Statement of Findings regarding the Approval of the Sacramento Valley – Antelope Subbasin 2024 Groundwater Sustainability Plan

California Department of Water Resources (DWR) | February 27th, 2025

Statement of Findings Regarding the Determination of Inadequate Status of the San Joaquin Valley – Pleasant Valley Subbasin 2024 Groundwater Sustainability Plan

California Department of Water Resources (DWR) | February 27th, 2025

Statewide Perspective on Chemicals of Concern and Connections Between Stream Water Quality and Land Use

California State Water Resources Control Board (SWRCB) | February 1st, 2012

The California Surface Waters Ambient Monitoring Program (SWAMP) is tasked with assessing water quality in all of California’s surface waters. The program

The California Surface Waters Ambient Monitoring Program (SWAMP) is tasked with assessing water quality in all of California’s surface waters. The program conducts monitoring directly and through collaborative partnerships, and provides numerous information products designed to support water resource management in California. The Stream Pollution Trends (SPoT) program is a statewide monitoring effort focused on the SWAMP priority of assessing the levels to which aquatic life beneficial uses are supported in California streams (SWAMP 2010). The program has three primary goals: Determine long-term trends in stream contaminant concentrations and effects statewide. Relate water quality indicators to land-use characteristics and management effort. Establish a network of sites throughout the state to serve as a backbone for collaboration with local, regional, and federal monitoring. The SPoT program is specifically designed to fill critical information needs for state, regional and local resource management programs, including Clean Water Act (CWA) §303d impaired waters listing, CWA §305b condition assessment, total maximum daily load (TMDL) assessment and allocation, non-point source program water quality assessment, stormwater and agricultural runoff management, pesticide registration and labeling, and local land use planning. SPoT is a long-term trends monitoring program that will help managers understand how water quality conditions are changing over time in relation to land use change and resource management practice implementation. This report covers the rst annual survey, so trends assessment will not begin until the second and third year surveys are included in the next SPoT report (due in 2012). The focus of this report is on identifying chemicals of concern and the watershed land uses associated with their presence in California streams. The data collected can be used in a space-for-time-swap approach to estimate the effect that further land use change (such as increasing urbanization) would have on stream water quality in California. The results indicate that, on a statewide basis, levels of most measured pollutants in stream sediment increased as urban land cover in their watersheds increased. Industrial compounds, some metals, and many pesticides were found at higher concentrations in urban watersheds than in agricultural or other watersheds statewide. Pyrethroid pesticides were detected in stream sediments from more than half of the SPoT watersheds, and were measured at concentrations associated with toxicity in more than a quarter of the total samples. DDTs and PCBs, both banned for more than three decades, are still commonly detected in California streams, with DDTs frequently exceeding sediment quality guidelines. PBDEs and PAHs were common in urban areas, and mercury was above guideline values in a small number of samples from urban watersheds and watersheds where it is geologically abundant. The data presented here describe the baseline condition for the SPoT long-term trends assessment. They also demonstrate a significant relationship between land use and stream pollution, and provide data directly relevant to a number of agency water quality protection programs.

Statistical Methods Development and Sampling Design Optimization to Support Trends Analysis for Loads of Polychlorinated Biphenyls from the Guadalupe River in San Jose, California, USA

San Francisco Estuary Institute (SFEI) | September 3rd, 2018

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP), with guidance from its Small Tributaries Loading Strategy (STLS) Team, has been conducting s

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP), with guidance from its Small Tributaries Loading Strategy (STLS) Team, has been conducting small tributary loading studies at several sites in the Bay Area since 2003. A current priority for the STLS is developing a strategy for measuring trends in pollutant loadings from small tributaries to the Bay.  This technical report presents the work to develop a statistical model for trends in loads of polychlorinated biphenyls (PCBs), and estimate the power for proposed monitoring designs as a basis for detecting trends for the Guadalupe River watershed (San Jose, California). The statistical approach builds upon the turbidity surrogate methodology that has been employed in the STLS since 2003. A novel, two-stage statistical modeling approach was used to incorporate the significant turbidity-PCB relationships that exist, and evaluate climatic, seasonal, and inter-annual factors as additional potential drivers of PCB loads. The longest-running time series of tributary monitoring by the STLS on the Guadalupe River was selected as the case study for developing and testing the statistical approach. As a result of this effort, a multiple linear regression model for detecting trends in PCB loads in the Guadalupe River was developed. 

Status and Trends of Delta-Suisun Services

California Department of Water Resources (DWR) | March 1st, 2007

Covering only about 1 percent of California’s area, the Sacramento-San Joaquin Delta, including Suisun Bay and Marsh (hereafter referred to as Delta-Suisun), contribute

Covering only about 1 percent of California’s area, the Sacramento-San Joaquin Delta, including Suisun Bay and Marsh (hereafter referred to as Delta-Suisun), contributes much more to the state and nation than one might expect from its small size. The Delta-Suisun provides a set of environmental and economic services whose benefits extend well beyond its borders. To help people gain a common understanding of these services, this report provides an overview of the existing status of these services and a perspective about how these services may change in the future. This report was prepared to highlight observations and to present a common understanding about the status and trends of key Delta-Suisun services. The Delta Risk Management Strategy (DRMS) is considering these observations while conducting a risk assessment for the Delta-Suisun and will report on its findings in spring 2007. Having a common understanding of the area’s services will benefit ongoing and new Delta-Suisun studies and initiatives. Information in this report will be considered by members of the Delta Vision Blue Ribbon Task Force and Stakeholder Coordination Group as they begin work on the Delta Vision and Strategic Plan.

Status and Understanding of Groundwater Quality in the Klamath Mountains Study Unit, 2010: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | August 6th, 2014

Groundwater quality in the Klamath Mountains (KLAM) study unit was investigated as part of the Priority Basin Project of the California Groundwater Ambient Monitoring and

Groundwater quality in the Klamath Mountains (KLAM) study unit was investigated as part of the Priority Basin Project of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in Del Norte, Humboldt, Shasta, Siskiyou, Tehama, and Trinity Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA Priority Basin Project was designed to provide a spatially unbiased, statistically robust assessment of the quality of untreated (raw) groundwater in the primary aquifer system. The assessment is based on water-quality data and explanatory factors for groundwater samples collected in 2010 by the USGS from 39 sites and on water-quality data from the California Department of Public Health (CDPH) water-quality database. The primary aquifer system was defined by the depth intervals of the wells listed in the CDPH water-quality database for the KLAM study unit. The quality of groundwater in the primary aquifer system may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. This study included two types of assessments: (1) a status assessment, which characterized the status of the current quality of the groundwater resource by using data from samples analyzed for volatile organic compounds, pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements, and (2) an understanding assessment, which evaluated the natural and human factors potentially affecting the groundwater quality. The assessments were intended to characterize the quality of groundwater resources in the primary aquifer system of the KLAM study unit, not the quality of treated drinking water delivered to consumers by water purveyors.

Status and Understanding of Groundwater Quality in the Mojave Basin Domestic-Supply Aquifer Study Unit, 2018: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | May 15th, 2024

Groundwater quality in the western part of the Mojave Desert in San Bernardino County, California, was investigated in 2018 as part of the California State Water Resource

Groundwater quality in the western part of the Mojave Desert in San Bernardino County, California, was investigated in 2018 as part of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment Program Priority Basin Project. The Mojave Basin Domestic-Supply Aquifer study unit (MOBS) region was divided into two study areas—floodplain and regional—to assess differences between the two major aquifers used for drinking water supply in the area. This assessment characterized the quality of ambient groundwater and not the quality of treated drinking water.

Status and Understanding of Groundwater Quality in the Northern Sierra Nevada Foothills Domestic-Supply Aquifer Study Units, 2015–17: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | May 25th, 2021

Status and Understanding of Groundwater Quality in the Redding–Red Bluff Shallow Aquifer Study Unit, 2019: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | February 9th, 2023

Groundwater quality in the north Sacramento Valley (NSV) was studied in the Redding–Red Bluff shallow aquifer study unit (referred to as the NSV shallow aquifer or NSV-

Groundwater quality in the north Sacramento Valley (NSV) was studied in the Redding–Red Bluff shallow aquifer study unit (referred to as the NSV shallow aquifer or NSV-SA) as part of the Priority Basin Project (PBP) of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is in Shasta and Tehama Counties and included two physiographic study areas: (1) the Redding area to the north and (2) the Red Bluff area to the south. The study was focused on groundwater resources used for domestic drinking-water supply, which are mostly drawn from shallower parts of aquifer systems than those of groundwater resources used for public drinking-water supply in the same area. This assessment characterized the quality of ambient groundwater in the aquifer before filtration or treatment, rather than the quality of drinking water delivered to the tap.

Status and understanding of groundwater quality in the Sacramento Metropolitan Domestic-Supply Aquifer study unit, 2017—California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | May 26th, 2022

Groundwater quality in the Sacramento Metropolitan Domestic-Supply Aquifer study unit (SacMetro-DSA) was studied from August to November 2017 as part of the second phase

Groundwater quality in the Sacramento Metropolitan Domestic-Supply Aquifer study unit (SacMetro-DSA) was studied from August to November 2017 as part of the second phase of the Priority Basin Project of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is in parts of Amador, Placer, Sacramento, and Sutter Counties, and the extent of the study unit was defined by the location of three California Department of Water Resources groundwater subbasins: the North American, the South American, and the Cosumnes. The SacMetro-DSA focused on groundwater resources used for domestic drinking-water supply, which generally correspond to shallower parts of aquifer systems than those of groundwater resources used for public drinking water supply in the same area. The assessments characterized the quality of untreated groundwater, not the quality of drinking water.