Spatial analysis of residential location at birth, PFAS in public water, and childhood cancers in Southern California (2000–2019)

Nature Portfolio (Springer Nature) | March 5th, 2026

Locations with significant increased risk of all cancers, leukemias, lymphomas, and other solid tumors were collocated with PFOS/PFOA contaminated water supplies. Referen

Locations with significant increased risk of all cancers, leukemias, lymphomas, and other solid tumors were collocated with PFOS/PFOA contaminated water supplies. Referent ORs for location were attenuated after adjusting for PFOS detection and in stratified analyses for children of US-born mothers but not for Mexico-born mothers. PFOS detection was associated with higher odds of neuroblastoma (OR = 1.51, 95% CI: 1.07, 2.13) and retinoblastoma (OR = 1.83, 95% CI: 1.19, 2.79), whereas all cancers (OR = 1.07; 95% CI: 0.97, 1.18), brain tumors (OR = 1.15, 95% CI: 0.96, 1.37), and other solid tumors (OR = 1.12, 95% CI: 0.98, 1.29) had non-significant associations. PFOA detection was associated with elevated risk of retinoblastoma (OR = 1.85, 95% CI: 1.14, 3.01).

Considerations and Pathways for Potential State Oversight of Community Water Systems’ Wildfire Fighting Efforts in California

University of California, Los Angeles (UCLA) | March 3rd, 2026

Since the Los Angeles Fires of January 2025, dramatic shifts have occurred in perceptions, expectations, and understanding of water systems’ role in fighting wildfires

Since the Los Angeles Fires of January 2025, dramatic shifts have occurred in perceptions, expectations, and understanding of water systems’ role in fighting wildfires in California. As a consequence, policy attention has increased regarding the potential for enhanced statewide oversight to enhance wildfire-fighting capacity across community water systems. No state in the U.S. has previously pursued this path. Water systems face many obstacles to fighting wildfires that they have not been expected or supported to overcome. At the same time, as wildfires become more urban and increasingly encroach into the service territories of community water systems, the concept introduces interesting questions and potential innovations in design and implementation that may be good investments as part of long-term climate change adaptation.

Delta-Mendota Subbasin Staff Assessment

California State Water Resources Control Board (SWRCB) | March 2nd, 2026

The Delta-Mendota Subbasin (subbasin) is located in the western portion of the San Joaquin Valley, in portions of Fresno, Madera, Merced, San Joaquin, San Benito, and Sta

The Delta-Mendota Subbasin (subbasin) is located in the western portion of the San Joaquin Valley, in portions of Fresno, Madera, Merced, San Joaquin, San Benito, and Stanislaus counties, and contains the cities of Dos Palos, Firebaugh, Gustine, Los Banos, Mendota, Newman, and Patterson. It is critically overdrafted and managed by 7 GSA Groups, comprised of 23 GSAs, which include: the Aliso Water District GSA Group, the Farmers Water District GSA Group, the Fresno County Management Areas A and B GSA Group, the Grassland GSA Group, the Northern Delta-Mendota GSA Group, the Central Delta-Mendota GSA Group, and the San Joaquin River Exchange Contractors GSA Group. During most years, agriculture accounts for more than 85% of groundwater use in the subbasin (Water Year 2019–Water Year 2024 Annual Reports). The state intervention process for the Delta-Mendota Subbasin was initiated in March 2023 when DWR determined the subbasin’s six 2022 GSPs were inadequate.  The GSAs released a single revised draft GSP in May 2024, which they adopted with slight revisions in July 2024 (2024 GSP). State Water Board staff evaluated the 2024 GSP to determine if identified deficiencies were resolved. The GSAs made significant progress. State Water Board staff concludes the GSAs amended the GSP such that a probationary designation of the Delta-Mendota Subbasin is unnecessary and recommends the Board return the subbasin to DWR’s jurisdiction for continued evaluation of local management under SGMA.

Water Quality in California

Public Policy Institute of California (PPIC) | February 23rd, 2026

Making Waves: One Water Quality Standardization Concept – A Leap for Sustainable Water Management

Elsevier | February 20th, 2026

Current water management frameworks are often disjointed, failing to consider the full range of potential water uses. This fragmentation leads to inconsistent regulations

Current water management frameworks are often disjointed, failing to consider the full range of potential water uses. This fragmentation leads to inconsistent regulations; for example, potable water production from wastewater often faces stricter quality standards than water sourced from even wastewater-impacted surface waters. This article proposes a use-based approach to water management, developing water quality standards that account for the economic, public health, and ecological needs of downstream users. We advocate for expanding the concept of water quality from simple pollutant removal to “building water” to match the needs of users so desired constituents are either left in the source water or added to treated water to meet specific user needs. This strategy requires a multidimensional, risk-based regulatory framework, supported by advances in data science and affordable measurement tools for effective enforcement. Such advancement enables a move beyond binary standards to foster sustainable global water resource management and mitigate scarcity.

Revisiting chlorophyll a thresholds for San Francisco Bay: Insights from observations of phytoplankton molecular abundance

Elsevier | February 14th, 2026

Harmful Algal Blooms (HABs) are a hazard for coastal environments worldwide; identifying screening thresholds of chlorophyll-a (chl-a) associated with inc

Harmful Algal Blooms (HABs) are a hazard for coastal environments worldwide; identifying screening thresholds of chlorophyll-a (chl-a) associated with increased risk of HABs is a management priority. Molecular surveillance of coastal phytoplankton and bivalve biotoxins could be used to link chl-a with HAB risk, but requires an understanding of whether the HAB risks increase uniformly as chl-a rises, or whether some taxa are disproportionately favored, and if these relationships vary by season. In this study, we present a novel use of molecular abundance data to investigate the scientific bases for estuarine chl-a thresholds protective against HABs. In San Francisco Bay (SFB), California, the relationship between molecular relative abundance (as measured by 18S metabarcoding) of nine different HAB taxa, absolute quantitative polymerase chain reaction (qPCR) abundance, and mussel toxin concentrations of a subset of the taxa were investigated for thresholds as a function of increasing chl-a. Our results show most HAB taxa did not increase in absolute or relative abundance during SFB’s spring bloom interval, when chl-a levels were highest (>10 µg/L) but the assemblage was dominated by non-harmful diatoms. However, several flagellated, mixotrophic taxa did increase above their molecular baseline in fall, and the combined probability of any HAB occurring above baseline was elevated when chl-a reached ∼4.6 µg/L in the fall. This work demonstrates the promise of molecular approaches in disentangling the seasonally complex interplay between stressors and phytoplankton/HAB community responses and has the potential to provide clearer, more cost-effective monitoring and mitigation strategies for managers.

Groundwater quality near an oil field in a stream-dominated recharge setting, California, USA

PLOS | February 12th, 2026

Alluvial valley aquifers are important sources of water supply in many areas but effects of co-located oil and gas development on these resources have not been widely rep

Alluvial valley aquifers are important sources of water supply in many areas but effects of co-located oil and gas development on these resources have not been widely reported, especially in settings where recharge is dominated by stream infiltration. Interpreting the presence of geochemical indicators in the context of hydrology, geology, and other factors provides a more complete understanding of the relations between groundwater and sources of oil-field fluids and aids in identifying risks associated with oil and gas development. Groundwater and Salinas River water samples were collected in an alluvial valley near the San Ardo Oil Field in Monterey County, California and analyzed for a wide range of dissolved chemical, gas, and isotopic constituents to determine if oil-field fluids (water and gas from oil-producing and non-producing zones) have mixed with fresh groundwater used for supply. Hydraulic gradients, age-dating tracers, and other geochemical indicators showed that recharge from the Salinas River has the potential to dilute oil-field fluids that might migrate or seep into the aquifer. Groundwater and Salinas River water collected downgradient of the San Ardo Oil Field showed little or no evidence of mixing with oil-field fluids. Some samples within the oil field contained trace amounts of hydrocarbons or elevated temperatures, indicating that any potential effects from oil-field activities are minor or have been diluted by recharge from the Salinas River. The two samples with the most geochemical evidence of potential mixing with oil-field fluids (SP-18 and GW-17) were collected west of or along the Los Lobos fault, where naturally occurring hydrocarbons are near the land surface. Those samples were also collected near active or inactive oil-field wells, and so anthropogenic activities and pathways could not be ruled out as a cause of trace detections of hydrocarbons and elevated temperatures in the aquifer.

Antecedent moisture enhances early warning of atmospheric river flood hazards

Publisher not available | February 12th, 2026

Atmospheric rivers are narrow bands of water vapor transport and serve as key drivers of water supplies and flood hazards in mid-latitude regions. The atmospheric river s

Atmospheric rivers are narrow bands of water vapor transport and serve as key drivers of water supplies and flood hazards in mid-latitude regions. The atmospheric river scale supports early-warning communication by ranking events from potentially beneficial to hazardous based on atmospheric forcing represented by water vapor transport magnitude and duration. However, the scale does not consider land-surface conditions that can influence how precipitation derived from water vapor translates into streamflow and flood hazards. Analyzing atmospheric river landfalls across catchments in California and central Chile, we show that divergences between atmospheric river rank and flood response are primarily explained by pre-existing soil moisture conditions. Based on this insight, we develop a simple modification to the atmospheric river scale that nearly doubles the scale’s correspondence with peak streamflow and increases the number of flood-generating atmospheric rivers classified as hazardous by more than 30%. These findings demonstrate that incorporating land-surface conditions can enhance early-warning hazard classification tools.

Confined Animal Facility Permitting and Reporting Under the Porter-Cologne Water Quality Control Act: An Analysis of Regional Board Activities

Stanford University | February 2nd, 2026

This white paper analyzes reports containing (1) data from 2023 for the five regions with the largest numbers of CAFs in California; and (2) data from 2024 from the regio

This white paper analyzes reports containing (1) data from 2023 for the five regions with the largest numbers of CAFs in California; and (2) data from 2024 from the region with the most CAFs in the state. We identify six central problems with the self-reporting regime: CAFs frequently underreport wastewater production, or fail to report it at all. CAFs frequently underreport manure production. CAFs do not disclose, or inadequately document, where waste goes. Most CAFs fail to report how much waste they apply to their crops. (Those that do typically report significant overapplication.) CAFs frequently fail to account for all nutrients in the waste they produce. Regional Boards do not adequately enforce reporting requirements.

Urban Water Management Plan Guidebook

California Department of Water Resources (DWR) | January 30th, 2026

In 1983, the State of California Legislature (Legislature) enacted the Urban Water Management Planning Act (UWMP Act). The UWMP Act requires an urban water supplier (Supp

In 1983, the State of California Legislature (Legislature) enacted the Urban Water Management Planning Act (UWMP Act). The UWMP Act requires an urban water supplier (Supplier) providing water for municipal purposes to more than 3,000 customers or serving more than 3,000 acre-feet annually to adopt an Urban Water Management Plan (UWMP) every five years, demonstrating water supply reliability in normal, single dry, and multiple dry water years. The UWMP Act also requires the California Department of Water Resources (DWR) to report to the Legislature on the status of UWMPs. Appendix A contains copies of the UWMP Act and other sections of the California Water Code relevant to UWMPs. Appendix B shows revisions to the UWMP Act and to Water Code. There have been no requirement changes since 2020; only definitions have been added or updated.