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.

California Fish and Game, Volume 39

California Department of Fish and Wildlife (CDFW) | April 2nd, 1953

Formation of California's Salton Sea in 1905-07 was not "accidental"

2020 Desert Symposium Field Guide and Proceedings | April 26th, 2020

It is widely thought that the Salton Sea was created accidentally in 1905-07 because of engineering negligence in the diversion of Colorado River water for agricultural u

It is widely thought that the Salton Sea was created accidentally in 1905-07 because of engineering negligence in the diversion of Colorado River water for agricultural use in California’s Imperial Valley. This is a misconception. Scientific data and historical records establish that formation of the Salton Sea was not accidental. The lake formed during 1905-07 in the same manner that numerous other large Salton Basin lakes did for at least tens of thousands of years from the Late Pleistocene through the late 19th century: as a result of the lower Colorado River’s natural hydrodynamic regime, floodplain morphodynamics, and established avulsion style in combination with changes in streamflow attributable to regional hydroclimate. A large body of scientific and historical evidence indicates the 1905-07 Colorado River flooding into the Salton Basin and the creation of a large lake there would have occurred regardless of man-made modifications to the river’s natural levee and distributary channels. In fact, the flooding would likely have been even worse in the absence of human intervention.

Fundamentals of estimating the net benefits of ecosystem preservation: The case of the Salton Sea

Hydrobiologia (Springer) | July 15th, 2008

This article, both theoretical and methodological in nature, argues the potential merits of using a net benefits’ framework as a tool to aid policy-makers in their eff

This article, both theoretical and methodological in nature, argues the potential merits of using a net benefits’ framework as a tool to aid policy-makers in their efforts to compare Salton Sea restoration alternatives and inform the public as to the potential magnitude and distribution of trade-offs associated with each alternative. A net benefits approach can provide a more accurate comparison and evaluation of the potential net returns from public spending on Salton Sea restoration than what wouldbe provided under the suggested criteria of current legislative mandates. Furthermore, a net benefits framework provides a more lucid and systematic accounting framework by which to enumerate the full array of benefits and costs of each alternative for policy analysis. Finally, net benefits’ analysis serves to add transparency to the decision-making process sothat the public gains an understanding of how its scarce resources, including both financial and natural capital, are being appropriated. Additionally, we illustrate and emphasize the importance of estimating the non-market values associated with many of the ecosystem services provided by the Salton Sea and describe the major techniques that do so.

Groundwater Availability within the Salton Sea Basin

Lawrence Livermore National Laboratory (LLNL) | January 29th, 2008

Haven or Hazard: The Ecology and Future of the Salton Sea

Pacific Institute | February 1st, 1999

California’s Salton Sea is a fertile oasis in the hostile desert of south-eastern California. It has been adopted by millions of birds migrating along the Pacific Flywa

California’s Salton Sea is a fertile oasis in the hostile desert of south-eastern California. It has been adopted by millions of birds migrating along the Pacific Flyway and also attracts human anglers and boaters. Rehabilitating the Salton Sea presents a huge challenge to the local, state, and federal officials that share responsibility for its health, as well as the health of those in surrounding communities. Originally published in February 1999,  Haven or Hazard: The Ecology and Future of the Salton Sea looks in detail at the condition of the Sea, the threats to the area, and possible solutions to protect its value for animals and people.

Hazard: The Future of the Salton Sea With No Restoration Project

Pacific Institute | May 1st, 2006

The Salton Sea lies on the brink of catastrophic change. The amount of water flowing into the Sea in the next twenty years will decrease by more than 40%, causing

The Salton Sea lies on the brink of catastrophic change. The amount of water flowing into the Sea in the next twenty years will decrease by more than 40%, causing its surface elevation to drop by more than 20 feet, rapidly shrinking its volume by more than 60%, tripling its salinity, and exposing more than 100 square miles of dusty lakebed to the desert’s blowing winds. These changes will cause four major impacts: Human health in the Imperial and Coachella valleys – currently home to more than 400,000 people and growing quickly – will be harmed by the estimated 33% increase in the amount of fine windblown dust in the basin. The Imperial Valley already suffers from the highest childhood asthma hospitalization rate in the state; the growing number of retirees living in both valleys are especially susceptible to poor air quality. Air quality in these two valleys – which already fails to meet state and federal air quality standards – would get much worse, increasing the cost of bringing these areas into compliance. Air quality-related litigation and state liability will increase. California has assumed ultimate responsibility for managing only those lands exposed due to a recent set of water transfers, constituting about half of the estimated 134 square miles exposed in 30 years. Responsibility for managing any dust blowing off the other 60 or so square miles will rest with the individual property owner. However, there is no clear way to determine which lands will be exposed due to the water transfers and which will be exposed due to other actions. Total air quality management costs at Owens Lake have exceeded $400 million. Costs at the Salton Sea could be higher. Many – if not most – of the hundreds of thousands of birds that currently use the Sea will lose their roosting and breeding habitats and their sources of food. The Sea’s fish will be almost entirely gone within a dozen years. Those birds that remain will suffer from disease and the reproductive deformities and failures that plagued the Kesterson National Wildlife Refuge twenty years ago. Some of the endangered and threatened species that use the Sea may be able to find other habitats, but others could suffer significant population losses. The tremendous scale of the Sea adds to its complexity, and the difficulty of finding a viable solution. The Sea currently runs almost 35 miles long, and 15 miles at its widest point, covering about 365 square miles. It has the largest surface area of any lake in California, yet is barely 50 feet at its deepest point. The Sea is 1/3 saltier than the ocean, and, fed by the fertilizers running off of neighboring fields, sustains incredible levels of biological productivity. Until recently, the amount of water entering the Sea was roughly balanced by the amount of water evaporating from its broad surface. Stabilizing the Sea at its current salinity would require the removal of more than four million tons of salt each year, assuming flows to the Sea do not change. But they will change. Under a set of agreements signed in 2003, the Imperial Valley has begun to transfer water to San Diego County, ultimately reducing flows to the Salton Sea. Other actions, including actions in Mexico, will also reduce the amount of water flowing to the Sea, by 45% or more in the next 30-40 years. These changes will dramatically decrease the size of the Salton Sea and the quality of its water. In September, 2003, the California legislature passed a set of laws that implement the 2003 water agreements and provide a 15-year reprieve for the Sea. The legislation offers the prospect of more than $300 million of restoration funds, but it does not guarantee a long-term restoration project for the Salton Sea. California’s Resources Agency will submit a Salton Sea Ecosystem Restoration Plan and related documents to the state legislature by December 31, 2006. The cost of any long-term restoration plan will almost certainly exceed a billion dollars. Although various private-public partnerships have been suggested, funding and implementation of any restoration plan is far from certain, especially given the lack of consensus on a preferred alternative.

Hazard’s Toll: The Costs of Inaction at the Salton Sea

Pacific Institute | September 3rd, 2014

The declining Salton Sea will impose massive public health and environmental costs on local residents and Californians generally, as described in the Pacific Institute re

The declining Salton Sea will impose massive public health and environmental costs on local residents and Californians generally, as described in the Pacific Institute report Hazard’s Toll. The continued failure to protect and preserve the Salton Sea, worsening air quality and the loss of valuable ecological habitat – combined with diminished recreational revenue and property devaluation – could cost as much as $70 billion over the next 30 years. The high costs of California’s 2007 plan for the Salton Sea have inhibited deliberation and deterred any meaningful investment in revitalizing the Salton Sea. Many decision-makers assume that delaying action at the Salton Sea will result in business as usual, with no additional costs. Hazard’s Toll makes clear that this is not the case. Because the Salton Sea has changed over the past decade and will soon enter a period of very rapid decline, the costs of inaction are escalating rapidly. Even at the low end of the costs estimated in Hazard’s Toll, the long-term social and economic costs of a deteriorating Salton Sea could approach $29 billion, well in excess of the project cost of the state’s plan. The consequences of continued inaction at the Salton Sea will be felt most directly by the 650,000 people who live in harm’s way of the Salton Sea’s dust, as well as by the birds and other life that depend on the lake. Hazard’s Toll estimates the costs of these consequences, for the first time. These considerable costs demonstrate the urgent need for action at the Salton Sea. The report also highlights a large number of important data gaps that should be addressed in the near future. Despite many decades of study and the impending decline of the Salton Sea, we still lack information on many factors affecting life and the economy in the region. These factors, combined with general uncertainty about population growth rates, climate change, and changing hydrologic conditions, suggest that the above estimates indicate a general magnitude of potential future costs, rather than precise projections.

Identifying Major Hydrologic Change Drivers in a Highly Managed Transboundary Endorheic Basin: Integrating Hydro-ecological Models and Time-Series Data Mining Techniques

American Geophysical Union (AGU) | August 23rd, 2022

The fragile balance of endorheic lakes in highly managed semi-arid basins with transboundary water issues has been altered by the intertwined effects of global warming an

The fragile balance of endorheic lakes in highly managed semi-arid basins with transboundary water issues has been altered by the intertwined effects of global warming and long-term water mismanagement to support agricultural and industrial demand. The alarming rate of global endorheic lakes’ depletion in recent decades necessitates formulating mitigation strategies for ecosystem restoration. However, detecting and quantifying the relative contribution of causal factors (climate variability and anthropogenic stressors) is challenging. This study developed a diagnostic multivariate framework to identify major hydrologic drivers of lake depletion in a highly managed endorheic basin with a complex water distribution system. The framework integrates the Soil and Water Assessment Tool (SWAT) simulations with time-series decomposition and clustering methods to identify the major drivers of change. This diagnostic framework was applied to the Salton Sea Transboundary Basin (SSTB), the host of the world's most impaired inland lake. The results showed signs of depletion across the SSTB since late 1998 with no significant changes in climate conditions. The time-series data mining of the SSTB water balance components indicated that decreases in lake tributary inflows (-16.4 Mm3 yr-2) in response to decline in Colorado River inflows, associated with state water transfer agreements, are causing the Salton Sea to shrink, not changes in the irrigation operation as commonly believed. The developed multivariate detection and attribution framework is useful for identifying major drivers of change in coupled natural-human systems.

Integrated Water Management Plan Evaluation: A review of the Salton Sea Authority's preferred project concept for rehabilitating the Salton Sea

U.S. Bureau of Reclamation (USBR) | March 11th, 2005

The USGS Salton Sea Science Office convened an experts workshop, from November 15-17 in Riverside, California, to evaluate a Salton Sea rehabilitation proposal known as t

The USGS Salton Sea Science Office convened an experts workshop, from November 15-17 in Riverside, California, to evaluate a Salton Sea rehabilitation proposal known as the Integrated Water Management Plan (IWMP) (also known as the ‘North Lake Plan’). Salton Sea Restoration: Preferred Project Report (Salton Sea Authority 2004) describes the IWMP and provided the basis for this evaluation. As described further in the following, the IWMP would build a causeway across the middle of the current Salton Sea, creating a smaller north lake that discharges into a proposed 20,000 acres of shallow-water wetlands in the southern portion of the Sea, and a terminal brine pool, as well as various treatment wetlands. A recently implemented water conservation and transfer agreement, along with several unrelated actions, will significantly decrease the volume of water flowing into southeastern California’s Salton Sea in the next 20 years, shrinking the Sea and increasing salinity beyond the tolerances of most of the species currently present. Future conditions at the Sea will be very different from current conditions, whether or not the IWMP is implemented. The surface elevation of the Salton Sea fluctuates by more than 0.3 meter (one foot) annually, primarily in response to agricultural irrigation patterns in the Imperial Valley. On January 1, 2005, the surface elevation of the Salton Sea was ~69.8 meters (228.86 feet) below mean sea level. The Sea is a terminal lake; the only outlet for its waters is via evaporation. The Sea is an officially-designated sump for the water draining from fields in the adjacent Coachella and Imperial Valleys; the Sea also receives agricultural and municipal drainage from the Mexicali Valley, in Baja California. The Sea is currently 33% saltier than the ocean and getting saltier each year. The Sea is also eutrophic, with extremely high levels of biological productivity, fed by fertilizers draining off of the fields in the basin. This productivity has attracted more than 400 species of birds to the area, including large numbers of breeding birds and special status species. The objective of the experts workshop evaluation process was to develop a credible description of the future physical and biological conditions created by implementation of the IWMP. The objective of the evaluation process was not to support or reject the proposal. This was a scientific review process. Economic and recreational impacts generated by implementation of the proposal, although important, were beyond the scope of this evaluation process and were not addressed. The evaluation did not concern itself with regulatory, policy, political or agency positions. Based on the scientific expertise of the participants, the evaluation sought to identify any critical flaws in the proposal, as well as major beneficial outcomes, major questions to be resolved, and considerations of importance in judging the effectiveness of the proposal. The views and opinions reflected in this report are those of the participants and do not necessarily represent the views or opinions of their agencies or affiliations, nor do they necessarily represent the views of the U.S. Bureau of Reclamation or U.S. Geological Survey.