Ground-water Quality in the Lompoc Plain, Santa Barbara County, California, 1983

U.S. Geological Survey (USGS) | June 13th, 1988

This report summarizes the results of a comprehensive study of ground-water quality in the Lompoc plain in western Santa Barbara County. Water-quality characteristics

This report summarizes the results of a comprehensive study of ground-water quality in the Lompoc plain in western Santa Barbara County. Water-quality characteristics in 1983 are described, and changes in water quality since the last comprehensive study in the early 1970's are documented. Ground water is the main source of water in the Lompoc plain. The younger alluvium is the major aquifer and consists predominantly of unconsolidated deposits of sand and gravel. The younger alluvium is as much as 180 feet thick and is divided into an upper member and a lower member throughout most of the plain. The lower member is the main water-bearing zone in the Lompoc plain. Long-term ground-water levels in most of the plain have not changed significantly since the 1940's. A seasonal water-level decline of about 15 feet in 1982 in the central part of the plain may be attributed to nearby military and agricultural pumping. Ground-water quality in the plain in 1983 tended to deteriorate from east to west. Dissolved-solids concentrations throughout the plain exceeded the U.S. Environmental Protection Agency secondary maximum contaminant level of 500 milligrams per liter for drinking water; in most of the plain, concentrations exceeded 1,000 milligrams per liter. In samples from some wells, concentrations of one or more of the following constituents sodium, chloride, nitrate, and iron exceeded primary or secondary maximum contaminant levels for drinking water. Concentrations of constituents in some samples also exceeded recommended levels for irrigation water. The predominant ions generally were calcium, magnesium, sulfate, and bicarbonate - except in the western part, where sodium and chloride were the predominant dissolved ions. From 1972 to 1983, dissolved-solids concentrations in the main water-bearing zone generally decreased in the central part of the plain but increased throughout most of the study area. The largest increases, greater than 1,000 milligrams per liter, were in the extreme western part of the plain.

Ground-Water Resources Inventory of the Lake Tahoe Basin, 2007

U.S. Geological Survey (USGS) | November 30th, 2007

Groundwater Characterization and Effects of Pumping in the Death Valley Regional Groundwater Flow System, Nevada and California, with Special Reference to Devils Hole

U.S. Geological Survey (USGS) | March 5th, 2020

Groundwater flow and development were characterized in four groundwater basins of the Death Valley regional flow system in Nevada and California with calibrated, groundwa

Groundwater flow and development were characterized in four groundwater basins of the Death Valley regional flow system in Nevada and California with calibrated, groundwater-flow models. Natural groundwater discharges in the Furnace Creek, Lower Amargosa, and Saratoga Spring areas were defined and distributed consistently with a revised hydrogeologic framework. This simplified hydrogeologic framework was limited to four hydraulically unique, hydrogeologic units: (1) basin fill; (2) carbonate rocks; (3) volcanic rocks; and (4) low-permeability granitic and siliciclastic rocks. Hydrogeologic units and division of carbonate and volcanic rocks between shallow and deep were supported by results from 271 aquifer tests and specific-capacity estimates. Greater than 90 percent of field-estimated transmissivity occurred within 1,600 feet (ft) of the water table. Pumping in the study area from 1960 to 2010 averaged 46,000 acre-feet per year (acre-ft/yr), which is 80 percent of the predevelopment discharge. The central Amargosa Desert and Pahrump Valley were the two primary pumping centers and measurably affected water levels across 900 square miles in 2018. Water levels in Devils Hole were a special focus because endangered Devils Hole pupfish (Cyprinodon diabolis) are affected by water-level declines. Pumping 42,100 acre-ft by Cappaert Enterprises, formerly Spring Meadows, Inc., caused a 2.3-ft water-level decline in Devils Hole, which temporarily reduced habitat of Devils Hole pupfish by 85 percent in 1972. If no pumping occurred, water levels in Devils Hole would have risen naturally about 1 ft between 1973 and 2018 from temporal variations in recharge. The 2.6-ft range of measured water-level changes in Devils Hole was simulated with a root-mean-square error of 0.2 ft during the 70-year period of record. Simulated water-level declines from pumping totaled 1.4 ft in 2018, with 25 and 34 percent attributed to pumping by Cappaert Enterprises and the central Amargosa Desert, respectively. Water levels in Devils Hole will decline at rates of 0.1–0.2 ft per decade if pumping from Ash Meadows groundwater basin and the central Amargosa Desert continue at current rates. Effects of future natural water-level fluctuations remain unknown. Ash Meadows and Alkali Flat–Furnace Creek Ranch groundwater basins are hydraulically connected near well AD-4, about 5 miles south of the town of Amargosa Valley, Nevada. About 40 percent of the discharge from the Furnace Creek area is recharged in the Ash Meadows groundwater basin. Basin fill in the central Amargosa Desert hydraulically connects carbonate rocks east of well AD-4 with saturated carbonate rocks in the Funeral Range. About 7 percent of the 960,000 acre-ft pumped from Ash Meadows and Alkali Flat–Furnace Creek Ranch groundwater basins prior to 2019 was captured discharge from springs and phreatophytes. Greater than 40 percent of the 2,080,000 acre-ft pumped from Pahrump Valley between 1910 and 2019 was capture that primarily discharged from Bennetts and Manse Springs. Simulated advective-flow distances and velocities from underground nuclear tests are within the range of advective transport calculations from tritium data and previous radionuclide transport investigations. Boundary conditions and flow rates from the regional model in this study are plausible for local-scale flow and radionuclide transport models. Simulated 165-year groundwater-flow paths do not extend into pumping areas and effects of regional pumping on advective transport are negligible.

Groundwater Geology and Hydrology of Death Valley National Park, California and Nevada

U.S. Department of the Interior (DOI) | December 3rd, 2012

Hydraulic-Property Estimates for Use With a Transient Ground-Water Flow Model of the Death Valley Regional Ground-Water Flow System, Nevada and California

U.S. Geological Survey (USGS) | July 2nd, 2001

The Death Valley regional ground-water flow system encompasses an area of about 43,500 square kilometers in southeastern California and southern Nevada, between latitu

The Death Valley regional ground-water flow system encompasses an area of about 43,500 square kilometers in southeastern California and southern Nevada, between latitudes 35° and 38°15′ north and longitudes 115° and 117° 45′ west. The study area is underlain by Quaternary to Tertiary basin-fill sediments and mafic-lava flows; Tertiary volcanic, volcaniclastic, and sedimentary rocks; Tertiary to Jurassic granitic rocks; Triassic to Middle Proterozoic carbonate and clastic sedimentary rocks; and Early Proterozoic igneous and metamorphic rocks. The rock assemblage in the Death Valley region is extensively faulted as a result of several episodes of tectonic activity. This study is comprised of published and unpublished estimates of transmissivity, hydraulic conductivity, storage coefficient, and anisotropy ratios for hydrogeologic units within the Death Valley region study area. Hydrogeologic units previously proposed for the Death Valley regional transient ground-water flow model, were recognized for the purpose of studying the distribution of hydraulic properties. Analyses of regression and covariance were used to assess if a relation existed between hydraulic conductivity and depth for most hydrogeologic units. Those analyses showed a weak, quantitatively indeterminate, relation between hydraulic conductivity and depth.

Hydrogeologic characterization of the Cahuilla Valley and Terwilliger Valley Groundwater Basins, Riverside County, California

U.S. Geological Survey (USGS) | December 19th, 2025

The relation between the groundwater and the amount of natural recharge to the Cahuilla Valley and Terwilliger Valley groundwater basins is not well understood. During th

The relation between the groundwater and the amount of natural recharge to the Cahuilla Valley and Terwilliger Valley groundwater basins is not well understood. During the 20th century, the reliance on groundwater near Anza, California, used for agricultural, domestic, and municipal reasons has increased, and there is the potential for changes in groundwater availability related to climate change. Several types of existing data were evaluated, and new data were collected for this study, with the goal of characterizing the region’s hydrogeology. The study’s scope included constructing a geologic framework model to show where the groundwater-bearing units are present and their relation to each other, estimating the major components of the groundwater budget, and understanding local short-term and regional long-term groundwater flow and how that has changed since the early 1900s.

Hydrogeologic characterization of the San Antonio Creek Valley watershed, Santa Barbara County, California

U.S. Geological Survey (USGS) | January 31st, 2022

Hydrogeologic Conceptual Model for the Owens Valley Groundwater Basin (6-12), Inyo and Mono Counties

Inyo County Water Department (ICWD) | January 27th, 2016

This report provides a hydrogeologic conceptual model of the Owens Valley Groundwater Basin (OVGB) compiled from numerous sources including the US Geological Survey, Los

This report provides a hydrogeologic conceptual model of the Owens Valley Groundwater Basin (OVGB) compiled from numerous sources including the US Geological Survey, Los Angeles Department of Water and Power, Inyo and Mono Counties, the California Department of Fish and Wildlife, and the California Department of Water Resources. Because groundwater and surface water systems are linked, both systems are described here, prefaced by a summary of the physical setting of the OVGB.

Hydrogeologic evaluation and numerical simulation of the Death Valley regional ground-water flow system, Nevada and California

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

Hydrogeology and Simulation of Groundwater Flow in the Lucerne Valley Groundwater Basin, California

U.S. Geological Survey (USGS) | June 28th, 2022

The Lucerne Valley is in the southwestern part of the Mojave Desert and is about 75 miles northeast of Los Angeles, California. The Lucerne Valley groundwater basin encom

The Lucerne Valley is in the southwestern part of the Mojave Desert and is about 75 miles northeast of Los Angeles, California. The Lucerne Valley groundwater basin encompasses about 230 square miles and is separated from the Upper Mojave Valley groundwater basin by splays of the Helendale Fault. Since its settlement, groundwater has been the primary source of water for agricultural, industrial, municipal, and domestic uses. Groundwater withdrawal from pumping has exceeded the amount of water recharged to the basin, causing groundwater declines of more than 100 feet between 1917 and 2016 in the center of the basin. The continued withdrawal has resulted in an increase in pumping costs, reduced well efficiency, and land subsidence near Lucerne Lake. Although the volume of pumping has declined in recent years, there is concern that new agricultural growth and limits on imported water will continue to strain the sustainability of the groundwater system.