Groundwater Quality in the Owens Valley, California

U.S. Geological Survey (USGS) | January 9th, 2013

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monito

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Owens Valley is one of the study areas being evaluated. The Owens study area is approximately 1,030 square miles (2,668 square kilometers) and includes the Owens Valley groundwater basin (California Department of Water Resources, 2003). Owens Valley has a semiarid to arid climate, with average annual rainfall of about 6 inches (15 centimeters). The study area has internal drainage, with runoff primarily from the Sierra Nevada draining east to the Owens River, which flows south to Owens Lake dry lakebed at the southern end of the valley. Beginning in the early 1900s, the City of Los Angeles began diverting the flow of the Owens River to the Los Angeles Aqueduct, resulting in the evaporation of Owens Lake and the formation of the current Owens Lake dry lakebed. Land use in the study area is approximately 94 percent (%) natural, 5% agricultural, and 1% urban. The primary natural land cover is shrubland. The largest urban area is the city of Bishop (2010 population of 4,000). Groundwater in this basin is used for public and domestic water supply and for irrigation. The main waterbearing units are gravel, sand, silt, and clay derived from surrounding mountains. Recharge to the groundwater system is primarily runoff from the Sierra Nevada, and by direct infiltration of irrigation. The primary sources of discharge are pumping wells, evapotranspiration, and underflow to the Owens Lake dry lakebed. The primary aquifers in Owens Valley are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells in Owens Valley are completed to depths between 210 and 480 feet (64 to 146 meters), consist of solid casing from the land surface to a depth of 50 to 80 feet (15 to 24 meters), and are screened or perforated below the solid casing

Groundwater quality in the Redding–Red Bluff shallow aquifer study unit of the northern Sacramento Valley, California

U.S. Geological Survey (USGS) | April 23rd, 2020

 This study was designed to provide a statistically representative assessment of the quality of groundwater resources used for domestic drinking water in the Redding–

 This study was designed to provide a statistically representative assessment of the quality of groundwater resources used for domestic drinking water in the Redding– Red Bluff study unit. A total of 50 wells were sampled between December 2018 and April 2019 (Shelton and others, 2020). Domestic wells in the study unit typically are drilled to depths of 80–338 feet (10th–90th percentiles; Shelton and others, 2020), which are shallower (p<0.001) than the depths of public-supply wells in the same area (typically 115–450 feet deep; Bennett and others, 2011). Water levels in domestic wells in the study unit typically are 15–163 feet below land surface (10th–90th percentiles; Shelton and others, 2020). 

Groundwater Quality in the Sacramento Metropolitan Shallow Aquifer, California

U.S. Geological Survey (USGS) | May 2nd, 2019

The Sacramento metropolitan (SacMetro) study unit covers approximately 3,250 square kilometers of the Central Valley along the eastern edge of the northern and southern e

The Sacramento metropolitan (SacMetro) study unit covers approximately 3,250 square kilometers of the Central Valley along the eastern edge of the northern and southern ends of the San Joaquin and Sacramento Valleys, respectively. Groundwater withdrawals supply a significant portion of the water-resource needs of the region. In the southern portion of the study unit, groundwater accounts for nearly 90 percent of water demand in the area (South Area Water Council, 2011).  Groundwater sampled in the SacMetro study unit comes from alluvial aquifers primarily composed of sediments derived from the Sierra Nevada Mountains to the east. Recharge to the groundwater system is primarily from the streams draining the Sierra Nevada, and from precipitation and infiltration of applied irrigation water (California Department of Water Resources, 2003). The public-supply aquifer system assessments of this area in 2005 found elevated concentrations of inorganic constituents including arsenic, iron, and manganese as well as of solvents in some wells (Bennett and others, 2010; 2011).  This study was designed to provide a statistically representative assessment of the quality of groundwater resources used for domestic drinking water in the SacMetro study unit. A complete listing of what was measured, including the sampling results, are presented in Bennett and others, 2019. A total of 49 wells were sampled between July 2017 and November 2017 (Bennett and others, 2019). The wells in the study were 32–160 meters deep, and water levels were 1–62 meters below land surface. 

Groundwater Quality in the San Fernando–San Gabriel Groundwater Basins, California

U.S. Geological Survey (USGS) | March 31st, 2012

Groundwater Quality in the San Francisco Bay Groundwater Basins, California

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

Groundwater Quality in the Santa Barbara Coastal Plain, California

U.S. Geological Survey (USGS) | August 1st, 2016

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California established the Groundwater Ambient Mo

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California established the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The Santa Barbara Coastal Plain is one of the study units. The Santa Barbara study unit covers more than 48 square miles in the Transverse and Selected Peninsular Ranges hydrogeologic province and includes parts of Santa Barbara and Ventura Counties (Davis and Kulongoski, 2016). The study unit is flanked by the Santa Ynez Mountains on the north and the Pacific Ocean on the south. The study unit consists of five coastal plain groundwater basins (California Department of Water Resources, 2003). These five groundwater basins are Goleta, Foothill, Santa Barbara, Carpinteria, and Montecito, from west to east.

Groundwater Quality in the Shallow Aquifers of the Madera– Chowchilla and Kings Subbasins, San Joaquin Valley, California

U.S. Geological Survey (USGS) | January 8th, 2018

Groundwater Quality in the Shallow Aquifers of the Tulare, Kaweah, and Tule Groundwater Basins and Adjacent Highlands areas, Southern San Joaquin Valley, California

U.S. Geological Survey (USGS) | January 11th, 2017

The Tulare Shallow Aquifer study unit covers approximately 2,320 square miles and consists of the Tulare, Kaweah, and Tule groundwater basins of the southern San Joaquin

The Tulare Shallow Aquifer study unit covers approximately 2,320 square miles and consists of the Tulare, Kaweah, and Tule groundwater basins of the southern San Joaquin Valley and adjacent highlands of the Sierra Nevada (California Department of Water Resources, 2003; Bennett and others, 2017). The freshwater aquifer system in the groundwater basins is composed of Quaternary-age alluvial and fluvial sediments primarily derived from the Sierra Nevada to the east and is divided into upper and lower zones by a clay-rich lacustrine unit, the Corcoran Clay (Faunt, 2009). The highlands have fractured rock aquifers composed primarily of Mesozoic-age granitic rocks. The hydrology of the southern San Joaquin Valley has been extensively altered by human activity, especially by agricultural development (Faunt, 2009). This study examined the quality of groundwater resources used for domestic drinking-water supply. Domestic wells in the study unit typically are drilled to depths of 150 to 500 feet (Bennett and others, 2017), which is shallower than the depths of public-supply wells in the same area (typically 300 to 1,400 feet deep; Burton and others, 2012). Water quality varies with depth in the groundwater system. This study was designed to provide a statistically representative assessment of groundwater resources used for domestic drinking water (Bennett and others, 2017). A total of 96 wells, distributed across the study unit, were sampled between November 2014 and April 2015. Previous groundwater studies in this area have found that nitrate, fumigants, microbial indicators, and several trace elements are present at elevated concentrations in some domestic wells (Burow and others, 1998; Jurgens and others, 2010; Harter and Lund, 2012; California State Water Resources Control Board, 2016).

Groundwater Quality in the Sierra Nevada, California

U.S. Geological Survey (USGS) | December 23rd, 2014

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monito

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project (PBP) of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The Sierra Nevada Regional study unit constitutes one of the study units being evaluated. The Sierra Nevada Regional (SNR) study unit covers approximately 25,000 square miles and includes the Sierra Nevada mountain and foothill regions. The study unit was divided into four study areas corresponding to the four major rock types present in the region: granitic rocks, metamorphic rocks, sedimentary deposits, and volcanic rocks (Shelton and others, 2010). In contrast to most other study units evaluated by the GAMA PBP, the SNR study unit consists primarily of fractured-bedrock aquifers. Most of the Sierra Nevada consists of granitic and metamorphic rocks. Groundwater is in fractures in the rocks. The fracture systems may be interconnected or isolated, resulting in variability in water levels, well yields, and water quality on local and regional scales (California Department of Water Resources, 2003). Sedimentary basins contain glacial, alluvial fan, fluvial, and lake sediments. Aquifers composed of different materials commonly contain groundwater with different chemical compositions.

Groundwater Quality in the South Coast Interior Basins, California

U.S. Geological Survey (USGS) | May 14th, 2014

The South Coast Interior Basins (SCI) study unit covers approximately 653 square miles and consists of the Livermore, Gilroy-Hollister, Cuyama Valley, Castac Lake Valley,

The South Coast Interior Basins (SCI) study unit covers approximately 653 square miles and consists of the Livermore, Gilroy-Hollister, Cuyama Valley, Castac Lake Valley, Cuddy Canyon Valley, Cuddy Ranch Area, Cuddy Valley, and Mil Potrero groundwater basins (California Department of Water Resources, 2003). These basins were grouped into three study areas based on geography: Livermore (LIV), Gilroy (GIL), and Cuyama (CUY) (Mathany and others, 2009). Average annual precipitation across the study unit varies among the three study areas—from more than 20 inches (in.) along the northwest margin of the LIV study area to less than 8 in. in the northern parts of the CUY study area. The study areas are drained by the Arroyo de la Laguna canal in LIV, the Pájaro River and the San Benito River in GIL, and the Cuyama River in CUY. The primary aquifer system consists of Plio-Pleistocene sedimentary formations, Tertiary to Holocene-age alluvial sedimentary sequences, and unconfined Holocene- age and Pleistoceneage alluvium. The primary aquifer system is defined as those parts of the aquifers corresponding to the perforated intervals of the public-supply wells listed in the California Department of Public Health (CDPH) database. Public-supply wells in the study unit are typically drilled to depths between 200 and 600 feet, consist of solid casing from the land surface to a depth of about 50 to 350 feet, and are perforated below the solid casing. Water quality in the primary aquifer system may differ from that in the shallower and deeper parts of the aquifer system. Land use within 500-meter buffer areas around the wells in the study unit is approximately 44 percent (%) agricultural, 29% urban, and 27% natural. Agricultural lands are mostly orchards, row crops, vineyards, or pastures. The largest urban areas are the cities of Livermore and Gilroy. Recharge to groundwater basins occurs as infiltration of spring and streamflow, direct infiltration of precipitation and irrigation, subsurface inflow, and engineered recharge (percolation ponds and river regulation). The primary sources of groundwater discharge are water pumped for irrigation and municipal supply, discharge to rivers and streams, and evaporation.