Regional nitrate and pesticide trends in ground water in the eastern San Joaquin Valley, California

American Society of Agronomy (ASA) | September 18th, 2008

Protection of ground water for present and future use requires monitoring and understanding of the mechanisms controlling long-term quality of ground water. In this stu

Protection of ground water for present and future use requires monitoring and understanding of the mechanisms controlling long-term quality of ground water. In this study, spatial and temporal trends in concentrations of nitrate and pesticides in ground water in the eastern San Joaquin Valley, California, were evaluated to determine the long-term effects of agricultural and urban development on regional ground-water quality. Trends in concentrations of nitrate, the nematocide 1,2-dibromo-3-chloropropane, and the herbicide simazine during the last two decades are generally consistent with known nitrogen fertilizer and pesticide use and with the position of the well networks in the regional ground-water fl ow system. Concentrations of nitrate and pesticides are higher in the shallow part of the aquifer system where domestic wells are typically screened, whereas concentrations are lower in the deep part of the aquifer system where public-supply wells are typically screened. Attenuation processes do not seem to significantly affect concentrations. Historical data indicate that concentrations of nitrate have increased since the 1950s in the shallow and deep parts of the aquifer system. Concentrations of nitrate and detection of pesticides in the deep part of the aquifer system will likely increase as the proportion of highly affected water contributed to these wells increases with time. Because of the time of travel between the water table and the deep part of the aquifer system, current concentrations in public-supply wells likely reflect the effects of 40- to 50-year-old management practices.

Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA

Applied Geochemistry (Elsevier) | September 21st, 2018

Chemical and isotopic data for water co-extracted with hydrocarbons in oil and gasfields are commonly used toexamine the source of the formation water and possible impact

Chemical and isotopic data for water co-extracted with hydrocarbons in oil and gasfields are commonly used toexamine the source of the formation water and possible impacts on groundwater in areas of oil and gas de-velopment. Understanding the geochemical variability of oil-field water could help to evaluate its origin anddelineate possible contamination of shallow aquifers in cases where oil-field water is released to the environ-ment. Here we report geochemical and multiple isotope (H, C, O, Sr, Ra) data from 22 oil wells, three sources ofproduced water that are disposed of in injection wells, and two surface disposal ponds in four oilfields in thesouthern San Joaquin Valley, California (Fruitvale, Lost Hills, North and South Belridge). Correlations betweenCl andδ18O, as well as other ions, and gradual increases in salinity with depth, indicate dilution of one or moresaline end-members by meteoric water. The saline end-members, represented by deep samples (610 m–2621 m)in three oil-bearing zones, are characterized by NaeCl composition, near-seawater Cl concentrations (median20,000 mg/L), enrichedδ18OeH2O (median 3.4‰), high ammonium (up to 460 mg-N/L), and relatively highradium activity (226Ra+228Ra = 12.3 Bq/L). The deepest sample has low Na/Cl (0.74), high Ca/Mg (5.0), andlow87Sr/86Sr (0.7063), whereas the shallower samples have higher Na/Cl (0.86–1.2), Ca/Mg near 1, and higher87Sr/86Sr (∼0.7083). The data are consistent with an original seawater source being modified by various depthand lithology dependent diagenetic processes. Dilution by meteoric water occurs naturally on the east side of thevalley, and in association with water-injection activities on the west side. Meteoric-waterflushing, particularlyon the east side, results in lower solute concentrations (minimum total dissolved solids 2730 mg/L) and totalradium (minimum 0.27 Bq/L) in oil-field water, and promotes biodegradation of dissolved organic carbon andhydrocarbon gases like propane. Acetate concentrations andδ13C of dissolved inorganic carbon indicate biogenicmethane production occurs in some shallow oil zones. Natural and human processes produce substantialvariability in the geochemistry of oil-field water that should be considered when evaluating mixing between oil-field waters and groundwater. The variability could result in uncertainty as to detecting the potential source andimpact of oil-field water on groundwater.

Regional water table (1994) and water-level changes in the Morongo Basin, San Bernardino County, California

U.S. Geological Survey (USGS) | July 1st, 1995

The Morongo Basin is in the Mojave Desert region of southern California, about 100 mi east of Los Angeles. Ground water is virtually the sole source of water in the Moro

The Morongo Basin is in the Mojave Desert region of southern California, about 100 mi east of Los Angeles. Ground water is virtually the sole source of water in the Morongo Basin. Increased pumping to meet the needs of an increasing resident population has resulted in ground-water overdraft in parts of the ground-water basin. Most of the water resources of the basin are managed by the Mojave Water Agency (MWA) and the U.S. Marine Corps Air/Ground Combat Center at Twentynine Palms (USMCAGCC). To help manage the ground-water resources, the MWA and the U.S. Marine Corps, Department of the Navy, requested the U.S. Geological Survey (USGS) to construct a regional water-table map of the Morongo ground-water basin. The purposes of this study were to construct a regional water-table map and determine areas of water-level change in the Morongo Basin. Existing data were evaluated and water levels were measured in selected wells throughout the Morongo Basin. Water-level measurements were used to construct a regional water-table map for 1994 conditions (fig. 1), and available historical water levels were used to construct hydrographs (shown in fig. 1) and determine water-level change at selected wells. Results of this study will aid the USGS in evaluating its current ground-water monitoring network in the Morongo Basin. In addition, information gained through this study will contribute to ongoing projects in the area, such as the Regional Aquifer-System Analysis (RASA) of Southern California.

Regional water table (1996) and water-level changes in the Mojave River, Morongo, and Fort Irwin ground-water basins, San Bernardino County

U.S. Geological Survey (USGS) | July 1st, 1997

Regional water table (1998) and ground-water-level changes in the Mojave River and the Morongo ground-water basins, San Bernardino County, California

U.S. Geological Survey (USGS) | July 1st, 2000

Regional Water Table (1998) and Ground-Water-Level Changes in the Mojave River, and the Morongo Ground-Water Basins, San Bernardino County, California

U.S. Geological Survey (USGS) | July 15th, 2000

The Mojave River and the Morongo groundwater basins are in the southwestern part of the Mojave Desert in southern California. Ground water from these basins supplies a ma

The Mojave River and the Morongo groundwater basins are in the southwestern part of the Mojave Desert in southern California. Ground water from these basins supplies a major part of the water requirements for the region. The rapid and continuous population growth in this area has resulted in ever-increasing demands on local ground-water resources. The continuing collection and interpretation of ground-water data helps local water districts, military bases, and private citizens gain a better understanding of the ground-water systems and, consequently, water availability.

Regional Water Table (2000) and Ground-Water-Level Changes in the Mojave River and the Morongo Ground-Water Basins, Southwestern Mojave Desert, California

U.S. Geological Survey (USGS) | July 1st, 2003

Regional water table (2002) and water-level changes in the Mojave River and the Morongo ground-water basins, Southwestern Mojave Desert, California

U.S. Geological Survey (USGS) | July 1st, 2004

Regional Water Table (2004) and water-level changes in the Mojave River and Morongo ground-water basins, southwestern Mojave Desert, California

U.S. Geological Survey (USGS) | July 1st, 2004

Regional water table (2010) in the Mojave River and Morongo groundwater basins, Southwestern Mojave Desert, California

U.S. Geological Survey (USGS) | February 23rd, 2012

Data for static water-levels measured in about 610 wells during January through June 2010 by the U.S. Geological Survey (USGS), the Mojave Water Agency (MWA), and other l

Data for static water-levels measured in about 610 wells during January through June 2010 by the U.S. Geological Survey (USGS), the Mojave Water Agency (MWA), and other local water districts were compiled to construct a regional water-table map, which shows the altitude of the water table and general direction of groundwater movement in and around the Mojave River and Morongo groundwater basins. Water-level contours from the 2008 water-level map (Stamos and others, 2009) were used as a guide to interpret the 2010 water-level contours in areas where 2010 water-level data were not available. In addition to being available on the interactive map,the 2010 water-level data and contours are shown for the entire area of the Mojave River and Morongo groundwater basins on Plate 1 greater detail of the Warren subbasin in the Morongo groundwater basin is shown on Plate 2. Historical water-level data from the National Water Information System (NWIS) database were used in conjunction with data collected for this study to construct 37 water-level hydrographs to show both long-term (1930 - 2010) and short-term (1990 - 2010) water-level changes in the Mojave River and Morongo groundwater basins. Water-level changes between spring 2008 and spring 2010 were determined by comparing water levels measured in the same well during both periods. Water-level changes between the studies on this website can be displayed on the interactive map by entering the years of interest.