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Loren F. Metzger

Publications and source records attributed to Loren F. Metzger.

17 recordsLinked to original sources
USGS2018

Preliminary groundwater salinity mapping near selected oil fields using historical water-sample data, central and southern California

The distribution of groundwater salinity was mapped for 31 oil fields and adjacent aquifers and summarized by 8 subregions across major oil-producing areas of central and southern California. The objectives of this study were to describe the distribution of groundwater near oil fields having total dissolved solids less than 10,000 milligrams per liter (mg/L) based on available data and to document where data gaps exist. Salinity was represented by the measured or calculated concentration of total dissolved solids (TDS) in samples of produced water obtained from petroleum wells and groundwater obtained from water wells. The water chemistry data were used to estimate the minimum depths of TDS greater than 3,000 mg/L and greater than 10,000 mg/L in areas near selected oil fields using historical water-chemistry data coupled with available well-location and construction information. The 10,000 mg/L threshold, representing the highest level of TDS concentration of water that could be considered as a potential source of drinking water, was present in all but 4 (Jasmin, Kern Bluff, Kern Front, and Mount Poso) of the 31 individual oil fields. Among petroleum wells, the median TDS concentration of produced water ranged from 500 mg/L for the Jasmin field to 32,636 mg/L for the Elk Hills field. Among water wells, median TDS concentrations, either reported or calculated from specific conductance, ranged from 151 mg/L for wells within 2 miles of the Ten Section field to 9,750 mg/L for wells within 2 miles of the combined North and South Belridge fields. In general, TDS across the eight geographic subregions increased with depth, but the relation of TDS with depth varied regionally. The most pronounced increases in TDS with depth were across the West Kern Valley Floor and West Kern Valley Margin subregions on the west side of the San Joaquin Valley, and in the vicinity of the Wilmington field in the Los Angeles Basin subregion; in these areas, relatively high TDS concentrations greater than 10,000 mg/L were present within the upper few hundred to several thousand feet of land surface. Total dissolved solids concentrations increased more gradually with depth in the Middle Kern Valley Floor subregion, in the South Kern Valley Margin subregion, in the vicinity of the Montebello and Santa Fe Springs fields in the Los Angeles Basin subregion, and in the Central Coast Basin subregion. The Kern Sierran Foothills and East Kern Valley Floor subregions, on the east side of the San Joaquin Valley, had the most gradual increases in TDS with depth. Fields in the East Kern Valley Floor subregion generally had groundwater and produced water with TDS less than 10,000 mg/L that extended to a large depth compared to most other subregions. Overall, the west side of the San Joaquin Valley in Kern County and the Wilmington field in Los Angeles County generally have the highest TDS values and the shallowest depths to high TDS. High TDS at relatively shallow depths on the west side of the San Joaquin Valley may be because of a combination of natural conditions and anthropogenic factors. In the vicinity of the Wilmington field in the Los Angeles Basin subregion, high TDS at relatively shallow depths is attributable at least in part to seawater intrusion. Fields on the east side of the San Joaquin Valley in Kern County have the lowest TDS and greatest depths to TDS greater than 10,000 mg/L because of their geologic setting adjacent to Sierra Nevada recharge areas. Reconnaissance salinity mapping was limited by several factors. The primary limitation was the lack of well-construction data for a significant number of water wells. Bottom perforation, well depth, or hole depth were not available for 35 percent of wells used for salinity mapping. A second limitation was variability in data quality. Total dissolved solids and specific conductance data were compiled from different data sources with varying degrees of documentation that ranged from comprehensive to very little or none. As a result, it was not always possible to assess the quality of the provided data with respect to either conditions at each well during sampling or the methodology used for sample collection and analysis. A third limitation was the lack of wells, either petroleum or water, and associated TDS data over large vertical intervals for some fields. As a result, the distribution of salinity and the depths at which TDS concentration exceeds the 3,000 and 10,000 mg/L thresholds could not always be precisely determined. This analysis highlights key gaps that need to be filled with additional analysis of other sources of information, such as borehole geophysical logs and new water sample or geophysical data collection.

California↗
USGS2015

Sources of high-chloride water and managed aquifer recharge in an alluvial aquifer in California, USA

As a result of pumping in excess of recharge, water levels in alluvial aquifers within the Eastern San Joaquin Groundwater Subbasin, 130 km east of San Francisco (California, USA), declined below sea level in the early 1950s and have remained so to the present. Chloride concentrations in some wells increased during that time and exceeded the US Environmental Protection Agency’s secondary maximum contaminant level of 250 mg/L, resulting in removal of some wells from service. Sources of high-chloride water include irrigation return in 16 % of sampled wells and water from delta sediments and deeper groundwater in 50 % of sampled wells. Chloride concentrations resulting from irrigation return commonly did not exceed 100 mg/L, although nitrate concentrations were as high as 25 mg/L as nitrogen. Chloride concentrations ranged from less than 100–2,050 mg/L in wells affected by water from delta sediments and deeper groundwater. Sequential electromagnetic logs show movement of high-chloride water from delta sediments to pumping wells through permeable interconnected aquifer layers. δD and δ18O data show most groundwater originated as recharge along the front of the Sierra Nevada, but tritium and carbon-14 data suggest recharge rates in this area are low and have decreased over recent geologic time. Managed aquifer recharge at two sites show differences in water-level responses to recharge and in the physical movement of recharged water with depth related to subsurface geology. Well-bore flow logs also show rapid movement of water from recharge sites through permeable interconnected aquifer layers to pumping wells.

California↗
USGS2014

Documentation of a groundwater flow model (SJRRPGW) for the San Joaquin River Restoration Program study area, California

To better understand the potential effects of restoration flows on existing drainage problems, anticipated as a result of the San Joaquin River Restoration Program (SJRRP), the U.S. Geological Survey (USGS), in cooperation with the U.S. Bureau of Reclamation (Reclamation), developed a groundwater flow model (SJRRPGW) of the SJRRP study area that is within 5 miles of the San Joaquin River and adjacent bypass system from Friant Dam to the Merced River. The primary goal of the SJRRP is to reestablish the natural ecology of the river to a degree that restores salmon and other fish populations. Increased flows in the river, particularly during the spring salmon run, are a key component of the restoration effort. A potential consequence of these increased river flows is the exacerbation of existing irrigation drainage problems along a section of the river between Mendota and the confluence with the Merced River. Historically, this reach typically was underlain by a water table within 10 feet of the land surface, thus requiring careful irrigation management and (or) artificial drainage to maintain crop health. The SJRRPGW is designed to meet the short-term needs of the SJRRP; future versions of the model may incorporate potential enhancements, several of which are identified in this report. The SJRRPGW was constructed using the USGS groundwater flow model MODFLOW and was built on the framework of the USGS Central Valley Hydrologic Model (CVHM) within which the SJRRPGW model domain is embedded. The Farm Process (FMP2) was used to simulate the supply and demand components of irrigated agriculture. The Streamflow-Routing Package (SFR2) was used to simulate the streams and bypasses and their interaction with the aquifer system. The 1,300-square mile study area was subdivided into 0.25-mile by 0.25-mile cells. The sediment texture of the aquifer system, which was used to distribute hydraulic properties by model cell, was refined from that used in the CVHM to better represent the natural heterogeneity of aquifer-system materials within the model domain. In addition, the stream properties were updated from the CVHM to better simulate stream-aquifer interactions, and water-budget subregions were refined to better simulate agricultural water supply and demand. External boundary conditions were derived from the CVHM. The SJRRPGW was calibrated for April 1961 to September 2003 by using groundwater-level observations from 133 wells and streamflow observations from 19 streamgages. The model was calibrated using public-domain parameter estimation software (PEST) in a semi-automated manner. The simulated groundwater-level elevations and trends (including seasonal fluctuations) and surface-water flow magnitudes and trends reasonably matched observed data. The calibrated model is planned to be used to assess the potential effects of restoration flows on agricultural lands and the relative capabilities of proposed SJRRP actions to reduce these effects.

California↗
USGS2012

Electromagnetic-induction logging to monitor changing chloride concentrations

Water from the San Joaquin Delta, having chloride concentrations up to 3590 mg/L, has intruded fresh water aquifers underlying Stockton, California. Changes in chloride concentrations at depth within these aquifers were evaluated using sequential electromagnetic (EM) induction logs collected during 2004 through 2007 at seven multiple-well sites as deep as 268 m. Sequential EM logging is useful for identifying changes in groundwater quality through polyvinyl chloride-cased wells in intervals not screened by wells. These unscreened intervals represent more than 90% of the aquifer at the sites studied. Sequential EM logging suggested degrading groundwater quality in numerous thin intervals, typically between 1 and 7 m in thickness, especially in the northern part of the study area. Some of these intervals were unscreened by wells, and would not have been identified by traditional groundwater sample collection. Sequential logging also identified intervals with improving water quality—possibly due to groundwater management practices that have limited pumping and promoted artificial recharge. EM resistivity was correlated with chloride concentrations in sampled wells and in water from core material. Natural gamma log data were used to account for the effect of aquifer lithology on EM resistivity. Results of this study show that a sequential EM logging is useful for identifying and monitoring the movement of high-chloride water, having lower salinities and chloride concentrations than sea water, in aquifer intervals not screened by wells, and that increases in chloride in water from wells in the area are consistent with high-chloride water originating from the San Joaquin Delta rather than from the underlying saline aquifer.

California↗
USGS2012

Groundwater data for selected wells within the Eastern San Joaquin Groundwater Subbasin, California, 2003-8

Data were collected by the U.S. Geological Survey from 2003 through 2008 in the Eastern San Joaquin Groundwater Subbasin, 80 miles east of San Francisco, California, as part of a study of the increasing chloride concentrations in groundwater processes. Data collected include geologic, geophysical, chemical, and hydrologic data collected during and after the installation of five multiple-well monitoring sites, from three existing multiple-well sites, and from 79 selected public-supply, irrigation, and domestic wells. Each multiple-well monitoring site installed as part of this study contained three to five 2-inch diameter polyvinyl chloride (PVC)-cased wells ranging in depth from 68 to 880 feet below land surface. Continuous water-level data were collected from the 19 wells installed at these 5 sites and from 10 existing monitoring wells at 3 additional multiple-well sites in the study area. Thirty-one electromagnetic logs were collected seasonally from the deepest PVC-cased monitoring well at seven multiple-well sites. About 200 water samples were collected from 79 wells in the study area. Coupled well-bore flow data and depth-dependent water-quality data were collected from 12 production wells under pumped conditions, and well-bore flow data were collected from 10 additional wells under unpumped conditions.

California↗
USGS2012

Test drilling and data collection in the Calaveras County portion of the Eastern San Joaquin Groundwater Subbasin, California, December 2009-June 2011

Two multiple-well monitoring sites were drilled in the Calaveras County portion of the Eastern San Joaquin Groundwater Subbasin, about 100 miles east of San Francisco, California, during December 2009 and January 2010. Site 3N/9E-12G1-4 was drilled to a depth of 503 feet below land surface (bls), and four wells were installed. Site 4N/9E-36A1-3 was drilled to a depth of 400 feet bls, and three wells were installed. Lithologic and geophysical data collected during test drilling indicated the presence of volcanic sands interspersed with lahar deposits that are characteristic of the Mehrten Formation to about 420 feet bls at site 12G1-4, and the presence of volcanic sands interspersed with clay that are characteristic of the Valley Springs Formation at site 36A1-3. In January 2010, water levels at site 12G1-4 ranged from 120 to 127 feet bls (the shallowest well at the site, 12G4, screened from 90 to 110 feet bls, was dry). Between May and November 2010, water levels declined as much as 22 feet in wells 12G1 and 12G2, the deepest wells at this site, and declined about 6 feet in shallower well 12G3. During this same period, water-levels declined less than 8 feet in the three wells at site 36A1-3. Water levels in all monitoring wells recovered to near-May-2010 levels by mid-spring 2011. Dissolved solids in the six sampled monitoring wells (residue on evaporation) ranged from 154 to 239 milligrams per liter (mg/L); arsenic concentrations ranged from 1.8 to 13 micrograms per liter (μg/L), and were greater than the U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) for arsenic of 10 μg/L in well 36A2. The oxygen-18 (δ 18 O) and deuterium (δD) stable-isotopic composition of water from the six monitoring wells and from nine domestic and public-supply wells sampled as part of this study ranged from -6.7 to -8.2 per mil (δ 18 O), and -50 to -60 per mil (δD), and was consistent with values expected for water recharged in the lower altitudes of the Sierra Nevada. Well 36A3, the shallowest well at site 36A1-3, was the only well that contained measurable tritium - indicative of water recharged after 1952. Carbon-14 activities from the six monitoring wells ranged from 76.0 to 18.9 percent modern carbon, and groundwater ages (time since recharge), not corrected for chemical reactions, ranged from 2,200 to 13,400 years before present.

California↗
USGS2010

Aquifer Storage Recovery (ASR) of chlorinated municipal drinking water in a confined aquifer

About 1.02 × 10 6 m 3 of chlorinated municipal drinking water was injected into a confined aquifer, 94–137 m below Roseville, California, between December 2005 and April 2006. The water was stored in the aquifer for 438 days, and 2.64 × 10 6 m 3 of water were extracted between July 2007 and February 2008. On the basis of Cl − data, 35% of the injected water was recovered and 65% of the injected water and associated disinfection by-products (DBPs) remained in the aquifer at the end of extraction. About 46.3 kg of total trihalomethanes (TTHM) entered the aquifer with the injected water and 37.6 kg of TTHM were extracted. As much as 44 kg of TTHMs remained in the aquifer at the end of extraction because of incomplete recovery of injected water and formation of THMs within the aquifer by reactions with free-chlorine in the injected water. Well-bore velocity log data collected from the Aquifer Storage Recovery (ASR) well show as much as 60% of the injected water entered the aquifer through a 9 m thick, high-permeability layer within the confined aquifer near the top of the screened interval. Model simulations of ground-water flow near the ASR well indicate that (1) aquifer heterogeneity allowed injected water to move rapidly through the aquifer to nearby monitoring wells, (2) aquifer heterogeneity caused injected water to move further than expected assuming uniform aquifer properties, and (3) physical clogging of high-permeability layers is the probable cause for the observed change in the distribution of borehole flow. Aquifer heterogeneity also enhanced mixing of native anoxic ground water with oxic injected water, promoting removal of THMs primarily through sorption. A 3 to 4-fold reduction in TTHM concentrations was observed in the furthest monitoring well 427 m downgradient from the ASR well, and similar magnitude reductions were observed in depth-dependent water samples collected from the upper part of the screened interval in the ASR well near the end of the extraction phase. Haloacetic acids (HAAs) were completely sorbed or degraded within 10 months of injection.

California↗
USGS2008

Source, Distribution, and Management of Arsenic in Water from Wells, Eastern San Joaquin Ground-Water Subbasin, California

Between 1974 and 2001 water from as many as one-third of wells in the Eastern San Joaquin Ground Water Subbasin, about 80 miles east of San Francisco, had arsenic concentrations greater than the U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) for arsenic of 10 micrograms per liter (ug/L). Water from some wells had arsenic concentrations greater than 60 ug/L. The sources of arsenic in the study area include (1) weathering of arsenic bearing minerals, (2) desorption of arsenic associated with iron and manganese oxide coatings on the surfaces of mineral grains at pH's greater than 7.6, and (3) release of arsenic through reductive dissolution of iron and manganese oxide coatings in the absence of oxygen. Reductive dissolution is responsible for arsenic concentrations greater than the MCL. The distribution of arsenic varied areally and with depth. Concentrations were lower near ground-water recharge areas along the foothills of the Sierra Nevada; whereas, concentrations were higher in deeper wells at the downgradient end of long flow paths near the margin of the San Joaquin Delta (fig. 1). Management opportunities to control high arsenic concentrations are present because water from the surface discharge of wells is a mixture of water from the different depths penetrated by wells. On the basis of well-bore flow and depth-dependent water-quality data collected as part of this study, the screened interval of a public-supply well having arsenic concentrations that occasionally exceed the MCL was modified to reduce arsenic concentrations in the surface discharge of the well. Arsenic concentrations from the modified well were about 7 ug/L. Simulations of ground-water flow to the well showed that although upward movement of high-arsenic water from depth within the aquifer occurred, arsenic concentrations from the well are expected to remain below the MCL.

Open-File Report↗
USGS2006

Sources of High-Chloride Water to Wells, Eastern San Joaquin Ground-Water Subbasin, California

As a result of pumping and subsequent declines in water levels, chloride concentrations have increased in water from wells in the Eastern San Joaquin Ground-Water Subbasin, about 80 miles east of San Francisco (Montgomery Watson, Inc., 2000). Water from a number of public-supply, agricultural, and domestic wells in the western part of the subbasin adjacent to the San Joaquin Delta exceeds the U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (SMCL) for chloride of 250 milligrams per liter (mg/L) (fig. 1) (link to animation showing chloride concentrations in water from wells, 1984 to 2004). Some of these wells have been removed from service. High-chloride water from delta surface water, delta sediments, saline aquifers that underlie freshwater aquifers, and irrigation return are possible sources of high-chloride water to wells (fig. 2). It is possible that different sources contribute high-chloride water to wells in different parts of the subbasin or even to different depths within the same well.

Open-File Report↗
USGS2006

Geohydrological characterization, water-chemistry, and ground-water flow simulation model of the Sonoma Valley area, Sonoma County, California

The Sonoma Valley, located about 30 miles north of San Francisco, is one of several basins in Sonoma County that use a combination of ground water and water delivered from the Russian River for supply. Over the past 30 years, Sonoma Valley has experienced rapid population growth and land-use changes. In particular, there has been a significant increase in irrigated agriculture, predominantly vineyards. To provide a better understanding of the ground-water/surface-water system in Sonoma Valley, the U.S. Geological Survey compiled and evaluated existing data, collected and analyzed new data, and developed a ground-water flow model to better understand and manage the ground-water system. The new data collected include subsurface lithology, gravity measurements, groundwater levels, streamflow gains and losses, temperature, water chemistry, and stable isotopes. Sonoma Valley is drained by Sonoma Creek, which discharges into San Pablo Bay. The long-term average annual volume of precipitation in the watershed is estimated to be 269,000 acre-feet. Recharge to the ground-water system is primarily from direct precipitation and Sonoma Creek. Discharge from the ground-water system is predominantly outflow to Sonoma Creek, pumpage, and outflow to marshlands and to San Pablo Bay. Geologic units of most importance for groundwater supply are the Quaternary alluvial deposits, the Glen Ellen Formation, the Huichica Formation, and the Sonoma Volcanics. In this report, the ground-water system is divided into three depth-based geohydrologic units: upper (less than 200 feet below land surface), middle (between 200 and 500 feet), and lower (greater than 500 feet). Synoptic streamflow measurements were made along Sonoma Creek and indicate those reaches with statistically significant gains or losses. Changes in ground-water levels in wells were analyzed by comparing historical contour maps with the contour map for 2003. In addition, individual hydrographs were evaluated to assess temporal changes by region. In recent years, pumping depressions have developed southeast of Sonoma and southwest of El Verano. Water-chemistry data for samples collected from 75 wells during 2002-04 indicate that the ground-water quality in the study area generally is acceptable for potable use. The water from some wells, however, contains one or more constituents in excess of the recommended standards for drinking water. The chemical composition of water from creeks, springs, and wells sampled for major ions plot within three groups on a trilinear diagram: mixed-bicarbonate, sodium-mixed anion, and sodium-bicarbonate. An area of saline ground water in the southern part of the Sonoma Valley appears to have shifted since the late 1940s and early 1950s, expanding in one area, but receding in another. Sparse temperature data from wells southwest of the known occurrence of thermal water suggest that thermal water may be present beneath a larger part of the valley than previously thought. Thermal water contains higher concentrations of dissolved minerals than nonthermal waters because mineral solubilities generally increase with temperature. Geohydrologic Characterization, Water-Chemistry, and Ground-Water Flow Simulation Model of the Sonoma Valley Area, Sonoma County, California Oxygen-18 (d18 O) and deuterium (dD) values for water from most wells plot along the global meteoric water line, indicating that recharge primarily is derived from the direct infiltration of precipitation or the infiltration of seepage from creeks. Samples from shallow- and intermediate-depth wells located near Sonoma Creek and (or) in the vicinity of Shellville plot to the right of the global meteoric water line, indicating that these waters are partly evaporated. The d18 O and dD composition of water from sampled wells indicates that water from wells deeper than 200 feet is isotopically lighter (more negative) than water from wells less than 200 feet deep, possibly indicating that older ground wate

California↗
USGS2006

Geohydrology and water chemistry of the Alexander Valley, Sonoma County, California

This study of the geohydrology and water chemistry of the Alexander Valley, California, was done to provide an improved scientific basis for addressing emerging water-management issues, including potential increases in water demand and changes in flows in the Russian River. The study tasks included (1) evaluation of existing geohydrological, geophysical, and geochemical data; (2) collection and analysis of new geohydrologic data, including subsurface lithologic data, ground-water levels, and streamflow records; and (3) collection and analysis of new water-chemistry data. The estimated total water use for the Alexander Valley for 1999 was approximately 15,800 acre-feet. About 13,500 acre-feet of this amount was for agricultural use, primarily vineyards, and about 2,300 acre-feet was for municipal/industrial use. Ground water is the main source of water supply for this area. The main sources of ground water in the Alexander Valley are the Quaternary alluvial deposits, the Glen Ellen Formation, and the Sonoma Volcanics. The alluvial units, where sufficiently thick and saturated, comprise the best aquifer in the study area. Average recharge to the Alexander Valley is estimated from a simple, basinwide water budget. On the basis of an estimated annual average of 298,000 acre-feet of precipitation, 160,000 acre-feet of runoff, and 113,000 to 133,000 acre-feet of evapotranspiration, about 5,000 to 25,000 acre-feet per year is available for ground-water recharge. Because this estimate is based on differences between large numbers, there is significant uncertainty in this recharge estimate. Long-term changes in ground-water levels are evident in parts of the study area, but because of the sparse network and lack of data on well construction and lithology, it is uncertain if any significant changes have occurred in the northern part of the study area since 1980. In the southern half of the study area, ground-water levels generally were lower at the end of the 2002 irrigation season than at the end of the 1980 season, which suggests that a greater amount of ground water is being pumped in the southern half of the study area in recent years compared with that pumped in the early 1980s. Water-chemistry data for samples collected from 11 wells during 2002-04 indicate that water quality in the study area generally is acceptable for potable use. Two wells, however, each contained one constituent (241 ?g/L of manganese and 1,350 ?g/L of boron) in excess of the recommended standards for drinking water (50 ?g/L and 1,000 ?g/L, respectively). The chemical composition of water from most of the wells sampled for major ions plot as a mixed cation-bicarbonate, magnesium-bicarbonate, or calcium-bicarbonate type water. The ionic composition of the historical and recent samples from wells in the Alexander Valley is similar to that of the historical surface-water samples collected from the Russian River near Healdsburg. This suggests a similar source of water, particularly for wells that are less than 200 feet total depth and perforated in Quaternary alluvial deposits. Water from deeper, non-alluvial wells may contain slightly higher concentrations of sodium as a result of cation exchange. Water samples collected from several wells over an approximately 30-year period suggest a progressive change in water chemistry over time. Samples from the southern part of the valley show a trend towards higher ionic concentrations and increasing concentrations of particular constituents such as sulfate.

California↗
USGS2003

Determination of specific yield and water-table changes using temporal microgravity surveys collected during the second injection, storage, and recovery test at Lancaster, Antelope Valley, California, November 1996 through April 1997

To evaluate the feasibility of artificially recharging the ground-water system in the Lancaster area of the Antelope Valley, California, the U.S. Geological Survey, in cooperation with the Los Angeles County Department of Public Works and the Antelope Valley-East Kern Water Agency, conducted a series of injection, storage, and recovery tests between September 1995 and September 1998. A key component of this study was to measure the response of the water table to injection, which was difficult because the water table averaged 300 feet below land surface. Rather than install many expensive piezometers, microgravity surveys were conducted to determine specific yield and to measure the development of a ground-water mound during the injection of about 1,050 acre-feet of fresh water into an alluvial-aquifer system. The surveys were done prior to, during, and near the end of a 5-month injection period (November 12, 1996, to April 17, 1997). Results of the surveys indicate increases in gravity of as much as 66 microgals between a bedrock reference station and 20 gravity stations within a 1-square-mile area surrounding the injection site. The changes were assumed to have been caused by changes in the ground-water elevation. Gravity and ground-water levels were measured simultaneously at an existing well (7N/12W-34B1). The coupled measurements were used to calculate a specific yield of 0.13 for the alluvial aquifer near the well. To determine the gravitational effect of the injection mound on the gravity measurements made near well 7N/12W-34B1, a two-dimensional gravity model was used. Results of the model simulation show that the effect on gravity associated with the mass of the injection mound was minor and thus had a negligible effect on the calculation of specific yield. The specific yield of 0.13, therefore, was used to infer water-level changes at other gravity stations within the study area. The gravity-derived water-level changes were compared with simulated water-table changes.

Water-Resources Investigations Report↗
USGS2003

Analysis of tests of subsurface injection, storage, and recovery of freshwater in Lancaster, Antelope Valley, California

Ground-water levels in Lancaster, California, declined more than 200 feet during the 20th century, resulting in reduced ground-water supplies and more than 6 feet of land subsidence. Facing continuing population growth, water managers are seeking solutions to these problems. Injection of imported, treated fresh water into the aquifer system when it is most available and least expensive, for later use during high-demand periods, is being evaluated as part of a management solution. The U.S. Geological Survey, in cooperation with the Los Angeles County Department of Public Works and the Antelope Valley-East Kern Water Agency, monitored a pilot injection program, analyzed the hydraulic and subsidence-related effects of injection, and developed a simulation/optimization model to help evaluate the effectiveness of using existing and proposed wells in an injection program for halting the decline of ground-water levels and avoiding future land subsidence while meeting increasing ground-water demand. A variety of methods were used to measure aquifer-system response to injection. Water levels were measured continuously in nested (multi-depth) piezometers and monitoring wells and periodically in other wells that were within several miles of the injection site. Microgravity surveys were done to estimate changes in the elevation of the water table in the absence of wells and to estimate specific yield. Aquifer-system deformation was measured directly and continuously using a dual borehole extensometer and indirectly using continuous Global Positioning System (GPS), first-order spirit leveling, and an array of tiltmeters. The injected water and extracted water were sampled periodically and analyzed for constituents, including chloride and trihalomethanes. Measured injection rates of about 750 gallons per minute (gal/min) per well at the injection site during a 5-month period showed that injection at or above the average extraction rates at that site (about 800 gal/min) was hydraulically feasible. Analyses of these data took many forms. Coupled measurements of gravity and water-level change were used to estimate the specific yield near the injection wells, which, in turn, was used to estimate areal water-table changes from distributed measurements of gravity change. Values of the skeletal components of aquifer-system storage, which are key subsidence-related characteristics of the system, were derived from continuous measurements of water levels and aquifer-system deformation. A numerical model of ground-water flow was developed for the area surrounding Lancaster and used to estimate horizontal and vertical hydraulic conductivities. A chemical mass balance was done to estimate the recovery of injected water. The ground-water-flow model was used to project changes in ground-water levels for 10 years into the future, assuming no injection, no change in pumping distribution, and forecasted increases in ground-water demand. Simulated ground-water levels decreased throughout the Lancaster area, suggesting that land subsidence would continue as would the depletion of ground-water supplies and an associated loss of well production capacity. A simulation/optimization model was developed to help identify optimal injection and extraction rates for 16 existing and 13 proposed wells to avoid future land subsidence and to minimize loss of well production capacity while meeting increasing ground-water demands. Results of model simulations suggest that these objectives can be met with phased installation of the proposed wells during the 10-year period. Water quality was not considered in the optimization, but chemical-mass-balance results indicate that a sustained injection program likely would have residual effects on the chemistry of ground water.

Califronia↗
USGS2002

Streamflow gains and losses along San Francisquito Creek and characterization of surface-water and ground-water quality, southern San Mateo and northern Santa Clara counties, California, 1996-97

San Francisquito Creek is an important source of recharge to the 22-square-mile San Francisquito Creek alluvial fan ground-water subbasin in the southern San Mateo and northern Santa Clara Counties of California. Ground water supplies as much as 20 percent of the water to some area communities. Local residents are concerned that infiltration and consequently ground-water recharge would be reduced if additional flood-control measures are implemented along San Francisquito Creek. To improve the understanding of the surface-water/ground-water interaction between San Francisquito Creek and the San Francisquito Creek alluvial fan, the U.S. Geological Survey (USGS) estimated streamflow gains and losses along San Francisquito Creek and determined the chemical quality and isotopic composition of surface and ground water in the study area.Streamflow was measured at 13 temporary streamflow-measurement stations to determine streamflow gains and losses along a 8.4-mile section of San Francisquito Creek. A series of five seepage runs between April 1996 and May 1997 indicate that losses in San Francisquito Creek were negligible until it crossed the Pulgas Fault at Sand Hill Road. Streamflow losses increased between Sand Hill Road and Middlefield Road where the alluvial deposits are predominantly coarse-grained and the water table is below the bottom of the channel. The greatest streamflow losses were measured along a 1.8-mile section of the creek between the San Mateo Drive bike bridge and Middlefield Road; average losses between San Mateo Drive and Alma Street and from there to Middlefield Road were 3.1 and 2.5 acre-feet per day, respectively.Downstream from Middlefield Road, streamflow gains and losses owing to seepage may be masked by urban runoff, changes in bank storage, and tidal effects from San Francisco Bay. Streamflow gains measured between Middlefield Road and the 1200 block of Woodland Avenue may be attributable to urban runoff and (or) ground-water inflow. Water-level measurements from nearby wells indicate that the regional water table may coincide with the channel bottom along this reach of San Francisquito Creek, particularly during the winter and early spring when water levels usually reach their maximum. Streamflow losses resumed below the 1200 block of Woodland Avenue, extending downstream to Newell Road. Discharge from a large storm drain between Newell Road and East Bayshore Road may account for the streamflow gains measured between these sites. Streamflow gains were measured between East Bayshore Road and the Palo Alto Municipal Golf Course, but this reach is difficult to characterize because of the probable influence of high tides.Estimated average streamflow losses totaled approximately 1,050 acre-feet per year for the reaches between USGS stream gage 11164500 at Stanford University (upstream of Junipero Serra Boulevard) and the Palo Alto Municipal Golf Course, including approximately 595 acre-feet per year for the 1.8-mile section between San Mateo Drive and Middlefield Road. Approximately 58 percent, or 550 acre-feet, of the total estimated average annual recharge from San Francisquito Creek occurs between the San Mateo Drive and Middlefield Road sites.The chemical composition of San Francisquito Creek water varies as a function of seasonal changes in hydrologic conditions. Measurements of specific conductance indicate that during dry weather and low flow, the dissolved-solids concentrations tends to be high, and during wet weather, the concentration tends to be low owing to dilution by surface water. Compared with water samples from upstream sites at USGS stream gage 11164500 and San Mateo Drive, the samples from the downstream sites at Alma Street and Woodland Avenue had low specific conductance; low concentrations of magnesium, sodium, sulfate, chloride, boron, and total dissolved solids; high nutrient concentrations; and light isotopic compositions indicating that urban runoff constitutes most of the streamflow

Water-Resources Investigations Report↗
USGS2001

Vertical-deformation, water-level, microgravity, geodetic, water-chemistry, and flow-rate data collected during injection, storage, and recovery tests at Lancaster, Antelope Valley, California, September 1995 through September 1998

A series of freshwater injection, storage, and recovery tests were conducted from September 1995 through September 1998 to evaluate the feasibility of artificially recharging ground water in the Lancaster area of the Antelope Valley, California. The tests used two production wells at a well field located in the southern part of the city of Lancaster. Monitoring networks were established at or in the vicinity of the test site to measure vertical deformation of the aquifer system, water-level fluctuations, land-surface deformation, water chemistry, and injection well flow rates during water injection and recovery. Data presented in this report were collected from a dual extensometer; 10 piezometers; 1 barometer; 27 active or abandoned production wells; 31 gravity stations; 124 bench marks; 1 permanent and 1 temporary continuous Global Positioning System (GPS) station; 3 tiltmeters; and 2 electromagnetic flowmeters from September 1995 through September 1998. This report discusses the location and design of the monitoring networks and the methods used to collect and process the data, and presents the data in tables and graphs.

Open-File Report↗
USGS1997

Ground-water development and the effects on ground-water levels and water quality in the town of Atherton, San Mateo County, California

The installation of at least 100 residential wells in the town of Atherton, California, during the 198792 drought has raised concerns about the increased potential for land subsidence and salt water intrusion. Data were collected and monitor ing networks were established to assess current processes and to monitor future conditions affect ing these processes. Data include recorded pump age, recorded operation time, and measured pumpage rates from 38 wells; water levels from 49 wells; water chemistry samples from 20 wells, and land-surface elevation data from 22 survey sites, including one National Geodetic Survey estab lished bench mark. Geologic, lithologic, climato logic, well construction, well location, and historical information obtained from available reports and local, state, and Federal agencies were used in this assessment. Estimates of annual residential pumpage from 269 assumed active residential wells in the study area indicate that the average annual total pumping rate is between 395 and 570 acre-feet per year. The nine assumed active institutional wells are estimated to pump a total of about 200 acre- feet per year, or 35 to 50 percent of the total resi dential pumpage. Assuming that 510 acre-feet per year is the best estimate of annual residential pumpage, total pumpage of 710 acre-feet per year would represent about 19 percent of the study area's total water supply, as estimated. Depth-to-water-level measurements in wells during April 1993 through September 1995 typically ranged from less than 20 feet below land surface nearest to San Francisco Bay to more than 70 feet below land surface in upslope areas near exposed bedrock, depending on the season. This range, which is relatively high historically, is attributed to above normal rainfall between 1993 and 1995. Water levels expressed as hydraulic heads indicate the presence of three different hydrologic subareas on the basis of hydraulic-head contour configurations and flow direction. That all measured hydraulic heads in the study area from April 1993 through September 1995 were above sea level indicates that saltwater intrusion was unlikely during this period. The chemistry of 20 well-water samples is characterized as a calcium magnesium carbonate bicarbonate type water. There is no evidence of saltwater intrusion from San Francisco Bay; how ever, water samples from wells nearest the bay and bedrock assemblages indicate a greater concentra tion of dissolved constituents and salinity. Dissolved-solids concentrations of water samples from wells in these areas exceeded 1,000 milli grams per liter, and several samples contained a substantial fraction of sodium and chloride. Water hardness for the 20 wells sampled averaged 471 milligrams per liter as calcium carbonate, which is classified as very hard. One well sample exceeded the primary maximum contaminant level for drinking water in nitrate, several wells exceeded the secondary maximum contaminant level for chloride and sulfate, and all wells sampled exceeded the secondary maximum contaminant level for total dissolved solids. Land-subsidence and the resultant damage because of excessive ground-water pumping, in combination with periodic drought, have a well- documented history in the south San Francisco Bay area. Land-elevation surveying data from 1934 to 1967 indicate that subsidence ranged from 0.1 to approximately 0.5 foot in the vicinity of the study area. It could not be determined from land- surface elevation surveying data from 1993 whether subsidence is currently occurring in the study area.

Water-Resources Investigations Report↗