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Results for “Ground Water Modeling Investigation Report”

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USGS2005

Development of a local meteoric water line for southeastern Idaho, western Wyoming, and south-central Montana

Linear-regression analysis was applied to stable hydrogen (H) and oxygen (O) isotope data in 72 snow-core and precipitation samples collected during 1999-2001 to determine the Local Meteoric Water Line (LMWL) for southeastern Idaho, western Wyoming, and south-central Montana. On the basis of (1) residuals from the regression model, (2) comparison of study-area deuterium-excess (d-excess) values with the global range of d-excess values, and (3) outlier analysis by means of Chauvenet's Criterion, values of four samples were excluded from final regression analysis of the dataset. Regression results for the 68 remaining samples yielded a LMWL defined by the equation ?H = 7.95 18O + 8.09 (r? = 0.98). This equation will be useful as a reference point for future studies in this area that use stable isotopes of H and O to determine sources of ground-water recharge, to determine water-mineral exchange, to evaluate surface-water and groundwater interaction, and to analyze many other geochemical and hydrologic problems.

Scientific Investigations Report↗

USGS1994

Analysis of ground-water flow along a regional flow path of the Midwestern Basins and Arches aquifer system in Ohio

A cross-sectional analysis of ground-water flow in central-western and northwestern Ohio was done as part of the Midwestern Basins and Arches Regional Aquifer-System Analysis project. The Midwestern Basins and Arches aquifer system is composed of carbonate bedrock of Silurian and Devonian age and overlying glacial flow analysis of the Scioto and Blanchard rivers in the study area were used to describe patrems of ground-water flow, to evaluate stream-aquifer interaction, and to quantify recharge and discharge within the ground-water-flow system along a regional ground-water-flow path. The selected regional flow path begins at a regional topographic high in Logan County, Ohio, and ends in Sandusky Bay (Lake Erie), a regional topographic low. Recharge to the ground-water system along the selected regional flow path was estimated from hydrograph separation of streamflow and averaged 3.24 inches per year. Computer model simulations indicate that 84 percent of the water entering the ground-water system flows less than 5 miles from point of recharge to point of discharge and no deeper than the upper surficial aquifers. The distance and depth that ground water travels and traveltime from point of recharge to point of discharge is controlled largely by where ground water enters the flow system. Ground water entering the flow system in the vicinity of major surface- water divides generally travels further, deeper, and longer than ground water entering the flow system elsewhere along the regional flow path. Particle tracking simulations substantiate the concept that the 80-mile-long regional flow path is within a continuous ground-water basin. Estimated traveltimes for ground-water from the regional high to Sandusky Bay range from 22,000 to 40,700 years, given a range of porosities from 8 to 22 percent for the carbonate-rock aquifer.

Ohio↗

USGS2002

Estimating ground-water inflow to lakes in central Florida using the isotope mass-balance approach

The isotope mass-balance approach was used to estimate ground-water inflow to 81 lakes in the central highlands and coastal lowlands of central Florida. The study area is characterized by a subtropical climate and numerous lakes in a mantled karst terrain. Ground-water inflow was computed using both steady-state and transient formulations of the isotope mass-balance equation. More detailed data were collected from two study lakes, including climatic, hydrologic, and isotopic (hydrogen and oxygen isotope ratio) data. For one of these lakes (Lake Starr), ground-water inflow was independently computed from a water-budget study. Climatic and isotopic data collected from the two lakes were similar even though they were in different physiographic settings about 60 miles apart. Isotopic data from all of the study lakes plotted on an evaporation trend line, which had a very similar slope to the theoretical slope computed for Lake Starr. These similarities suggest that data collected from the detailed study lakes can be extrapolated to the rest of the study area. Ground-water inflow computed using the isotope mass-balance approach ranged from 0 to more than 260 inches per year (or 0 to more than 80 percent of total inflows). Steady-state and transient estimates of ground-water inflow were very similar. Computed ground-water inflow was most sensitive to uncertainty in variables used to calculate the isotopic composition of lake evaporate (isotopic compositions of lake water and atmospheric moisture and climatic variables). Transient results were particularly sensitive to changes in the isotopic composition of lake water. Uncertainty in ground-water inflow results is considerably less for lakes with higher ground-water inflow than for lakes with lower ground-water inflow. Because of these uncertainties, the isotope mass-balance approach is better used to distinguish whether ground-water inflow quantities fall within certain ranges of values, rather than for precise quantification. The lakes fit into three categories based on their range of ground-water inflow: low (less than 25 percent of total inflows), medium (25-50 percent of inflows), and high (greater than 50 percent of inflows). The majority of lakes in the coastal lowlands had low ground-water inflow, whereas the majority of lakes in the central highlands had medium to high ground-water inflow. Multiple linear regression models were used to predict ground-water inflow to lakes. These models help identify basin characteristics that are important in controlling ground-water inflow to Florida lakes. Significant explanatory variables include: ratio of basin area to lake surface area, depth to the Upper Floridan aquifer, maximum lake depth, and fraction of wetlands in the basin. Models were improved when lake water-quality data (nitrate, sodium, and iron concentrations) were included, illustrating the link between ground-water geochemistry and lake chemistry. Regression models that considered lakes within specific geographic areas were generally poorer than models for the entire study area. Regression results illustrate how more simplified models based on basin and lake characteristics can be used to estimate ground-water inflow. Although the uncertainty in the amount of ground-water inflow to individual lakes is high, the isotope mass-balance approach was useful in comparing the range of ground-water inflow for numerous Florida lakes. Results were also helpful in understanding differences in the geographic distribution of ground-water inflow between the coastal lowlands and central highlands. In order to use the isotope mass-balance approach to estimate inflow for multiple lakes, it is essential that all the lakes are sampled during the same time period and that detailed isotopic, hydrologic, and climatic data are collected over this same period of time. Isotopic data for Florida lakes can change over time, both seasonally and interannually, primarily because of differ

Water-Resources Investigations Report↗

USGS2022

Hydrogeology and simulation of groundwater flow in the Lucerne Valley groundwater basin, California

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. To address these concerns, the U.S. Geological Survey entered into a cooperative agreement with the Mojave Water Agency to develop a better understanding of the Lucerne Valley hydrogeologic system and provide tools to help evaluate and manage the effects of future development in the Lucerne Valley. The objectives of this study were to (1) improve the understanding of the aquifer system, (2) improve the understanding of subsidence in the basin, and (3) incorporate the understanding into a groundwater-flow model that can be used to help manage the groundwater resources in the Lucerne Valley. The model developed for this study covers the period of 1942–2016 and can help evaluate various proposed water-management scenarios during different climatic and hydrologic conditions. The aquifer system consists of a shallow aquifer, a confining unit, and middle and lower aquifers. These layered water-bearing units were identified based on geologic units of the mostly unconsolidated sediments and hydrologic properties. These alluvial deposits consist of clay, silt, sand, and gravel; some places also contain clay and silty clay lacustrine deposits. Several faults act, at least in part, as barriers to groundwater flow on the eastern, southern, and western edges of the basin. Present-day natural recharge is primarily from the infiltration of runoff from the San Bernardino Mountains to the south; however, stable and radioactive isotopes show that groundwater from the middle of the Lucerne Valley was older than about 10,000 years and probably was recharged as infiltration from streams draining the mountains in the Mojave Desert to the north, which probably does not occur under present-day climatic conditions. The annual average natural recharge for 1942–2016, estimated by a Basin Characterization Model, was about 635 acre-feet per year; the average amount of treated wastewater effluent transferred to the Lucerne Valley for artificial recharge annually ranged from about 1,500 to 4,000 acre-feet per year during 1980–2016. Pumpage estimates for 1942–2016 ranged from about 3,000 acre-feet in 1942 to about 18,300 acre-feet in 1984. The total cumulative amount of groundwater removed from the basin by pumping between 1942 and 2016 was estimated to be about 700,000 acre-feet, which was about 10 times greater than the cumulative amount of recharge to the entire Lucerne Valley groundwater basin. Before groundwater development, the direction of groundwater flow was from the southern part of the basin northward to discharge areas near Lucerne Lake, where it discharged through springs along the Helendale Fault and by evapotranspiration. Since the early 1900s, groundwater-level declines have mostly eliminated the areas where natural discharge occurred and exceeded 100 feet in the middle of the basin between the early 1950s and mid-1990s, and as much as 25 feet near the margins from about the mid-1950s to 2000s. A decrease in the rate of pumping after the mid-1990s lessened the hydraulic stress on the middle and lower aquifers and enabled hydraulic heads in the middle of the basin to recover slightly as groundwater near the margins of the basin moved toward the pumping depression. Although trends in groundwater levels in the center of the basin have reversed since the mid-1990s, levels at the basin margins continue to decline as the movement of groundwater from the margins fills the pumping depression and gradually flattens the groundwater table throughout the basin. The long-term extraction of groundwater and associated dewatering of the fine-grained sediments present within the aquifer system has resulted in aquifer compaction and consequently land subsidence, primarily near Lucerne Lake. Analysis of interferometric synthetic aperture radar data shows that almost 11 inches of land subsidence has occurred south of Lucerne Lake between April 1992 and November 2009; less subsidence occurred elsewhere in the basin during this period. This differential land subsidence has caused fissures and cracks in the ground surface, which have buckled the pavement and undercut roads in several locations. The Lucerne Valley Hydrologic Model was developed using the finite-difference groundwater modeling software One Water Hydrologic Model to represent the hydrologic conditions and stresses during 1942–2016. The model has a uniform grid of approximately 92 acres per cell (2,000 feet by 2,000 feet) and has four layers representing the water-bearing units. The results from the calibrated model simulations indicated that groundwater pumpage exceeded recharge, resulting in an estimated net cumulative depletion of groundwater storage (discharge minus recharge) of about 465,000 acre-feet from 1942 to 2016. The model simulated as much as 7.5 feet (90 inches; 2,286 millimeters) of aquifer compaction, which indicates the extensive fine-grained deposits and measured subsidence near Lucerne Lake.

California↗

USGS1985

Effects of sanitary sewers on ground-water levels and streams in Nassau and Suffolk Counties, New York; part 3: Development and application of southern Nassau County model

By 1990, sanitary sewers in Nassau County Sewage Disposal Districts 2 and 3 and Suffolk County Southwest Sewer District will discharge to the ocean 140 cu ft of water per second that would otherwise be returned to the groundwater system through septic tanks and similar systems. To evaluate the effects of this loss on groundwater levels and streamflow, the U.S. Geological Survey developed a groundwater flow model that couples a fine-scale subregional model to a regional model of a larger scale. The regional model generates flux boundary conditions for the subregional model, and the subregional model provides detail in the area of concern. Results indicate that the water table will decline by as much as 90% from conditions in the early 1970's. This report is one of a three-part series describing the predicted hydrologic effects of sewers in southern Nassau and southwestern Suffolk Counties.

New York↗

USGS1984

Ground-water resources of the Mattapoisett River aquifer, Plymouth County, Massachusetts: Summary for water-resource managers

Proposed increases in municipal pumpage in the Mattapoisett River valley will triple ground-water withdrawals in the next two decades. Because of State and local concern about the long-term effects of these withdrawals on ground-water levels and streamflow, a digital ground-water-flow model was developed to assist water-resource management. Ten development scenarios representing existing and proposed withdrawals were simulated using drought conditions. Under conditions simulating 1965, the driest year of record, predicted water levels in the aquifer are as much as 9 feet lower than average. Under severely dry conditions, simulating only enough recharge to keep the river flowing with no pumping, the predicted water levels are as much as 19 feet lower than average. During the greatest pumping demands, the predicted drawdown in five wells could cause well failure. Simulated pumping demands in six scenarios use all available ground-water discharge. Under severely dry conditions, it is predicted that the downstream half of the river will stop flowing under most pumping plans. (USGS)

Massachusetts↗

USGS1999

Simulation of stage and hydrologic budget for Shell Lake, Washburn County, Wisconsin

A model that simulates lake stage was developed to test the current understanding of the hydrology of Shell Lake, Wisconsin and to provide a tool for predicting the effects of withdrawing lake water on future lake stages. The model code is written in Fortran and simulates daily lake stage by summing estimates of hydrologic-budget components - precipitation falling on the lake surface, water evaporating from the lake surface, runoff (consisting of overland flow to the lake and intermittent streams flowing into the lake), and ground-water flow out of the lake. The model was calibrated to intermittent lake stage measurements for the period 1948-98. The hydrologic budget model was coupled to UCODE, a parameter estimation model, to aid in estimating runoff coefficients. Trends in stage simulated by the calibrated model compare reasonably well with historical stage trends. The root mean square of the differences of simulated and measured daily lake stage for the period 1948-98 is 0.54 foot. Predictive simulations indicate that withdrawing lake water is an effective way of reducing lake stage. Several years of pumping for at least 200 days per year at rates of 1,000 to 2,000 gallons per minute would have been required to reduce 1990's high stages by about one foot.

Wisconsin↗

USGS1979

Chemical analyses of ground water related to geothermal investigations in the Teton River area, eastern Idaho

Water samples were collected from 31 wells and springs in eastern Idaho and western Wyoming to help evaluate the potential geothermal resources in the Teton River area, Idaho. The water analyses included the common anions and cations, oxygen-18, deuterium, and several minor elements. Actual temperatures of the sampled thermal waters ranged from 23° to 49°C. Estimated aquifer temperatures, as derived from geochemical thermometers, ranged from 45° to 145°C based on silica concentrations and 45° to 205°C based on sodium-potassium-calcium ratios. Using the cation thermometer, two analyses indicated aquifer temperatures that were lower than the actual measured temperatures. Estimated temperatures using a mixing-model method ranged from 205° to 320°C, the higher temperature being of questionable value. The different methods used to estimate aquifer temperatures showed little correlation. On the basis of isotope data, the warm waters may be of local meteoric origin and have not been heated enough to react significantly with the aquifer rocks, or they originated as precipitation at high altitude and great distance from the area.

Idaho↗

USGS1999

Numerical simulation of vertical ground-water flux of the Rio Grande from ground-water temperature profiles, central New Mexico

An important gap in the understanding of the hydrology of the Middle Rio Grande Basin, central New Mexico, is the rate at which water from the Rio Grande recharges the Santa Fe Group aquifer system. Several methodologies-including use of the Glover-Balmer equation, flood pulses, and channel permeameters- have been applied to this problem in the Middle Rio Grande Basin. In the work presented here, ground-water temperature profiles and ground-water levels beneath the Rio Grande were measured and numerically simulated at four sites. The direction and rate of vertical ground-water flux between the river and underlying aquifer was simulated and the effective vertical hydraulic conductivity of the sediments underlying the river was estimated through model calibration. Seven sets of nested piezometers were installed during July and August 1996 at four sites along the Rio Grande in the Albuquerque area, though only four of the piezometer nests were simulated. In downstream order, these four sites are (1) the Bernalillo site, upstream from the New Mexico State Highway 44 bridge in Bernalillo (piezometer nest BRN02); (2) the Corrales site, upstream from the Rio Rancho sewage treatment plant in Rio Rancho (COR01); (3) the Paseo del Norte site, upstream from the Paseo del Norte bridge in Albuquerque (PDN01); and (4) the Rio Bravo site, upstream from the Rio Bravo bridge in Albuquerque (RBR01). All piezometers were completed in the inner-valley alluvium of the Santa Fe Group aquifer system. Ground-water levels and temperatures were measured in the four piezometer nests a total of seven times in the 24-month period from September 1996 through August 1998. The flux between the surface- and ground-water systems at each of the field sites was quantified by one-dimensional numerical simulation of the water and heat exchange in the subsurface using the heat and water transport model VS2DH. Model calibration was aided by the use of PEST, a model-independent computer program that uses nonlinear parameter estimation. Mean vertical hydraulic conductivities were estimated by model calibration and range from 1.5x10 -5 to 5.8x10 -6 meters per second (m/s). Mean simulated vertical ground-water flux for the BRN02 piezometer nest is 3.30x10 -7 m/s; for the COR01 piezometer nest is 3.58x10 -7 m/s; for the PDN01 piezometer nest is 4.22x10 -7 m/s; and for the RBR01 piezometer nest is 2.05x10 -7 m/s. Comparison of the simulated vertical fluxes and vertical hydraulic conductivities derived from this study with values from other studies in the Middle Rio Grande Basin indicate agreement between 1 and 3.5 orders of magnitude for hydraulic conductivity and within 1 order of magnitude for vertical flux.

New Mexico↗

USGS2003

Trends in nitrogen concentration and nitrogen loads entering the South Shore Estuary Reserve from streams and ground-water discharge in Nassau and Suffolk counties, Long Island, New York, 1952–97

The 13 major south-shore streams in Nassau and Suffolk Counties, Long Island, New York with adequate long-term (1971-97) water-quality records, and 192 south-shore wells with sufficient water-quality data, were selected for analysis of geographic, seasonal, and long-term trends in nitrogen concentration. Annual total nitrogen loads transported to the South Shore Estuary Reserve (SSER) from 11 of these streams were calculated using long-term discharge records. Nitrogen loads from shallow and deep ground water also were calculated using simulated ground-water discharge of 1968-83 hydrologic conditions. Long-term declines in stream discharge occurred in East Meadow Brook, Bellmore Creek and Massapequa Creek in response to extensive sewering in Nassau County. The smallest longterm annual discharge to the SSER was from the westernmost stream, Pines Brook, which is in an area in which the water table has been lowered by sewers since 1952. The three largest average annual discharges to the SSER were from the Connetquot River, Carlls River, and Carmans River in Suffolk County; the discharges from each of these streams were at least twice those of the other streams considered in this study. Total nitrogen concentrations in streams show a geographic trend with a general eastward increase in median total nitrogen concentration in Nassau County and a decreasing trend from Massapequa Creek eastward into Suffolk County. Total nitrogen concentrations in streams generally are lowest during summer and highest in winter as a result of seasonal fluctuations in chemical reactions and biological activity. The greatest seasonal difference in median total nitrogen concentration was at Carlls River with values of 3.4 and 4.2 mg/L (milligrams per liter) as N during summer (April through September) and winter (October through March), respectively. Streams affected by the completion of sewer districts show long-term (1971-97) trends of decreasing total nitrogen concentration and streams showing an increase in total nitrogen concentration are in unsewered areas with increased urbanization. Discharges from shallow ground water (upper glacial aquifer) and deep ground water (upper part of Magothy aquifer) were simulated from a ground-water-flow model calibrated to steadystate (1968-83) conditions. Simulated discharges from shallow-ground-water system in Nassau County were 10,700 Mgal/yr (million gallons per year) or 40,500,000 m 3 /yr (cubic meters per year), and those from Suffolk County were 52,300 Mgal/yr or 198,000,000 m 3 /yr. Discharges from deep-ground-water system in Nassau County were 4,900 Mgal/yr or 18,500,000 m 3 /yr, and those in Suffolk County were 12,700 Mgal/yr or 48,200,000 m 3 /yr. Ground-water concentrations of nitrogen decrease with depth and from west to east. The shallow ground water median nitrogen concentration for each county was determined using 1,155 samples collected at 167 shallow wells (125 feet deep or less) within 1 mile of the shore. The deep ground water median nitrate concentration (nitrate represented almost all of the total nitrogen) for each county was determined using 112 samples collected at 25 deep wells (greater than 125 feet deep) within 1 mile of the shore. The median nitrogen concentration for the shallow and median nitrate concentration for the deep ground water in Nassau County were 3.85 and 0.15 mg/L as N, during 1952–97; the corresponding concentrations for Suffolk County were 1.74 and <0.10 (less than 0.10) mg/L as N, during 1952–97. Nitrogen loads discharged from streams to the SSER for each year during 1972–97 were calculated as the annual total nitrogen concentration multiplied by the annual discharge. These values were calculated only for the seven streams for which sufficient data were available. The largest long-term (1972–97) average annual nitrogen load from Carlls River was 104 ton/yr or 94,300 kg/yr—about twice that of Connetquot River (54 ton/yr or 48,900 kg/yr) and over three times that of Carmans River (33 ton/yr or 29,900 kg/yr). The smallest annual mean nitrogen load was from Pines Brook, which has the lowest annual mean discharge of all streams analyzed. The nitrogen load carried to the SSER by ground-water discharge in shallow-ground-water system in Nassau and Suffolk Counties was calculated as the simulated discharge for each county multiplied by the respective median nitrogen concentration, and loads from deep-ground-water system were calculated as the simulated discharge for each county multiplied by the respective median nitrate concentration. All discharges were obtained from the U.S. Geological Survey's Long Island ground-water-flow model. The resultant nitrogen loads discharged to the SSER from shallow ground water were 172 ton/yr (156,000 kg/yr) from Nassau County and 380 ton/yr (345,000 kg/yr) from Suffolk County; equaling 552 ton/yr entering the SSER. Those from deep ground water were 3 ton/yr (2,700 kg/yr) from Nassau County and <0.5 ton/yr (480 kg/yr) from Suffolk County; equaling about 3.5 ton/yr entering the SSER. The sum of both stream loads and groundwater loads results in the total load to the SSER. The largest calculated total nitrogen load entering the SSER from both streams and ground water occurred in 1979 with a total load of 1,260 ton/yr (1,140,000 kg/yr). The smallest calculated nitrogen load entering the SSER occurred in 1995 with a total load of 725 ton/yr (658,000 kg/yr).

New York↗

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↗

USGS1985

Hydrology, water quality, and ground-water-development alternatives in the Chipuxet ground-water reservoir, Rhode Island

A glacial sand and gravel aquifer in the Chipuxet River basin of Rhode Island forms a ground-water reservoir that could yield as much as 8.6 million gallons per day to wells; however, some streams would go dry for extended periods of time. The State Water Resources Board has tested five site that it proposes to develop for a public supply of 3 million gallons per day. A digital model was used to determine how withdrawal at this rate from alternative combinations of wells would affect water levels and streamflow. Results show that withdrawal of 3 million gallons per day would have a minimal effect on water levels, but that withdrawal at this rate from some well combinations could cause the Chipuxet River to have little or no flow for 90 consecutive days on the average of 1 year in 20. Quality of ground water is generally good, but leaching of fertilizers applied to croplands, which overlie much of the aquifer, has caused locally excessive concentrations of nitrate. Induced infiltration of surface water through organic sediments that line the bottoms of ponds and streams also seems to be the cause of elevated concentrations of manganese in water from some heavily pumped wells. (USGS)

Water-Resources Investigations Report↗

USGS2009

Geographic information systems, remote sensing, and spatial analysis activities in Texas, 2008-09

Geographic information system (GIS) technology has become an important tool for scientific investigation, resource management, and environmental planning. A GIS is a computer-aided system capable of collecting, storing, analyzing, and displaying spatially referenced digital data. GIS technology is useful for analyzing a wide variety of spatial data. Remote sensing involves collecting remotely sensed data, such as satellite imagery, aerial photography, or radar images, and analyzing the data to gather information or investigate trends about the environment or the Earth's surface. Spatial analysis combines remotely sensed, thematic, statistical, quantitative, and geographical data through overlay, modeling, and other analytical techniques to investigate specific research questions. It is the combination of data formats and analysis techniques that has made GIS an essential tool in scientific investigations. This fact sheet presents information about the technical capabilities and project activities of the U.S. Geological Survey (USGS) Texas Water Science Center (TWSC) GIS Workgroup during 2008 and 2009. After a summary of GIS Workgroup capabilities, brief descriptions of activities by project at the local and national levels are presented. Projects are grouped by the fiscal year (October-September 2008 or 2009) the project ends and include overviews, project images, and Internet links to additional project information and related publications or articles.

Fact Sheet↗

USGS1977

Digital-model evaluation of the ground-water resources in Ocotillo-Coyote Wells Basin, Imperial County, California

A flow model using finite-element techniques has been constructed for an alluvial aquifer in the Ocotillo-Coyote Wells Basin, Imperial County, Calif. Natural recharge is about 2,600 acre-feet per year, and estimated ground water in storage is 640 ,000 acre-feet. Pumpage totaled 880 acre-feet in 1975. The computed decline from steady-state conditions in 1925 to December 1975 was 15 feet in Ocotillo. The projected decline from 1976 to 1995 with annual pumpage of 1,000 acre-feet is 6 feet and with annual pumpage of 2,000 acre-feet is 17 feet in Ocotillo. In the latter projection, continued pumping after 1995 may cause saline water to flow toward the potable ground water in and around Ocotillo. (Woodard-USGS)

California↗

USGS1997

Digital simulation of ground-water flow in the Warwick Aquifer, Fort Totten Indian Reservation, North Dakota

The demand for water from the Warwick aquifer, which underlies the Fort Totten Indian Reservation in northeastern North Dakota, has been increasing during recent years. Therefore, the Spirit Lake Sioux Nation is interested in resolving questions about the quantity and quality of water in the aquifer and in developing a water-management plan for future water use. A study was conducted to evaluate the surface-water and ground-water resources of the Fort Totten Indian Reservation and, in particular, the ground-water resources in the area of the Warwick aquifer. A major component of the study, addressed by this report, was to define the ground-water flow system of the aquifer. The Warwick aquifer consists of outwash deposits of the Warwick outwash plain that are as much as 30 feet thick and buried-valley deposits beneath the outwash plain that are as much as 200 feet thick. The aquifer is bounded on the north and west by end-moraine deposits and Devils Lake, on the south by the Sheyenne River Valley, and on the east by outwash deposits and ravines. The aquifer is underlain by Pierre Shale or by glacial till, clay, or silt. Ground-water gradients generally are small and rarely are more than 3 or 4 feet per mile. From 1982 to 1993, withdrawals from the Devils Lake well field averaged 1.5 cubic feet per second, and withdrawals from irrigation wells averaged 1.29 cubic feet per second. The combined discharge from springs may be about 3 cubic feet per second. During the early 1990s, the Warwick aquifer probably was in a steady-state condition with regard to storage change in the aquifer. A finite-difference, three-dimensional, ground-water flow model provided a reasonable simulation of ground-water flow in the Warwick aquifer. The aquifer was divided vertically into two layers and horizontally into a grid of 83 by 109 cells, each measuring 656 feet (200 meters) per side. The steady-state simulation was conducted using 1992 pumpage rates and October 1992 water levels. The mean absolute difference between simulated and derived water-level altitudes during final calibration of the model was 1.52 feet. The two transient simulations were conducted for 20 time intervals of 1 year each using both the small and large storage estimates, doubled 1992 pumpage from the Devils Lake well field, 1992 irrigation pumpage, and initial water-level altitudes simulated by the October 1992 steady-state simulation. In the simulation using the small storage estimate and doubled pumpage, model cells in the area of the well field went dry after 13 years. Assumptions made in the design of the model generally are supported by the digital simulation. Except in the area of Warwick Springs and smaller springs, lateral and basal boundaries of the aquifer are impermeable. The flow system is dominated by recharge and evapotranspiration. Recharge rates obtained during the calibration process were lower in topographically high areas than in topographically low areas. Hydraulic conductivity in the area of the Devils Lake well field was larger than that in the rest of the aquifer.

Water-Resources Investigations Report↗

USGS2007

Hydrostratigraphic Framework and Selection and Correlation of Geophysical Log Markers in the Surficial Aquifer System, Palm Beach County, Florida

The surficial aquifer system is the major source of freshwater for public water supply in Palm Beach County, Florida, yet many previous studies of the hydrogeology of this aquifer system have focused only on the eastern one-half to one-third of the county in the more densely populated coastal area (Land and others, 1973; Swayze and others, 1980; Swayze and Miller, 1984; Shine and others, 1989). Population growth in the county has resulted in the westward expansion of urbanized areas into agricultural areas and has created new demands on the water resources of the county. Additionally, interest in surface-water resources of central and western areas of the county has increased. In these areas, plans for additional surface-water storage reservoirs are being made under the Comprehensive Everglades Restoration Plan originally proposed by the U.S. Army Corps of Engineers and the South Florida Water Management District (1999), and stormwater treatment areas have been constructed by the South Florida Water Management District. Surface-water and ground-water interactions in the Everglades are thought to be important to water budgets, water quality, and ecology (Harvey and others, 2002). Most of the previous hydrogeologic and ground-water flow simulation studies of the surficial aquifer system have not utilized a hydrostratigraphic framework, in which stratigraphic or sequence stratigraphic units, such as those proposed in Cunningham and others (2001), are delineated in this stratigraphically complex aquifer system. A thick zone of secondary permeability mapped by Swayze and Miller (1984) was not subdivided and was identified as only being within the Anastasia Formation of Pleistocene age. Miller (1987) published 11 geologic sections of the surficial aquifer system, but did not delineate any named stratigraphic units in these sections. This limited interpretation has resulted, in part, from the complex facies changes within rocks and sediments of the surficial aquifer system and the seemingly indistinct and repetitious nature of the most common lithologies, which include sand, shell, sandstone, and limestone. Model construction and layer definition in a simulation of ground-water flow within the surficial aquifer system of Palm Beach County utilized only the boundaries of one or two major hydrogeologic zones, such as the Biscayne aquifer and surficial aquifer system; otherwise layers were defined by average elevations rather than geologic structure or stratigraphy (Shine and others, 1989). Additionally, each major permeable zone layer in the model was assumed to have constant hydraulic conductivity with no allowance for the possibility of discrete (thin) flow zones within the zone. The key to understanding the spatial distribution and hydraulic connectivity of permeable zones in the surficial aquifer system beneath Palm Beach County is the development of a stratigraphic framework based on a consistent method of county-wide correlation. Variability in hydraulic properties in the system needs to be linked to the stratigraphic units delineated in this framework, and proper delineation of the hydrostratigraphic framework should provide a better understanding and simulation of the ground-water flow system. In 2004, the U.S. Geological Survey, in cooperation with the South Florida Water Management District, initiated an investigation to develop a hydrostratigraphic framework for the surficial aquifer system in Palm Beach County.

Scientific Investigations Map↗

USGS1996

Assessment of the fresh- and brackish-water resources underlying Dunedin and adjacent areas of northern Pinellas County, Florida

The city of Dunedin is enhancing their potable ground-water resources through desalination of brackish ground water. An assessment of the fresh- and brackish-water resources in the Upper Floridan aquifer was needed to estimate the changes that may result from brackish-water development. The complex hydrogeologic framework underlying Dunedin and adjacent areas of northern Pinellas County is conceptualized as a multilayered sequence of permeable zones and confining and semiconfining units. The permeable zones contain vertically spaced, discrete, water-producing zones with differing water quality. Water levels, water-level responses, and water quality are highly variable among the different permeable zones. The Upper Floridan aquifer is best characterized as a local flow system in most of northern Pinellas County. Pumping from the Dunedin well field is probably not influencing water levels in the aquifer outside Dunedin, but has resulted in localized depressions in the potentiometric surface surrounding production-well clusters. The complex geologic layering combined with the effects of production-well distribution probably contribute to the spatial and temporal variability in chloride concentrations in the Dunedin well field. Chloride concentrations in ground water underlying the Dunedin well field vary both vertically and laterally. In general, water-quality rapidly changes below depths of 400 feet below sea level. Additionally, randomly distributed water-producing zones with higher chloride concentrations may occur at shallow, discrete intervals above 400 feet. A relation between chloride concentration and distance from St. Joseph Sound is not apparent; however, a possible relation exists between chloride concentration and production-well density. Chloride-concentration data from production wells show a consistently increasing pattern that has accelerated since the late 1980's. Chloride-concentration data from 15 observation wells show increasing trends for 6 wells, decreasing trends for 3 wells, and no trend for 6 wells. The current and future, fresh- and brackish-water resources were evaluated using a numerical ground-water flow and solute-transport model. Simulation results indicate that the hydraulic conductivity of the uppermost permeable zone (upper zone A) of the Upper Floridan aquifer is four times greater than the two underlying permeable zones (lower zone A and zone B). The simulated hydraulic conduc- tivities of the semiconfining units are four orders of magnitude less than the permeable zones. Simulation results show the importance of semiconfining units as a mechanism for retarding the vertical movement of higher salinity ground water. Simulation results indicate that pumping from the brackish-water zone does not negatively influence the chloride-concentration trends in the overlying fresh-water zone; however, chloride changes in the fresh-water zone will continue to occur due to the continuation of current fresh-water withdrawals. Chloride changes in the brackish-water zone will occur from pumping brackish water.

Florida↗

USGS1983

Water-level changes in the high plains regional aquifer, northwestern Oklahoma, predevelopment to 1980

During 1978, the U.S. Geological Survey began a 5-year study of the High Plains regional aquifer system to provide hydrologic information for evaluation of the effects of long-term development of the aquifer and to develop computer models for prediction of aquifer response to alternative changes in ground-water management (Weeks, 1978). This report is one of a series presenting hydrologic information of the High Plains aquifer in Oklahoma. The predevelopment to 1980 water-level changes in the High Plains regional aquifer in Oklahoma are shown for Harper, Ellis, Woodward, Dewey, and Roger Mills Counties, on the east, and for the Oklahoma Panhandle, consist- ing of Cimarron, Texas, and Beaver Counties, on the west. About 1,470 water-level measurements in the Panhandle were used in compiling the predevelopment water-table map (Havens, 1982c). In the remaining area to the east about 150 water-level measurements from the 1950's to the 1970's are representative of predevelopment water levels. For the 1980 water-table map, about 330 measurements were made in the Panhandle and about 350 measurements in the eastern area by the Oklahoma Water Resources Board (Havens, 1982b).

Water-Resources Investigations Report↗