Assessment of the Economic Impacts of California's Drought on Urban Areas

Rand Corporation (Rand) | September 6th, 1993

At the Great Salt Lake, record salinity and low water imperils millions of birds

American Association for the Advancement of Science (AAAS) | September 9th, 2022

Utah’s Great Salt Lake is smaller and saltier than at any time in recorded history. In July, the U.S. Geological Survey (USGS) reported that the world’s third-largest

Utah’s Great Salt Lake is smaller and saltier than at any time in recorded history. In July, the U.S. Geological Survey (USGS) reported that the world’s third-largest saline lake had dropped to the lowest level ever documented. And last week researchers measured the highest salt concentrations ever seen in the lake’s southern arm, a key bird habitat. Salinity has climbed to 18%, exceeding a threshold at which essential microorganisms begin to die. The trends, driven by drought and water diversion, have scientists warning that a critical feeding ground for millions of migrating birds is at risk of collapse. “We’re into uncharted waters,” says biochemist Bonnie Baxter of Westminster College, who has been documenting the lake’s alarming changes. “One week the birds are gone from a spot we usually see them. The next week we see dead flies along the shore. And each week we have to walk further to reach the water.” After years of inaction, the prospect of a dying lake, plus the risk of harmful dust blowing from the dry lakebed, is galvanizing policymakers to find ways to restore water to the shrinking lake.

Atmospheric Rivers as Drought Busters on the U.S. West Coast

U.S. Geological Survey (USGS) | April 25th, 2013

Atmospheric rivers (ARs) have, in recent years, been recognized as the cause of the large majority of major floods in rivers all along the U.S. West Coast and as the sour

Atmospheric rivers (ARs) have, in recent years, been recognized as the cause of the large majority of major floods in rivers all along the U.S. West Coast and as the source of 30%–50% of all precipitation in the same region. The present study surveys the frequency with which ARs have played a critical role as a common cause of the end of droughts on the West Coast. This question was based on the observation that, in most cases, droughts end abruptly as a result of the arrival of an especially wet month or, more exactly, a few very large storms. This observation is documented using both Palmer Drought Severity Index and 6-month Standardized Precipitation Index measures of drought occurrence for climate divisions across the conterminous United States from 1895 to 2010. When the individual storm sequences that contributed most to the wet months that broke historical West Coast droughts from 1950 to 2010 were evaluated, 33%–74% of droughts were broken by the arrival of landfalling AR storms. In the Pacific Northwest, 60%–74%of all persistent drought endings have been brought about by the arrival of AR storms. In California, about 33%–40% of all persistent drought endings have been brought about by landfalling AR storms, with more localized low pressure systems responsible for many of the remaining drought breaks.

Atmospheric Rivers, Floods and the Water Resources of California

Water (MDPI) | April 5th, 2011

California’s highly variable climate and growing water demands combine to pose both water-supply and flood-hazard challenges to resource managers. Recently important ef

California’s highly variable climate and growing water demands combine to pose both water-supply and flood-hazard challenges to resource managers. Recently important efforts to more fully integrate the management of floods and water resources have begun, with the aim of benefitting both sectors. California is shown here to experience unusually large variations in annual precipitation and streamflow totals relative to the rest of the US, variations which mostly reflect the unusually small average number of wet days per year needed to accumulate most of its annual precipitation totals (ranging from 5 to 15 days in California). Thus whether just a few large storms arrive or fail to arrive in California can be the difference between a banner year and a drought. Furthermore, California receives some of the largest 3-day storm totals in the country, rivaling in this regard the hurricane belt of the southeastern US. California’s largest storms are generally fueled by landfalling atmospheric rivers (ARs). The fractions of precipitation and streamflow totals at stations across the US that are associated with ARs are documented here and, in California, contribute 20–50% of the state’s precipitation and streamflow. Prospects for long-lead forecasts of these fractions are presented. From a meteorological perspective, California’s water resources and floods are shown to derive from the same storms to an extent that makes integrated flood and water resources management all the more important.

August 2025 Most Probable 24-Month Study

U.S. Bureau of Reclamation (USBR) | August 15th, 2025

The August 2024 24-Month Study projected the January 1, 2025, Lake Mead elevation to be below 1,075 feet and above 1,050 feet. Consistent with Section 2.D.1 of the Interi

The August 2024 24-Month Study projected the January 1, 2025, Lake Mead elevation to be below 1,075 feet and above 1,050 feet. Consistent with Section 2.D.1 of the Interim Guidelines, a Shortage Condition consistent with Section 2.D.1.a will govern the operation of Lake Mead for calendar year (CY) 2025. In addition, Section III.B of Exhibit 1 to the Lower Basin Drought Contingency Plan (DCP) Agreement will also govern the operation of Lake Mead for CY 2025. Lower Basin projections for Lake Mead take into consideration additional conservation efforts under the LC Conservation Program. The August 2025 24-Month Study projected the January 1, 2026, Lake Powell elevation to be less than 3,575 feet and at or above 3,525 feet and the Lake Mead elevation to be at or above 1,025 feet. Consistent with Section 6.C.1 of the Interim Guidelines, and Section 6.E of the 2024 Interim Guidelines SEIS ROD, the operational tier for Lake Powell in WY 2026 is the Mid-Elevation Release Tier and the water year release volume from Lake Powell is projected to be 7.48 maf. Given the hydrologic variability of the Colorado River System, the actual water year 2026 operations, and being consistent with Section 6.E of the 2024 Interim Guidelines SEIS ROD, the projected release from Lake Powell in water year 2026 may be less than 7.48 maf. The August 2025 24-Month Study projected the January 1, 2026, Lake Mead elevation to be below 1,075 feet and above 1,050 feet. Consistent with Section 2.D.1 of the Interim Guidelines, a Shortage Condition consistent with Section 2.D.1.a will govern the operation of Lake Mead for CY 2026. In addition, Section III.B of Exhibit 1 to the Lower Basin DCP Agreement will also govern the operation of Lake Mead for CY 2026. Lower Basin projections for Lake Mead take into consideration additional conservation efforts under the LC Conservation Program. The 2026 operational tier determinations for Lake Powell and Lake Mead will be documented in the 2026 AOP, which is currently in development. Related scenarios: August 2025 Probable Minimum 24-Month Study August 2025 Probable Maximum 24-Month Study

August 2025 Probable Maximum 24-Month Study

U.S. Bureau of Reclamation (USBR) | August 15th, 2025

In addition to the August 2025 24-Month Study based on the Most Probable inflow scenario, and in accordance with the Upper Basin Drought Response Operations Agreement (DR

In addition to the August 2025 24-Month Study based on the Most Probable inflow scenario, and in accordance with the Upper Basin Drought Response Operations Agreement (DROA), Reclamation has conducted additional model runs in August to determine a possible range of reservoir elevations. Probable minimum and probable maximum model runs are conducted in January, April, August, and October, or when necessary to incorporate changing conditions. The Probable Minimum inflow scenario reflects a dry hydrologic condition which statistically would be exceeded 90% of the time. The Most Probable inflow scenario reflects a median hydrologic condition which statistically would be exceeded 50% of the time. The Probable Maximum inflow scenario reflects a wet hydrologic condition which statistically would be exceeded 10% of the time. There is approximately an 80% probability that a future elevation will fall inside the range of the minimum and maximum inflow scenarios. Additionally, there are possible inflow scenarios that would result in reservoir elevations falling outside the ranges indicated in these reports. Related scenarios: August 2025 Most Probable 24-Month Study August 2025 Probable Minimum 24-Month Study

August 2025 Probable Minimum 24-Month Study

U.S. Bureau of Reclamation (USBR) | August 15th, 2025

In addition to the August 2025 24-Month Study based on the Most Probable inflow scenario, and in accordance with the Upper Basin Drought Response Operations Agreement (DR

In addition to the August 2025 24-Month Study based on the Most Probable inflow scenario, and in accordance with the Upper Basin Drought Response Operations Agreement (DROA), Reclamation has conducted additional model runs in August to determine a possible range of reservoir elevations. Probable minimum and probable maximum model runs are conducted in January, April, August, and October, or when necessary to incorporate changing conditions. The Probable Minimum inflow scenario reflects a dry hydrologic condition which statistically would be exceeded 90% of the time. The Most Probable inflow scenario reflects a median hydrologic condition which statistically would be exceeded 50% of the time. The Probable Maximum inflow scenario reflects a wet hydrologic condition which statistically would be exceeded 10% of the time. There is approximately an 80% probability that a future elevation will fall inside the range of the minimum and maximum inflow scenarios. Additionally, there are possible inflow scenarios that would result in reservoir elevations falling outside the ranges indicated in these reports. Related scenarios: August 2025 Most Probable 24-Month Study August 2025 Probable Maximum 24-Month Study  

Basin-scale responses of groundwater-resource quality to drought and recovery, San Joaquin Valley, California

Hydrological Processes (Wiley) | April 15th, 2024

Groundwater-resource quality is assumed to be less responsive to drought compared to that of surface water due to relatively long transit times of recharge to drinking-su

Groundwater-resource quality is assumed to be less responsive to drought compared to that of surface water due to relatively long transit times of recharge to drinking-supply wells. Here, we evidence dynamic perturbations in aquifer pressure dynamics during drought and subsequent recovery periods cause dramatic shifts in groundwater quality on a basin scale. We used a novel application of time-series clustering on annual nitrate anomalies at >450 public-supply wells (PSWs) across California's San Joaquin Valley during 2000–22 to group subpopulations of wells with similar water-quality responses to drought. Additionally, we statistically evaluated the direction and magnitude of multi-constituent water-quality changes across the San Joaquin Valley using a broader dataset of >3000 PSWs with data during two select hydrologic stress periods representing an extreme drought (2012–16) and subsequent recovery (2016–19). Results of time-series clustering and stress-period change analyses corroborate a predominant regional response to pumping stress characterized by increased concentrations of anthropogenic constituents (nitrate, total dissolved solids) and decreased concentrations of geogenic constituents (arsenic, fluoride), which largely reversed during recovery. Cluster analysis also identified a secondary, less commonly occurring group of PSWs where nitrate decreased during drought, but explanatory factor analysis was not able to discern hydrogeologic drivers for these two divergent response patterns. Long-term tracer data support the hypothesis that the predominant regional signal of nitrate increase during drought is caused by enhanced capture of modern-aged groundwater by PSWs during periods of pumping stress, which can drive rapid changes in water quality on seasonal and multiannual timescales. Pumping-induced migration of modern, oxic groundwater to depth during drought may affect geochemical conditions in deeper portions of regional aquifers controlling the mobility of geogenic contaminants over the long term.

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.

Broadening understandings of drought: the climate vulnerability of farmworkers and rural communities in California (USA)

Environmental Science & Policy (Elsevier) | November 1st, 2018

The vulnerability of food and agricultural systems to climate variability and change is extensively studied. However, the vulnerability of agricultural labor is largely

The vulnerability of food and agricultural systems to climate variability and change is extensively studied. However, the vulnerability of agricultural labor is largely ignored in climate vulnerability and adaptation studies, especially in the context of developed countries. This research examines the drought vulnerability of farmworkers both in the fields and in their communities by analyzing how changes in water resources and agricultural practices impact socioeconomic drought. A combination of surveys and semi-structured interviews with farmworkers, farmers, and social service providers in California’s San Joaquin Valley is used to identify the impacts of drought on agricultural labor, water security, food security, and health. Findings demonstrate that drought impacts and vulnerabilities are multi-scalar and uneven. Agricultural drought adaptations, including increase in groundwater pumping and changes in crops, reshapes the vulnerability of farmworkers and rural communities. There is a need for continued interdisciplinary research on the socioeconomic dimensions of drought as well as increased representation of needs and vulnerabilities of farmworkers and rural communities in drought and climate change adaptation planning.