idling vehicles, high off-road activity, commercial truck traffic, and agricultural burning. Compounding this, communities in the Eastern Coachella Valley and Imperial Valley have for decades also faced social and economic challenges. While these vibrant communities have rich cultural and natural resources, they suffer from decades of underinvestment. Residents have highlighted that local communities struggle with poor air quality, health issues, low broadband access, unreliable electricity, limited access to recreational opportunities, inadequate transportation systems, and underfunded public health infrastructure and services. These challenges make it difficult to overcome the growing environmental challenges related to the Sea.

Salton Sea Management Program Conceptual Project Implementation and Cost Estimates to Meet State Board Targets

California Natural Resources Agency (CNRA) | April 27th, 2017

The Salton Sea Management Program (SSMP) has developed a 10-year plan for Phase I that envisions a range of activities for habitat creation and dust management as

The Salton Sea Management Program (SSMP) has developed a 10-year plan for Phase I that envisions a range of activities for habitat creation and dust management as the Salton Sea recedes over 2018–2028. The California State Water Resources Control Board (SWRCB), through an order revising Order WRO 2002–0013, outlines annual and cumulative target areas for restoration through creation of habitat and dust suppression projects. These targets are defined for each year, ranging from a cumulative 500 acres by January 1, 2019, to a cumulative 29,800 acres by January 1, 2029, with a minimum 50 percent of the area being designated for fish and wildlife habitat projects. Areas around the sea are proposed for restoration projects, specifically at the southern end of the sea near the inflows of the Alamo and New rivers, and the northern end of the sea near the inflow of the Whitewater River. In a prior document (Salton Sea Management Plan Phase I: 10 Year Plan, March 2018), an overview of the project areas and activities was presented. This document presents a high-level plan for achieving the annual goals in the SWRCB order, by means of creation of wet habitat and dust control areas in different parts of the Salton Sea lakebed. This document identifies conceptual habitat ponds to be created, the associated wetted areas, and the additional dust control areas required to meet the order targets. For each of the conceptual project areas, there are estimates for berm lengths, heights, and needs for additional infrastructure, such as pumps and pipelines, causeways for equipment access, and levee extensions along river channels for flood protection of newly created habitat. Planned cross sections for the different types of linear structures are shown. Cost estimates are provided for each of the project areas over time to develop a total cost estimate. The conceptual habitat and dust control areas are based on the best current information on Salton Sea bathymetry, and demonstrate a reasonable path forward to attain the State Board order targets. The costs associated with these targets as presented in this document can be used for additional planning as part of the SSMP over the next decade. It is recognized that the actual footprints of individual projects may change in future years as better information becomes available on lakebed elevations, and relationships with other non-SSMP projects for habitat and dust control are better understood. These cost estimates are a refinement of estimates presented in the Salton Sea Management Plan Phase I: 10-Year Plan (March 2017). The cost estimates incorporate the best available cost information, and include the development of conceptual berm designs and supporting infrastructure, such as water diversions, pumps, and pipelines, and levees for river extensions. For these reasons, the cost estimate presented here supersedes the March 2017 estimate of $383 million for the 10-year implementation. But, all cost estimates at this stage are considered preliminary, and subject to revision as new field and construction data become available, and as designs are adjusted to best meet overall program needs. In the remainder of this document, two key topics are presented. In Chapter 2, there are estimates of the projected elevations of the Salton Sea over the 2018–2028 period, based on a hydrologic model of the sea. This is needed to allow estimation of exposed lakebed with the goal of constructing new habitat under dry conditions. Proposed conceptual project footprints, design and cost assumptions, and cost summaries are presented in Chapter 3.

Salton Sea Management Program Phase 1: 10-Year Plan Imperial and Riverside Counties, California Draft Environmental Assessment

U.S. Army Corps of Engineers (USACE) | June 21st, 2022

This Environmental Assessment (EA) was prepared pursuant to the National Environmental Policy Act (NEPA) and analyzes and discloses the effects of the implementation of t

This Environmental Assessment (EA) was prepared pursuant to the National Environmental Policy Act (NEPA) and analyzes and discloses the effects of the implementation of the Salton Sea Management Program’s (SSMP’s) Phase 1: 10-Year Plan (SSMP 10-Year Plan or Applicant’s Proposed Project) being proposed by CNRA (California Natural Resource Agency), California Department of Water Resources (DWR), and the California Department of Fish and Wildlife (CDFW), collectively known as the SSMP team. The SSMP team is seeking Department of the Army (DA) authorization from the United States Army Corps of Engineers (Corps), Los Angeles District, pursuant to Section 404 of the Clean Water Act (CWA; 33 USC §1344). The SSMP 10-Year Plan proposes to implement a total of 29,800 acres of aquatic habitat restoration and dust suppression projects around the perimeter of the Salton Sea. At least 50 percent of the project acreage will be created as habitat for fish and wildlife that depend on the Salton Sea ecosystem and the remainder will be projects to suppress dust.

Salton Sea Management Program Phase I: 10-Year Plan

California Natural Resources Agency (CNRA) | March 1st, 2017

Under the leadership of Governor Edmund G Brown Jr., the 2014 California Water Action Plan set forth a vision for California water management that balances statew

Under the leadership of Governor Edmund G Brown Jr., the 2014 California Water Action Plan set forth a vision for California water management that balances statewide water supply security with the protection of public, economic and ecological health. The Salton Sea offers a unique opportunity to preserve these values by leveraging a convergence of support from federal, state, and local stakeholders for a smaller and sustainable sea achieved through the projects outlined in this plan. The Salton Sea is California’s largest lake. Thirty-five miles long and 15 miles wide, the desert lake extends from the Coachella Valley into the Imperial Valley. Though saltier than the ocean, the Sea supports an abundance of fish, a food source for millions of migratory birds on the Pacific Flyway. Managing the Sea’s natural, agricultural, andmunicipal water inflows to maximize bird and fish habitat and minimize fine-particle air pollution will allow California to protect regional health, ecological wealth and a stable water supply. The Salton Sea formed in the Salton Trough in Imperial and Riverside counties. Much of the trough is below sea level and has a long history of periodic inundation from the shifting delta of the Colorado River or from infrequent storm events. The last Colorado River inundation of the area occurred in 1905 when an irrigation canal inlet gate failed and flooded much of the area. Since then, lake inflows have been primarily from agricultural activities in the area. Inflows from the New and Alamo rivers are primarily farm return flow water, although there is some inflow from Mexico, particularly during large precipitation events. Over the last several decades, water levels at the Salton Sea have declined and salinity concentrations have increased due to climate fluctuations, agricultural conservation measures, cropping practices and reduced inflows from Mexico. Recent water transfers from the Imperial Valley have further accelerated the rate of lake elevation decline and have increased the rate of salinity concentration. Declining lake levels threaten important bird habitat and pose public health risk due to particulate air pollution. Over the last 40 years numerous ideas and plans have been proposed by various entities to restore the Salton Sea. None have been implemented for a variety of reasons, including lack of a shared vision, funding constraints, and reduced inflows. In 2015, Governor Edmund G. Brown Jr. formed the Salton Sea Task Force with principle staff and members of various state agencies to identify short- and medium- term goals to respond to air quality and ecological threats at the Salton Sea. The Task Force developed actions for the Salton Sea that included: Develop and implement the Salton Sea Management Program through departments within the California Natural Resources and Environmental Protection Agencies Improve public outreach and local partnerships Accelerate project implementation and delivery Meet a short-term goal of 9,000 acres to 12,000 acres of dust suppression and habitat projects Establish a medium-term goal of 18,000 acres to 25,000 acres of dust suppression and habitat projects. The State’s Salton Sea Management Plan (SSMP) has several phases of development to protect air quality and ecosystem values at the Salton Sea. This draft technical memorandum prepared by the State of California outlines the SSMP’s first, 10-year phase (Phase I Plan). It will guide State and federal actions to meet the commitments outlined in the Memorandum of Understanding (MOU) executed on August 31, 2016, and amended on January 18, 2017 by the Department of Interior (DOI) and the California Natural Resource Agency (CNRA). The MOU, among other things, identified a goal of developing projects to protect or improve air quality, wildlife habitat, and water quality as necessary to minimize human health and ecosystem impact at the Salton Sea in the mid-term. While guided by the MOU, the SSMP is a longer-term process that has been developed and will be implemented by the State of California. This first phase of development has been planned to expedite construction of habitat and to suppress dust on areas of playa that have been or will be exposed at the Salton Sea by 2028. The Phase I Plan outlines the process for developing additional management measurements for the Salton Sea that will be implemented in later phases. The Phase I Plan also addresses the requirements of Assembly Bill 1095 (Garcia 2015) by including those projects deemed “shovel-ready projects” and including estimates of cost. Those projects include: Water backbone infrastructure, which will provide conveyance of river and Salton Sea water to air quality and habitat projects. SSMP air quality and habitat projects associated with the water backbone infrastructure The CNRA’s Phase I Species Conservation Habitat Project (saline impoundments along the southern shore to support fish and wildlife) Red Hill Bay Project, an effort of the U.S. Fish and Wildlife Service and Imperial Irrigation District to restore habitat on the southeastern shore. Torres-Martinez Wetland project, an effort of the Torres Martinez Desert Cahuilla Indians to build shallow wetlands along the northern edge of the Salton Sea. The Phase I Plan considers the implications of the 17-year drought on the Colorado River. The drought may force reductions of Colorado River water to the Lower Basin States, which in turn could impact inflows to the Salton Sea. The U.S. Bureau of Reclamation, seven Colorado River basin states and key principals of several water management agencies have been developing a Drought Contingency Plan (DCP) that includes implemented and proposed actions to address the potential water shortage. The Department of Interior Order No. 3344 - Actions to Address Effects of Historic Drought on Colorado River Water Supplies (DOI, January18, 2017) further outlines the details of the DCP. One component of the Phase I Plan is to evaluate the current hydrologic modeling for the Salton Sea and to include some of the proposed actions in the model to evaluate their potential impact to Salton Sea inflows.   As the Air Quality Planning and Implementation section of this document notes, the air quality mitigation will consist of measures to keep exposed playa wet or vegetated. A series of Best Available Control Measures (BACM) are being evaluated by the Quantification Settlement Agreement (QSA) Water Transfer mitigation program, which was created under a 2003 agricultural-to-urban water transfer agreement involving the State of California, the Imperial Irrigation District, Coachella Valley Water District, and the San Diego County Water Authority. The work of determining these best strategies will be paid for by the QSA Joint Powers Authority. The Phase I Plan involves coordination among Imperial Irrigation District, Imperial County Air Pollution Control District, South Coast Air Quality Management District and other agencies to ensure that the latest information about how lakebed exposure may affect air quality is included in the development of BACM pilot projects. In order to provide ample time for public input into this plan, the SSMP will schedule several regional workshops to solicit input from community members and stakeholders as well as provide necessary time for general public comment. This process will be announced via the program’s website. Associated documents: Salton Sea Management Program Conceptual Project Implementation and Cost Estimates to Meet State Board Targets, 4/27/2018 Appendix 1. Figures Appendix 2. Cost Projections Appendix 3. Ten-Year Phase I Plan Schedule Plan Spanish Translation: Programa de Gestión de Salton Sea Fase I: Plan de 10 Años *Plan appendices index from California Natural Resources Agency.

Salton Sea Management Program Phase I: 10-Year Plan Appendix 1. Figures

California Natural Resources Agency (CNRA) | March 1st, 2017

Salton Sea Management Program Phase I: 10-Year Plan Appendix 2. Cost Projections

California Natural Resources Agency (CNRA) | March 1st, 2017

Salton Sea Management Program Phase I: 10-Year Plan Appendix 3. Plan Schedule

California Natural Resources Agency (CNRA) | March 1st, 2017