Groundwater Quality in Coachella 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. Coachella Valley is one of the study areas being evaluated. The Coachella study area is approximately 820 square miles (2,124 square kilometers) and includes the Coachella Valley groundwater basin (California Department of Water Resources, 2003). Coachella Valley has an arid climate, with average annual rainfall of about 6 inches (15 centimeters). The runoff from the surrounding mountains drains to rivers that flow east and south out of the study area to the Salton Sea. Land use in the study area is approximately 67 percent (%) natural, 21% agricultural, and 12% urban. The primary natural land cover is shrubland. The largest urban areas are the cities of Indio and Palm Springs (2010 populations of 76,000 and 44,000, respectively). Groundwater in this basin is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay derived from surrounding mountains. The primary aquifers in Coachella 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 Coachella Valley are completed to depths between 490 and 900 feet (149 to 274 meters), consist of solid casing from the land surface to a depth of 260 to 510 feet (79 to 155 meters), and are screened or perforated below the solid casing. Recharge to the groundwater system is primarily runoff from the surrounding mountains, and by direct infiltration of irrigation. The primary sources of discharge are pumping wells, evapotranspiration, and underflow to the Salton Sea and Imperial Valley areas.

Groundwater quality in shallow aquifers in the western Mojave Desert, California

U.S. Geological Survey (USGS) | May 28th, 2019

 The Mojave Basin Shallow Aquifer study unit (Mojave) covers approximately 4,680 square kilometers (2,908 square miles) in the western part of the Mojave Desert in San B

 The Mojave Basin Shallow Aquifer study unit (Mojave) covers approximately 4,680 square kilometers (2,908 square miles) in the western part of the Mojave Desert in San Bernardino County. The study unit consists of groundwater basins along the Mojave River, the El Mirage Valley groundwater basin, and part of the Harper Valley groundwater basin. The Mojave study unit was divided into two study areas—the floodplain study area along the Mojave River and the regional study area surrounding and underlying the floodplain study area. Aquifers in the floodplain study area consist of coarse granitic river-channel and floodplain alluvium deposited by the Mojave River.  Aquifers in the regional study area consist of alluvium derived from older stream deposits, locally derived alluvial fans, playa lake deposits, and fractured bedrock (Stamos and others, 2001; Groover and Izbicki, 2019). This study examined the quality of groundwater resources used for domestic drinking-water supply. 

Groundwater quality in the Cascade Range and Modoc Plateau, California

U.S. Geological Survey (USGS) | April 1st, 2015

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. The Cascade Range and Modoc Plateau area constitutes one of the study units being evaluated.

Groundwater Quality in the Colorado River Basins, 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. Four groundwater basins along the Colorado River make up one of the study areas being evaluated. The Colorado River study area is approximately 884 square miles (2,290 square kilometers) and includes the Needles, Palo Verde Mesa, Palo Verde Valley, and Yuma groundwater basins (California Department of Water Resources, 2003). The Colorado River study area has an arid climate and is part of the Sonoran Desert. Average annual rainfall is about 3 inches (8 centimeters). Land use in the study area is approximately 47 percent (%) natural (mostly shrubland), 47% agricultural, and 6% urban. The primary crops are pasture and hay. The largest urban area is the city of Blythe (2010 population of 21,000). Groundwater in these basins is used for public and domestic water supply and for irrigation. The main waterbearing units are gravel, sand, silt, and clay deposited by the Colorado River or derived from surrounding mountains. The primary aquifers in the Colorado River study area 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 the Colorado River basins are completed to depths between 230 and 460 feet (70 to 140 meters), consist of solid casing from the land surface to a depth of 130 of 390 feet (39 to 119 meters), and are screened or perforated below the solid casing. The main source of recharge to the groundwater systems in the Needles, Palo Verde Mesa, and Palo Verde Valley basins is the Colorado River; in the Yuma basin, the main source of recharge is from subsurface flow from the groundwater basins to the west. Groundwater discharge is primarily to pumping wells, evapotranspiration, and, locally, to the Colorado River.

Groundwater Quality in the North San Francisco Bay Shallow Aquifer, California

U.S. Geological Survey (USGS) | February 23rd, 2018

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

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. The North San Francisco Bay Shallow Aquifer constitutes one of the study units being evaluated.

Groundwater Quality in the Northern Coast Ranges Groundwater Basins, California

U.S. Geological Survey (USGS) | February 1st, 2015

The Northern Coast Ranges (NOCO) study unit is 633 square miles and consists of 35 groundwater basins and subbasins (California Department of Water Resources, 2003; Matha

The Northern Coast Ranges (NOCO) study unit is 633 square miles and consists of 35 groundwater basins and subbasins (California Department of Water Resources, 2003; Mathany and Belitz, 2015). These basins and subbasins were grouped into two study areas based primarily on locality. The groundwater basins and subbasins located inland, not adjacent to the Pacific Ocean, were aggregated into the Interior Basins (NOCO-IN) study area. The groundwater basins and subbasins adjacent to the Pacific Ocean were aggregated into the Coastal Basins (NOCO-CO) study area (Mathany and others, 2011). The primary aquifer system in the NOCO-IN study area occurs in alluvial basins made up of sand, silt, gravel, clay, and thin volcanic ash layers or lenses. Groundwater movement in the NOCO-IN study area follows the topography and direction of surface-water features. In the NOCO-CO study area, groundwater is present in alluvial fan, floodplain, and terrace deposits. Groundwater movement in the NOCO-CO study area is from east to west towards the Pacific Ocean. The primary aquifer system in the study unit generally is defined as those parts of the aquifer system corresponding to the perforated intervals of sites listed in the California Department of Public Health (CDPH) database of public drinking-water supply sources. Well depths in the NOCO-IN study area ranged from 36 to 400 feet below land surface (ft bls), and depths to top-of-perforations ranged from 15 to 148 ft bls. In the NOCO-CO study area, well depths ranged from 15 to 400 ft bls, and depths to top-of-perforations ranged from 10 to 356 ft bls. Water quality in the primary aquifer system may differ from that in the shallower and deeper parts of the aquifer system. Average annual rainfall in the NOCO study unit ranges from 22 to 79 inches. In the NOCO-IN study area, the climate is classified as Mediterranean, with warm to hot, dry summers and cold, wet winters. In the NOCO-CO study area, the climate is influenced by the Pacific Ocean and is characterized by cool to mild summers and cold, wet winters. The study unit is drained by several rivers and their principal tributaries: the Eel, Russian, Mad, Navarro, Smith, Klamath, Noyo, and Big Rivers. Land use in the study unit is about 60 percent (%) natural (mostly grassland and forest), 29% agricultural, and 11% urban. The primary uses of agricultural lands are pasture, row crops, hay, vineyards, and timberlands. The largest urban areas are the cities of Crescent City, Arcata, Eureka, Fort Bragg, Willits, Ukiah, and Lakeport. Recharge to the groundwater system is primarily from mixture of ambient sources, including direct percolation of precipitation and irrigation waters, infiltration of runoff from surrounding hills/areas, seepage from rivers and creeks, and subsurface inflow (from non-alluvial geologic units that bound the alluvial basins). The primary sources of discharge are evaporation, discharge to streams, and water pumped for municipal supply and irrigation.

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 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).