South Lahontan

Priorities for California’s Water -- Stewarding the Wet Years

Public Policy Institute of California (PPIC) | November 2nd, 2023

The 2023 water year provided a case study of California’s increasingly volatile climate, with large swings between wet and dry conditions both within and between years.

The 2023 water year provided a case study of California’s increasingly volatile climate, with large swings between wet and dry conditions both within and between years. It highlighted our need to better navigate multiple imperatives: storing more water during intense wet periods to build water supply reliability, protecting communities and infrastructure against the threat of increasingly damaging floods, and taking better advantage of wet years to improve the health of freshwater ecosystems and native fish and wildlife.

Priorities for California’s Water: Are We Ready for Climate Change?

Public Policy Institute of California (PPIC) | November 12th, 2024

California faces many immediate challenges around water management, but as the record-breaking heat of 2024 makes clear, temperatures are rising—and Californians are co

California faces many immediate challenges around water management, but as the record-breaking heat of 2024 makes clear, temperatures are rising—and Californians are contending with the consequences. In a PPIC poll earlier this year, residents named climate change, forest fires and wildfires, and water supply and drought as the most important environmental issues facing the state. 

Projected Brackish Water Desalination Projects in California

California Department of Water Resources (DWR) | February 20th, 2024

California’s Water Supply Strategy: Adapting to a Hotter, Drier Future (Water Supply Strategy), adopted by the Newsom Administration in 2022, identifies multiple action

California’s Water Supply Strategy: Adapting to a Hotter, Drier Future (Water Supply Strategy), adopted by the Newsom Administration in 2022, identifies multiple actions necessary to bolster water supply reliability in the face of climate change. The first set of actions drive the development of new water supplies and set explicit goals for expanding the production of both recycled and desalinated water. Action 1.2 includes specific targets for expanded brackish water desalination: 28,000 acre-feet by 2030, and 84,000 acre-feet by 2040. The Water Supply Strategy identifies five steps toward achieving this goal.

Proposed Health-Protective Concentration for the Noncancer Effects of Hexavalent Chromium in Drinking Water

California Environmental Protection Agency (CalEPA) | November 21st, 2023

Public Review Draft Report to the Legislature on the Results of the Indoor Residential Water Use Study

Publisher not available | May 11th, 2021

Water planning has always been important for urban retail water suppliers (Suppliers) but is even more critical today, as development progresses and California grapples w

Water planning has always been important for urban retail water suppliers (Suppliers) but is even more critical today, as development progresses and California grapples with frequent droughts and expected long-term climate impacts. Prior to the adoption of the Urban Water Management Planning (UWMP) Act in 1983, there were no specific requirements that mandated urban water suppliers to conduct long-term water resources planning. While many Suppliers did conduct long-term water planning, those that did not were more vulnerable to supply disruptions during dry periods and catastrophic events. Urban water management planning is needed at the local level because only local Suppliers have the knowledge and ability to tailor their planning to their unique conditions and involve their local community in the planning effort. Click here for the DWR press release

Quantifying the Relationship Between Atmospheric River Origin Conditions and Landfall Temperature

American Geophysical Union (AGU) | October 11th, 2022

The temperature of landfalling atmospheric rivers (ARs) has direct implications for regional water resources. Compared to cool ARs, warm ARs can result in more surface ru

The temperature of landfalling atmospheric rivers (ARs) has direct implications for regional water resources. Compared to cool ARs, warm ARs can result in more surface runoff and flooding, less water availability via low snow accumulations and enhanced snowmelt, and greater challenges for storm forecasting and reservoir operations. Based on case studies, ARs with subtropical origin locations and warm origin conditions are assumed to be associated with warmer landfall temperatures—though, to date, this has not yet been demonstrated systematically. We analyze North Pacific ARs that made landfall along the West Coast of North America from 1980 to 2017. We find that ARs originating over the subtropical Pacific Ocean near Hawaii (“Pineapple Express”-type ARs) are indeed 1.5°C warmer and 2 kg/m2 moister in winter than ARs originating elsewhere. We extend this analysis for the full study population of ARs by quantifying AR origin conditions, including the spatial distribution of origin temperature, moisture content, and integrated vapor transport (IVT). We use fixed effects multivariate regression to quantify the relative influence of the origin conditions on landfall temperature. Our regression models show that AR origins with lower latitudes, longer AR lifetimes, and stronger IVT are associated with warmer landfall temperatures and that ARs that start warm generally stay warm. We also find that the phase of the El Niño/Southern Oscillation does not exhibit a consistent relationship with AR landfall temperature. Overall, our results partially affirm—yet also complicate—common assumptions about the role of different origin conditions in landfalling AR temperature.

Racanelli Decision: Detailed summary of the decision

Department of Justice (DOJ) | November 16th, 2007

At their meeting on October 25, 2007, the Delta Vision Blue Ribbon Task Force members asked for a summary of United States v. State Water Resources Control Board (1986) 1

At their meeting on October 25, 2007, the Delta Vision Blue Ribbon Task Force members asked for a summary of United States v. State Water Resources Control Board (1986) 182 Cal.App.3d 82, commonly referred to as the “Racanelli Decision,” after the appellate judge who wrote the opinion. We repeat the Court’s own very short summary of the case, followed by a more detailed summary of the decision.

Rapid decline of California’s native inland fishes: a status assessment

University of California, Davis (UC Davis) | November 1st, 2010

Degradation of freshwater ecosystems is a global crisis best understood through intensive study of well-studied regional faunas. A quantitative protocol was used

Degradation of freshwater ecosystems is a global crisis best understood through intensive study of well-studied regional faunas. A quantitative protocol was used to determine conservation status of all 129 freshwater fishes native to California. Seven (5%) are extinct; 34 (26%) qualified for listing as endangered or threatened species; 32 (25%) were rated as imperiled, qualifying as California Species of Special Concern, with potential for listing; 34 (26%) rated being on a watch list and 22 (17%) were found to be relatively secure. Of 31 species officially listed under federal and state endangered species acts, 17 (55%) clearly qualified for listing under our criteria and 12 (39%) were rated as species of special concern. Conversely, of 34 extant species with the lowest ratings under our criteria, only 17 (50%) were officially listed. Climate change, area occupied and anthropogenic threats had the largest negative impact on status. Of the 15 categories of anthropogenic threats analyzed, those most likely to diminish status were alien species, agriculture and dams. Overall, 83% of California’s freshwater fishes are extinct, endangered, or in decline, a 16% increase since 1995 and a 21% increase since 1989. The decline seen in California’s inland fishes is probably typical of declines in areas that are less well documented, indicating a strong need for better methods of conservation of freshwater ecosystems.

Recent decreases in snow water storage in western North America

Nature Portfolio (Springer Nature) | May 22nd, 2023

Mountain snowpacks act as natural water towers, storing winter precipitation until summer months when downstream water demand is greatest. We introduce a Snow Storage Ind

Mountain snowpacks act as natural water towers, storing winter precipitation until summer months when downstream water demand is greatest. We introduce a Snow Storage Index (SSI), representing the temporal phase difference between daily precipitation and surface water inputs—sum of rainfall and snowmelt into terrestrial systems—weighted by relative magnitudes. Different from snow water equivalent or snow fraction, the SSI represents the degree to which the snowpack delays the timing and magnitude of surface water inputs relative to precipitation, a fundamental component of how snow water storage influences the hydrologic cycle. In western North America, annual SSI has decreased (p 

Recharge Area Identification, Utilization, and Protection Resource Management Strategy

California Department of Water Resources (DWR) | April 29th, 2024

This resource management strategy (RMS) advances water supply augmentation, resilience, and equity in California by providing summaries of the state of knowledge, applica

This resource management strategy (RMS) advances water supply augmentation, resilience, and equity in California by providing summaries of the state of knowledge, applications, and available information and resources on recharge area identification, utilization, and protection.