Groundwater quality in Coachella Valley, California

Fact Sheet, 2012

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 Mojave River make up one of the study areas being evaluated. The Mojave Study Area Overview of Water Quality GAMA's Priority Basin Project evaluates the quality of untreated groundwater. However, for context, benchmarks established for drinking-water quality are used for comparison. Benchmarks and definitions of high, moderate, and low concentrations are discussed in the inset box on page 3. The USGS sampled 52 wells for this assessment; data from the California Department of Public Health database were used to supplement USGS data. Many inorganic constituents occur naturally in groundwater. The concentrations of the inorganic constituents can be affected by natural processes as well as by human activities. In the Mojave study area, one or more inorganic constituents were present at high concentrations in 28% of the primary aquifers and at moderate concentrations in 36%. Organic constituents are present in products used in the home, business, industry, and agriculture. Organic constituents can enter the groundwater system through normal usage, spills, or improper disposal. In the Mojave study area, organic constituents were present at high concentrations in 2% of the primary aquifers and at moderate concentrations in 6%. The Mojave study area is approximately 1,500 square miles (3,885 square kilometers) and includes four contiguous groundwater basins: Upper, Middle, and Lower Mojave River Groundwater Basins, and the El Mirage Valley (California Department of Water Resources, 2003). The Mojave study area has an arid climate, and is part of the Mojave Desert. Average annual rainfall is about 6 inches (15 centimeters). Land use in the study area is approximately 82 percent (%) natural (mostly shrubland), 4% agricultural, and 14% urban. The primary crops are pasture and hay. The largest urban areas are the cities of Victorville, Hesperia, and Apple Valley (2010 populations of 116,000, 90,000 and 69,000, respectively). Groundwater in these basins 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 the Mojave 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 Mojave study area are completed to depths between 200 and 600 feet (18 to 61 meters), consist of solid casing from the land surface to a depth of 130 to 420 feet (40 to 128 meters), and are screened or perforated below the solid casing. Recharge to the groundwater system is primarily runoff from the mountains to the south, mostly through the Mojave River channel. The primary sources of discharge are pumping wells and evapotranspiration. High Moderate CONSTITUENT CONCENTRATIONS Low or not detected Pie charts illustrate the proportion of the primary aquifers, on an areal basis with concentrations in three specified categories.

Fact sheet /, 2010

Groundwater provides more than 40 percent of Californian's drinking water. To protect this vital resource, the State of California has created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. This program will provide a comprehensive assessment of the State's groundwater quality. The Central Eastside is one of the study units being evaluated. The Central Eastside Study Unit The Central Eastside study unit is located in California's San Joaquin Valley. The 1,695 square mile study unit includes three groundwater subbasins: Modesto, Turlock, and Merced (California Department of Water Resources, 2003). The primary waterbearing units consist of discontinuous lenses of gravel, sand, silt, and clay, which are derived largely from the Sierra Nevada Mountains to the east. Public-supply wells provide most of the drinking water supply in the Central Eastside. Consequently, the primary aquifer in the Central Eastside study unit is defined as that part of the aquifer corresponding to the perforated interval of wells listed in the California Department of Public Health database. Public-supply wells are typically drilled to depths of 200 to 350 feet, consist of solid casing from the land surface to a depth of about 100 to 200 feet, and they are perforated below the solid casing. Water quality in the shallower and deeper parts of the aquifer system may differ from that in the primary aquifer. The Central Eastside study unit has hot and dry summers and cool, moist, winters. Average annual rainfall ranges from 11 to 15 inches. The Stanislaus, Tuolumne, and Merced Rivers, with headwaters in the Sierra Nevada Mountains, are the primary streams traversing the study unit. Land use in the study unit is approximately 59 percent (%) agricultural, 34% natural (primarily grassland), and 7% urban. The primary crops are almonds, walnuts, peaches, grapes, grain, corn, and alfalfa. The largest urban areas (2003 population in parentheses) are the cities of Modesto (206,872), Turlock (63,467), and Merced (69,512). Municipal water use accounts for about 5% of the total water use in the Central Eastside study unit, with the remainder used for irrigated agriculture. Groundwater

Fact sheet /, 2012

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. Indian Wells Valley is one of the study areas being evaluated. The Indian Wells Study Area Overview of Water Quality GAMA's Priority Basin Project evaluates the quality of untreated groundwater. However, for context, benchmarks established for drinking-water quality are used for comparison. Benchmarks and definitions of high, moderate, and low concentrations are discussed in the inset box on page 3. The USGS sampled 13 wells for this assessment; data from the California Department of Public Health database were used to supplement USGS data. Many inorganic constituents occur naturally in groundwater. The concentrations of the inorganic constituents can be affected by natural processes as well as by human activities. In the Indian Wells study area, one or more inorganic constituents were present at high concentrations in 62% of the primary aquifers and at moderate concentrations in 23%. Organic constituents are present in products used in the home, business, industry, and agriculture. Organic constituents can enter the groundwater system through normal usage, spills, or improper disposal. In the Indian Wells study area, no organic constituents were present at high or moderate concentrations in the primary aquifers.

Fact Sheet

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 subbasins in the southeast portion of the San Joaquin Valley constitute one of the study units being evaluated. Organic constituents Inorganic constituents High Moderate CONSTITUENT CONCENTRATIONS Low or not detected Values are a percentage of the area of the primary aquifers with concentrations in the three specified categories. Values on piechart may not equal 100 due to rounding of percentages.

Scientific Investigations Report, 2012

Groundwater quality in the southern San Joaquin Valley was investigated from October 2005 through March 2006 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. There are two study units located in the southern San Joaquin Valley: the Southeast San Joaquin Valley (SESJ) study unit and the Kern County Subbasin (KERN) study unit. The GAMA Priority Basin Project in the SESJ and KERN study units was designed to provide a statistically unbiased, spatially distributed assessment of untreated groundwater quality within the primary aquifers. The status assessment is based on water-quality and ancillary data collected in 2005 and 2006 by the USGS from 130 wells on a spatially distributed grid, and water-quality data from the California Department of Public Health (CDPH) database. Data was collected from an additional 19 wells for the understanding assessment. The aquifer systems (hereinafter referred to as primary aquifers) were defined as that part of the aquifer corresponding to the perforation interval of wells listed in the CDPH database for the SESJ and KERN study units. The status assessment of groundwater quality used data from samples analyzed for anthropogenic constituents such as volatile organic compounds (VOCs) and pesticides, as well as naturally occurring inorganic constituents such as major ions and trace elements. The status assessment is intended to characterize the quality of untreated groundwater resources within the primary aquifers in the SESJ and KERN study units, not the quality of drinking water delivered to consumers. Although the status assessment applies to untreated groundwater, Federal and California regulatory and non-regulatory water-quality benchmarks that apply to drinking water are used to provide context for the results. top-of-perforations in the KERN study unit. Organic constituents and constituents of special interest, like many inorganic constituents, were correlated with well depth, groundwater age, and DO. Unlike most trace elements, however, solvent and pesticide detections, and total trihalomethanes (THM), DBCP, and perchlorate concentrations decreased with increasing well depth. Volatile organic compound, solvent, and pesticide detections, and THM concentrations also were lower in older (pre-modern) groundwater than in modern-age groundwater. Solvent detections and total THM, DBCP, and perchlorate concentrations increased with increasing DO concentrations.

Data Series, 2008

Groundwater quality in the approximately 2,100 squaremile Southern Sacramento Valley study unit (SSACV) was investigated from March to June 2005 as part of the Statewide Basin Assessment Project of GroundWater Ambient Monitoring and Assessment (GAMA) Program. This study was designed to provide a spatially unbiased assessment of raw groundwater quality within SSACV, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 83 wells in Placer, Sacramento, Solano, Sutter, and Yolo Counties. Sixty-seven of the wells were selected using a randomized grid-based method to provide statistical representation of the study area. Sixteen of the wells were sampled to evaluate changes in water chemistry along groundwater flow paths. Four additional samples were collected at one of the wells to evaluate water-quality changes with depth. The GAMA Statewide Basin Assessment project was developed in response to the GroundWater Quality Monitoring Act of 2001 and is being conducted by the California State Water Resources Control Board (SWRCB) in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory (LLNL). The groundwater samples were analyzed for a large number of man-made organic constituents (volatile organic compounds [VOCs], pesticides and pesticide degradates, pharmaceutical compounds, and wastewater-indicator constituents), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (tritium, and carbon-14, and stable isotopes of hydrogen, oxygen, and carbon), and dissolved noble gases also were measured to help identify the source and age of the sampled ground water. Quality-control samples (blanks, replicates, matrix spikes) were collected at ten percent of the wells, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. Assessment of the quality-control data resulted in censoring of less than 0.03 percent of the analyses of groundwater samples. This study did not evaluate the quality of water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, and (or) blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is served to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and California Department of Health Services (CADHS) (Maximum Contaminant Levels [MCLs], notification levels [NLs], or lifetime health advisories [HA-Ls]) and thresholds established for aesthetic concerns (Secondary Maximum Contaminant Levels [SMCLs]). All wells were sampled for organic constituents and selected general water quality parameters; subsets of wells were sampled for inorganic constituents, nutrients, and radioactive constituents. Volatile organic compounds were detected in 49 out of 83 wells sampled and pesticides were detected in 35 out of 82 wells; all detections were below health-based thresholds, with the exception of 1 detection of 1,2,3-trichloropropane above a NL. Of the 43 wells sampled for trace elements, 27 had no detections of a trace element above a health-based threshold and 16 had at least one detection above. Of the 18 trace elements with health-based thresholds, 3 (arsenic, barium, and boron) were detected at concentrations higher an MCL. Of the 43 wells sampled for nitrate, only 1 well had a detection above the MCL. Twenty wells were sampled for radioactive constituents; only 1 (radon-222) was measured at activities higher than the proposed MCL. Radon-222 was detected below the threshold in 7 wells and above the threshold in 13 wells. SMCLs have been established for nine constituents or parameters analyzed in SSACV. Six were measured at levels higher than an SMCL: chloride, iron, manganese, pH, specific conductance, and total dissolved solids. Chloride, iron, manganese, pH, and total dissolved solids were measured in 43 wells: 27 wells had no measurements above a threshold and 16 wells had a measurement above a threshold. Specific conductance was measured in 83 wells. In 68 wells, specific conductance was measured lower than the threshold and in 15 wells it was measured above the threshold Study areas North American (NAM) Solano (SOL) South American (SAM) EXPLANATION Suisun-Fairfield (SUI) Uplands (QPC) Yolo (YOL) Hydrogeologic Setting of the Southern Sacramento Valley Study Unit The Southern Sacramento Valley GAMA study unit lies within the Central Valley and partly within the North Coast Ranges hydrogeologic provinces described by Belitz and others (2003) (fig. 1). The Southern Sacramento Valley GAMA study unit covers an area of approximately 2,100 mi 2 and includes parts of Placer,

Fact Sheet, 2012

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. Antelope Valley is one of the study areas being evaluated. The Antelope Study Area Overview of Water Quality GAMA's Priority Basin Project evaluates the quality of untreated groundwater. However, for context, benchmarks established for drinkingwater quality are used for comparison. Benchmarks and definitions of high, moderate, and low concentrations are discussed in the inset box on page 3. The USGS sampled 56 wells for this assessment; data from the California Department of Public Health database were used to supplement USGS data. Many inorganic constituents occur naturally in groundwater. The concentrations of the inorganic constituents can be affected by natural processes as well as by human activities. In the Antelope Valley study area, one or more inorganic constituents were present at high concentrations in 30% of the primary aquifers and at moderate concentrations in 30%. Organic constituents are found in products used in the home, business, industry, and agriculture. Organic constituents can enter the groundwater system through normal usage, spills, or improper disposal. In the Antelope Valley study area, organic constituents were present at moderate concentrations in 2% of the primary aquifers. The Antelope study area is approximately 1,600 square miles (4,144 square kilometers) and includes the Antelope Valley groundwater basin (California Department of Water Resources, 2003). Antelope Valley has an arid climate and is part of the Mojave Desert. Average annual rainfall is about 6 inches (15 centimeters). The study area has internal drainage, with runoff from the surrounding mountains draining towards dry lakebeds in the lower parts of the valley. Land use in the study area is approximately 68 percent (%) natural (mostly shrubland and grassland), 24% agricultural, and 8% urban. The primary crops are pasture and hay. The largest urban areas are the cities of Palmdale and Lancaster (2010 populations of 152,000 and 156,000, 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 Antelope 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 Antelope Valley are completed to depths between 360 and 700 feet (110 to 213 meters), consist of solid casing from the land surface to a depth of 180 to 350 feet (55 to 107 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 and sewer and septic systems. The primary sources of discharge are pumping wells and evapotranspiration near the dry lakebeds. High Moderate CONSTITUENT CONCENTRATIONS Low or not detected Pie charts illustrate the proportion of the primary aquifers, on an areal basis, with concentrations in the three specified categories.

Fact sheet /, 2011

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 Southern Sacramento Valley is one of the study units being evaluated. Organic constituents Inorganic constituents High Moderate CONSTITUENT CONCENTRATIONS Low or not detected Values are a percentage of the area of the primary aquifers with concentrations in the three specified categories.

Fact Sheet, 2012

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 Overview of Water Quality GAMA's Priority Basin Project evaluates the quality of untreated groundwater. However, for context, benchmarks established for drinkingwater quality are used for comparison. Benchmarks and definitions of high, moderate, and low concentrations are discussed in the inset box on page 3. The USGS sampled 20 wells for this assessment; data from the California Department of Public Health database were used to supplement USGS data. Many inorganic constituents occur naturally in groundwater. The concentrations of the inorganic constituents can be affected by natural processes as well as by human activities. In the Colorado River study area, one or more inorganic constituents were present at high concentrations in 45% of the primary aquifers and at moderate concentrations in 35%. Organic constituents are present in products used in the home, business, industry, and agriculture. Organic constituents can enter the groundwater system through normal usage, spills, or improper disposal. In the Colorado River study area, organic constituents were present at moderate concentrations in 10% of the primary aquifers.

Fact sheet /, 2011

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 Northern Sacramento Valley is one of the study units being evaluated. Organic constituents Inorganic constituents High Moderate CONSTITUENT CONCENTRATIONS Low or not detected Values are a percentage of the area of the primary aquifers with concentrations in the three specified categories.