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.

Status and Understanding of Groundwater Quality in the San Francisco Bay Groundwater Basins, 2007: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | March 29th, 2013

Groundwater quality in the approximately 620-square-mile (1,600-square-kilometer) San Francisco Bay study unit was investigated as part of the Priority Basin Project of t

Groundwater quality in the approximately 620-square-mile (1,600-square-kilometer) San Francisco Bay study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in the Southern Coast Ranges of California, in San Francisco, San Mateo, Santa Clara, Alameda, and Contra Costa 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.

Status and Understanding of Groundwater Quality in the Santa Clara River Valley, 2007: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | September 26th, 2011

Groundwater quality in the approximately 460-square-mile Santa Clara River Valley study unit was investigated from April through June 2007 as part of the Priority Basin P

Groundwater quality in the approximately 460-square-mile Santa Clara River Valley study unit was investigated from April through June 2007 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project is conducted by the U.S. Geological Survey (USGS) in collaboration with the California State Water Resources Control Board and the Lawrence Livermore National Laboratory. The Santa Clara River Valley study unit contains eight groundwater basins located in Ventura and Los Angeles Counties and is within the Transverse and selected Peninsular Ranges hydrogeologic province.

Status of California's Wadeable Perennial Streams (2000-2007)

California State Water Resources Control Board (SWRCB) | October 1st, 2011

The Surface Water Ambient Monitoring Program’s (SWAMP) Perennial Streams Assessment (PSA) surveys measure the ability of California’s perennial wadeable str

The Surface Water Ambient Monitoring Program’s (SWAMP) Perennial Streams Assessment (PSA) surveys measure the ability of California’s perennial wadeable streams (some 85,000 km) to support aquatic life. PSA surveys found half (50%) of the wadeable perennial stream length in California to be in relatively good biological condition, while about 22% is in very degraded biological condition. The statewide distribution of good, degraded and very degraded sites shows that most high quality streams in good biological condition are located in the mountainous regions of the state. Streams with the most degraded biology tend to be found in low-lying agricultural and urban areas in the central valley and parts of the coast.

Status of Water Quality in Groundwater Resources Used for Drinking-Water Supply in the Southeastern San Joaquin Valley, 2013–15: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | April 25th, 2024

The California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) investigated water quality of groundwater resources used for drinki

The California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) investigated water quality of groundwater resources used for drinking-water supplies in the Madera-Chowchilla, Kings, Kaweah, Tule, and Tulare Lake groundwater subbasins of the southeastern San Joaquin Valley during 2013–15. The study focused primarily on groundwater resources used for domestic-supply wells in the southeastern San Joaquin Valley (SESJV-D), which correspond mostly to shallower parts of aquifer systems, compared to the groundwater resources used for public-supply wells in the southeastern San Joaquin Valley (SESJV-P). The investigation had three components: (1) characterization of the status of water quality in the SESJV-D, (2) comparison between water quality in the SESJV-D and SESJV-P, and (3) identification of natural and anthropogenic factors that potentially could affect water quality in these resources.

Status of Water-Quality Conditions in the United States, 2010–20, Chapter C of U.S. Geological Survey Integrated Water Availability Assessment—2010–20

U.S. Geological Survey (USGS) | January 15th, 2025

Key findings related to groundwater and surface water quality problems that affect water availability include the following: Drinking-water use is affected by geogen

Key findings related to groundwater and surface water quality problems that affect water availability include the following: Drinking-water use is affected by geogenic and anthropogenic contaminants. Elevated concentrations of arsenic, manganese, strontium, radium, adjusted gross alpha, and nitrate are common in drinking water aquifers serving more than 30 million people in the United States. About one-third of stream miles assessed as surface-water sourced drinking-water supply are impaired with respect to drinking-water use, most commonly because of non-mercury metals and salinity. Health-based drinking-water violations at public water systems may disproportionately affect socially vulnerable communities. People with domestic wells as their drinking-water source are more prone to exposure to contaminants compared to people served by public water systems. Ecological water uses are predominantly limited by nutrients, sediment, temperature, pathogens, salinity, and pesticides. Contaminants without or historically without regulatory thresholds (for example, polyfluoroalkyl substances [PFAS]) have been underrepresented in previous assessments and also likely contribute to ecological degradation and human exposure. Water availability for human and ecological use is limited by elevated constituent concentrations in surface water and groundwater because of human activities. Human activities include sources (for example, inorganic and organic chemicals), processes (for example, dredging), or permanent landscape modifications (for example, dams, urbanization). Interactions between groundwater and surface water can influence water quality. Surface-water recharge can be a source of contaminants to aquifers, whereas groundwater discharge, with slow transport times, results in long-term, lagged delivery of pollutants to surface waters (especially nitrate, chloride, PFAS, and other constituents). Little information exists regarding human-health exposure risks from mixtures of geogenic and anthropogenic drinking-water contaminants. Co-occurrence and mixtures of multiple water-quality constituents, taken together, can cause compounding negative effects on water availability but mixtures are rarely measured in standard monitoring protocols. Alternative water resources could increase water availability by providing additional supply from non-traditional sources such as reclaimed wastewater, brackish and saline water, and produced water from oil and gas development. Companion chapters: U.S. Geological Survey Integrated Water Availability Assessment—2010–20, Chapter A Water Supply in the Conterminous United States, Alaska, Hawaii, and Puerto Rico, Water Years 2010–20, Chapter B Water Use Across the Conterminous United States, Water Years 2010–20, Chapter D  Climate Change and Future Water Availability in the United States, Chapter E  Integrated Water Availability in the Conterminous United States, 2010–20, Chapter F