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USGS1998

Optimization of ground-water withdrawal in the lower Fox River communities, Wisconsin

Pumping from closely spaced wells in the Central Brown County area and the Fox Cities area near the north shore of Lake Winnebago has resulted in the formation of deep cones of depression in the vicinity of the two pumping centers. Water-level measurements indicate there has been a steady decline in water levels in the vicinity of these two pumping centers for the past 50 years. This report describes the use of ground-water optimization modeling to efficiently allocate the ground-water resources in the Lower Fox River Valley. A 3-dimensional ground-water flow model was used along with optimization techniques to determine the optimal withdrawal rates for a variety of management alternatives. The simulations were conducted separately for the Central Brown County area and the Fox Cities area. For all simulations, the objective of the optimization was to maximize total ground-water withdrawals. The results indicate that ground water can supply nearly all of the projected 2030 demand for Central Brown County municipalities if all of the wells are managed (including the city of Green Bay), 8 new wells are installed, and the water-levels are allowed to decline to 100 ft below the bottom of the confining unit. Ground water can supply nearly all of the projected 2030 demand for the Fox Cities if the municipalities in Central Brown County convert to surface water; if Central Brown County municipalities follow the optimized strategy described above, there will be a considerable shortfall of available ground water for the Fox Cities communities. Relaxing the water-level constraint in a few wells, however, would likely result in increased availability of water. In all cases examined, optimization alternatives result in a rebound of the steady-state water levels due to projected 2030 withdrawal rates to levels at or near the bottom of the confining unit, resulting in increased well capacity. Because the simulations are steady-state, if all of the conditions of the model remain the same these withdrawal rates would be sustainable in perpetuity.

Wisconsin↗
USGS1998

Fish communities and their relation to physical and chemical characteristics of streams from selected environmental settings in the Lower Susquehanna River basin, 1993-95

Studies of fish-community composition were conducted annually in selected reaches (from 100 to 303 meters in length) on seven streams from June 1993 to June 1995 within the Lower Susquehanna River Basin. In 1994, additional reaches were selected on three of the streams, resulting in a total of 28 samples. The study reaches were selected on the basis of type of bedrock and land use/land cover; the major emphasis was on agricultural land use or areas in transition from agricultural to commercial, industrial, and residential land uses. At each reach, environmental characteristics consisting of instream and riparian habitat conditions, hydrology, and water quality were determined. The relation of fish communities at these reaches to physical and chemical characteristics of streams was analyzed to determine if the fish communities differed temporally or spatially. Data were analyzed by parametric and multivariate techniques. During the course of the study, a total of 33,143 fish were collected, consisting of 39 species representing 8 families. Cyprinidae (minnows) were dominant with 17 species, followed by Centrarchidae (sunfishes) with 7 species and Percidae (perches and darters) with 4 species. Three species?blacknose dace ( Rhinichthys atratulus ), white sucker ( Catostomus commersoni ), and the sculpins ( Cottus spp)?accounted for 49 percent of the total fish collected. The environmental variables most closely related to the fish communities present at the reaches were mean channel width, mean water temperature, mean canopy angle, and suspended-sediment concentrations. These variables accounted for about 79 percent of the variation in the environmental-species relation. Channel width and mean water temperature are correlated with stream size variables. The stream size gradient is the most influential variable to the fish communities studied in the Lower Susquehanna River Basin.

Water-Resources Investigations Report↗
USGS1998

Techniques for estimating peak-flow magnitude and frequency relations for South Dakota streams

A generalized skew coefficient analysis was completed for South Dakota to test the validity of using the generalized skew coefficient map in Bulletin 17B of the 1982 United States Water Resources Council, ?Guidelines for Determining Flood Flow Frequency.? Results of the analysis indicate that the Bulletin 17B generalized skew coefficient map generally provides adequate generalized skew coefficients for estimating peakflow magnitudes and frequencies for South Dakota gaging stations. Peak-flow records through 1994 for 197 continuous- and partial-record streamflow-gaging stations that had 10 or more years of unregulated systematic record were used in a generalized leastsquares regression analysis that relates peak flows for selected recurrence intervals to selected basin characteristics. Peak-flow equations were developed for recurrence intervals of 2, 5, 10, 25, 50, 100, and 500 years for seven hydrologic subregions in South Dakota. The peak-flow equations are applicable to natural-flow streams that have drainage areas less than or equal to 1,000 square miles. The standard error of estimate for the seven hydrologic subregions ranges from 22 to 110 percent for the 100-year peak-flow equations. Weighted peak flows for various frequencies based on gaging-station data and the regional regression equations are provided for each gaging station. Examples are given for (1) determining peak-flow magnitudes and frequencies for ungaged sites on ungaged streams; (2) determining weighted peak-flow magnitudes and frequencies for gaging stations; and (3) using the drainage-area ratio method for determining peakflow magnitudes and frequencies for ungaged sites near a gaging station on the same stream and ungaged sites between two gaging stations on the same stream.

Water-Resources Investigations Report↗
USGS1998

Quality-Assurance/Quality-Control Manual for Collection and Analysis of Water-Quality Data in the Ohio District, US Geological Survey

The U.S. Geological Survey (USGS), Water Resources Division (WRD), requires that quality-assurance/quality-control (QA/QC) activities be included in any sampling and analysis program. Operational QA/QC procedures address local needs while incorporating national policies. Therefore, specific technical policies were established for all activities associated with water-quality project being done by the Ohio District. The policies described in this report provide Ohio District personnel, cooperating agencies, and others with a reference manual on QA/QC procedures that are followed in collecitng and analyzing water-quality samples and reporting water-quality information in the Ohio District. The project chief, project support staff, District Water-Quality Specialist, and District Laboratory Coordinator are all involved in planning and implementing QA/QC activities at the district level. The District Chief and other district-level managers provide oversight, and the Regional Water-Quality Specialist, Office of Water Quality (USGS headquarters), and the Branch of Quality Systems within the Office of Water Quality create national QA/QC polices and provide assistance to District personnel. In the literature, the quality of all measurement data is expressed in terms of precision, variability, bias, accuracy, completeness, representativeness, and comparability. In the Ohio District, bias and variability will be used to describe quality-control data generated from samples in the field and laboratory. Each project chief must plan for implementation and financing of QA/QC activities necessary to achieve data-quality objectives. At least 15 percent of the total project effort must be directed toward QA/QC activities. Of this total, 5-10 percent will be used for collection and analysis of quality-control samples. This is an absolute minimum, and more may be required based on project objectives. Proper techniques must be followed in the collection and processing of surface-water, ground-water, biological, precipitation, bed-sediment, bedload, suspended-sediment, and solid-phase samples. These techniques are briefly described in this report and are extensively documented. The reference documents listed in this report will be kept by the District librarian and District Water-Quality Specialist and updated regularly so that they are available to all District staff. Proper handling and documentation before, during, and after field activities are essential to ensure the integrity of the sample and to correct erroneous reporting of data results. Field sites are to be properly identified and entered into the data base before field data-collection activities begin. During field activities, field notes are to be completed and sample bottles appropriately labeled a nd stored. After field activities, all paperwork is to be completed promptly and samples transferred to the laboratory within allowable holding times. All equipment used by District personnel for the collection and processing of water-quality samples is to be properly operated, maintained, and calibrated by project personnel. This includes equipment for onsite measurement of water-quality characteristics (temperature, specific conductance, pH, dissolved oxygen, alkalinity, acidity, and turbidity) and equipment and instruments used for biological sampling. The District Water-Quality Specialist and District Laboratory Coordinator are responsible for preventive maintenance and calibration of equipment in the Ohio District laboratory. The USGS National Water Quality Laboratory in Arvada, Colo., is the primary source of analytical services for most project work done by the Ohio District. Analyses done at the Ohio District laboratory are usually those that must be completed within a few hours of sample collection. Contract laboratories or other USGS laboratories are sometimes used instead of the NWQL or the Ohio District laboratory. When a contract laboratory is used, the projec

Water-Resources Investigations Report↗
USGS1998

Quantification of deep percolation from two flood-irrigated alfalfa fields, Roswell Basin, New Mexico

For many years water management in the Roswell ground-water basin (Roswell Basin) and other declared basins in New Mexico has been the responsibility of the State of New Mexico. One of the water management issues requiring better quantification is the amount of deep percolation from applied irrigation water. Two adjacent fields, planted in alfalfa, were studied to determine deep percolation by the water-budget, volumetric-moisture, and chloride mass-balance methods. Components of the water-budget method were measured, in study plots called borders, for both fields during the 1996 irrigation season. The amount of irrigation water applied in the west border was 95.8 centimeters and in the east border was 169.8 centimeters. The total amount of precipitation that fell during the irrigation season was 21.9 centimeters. The increase in soil-moisture storage from the beginning to the end of the irrigation season was 3.2 centimeters in the west border and 8.8 centimeters in the east border. Evapotranspiration, as estimated by the Bowen ratio energy balance technique, in the west border was 97.8 centimeters and in the east border was 101.0 centimeters. Deep percolation determined using the water-budget method was 16.4 centimeters in the west border and 81.6 centimeters in the east border. An average deep percolation of 22.3 centimeters in the west border and 31.6 centimeters in the east border was determined using the volumetric-moisture method. The chloride mass-balance method determined the multiyear deep percolation to be 15.0 centimeters in the west border and 38.0 centimeters in the east border. Large differences in the amount of deep percolation between the two borders calculated by the water-budget method are due to differences in the amount of water that was applied to each border. More water was required to flood the east border because of the greater permeability of the soils in that field and the smaller rate at which water could be applied.

New Mexico↗
USGS1998

Application of nonlinear-regression methods to a ground-water flow model of the Albuquerque Basin, New Mexico

This report documents the application of nonlinear-regression methods to a numerical model of ground-water flow in the Albuquerque Basin, New Mexico. In the Albuquerque Basin, ground water is the primary source for most water uses. Ground-water withdrawal has steadily increased since the 1940's, resulting in large declines in water levels in the Albuquerque area. A ground-water flow model was developed in 1994 and revised and updated in 1995 for the purpose of managing basin ground- water resources. In the work presented here, nonlinear-regression methods were applied to a modified version of the previous flow model. Goals of this work were to use regression methods to calibrate the model with each of six different configurations of the basin subsurface and to assess and compare optimal parameter estimates, model fit, and model error among the resulting calibrations. The Albuquerque Basin is one in a series of north trending structural basins within the Rio Grande Rift, a region of Cenozoic crustal extension. Mountains, uplifts, and fault zones bound the basin, and rock units within the basin include pre-Santa Fe Group deposits, Tertiary Santa Fe Group basin fill, and post-Santa Fe Group volcanics and sediments. The Santa Fe Group is greater than 14,000 feet (ft) thick in the central part of the basin. During deposition of the Santa Fe Group, crustal extension resulted in development of north trending normal faults with vertical displacements of as much as 30,000 ft. Ground-water flow in the Albuquerque Basin occurs primarily in the Santa Fe Group and post-Santa Fe Group deposits. Water flows between the ground-water system and surface-water bodies in the inner valley of the basin, where the Rio Grande, a network of interconnected canals and drains, and Cochiti Reservoir are located. Recharge to the ground-water flow system occurs as infiltration of precipitation along mountain fronts and infiltration of stream water along tributaries to the Rio Grande; subsurface flow from adjacent regions; irrigation and septic field seepage; and leakage through the Rio Grande, canal, and Cochiti Reservoir beds. Ground water is discharged from the basin by withdrawal; evapotranspiration; subsurface flow; and flow to the Rio Grande, canals, and drains. The transient, three-dimensional numerical model of ground-water flow to which nonlinear-regression methods were applied simulates flow in the Albuquerque Basin from 1900 to March 1995. Six different basin subsurface configurations are considered in the model. These configurations are designed to test the effects of (1) varying the simulated basin thickness, (2) including a hypothesized hydrogeologic unit with large hydraulic conductivity in the western part of the basin (the west basin high-K zone), and (3) substantially lowering the simulated hydraulic conductivity of a fault in the western part of the basin (the low-K fault zone). The model with each of the subsurface configurations was calibrated using a nonlinear least- squares regression technique. The calibration data set includes 802 hydraulic-head measurements that provide broad spatial and temporal coverage of basin conditions, and one measurement of net flow from the Rio Grande and drains to the ground-water system in the Albuquerque area. Data are weighted on the basis of estimates of the standard deviations of measurement errors. The 10 to 12 parameters to which the calibration data as a whole are generally most sensitive were estimated by nonlinear regression, whereas the remaining model parameter values were specified. Results of model calibration indicate that the optimal parameter estimates as a whole are most reasonable in calibrations of the model with with configurations 3 (which contains 1,600-ft-thick basin deposits and the west basin high-K zone), 4 (which contains 5,000-ft-thick basin de

New Mexico↗
USGS1998

Detailed study of selenium and selected constituents in water, bottom sediment, soil, and biota associated with irrigation drainage in the San Juan River area, New Mexico, 1991-95

In response to increasing concern about the quality of irrigation drainage and its potential effects on fish, wildlife, and human health, the U.S. Department of the Interior began the National Irrigation Water Quality Program (NIWQP) to investigate these concerns at irrigation projects sponsored by the Department. The San Juan River area in northwestern New Mexico was one of the areas designated for study. Study teams composed of scientists from the U.S. Geological Survey, the U.S. Fish and Wildlife Service, the Bureau of Reclamation, and the Bureau of Indian Affairs collected water, bottom-sediment, soil, and biological samples at 61 sites in the San Juan River area during 1993-94. Supplemental data collection conducted during 1991-95 by the Bureau of Indian Affairs and its contractor extended the time period and sampling sites available for analysis. Analytical chemistry performed on samples indicated that most potentially toxic elements other than selenium generally were not high enough to be of concern to fish, wildlife, and human health. Element concentrations in some water, bottom-sediment, soil, and biological samples exceeded applicable standards and criteria suggested by researchers in current literature. Selenium concentrations in water samples from 28 sites in the study area exceeded the 2-microgramper-liter (lg/L) wildlife-habitat standard. Vanadium concentrations in water exceeded the 100-Kg/L standard for livestock-drinking water at one site. In biota, selenium and aluminum concentrations regularly equaled or exceeded avian dietary threshold concentrations. In bottom sediment and soil, element concentrations above the upper limit of the baseline range for western soils were: selenium, 24 exceedances; lead, 2 exceedances; molybdenum, 2 exceedances;strontium, 4 exceedances; and zinc, 4 exceedances. Concentrations of total selenium in bottom-sediment and soil samples were significantly greater for Cretaceous than for non-Cretaceous soil types in the study area and were generally similar for habitats within and outside irrigation-affected areas. Mean and median total-selenium concentrations in samples from areas with Cretaceous soil types were 4.6 and 2.2 micrograms per gram (ps/g), respectively. Mean and median total-selenium concentrations in samples from areas with non-Cretaceous soil types were 0.6 and 0.15 pg/g, respectively. Samples from the study area had low concentrations of organic constituents. Organochlorine pesticides and polychlorinated biphenyls were detected in a few biological samples at low concentrations. Polycyclic aromatic hydrocarbon (PAH) compounds were not detected in whole-water samples collected using conventional water-sampling techniques. In tests involving the use of semipermeable-membrane devices to supplement conventional water assays for PAH's, low concentrations of PAH's were found at several locations in the Hammond Irrigation Supply Canal, but were not detected in the Hammond ponds at the downstream reach of the Hammond irrigation service area. PAH compounds do not appear to reach the San Juan River through the Hammond Canal. Data indicate that water samples from irrigation-drainage-affected habitats had increased mean selenium concentrations compared with samples from irrigation-delivery habitat. The mean selenium concentration in water was greatest at seeps and tributaries draining irrigated land (17 μg/L); less in irrigation drains and in ponds on irrigated land (61.tg/L); and least in backwater, the San Juan River, and irrigation-supply water (0.5 - 0.6 μg/L). Statistical tests imply that irrigation significantly increases selenium concentrations in water samples when a Department of the Interior irrigation project is developed on selenium-rich sediments. Water samples from sites with Cretaceous soils had significantly greater selenium concentrations than water samples from sites with non-Cretaceous soils. Water samples from Department of the Interior project irrigation-drainage sites developed on Cretaceous soils contained a mean selenium concentration about 10 times greater than those in samples from Department of the Interior project sites developed on non-Cretaceous soils. Selenium was much less concentrated in water than in bottom sediment, soil, or biota in the study area. The range in concentrations of dissolved selenium in water was less than 1 ptg/L to 37 1.1g/L (less than 1 to 37 parts per billion). The range in concentrations of total selenium in bottom sediment and soil was less than 0.1 to 23lig/g (less than 100 to 23,000 parts per billion). The range in concentration of selenium in biota was less than 0.1 to 24.0 fig/g (less than 100 to 24,000 parts per billion). Data indicated that bioaccumulation and leaching from soil were the important processes at the study area that lead to elevated levels of selenium. Other processes examined included: (1) evapoconcentration of selenium; (2) atmospheric deposition of aerosols containing selenium; and (3) contamination of surface water by point-source or non-point-source discharges. Selenium concentrations in biological samples were evaluated by a number of variables including: (1) media sampled (emergent and submergent plants, nektonic and benthic invertebrates, omnivore/herbivore and carnivore fish, and terrestrial and aquatic amphibians); (2) habitat (San Juan River main-stem reaches, backwaters, tributary reaches, irrigation delivery or drainage canals, and ponds); (3) irrigation project area and reference sites; and (4) soil type (non-Cretaceous or Cretaceous soils). Graphical techniques and nonparametric statistical tests were applied to determine the influence of selected physiographic variables on selenium concentrations in biological samples collected in the San Juan River area. Species of sucker and of smaller fish contained significantly higher selenium concentrations in the upstream portion of the river where a productive community of plants and animals is found that is associated with warming, nutrient-rich waters discharged from an upstream reservoir. Selenium concentrations in algae, odonates, and mosquitofish collected from both irrigation-drain and pond habitats underlain by Cretaceous soils were significantly greater than in those collected from similar habitats underlain by non-Cretaceous soils. Investigators conclude that the major factor affecting the variability of selenium accumulation in biota at aquatic habitats was the presence of underlying Cretaceous soils. Median selenium concentrations were less than 2 lAg/g for plant samples, less than 7 μg/g for invertebrate samples, and less than 6 lAg/g for whole-fish samples collected from aquatic habitats underlain by non-Cretaceous soils. Similar samples collected from aquatic habitats underlain by Cretaceous soils contained median selenium concentrations two to five times greater. Leaching of selenium from Cretaceous soils in the San Juan River area increases the accumulation of selenium concentrations in the biota and thereby increases the exposure and potential health risks associated with selenium to migratory birds, fish, and other wildlife that use these aquatic habitats extensively. Aquatic habitats presenting the greatest average exposure to excess selenium concentrations in the diets of resident wildlife are from consumption of plants, invertebrates, and fish at irrigation-drain habitats underlain by Cretaceous soils. Of the irrigation projects evaluated in the San Juan River area, the highest median selenium concentrations in algae, cattail leaves, odonate nymphs, mosquitofish, and leopard frog samples from the study area were collected from the east hogback irrigation drain.

New Mexico↗
USGS1999

Geology and ground-water resources of the Lawrenceville area, Georgia

The population of the Atlanta Metropolitan area continues to grow at a rapid pace and the demand for water supplies steadily increases. Exploration for ground-water resources, as a supplement to surface-water supplies, is being undertaken by many city and county governments. The application of effective investigative methods to characterization of the complex igneous and metamorphic fractured bedrock aquifers of the Piedmont physiographic province is essential to the success of these ground-water exploration programs. The U.S. Geological Survey, in cooperation with the City of Lawrenceville, Ga., began a study in December 1994 to apply various investigative techniques for field characterization of fractured crystalline-bedrock aquifers near Lawrenceville. Five major lithologic units were mapped in the Lawrenceville, Ga., area as part of an ongoing study of ground-water resources-amphibolite, biotite gneiss, button schist, granite gneiss, and quartzite/aluminous schist. These units generally are thin in outcrop width, have low angles of dip (nearly 0 to 20 degrees, dip reversals occur over short distances), and exhibit some shearing characteristics. The most productive unit for ground-water resources, on the basis of subsurface data collected through 1997, is the amphibolite. Historically, two wells drilled into this unit are recognized as having possibly the highest yields in the Piedmont region of northern Georgia. The City of Lawrenceville refurbished one well at the Rhodes Jordan Wellfield in 1990, and has pumped this well at an average rate of about 230 gallons per minute since 1995. In general, the composition of water collected from the bedrock wells, regolith wells, and City Lake is similar; calcium and bicarbonate are the dominant cation and anion, respectively. Water from the regolith wells and the lake have lower concentrations of major ions than does water from the bedrock wells. Many of the ground-water samples collected from the Rhodes Jordan Wellfield during October-November 1995, and from the wellfield and three additional observation well sites during August 1996, contain volatile organic compounds. Volatile organic compounds were detected in ground-water samples collected from several bedrock and regolith wells located in urban areas. Trace concentrations of tetrachloroethylene, trichloroethylene, 1,1-dichloroethane, trichlorofluoromethane, 1,1,1-trichloroethane, and cis-1,2-dichloroethene were detected. Methyl-tert-butyl ether (MTBE)-a compound used to increase the octane level in gasoline-was detected at concentrations above expected urban background levels in bedrock wells in the Rhodes Jordan Wellfield. Concentrations of MTBE ranged from 0.6 to 12 micrograms per liter in October-November 1995, and from 0.6 to 26 micrograms per liter in August 1996. Continuous ground-water-level data suggest that the fractured crystalline-bedrock aquifer (amphibolite unit) at the Rhodes Jordan Wellfield, generally is dewatered to a depth near a productive fracture during the regular pumping cycle of 18 hours per day, 5 days on and 2 days off per week. However, when the stress on the aquifer is increased by extending the pumping period up to as much as 18 days, or by pumping longer that 18 hours per day, the aquifer exhibits an unusual condition of recovery. Areal effects of pumping have been observed at distances of as much as one mile, extending across surface-water drainage divides.

Georgia↗
USGS1999

Characteristics of fractures in crystalline bedrock determined by surface and borehole geophysical surveys, eastern surplus superfund site, Meddybemps, Maine

Surface and borehole geophysical methods were used to determine fracture orientation in crystalline bedrock at the Eastern Surplus Superfund Site in Meddybemps, Maine. Fracture-orientation information is needed to address concerns about the fate of contaminants in ground water at the site. Azimuthal square-array resistivity surveys were conducted at 3 locations at the site, borehole-acoustic televiewer and borehole-video logs were collected in 10 wells, and single-hole directional radar surveys were conducted in 9 wells. Borehole-video logs were used to supplement the results of other geophysical techniques and are not described in this report. Analysis of azimuthal square-array resistivity data indicated that high-angle fracturing generally strikes northeast-southwest at the three locations. Borehole-acoustic televiewer logs detected one prominent low-angle and two prominent high-angle fracture sets. The low-angle fractures strike generally north-northeast and dip about 20 degrees west-northwest. One high-angle fracture set strikes north-northeast and dips east-southeast; the other high-angle set strikes east-northeast and dips south-southeast. Single-hole directional radar surveys identified two prominent fracture sets: a low-angle set striking north-northeast, dipping west-northwest; and a high-angle fracture set striking north-northeast, dipping east-southeast. Two additional high-angle fracture sets are defined weakly, one striking east-west, dipping north; and a second striking east-west, dipping south. Integrated results from all of the geophysical surveys indicate the presence of three primary fracture sets. A low-angle set strikes north-northeast and dips west-northwest. Two high-angle sets strike north-northeast and east-northeast and dip east-southeast and south-southeast. Statistical correction of the fracture data for orientation bias indicates that high-angle fractures are more numerous than observed in the data but are still less numerous than the low-angle fractures. The orientation and distribution of water-yielding fractures sets were determined by correlating the fracture data from this study with previously collected borehole-flowmeter data. The water-yielding fractures are generally within the three prominent fracture sets observed for the total fracture population. The low-angle water-yielding fractures primarily strike north-northeast to west-northwest and dip west-northwest to south-southwest. Most of the high-angle water-yielding fractures strike either north-northeast or east-west and dip east-southeast or south. The spacing between water-yielding fractures varies but the probable average spacing is estimated to be 30 feet for low-angle fractures; 27 feet for the east-southeast dipping, high-angle fractures; and 43 feet for the south-southeast dipping, high-angle fractures. The median estimated apparent transmissivity of individual water-yielding fractures or fracture zones was 0.3 feet squared per day and ranged from 0.01 to 382 feet squared per day. Ninety-five percent of the water-yielding fractures or fracture zones had an estimated apparent transmissivity of 19.5 feet squared per day or less. The orientation, spacing, and hydraulic properties of water-yielding fractures identified during this study can be used to help estimate recharge, flow, and discharge of ground water contaminants. High-angle fractures provide vertical pathways for ground water to enter the bedrock, interconnections between low-angle fractures, and, subsequently, pathways for water flow within the bedrock along fracture planes. Low-angle fractures may allow horizontal ground-water flow in all directions. The orientation of fracturing and the hydraulic properties of each fracture set strongly affect changes in ground-water flow under stress (pumping) conditions.

Maine↗
USGS1999

Estimating Concentrations of Road-Salt Constituents in Highway-Runoff from Measurements of Specific Conductance

Discrete or composite samples of highway runoff may not adequately represent in-storm water-quality fluctuations because continuous records of water stage, specific conductance, pH, and temperature of the runoff indicate that these properties fluctuate substantially during a storm. Continuous records of water-quality properties can be used to maximize the information obtained about the stormwater runoff system being studied and can provide the context needed to interpret analyses of water samples. Concentrations of the road-salt constituents calcium, sodium, and chloride in highway runoff were estimated from theoretical and empirical relations between specific conductance and the concentrations of these ions. These relations were examined using the analysis of 233 highwayrunoff samples collected from August 1988 through March 1995 at four highway-drainage monitoring stations along State Route 25 in southeastern Massachusetts. Theoretically, the specific conductance of a water sample is the sum of the individual conductances attributed to each ionic species in solution-the product of the concentrations of each ion in milliequivalents per liter (meq/L) multiplied by the equivalent ionic conductance at infinite dilution-thereby establishing the principle of superposition. Superposition provides an estimate of actual specific conductance that is within measurement error throughout the conductance range of many natural waters, with errors of less than ?5 percent below 1,000 microsiemens per centimeter (?S/cm) and ?10 percent between 1,000 and 4,000 ?S/cm if all major ionic constituents are accounted for. A semi-empirical method (adjusted superposition) was used to adjust for concentration effects-superposition-method prediction errors at high and low concentrations-and to relate measured specific conductance to that calculated using superposition. The adjusted superposition method, which was developed to interpret the State Route 25 highway-runoff records, accounts for contributions of constituents other than calcium, sodium, and chloride in dilute waters. The adjusted superposition method also accounts for the attenuation of each constituent's contribution to conductance as ionic strength increases. Use of the adjusted superposition method generally reduced predictive error to within measurement error throughout the range of specific conductance (from 37 to 51,500 ?S/cm) in the highway runoff samples. The effects of pH, temperature, and organic constituents on the relation between concentrations of dissolved constituents and measured specific conductance were examined but these properties did not substantially affect interpretation of the Route 25 data set. Predictive abilities of the adjusted superposition method were similar to results obtained by standard regression techniques, but the adjusted superposition method has several advantages. Adjusted superposition can be applied using available published data about the constituents in precipitation, highway runoff, and the deicing chemicals applied to a highway. This semi-empirical method can be used as a predictive and diagnostic tool before a substantial number of samples are collected, but the power of the regression method is based upon a large number of water-quality analyses that may be affected by a bias in the data.

Water-Resources Investigations Report↗
USGS1999

Estimates of ground-water discharge as determined from measurements of evapotranspiration, Ash Meadows area, Nye County, Nevada

Ash Meadows is one of the major discharge areas within the regional Death Valley ground-water flow system of southern Nevada and adjacent California. Ground water discharging at Ash Meadows is replenished from inflow derived from an extensive recharge area that includes the eastern part of the Nevada Test Site (NTS). Currently, contaminants introduced into the subsurface by past nuclear testing at NTS are the subject of study by the U.S. Department of Energy's Environmental Restoration Program. The transport of any contaminant in contact with ground water is controlled in part by the rate and direction of ground-water flow, which itself depends on the location and quantity of ground water discharging from the flow system. To best evaluate any potential risk associated with these test-generated contaminants, studies were undertaken to accurately quantify discharge from areas downgradient from the NTS. This report presents results of a study to refine the estimate of ground-water discharge at Ash Meadows. The study estimates ground-water discharge from the Ash Meadows area through a rigorous quantification of evapotranspiration (ET). To accomplish this objective, the study identifies areas of ongoing ground-water ET, delineates unique areas of ET defined on the basis of similarities in vegetation and soil-moisture conditions, and computes ET rates for each of the delineated areas. A classification technique using spectral-reflectance characteristics determined from satellite images recorded in 1992 identified seven unique units representing areas of ground-water ET. The total area classified encompasses about 10,350 acres dominated primarily by lush desert vegetation. Each unique area, referred to as an ET unit, generally consists of one or more assemblages of local phreatophytes. The ET units identified range from sparse grasslands to open water. Annual ET rates are computed by energy-budget methods from micrometeorological measurements made at 10 sites within six of the seven identified ET units. Micrometeorological data were collected for a minimum of 1 year at each site during 1994 through 1997. Evapotranspiration ranged from 0.6 foot per year in a sparse, dry saltgrass environment to 8.6 feet per year over open water. Ancillary data, including water levels, were collected during this same period to gain additional insight into the evapotranspiration process. Water levels measured in shallow wells showed annual declines of more than 10 feet and daily declines as high as 0.3 foot attributed to water losses associated with evapotranspiration. Mean annual ET from the Ash Meadows area is estimated at 21,000 acre-feet. An estimate of ground-water discharge, based on this ET estimate, is presented as a range to account for uncertainties in the contribution of local precipitation. The estimates given for mean annual ground-water discharge range from 18,000 to 21,000 acre-feet. The low estimate assumes a large contribution from local precipitation in computed ET rates; whereas, the high estimate assumes no contribution from local precipitation. The range presented is only slightly higher than previous estimates of ground-water discharge from the Ash Meadows area based primarily on springflow measurements.

Nevada↗
USGS1999

Application of continuous seismic-reflection techniques to delineate paleochannels beneath the Neuse River at U.S. Marine Corps Air Station, Cherry Point, North Carolina

A continuous seismic-reflection profiling survey was conducted by the U.S. Geological Survey on the Neuse River near the Cherry Point Marine Corps Air Station during July 7-24, 1998. Approximately 52 miles of profiling data were collected during the survey from areas northwest of the Air Station to Flanner Beach and southeast to Cherry Point. Positioning of the seismic lines was done by using an integrated navigational system. Data from the survey were used to define and delineate paleochannel alignments under the Neuse River near the Air Station. These data also were correlated with existing surface and borehole geophysical data, including vertical seismic-profiling velocity data collected in 1995. Sediments believed to be Quaternary in age were identified at varying depths on the seismic sections as undifferentiated reflectors and lack the lateral continuity of underlying reflectors believed to represent older sediments of Tertiary age. The sediments of possible Quaternary age thicken to the southeast. Paleochannels of Quaternary age and varying depths were identified beneath the Neuse River estuary. These paleochannels range in width from 870 feet to about 6,900 feet. Two zones of buried paleochannels were identified in the continuous seismic-reflection profiling data. The eastern paleochannel zone includes two large superimposed channel features identified during this study and in re-interpreted 1995 land seismic-reflection data. The second paleochannel zone, located west of the first paleochannel zone, contains several small paleochannels near the central and south shore of the Neuse River estuary between Slocum Creek and Flanner Beach. This second zone of channel features may be continuous with those mapped by the U.S. Geological Survey in 1995 using land seismic-reflection data on the southern end of the Air Station. Most of the channels were mapped at the Quaternary-Tertiary sediment boundary. These channels appear to have been cut into the older sediments and deepen in a southerly or downgradient direction. If these paleochannels continue beneath the Marine Corps Air Station and are filled with permeable sediment, they may act as conduits for ground-water flow or movement of contaminants between the surficial and underlying freshwater aquifers where confining units are breached.

North Carolina↗
USGS1999

Use of environmental tracers to evaluate ground-water age and water-quality trends in a buried-valley aquifer, Dayton area, southwestern Ohio

Chlorofluorocarbons (CFC method) and tritium and helium isotopes (3H-3He method) were used as environmental tracers to estimate ground-water age in conjunction with efforts to develop a regional ground-water flow model of the buried-valley aquifer in the Dayton area, southwestern Ohio. This report describes results of CFC and water-quality sampling, summarizes relevant aspects of previously published work, and describes the use of 3H-3He ages to characterize temporal trends in ground-water quality of the buried-valley aquifer near Dayton, Ohio. Results of CFC sampling indicate that approximately 25 percent of the 137 sampled wells were contaminated with excess CFC's that rendered the ground water unsuitable for age dating. Evaluation of CFC ages obtained for the remaining samples indicated that the CFC compounds used for dating were being affected by microbial degradation. The degradation occurred under anoxic conditions that are found in most parts of the buried-valley aquifer. As a result, ground-water ages derived by the CFC method were too old and were inconsistent with measured tritium concentrations and independently derived 3H-3He ages. Limited data indicate that dissolved methane may play an important role in the degradation of the CFC's. In contrast, the 3H-3He technique was found to yield ground-water ages that were chemically and hydrologically reasonable. Ground-water ages derived by the 3H-3He technique were compared to values for selected water- quality characteristics to evaluate temporal trends in ground-water quality in the buried- valley aquifer. Distinct temporal trends were not identified for pH, alkalinity, or calcium and magnesium because of rapid equilibration of ground-water with calcite and dolomite in aquifer sediments. Temporal trends in which the amount of scatter and the number of outlier concentrations increased as ground-water age decreased were noted for sodium, potassium, boron, bromide, chloride, ammonia, nitrate, phosphate, sulfate, and organic carbon. Elevated concentrations of these constituents in shallow ground water are probably related to human activities. Temporal trends in which concentrations declined as ground-water age increased may reflect natural processes that reduce constituent concentrations to low levels. For example, the absence of nitrate detections in ground water recharged before 1980 may indicate natural removal of nitrate by bacterially mediated denitrification. Temporal trends observed for dissolved oxygen, iron, nitrate and silica indicate that these constituents may help identify recently (post-1990) recharged ground water.

Ohio↗
USGS1999

Hydrologic assessment of the Upper Dorr Run Watershed, Hocking County, Ohio, 1998

The Upper Dorr Run Watershed in Hocking County, Ohio, has been mined several times for coal and clay since 1913 and is a significant source of acid mine drainage to the Hocking River. To assess the surface-water hydrology of the site, a topographic map showing the location of springs and other hydrologic features of interest was prepared using aerial photography and field surveying and mapping techniques. Discharge and water-quality measurements at six springs and one stream site were made during field investigations in June 1998. Discharge and water quality observed at a downstream weir on Upper Dorr Run represents the combined discharge from springs plus ground-water inflow. Discharges from springs to surface water were generally small (less than 0.3 cubic foot per second), but one spring constituted 56 percent of the total discharge measured at the downstream weir. The total flow at an intermediate measurement site was less than the combined discharge of the upgradient springs because of evaporation, transpiration, and ground-water flow beneath the stream channel. The total flow at the weir was greater than the combined discharge of all springs, primarily because two potential sources of water were not included in field measurements. The water quality in Upper Dorr Run is strongly affected by acid mine drainage as indicated by pH less than 4, elevated acidity, and elevated concentrations of dissolved sulfate and dissolved iron. Concentrations of chemical constituents in the water were lower at the downstream weir than at the source springs because of residence times in ponds and chemical interactions between the water and the atmosphere. Acidity loads during the sampling period were significantly higher from the Lower Kittanning (No. 5) coal (272 kilograms per day) than from the Upper Kittanning (No. 6) coal (17.7 kilograms per day). Comparison of data obtained in 1998 to data obtained in 1982 showed that quality of water of selected sampling sites had not changed appreciably in 16 years.

Water-Resources Investigations Report↗
USGS1999

Effectiveness of streambank-stabilization techniques along the Kenai River, Alaska

The Kenai River in southcentral Alaska is the State's most popular sport fishery and an economically important salmon river that generates as much as $70 million annually. Boatwake-induced streambank erosion and the associated damage to riparian and riverine habitat present a potential threat to this fishery. Bank-stabilization techniques commonly in use along the Kenai River were selected for evaluation of their effectiveness at attenuating boatwakes and retarding streambank erosion. Spruce trees cabled to the bank and biodegradable man-made logs (called 'bio-logs') pinned to the bank were tested because they are commonly used techniques along the river. These two techniques were compared for their ability to reduce wake heights that strike the bank and to reduce erosion of bank material, as well as for the amount and quality of habitat they provide for juvenile chinook salmon. Additionally, an engineered bank-stabilization project was evaluated because this method of bank protection is being encouraged by managers of the river. During a test that included 20 controlled boat passes, the spruce trees and the bio-log provided a similar reduction in boatwake height and bank erosion; however, the spruce trees provided a greater amount of protective habitat than the bio-log. The engineered bank-stabilization project eroded less during nine boat passes and provided more protective cover than the adjacent unprotected natural bank. Features of the bank-stabilization techniques, such as tree limbs and willow plantings that extended into the water from the bank, attenuated the boatwakes, which helped reduce erosion. These features also provided protective cover to juvenile salmon.

Alaska↗
USGS1999

Sources and chronology of nitrate contamination in spring waters, Suwannee River basin, Florida

A multi-tracer approach, which consisted of analyzing water samples for n aturally occurring chemical and isotopic indicators, was used to better understand sources and chronology of nitrate contamination in spring wate rs discharging to the Suwannee and Santa Fe Rivers in northern Florida. Dur ing 1997 and 1998, as part of a cooperative study between the Suwannee River Water Management District and the U.S. Geological Survey, water samples were collected and analyzed from 24 springs and two wells for major ions, nutrients, dissolved organic carbon, and selected environmental isotopes [18O/16O, D/H, 13C/12C, 15N/14N]. To better understand when nitrate entered the ground-water system, water samples were analyzed for chlorofluorocarbons (CFCs; CCl3F, CCl2F2, and C2Cl3F3) and tritium (3H); in this way, the apparent ages and residence times of spring waters and water from shallow zones in the Upper Floridan aquifer were determined. In addition to information obtained from the use of isotopic and other chemical tracers, information on changes in land-use activities in the basin during 1954-97 were used to estimate nitrogen inputs from nonpoint sources for five counties in the basin. Changes in nitrate concentrations in spring waters with time were compared with estimated nitrogen inputs for Lafayette and Suwannee Counties. Agricultural activities [cropland farming, animal farming operations (beef and dairy cows, poultry, and swine)] along with atmospheric deposition have contributed large quantities of nitrogen to ground water in the Suwannee River Basin in northern Florida. Changes in agricultural land use during the past 40 years in Alachua, Columbia, Gilchrist, Lafayette, and Suwannee Counties have contributed variable amounts of nitrogen to the ground-water system. During 1955-97, total estimated nitrogen from all nonpoint sources (fertilizers, animal wastes, atmospheric deposition, and septic tanks) increased continuously in Gilchrist and Lafayette Counties. In Suwannee, Alachua, and Columbia Counties, estimated nitrogen inputs from all nonpoint sources peaked in the late 1970's corresponding to the peak use in fertilizer during this time. Fertilizer use in Columbia, Gilchrist, Lafayette, and Suwannee Counties increased substantially during 1993-97. The heavy use of fertilizers in the basin is corroborated by nitrogen isotope data. Values of d15N of nitrate (d15N-NO3) in spring waters range from 2.7 per mil (SUW718971) to 10.6 per mil (Poe Spring) with a median of 5.4 per mil. The range of values indicates that nitrate in the sampled spring waters most likely originates from a mixture of inorganic (fertilizers) and organic (animal wastes) sources; however, higher d15N values for Poe and Lafayette Blue Springs indicate that an organic source of nitrogen probably is contributing nitrate to these spring waters. Water samples from two wells sampled in Lafayette County have high d15N-NO3 values of 11.0 and 12.1 per mil, indicating the predominance of an organic source of nitrate. These two wells are located near dairy and poultry farms, where leachate from animal wastes may contribute nitrate to ground water. Dissolved-gas data (nitrogen, argon, and oxygen) indicate that denitrification has not removed large amounts of nitrate from the ground-water system. Thus, variations in d15N-NO3 values of spring waters can be attributed to variations in d15N-NO3 values of ground-water recharge, and can be used to obtain information about source(s) of nitrate. Extending the use of age-dating techniques (CFCs and 3H) to spring waters in complex karst systems required the use of several different approaches for estimating age and residence time of ground water discharging to springs. These approaches included the use of a simple reservoir model, a piston-flow model, an exponential model, and a binary-mixing model. When age data (CFC-11, CFC-113, and 3H) are combined for all springs, models that incorporate exponential mixtures seem to provide reliable estimates of average residence times of ground water discharging to springs. Whereas, data for some individual springs fit a binary-mixing model with more than 50 percent young water (recharged within the past 5 years), data from other individual springs fit a piston-flow model with a water age of about 25 years. The young ages of several spring waters (such as SUW718971, SUW725971, and Ginnie Spring) indicate the high vulnerability of the springs to contamination. For most springs, CFCs suggest that a large fraction of the water is more than 20 years old. Springs with lower flows tend to have young ages (shallow ground-water flow systems), whereas springs with higher flows tend to have older ages (deep ground-water flow systems). The chemical composition of spring waters can be used as a qualitative indicator of age and ground-water residence time. Nitrate-nitrogen concentrations and dissolved oxygen in spring waters are inversely related to the apparent ages of spring waters and ground-water residence time in the basin. Silica concentrations increase as the age of spring waters increase. Long-term trends in nitrate concentrations in selected spring waters were compared with estimated inputs of nitrogen from various sources in Suwannee and Lafayette Counties. In both counties, trends in nitrate concentrations in spring waters closely followed the estimated contribution of nitrogen from fertilizers. Decreasing nitrate concentrations in spring waters from Suwannee County followed the decrease in estimated fertilizer use from the mid-1970's to the early 1990's. Increasing nitrate concentrations in sprin g waters from Lafayette County followed the steady increase in fertilizer use from the early 1960's to the mid-1990's The relation between the concentration of nitrate in ground water and the amount of nitrogen that is added to a ground-water contributing area for a spring is controlled by complex interactions among hydrogeologic, land-use, and climatic factors, as well as several other land-management factors. Spring waters represent mixtures of converging flow paths that contain ground water with a range of ages. Even if nitrogen inputs were reduced substantially, it may take decades for nitrate concentrations in the ground-water system to return to near background levels.

Florida↗
USGS2001

Simulation of a long-term aquifer test conducted near the Rio Grande, Albuquerque, New Mexico

A long-term aquifer test was conducted near the Rio Grande in Albuquerque during January and February 1995 using 22 wells and piezometers at nine sites, with the City of Albuquerque Griegos 1 production well as the pumped well. Griegos 1 discharge averaged about 2,330 gallons per minute for 54.4 days. A three-dimensional finite-difference ground-water-flow model was used to estimate aquifer properties in the vicinity of the Griegos well field and the amount of infiltration induced into the aquifer system from the Rio Grande and riverside drains as a result of pumping during the test. The model was initially calibrated by trial-and-error adjustments of the aquifer properties. The model was recalibrated using a nonlinear least-squares regression technique. The aquifer system in the area includes the middle Tertiary to Quaternary Santa Fe Group and post-Santa Fe Group valley- and basin-fill deposits of the Albuquerque Basin. The Rio Grande and adjacent riverside drains are in hydraulic connection with the aquifer system. The hydraulic-conductivity values of the upper part of the Santa Fe Group resulting from the model calibrated by trial and error varied by zone in the model and ranged from 12 to 33 feet per day. The hydraulic conductivity of the inner-valley alluvium was 45 feet per day. The vertical to horizontal anisotropy ratio was 1:140. Specific storage was 4 x 10-6 per foot of aquifer thickness, and specific yield was 0.15 (dimensionless). The sum of squared errors between the observed and simulated drawdowns was 130 feet squared. Not all aquifer properties could be estimated using nonlinear regression because of model insensitivity to some aquifer properties at observation locations. Hydraulic conductivity of the inner-valley alluvium, middle part of the Santa Fe Group, and riverbed and riverside-drain bed and specific yield had low sensitivity values and therefore could not be estimated. Of the properties estimated, hydraulic conductivity of the upper part of the Santa Fe Group was estimated to be 12 feet per day, the vertical to horizontal anisotropy ratio was estimated to be 1:82, and specific storage was estimated to be 1.2 x 10-6 per foot of aquifer thickness. The overall sum of squared errors between the observed and simulated drawdowns was 87 feet squared, a significant improvement over the model calibrated by trial and error. At the end of aquifer-test pumping, induced infiltration from the Rio Grande and riverside drains was simulated to be 13 percent of the total amount of water pumped. The remainder was water removed from aquifer storage. After pumping stopped, induced infiltration continued to replenish aquifer storage. Simulations estimated that 5 years after pumping began (about 4.85 years after pumping stopped), 58 to 72 percent of the total amount of water pumped was replenished by induced infiltration from the Rio Grande surface-water system.

Water-Resources Investigations Report↗
USGS2000

Biodegradation of chlorinated ethenes at a karst site in middle Tennessee

This report presents results of field and laboratory investigations examining the biodegradation of chlorinated ethenes in a karst aquifer contaminated with trichloroethylene (TCE). The study site, located in Middle Tennessee, was selected because of the presence of TCE degradation byproducts in the karst aquifer and available site hydrologic and chlorinated-ethene information. Additional chemical, biological, and hydrologic data were gathered to evaluate whether the occurrence of TCE degradation byproducts in the karst aquifer was the result of biodegradation within the aquifer or simply transport into the aquifer. Geochemical analysis established that sulfate-reducing conditions, essential for reductive dechlorination of chlorinated solvents, existed in parts of the contaminated karst aquifer. Other areas of the aquifer fluctuated between anaerobic and aerobic conditions and contained compounds associated with cometabolism, such as ethane, methane, ammonia, and dissolved oxygen. A large, diverse bacteria population inhabits the contaminated aquifer. Bacteria known to biodegrade TCE and other chlorinated solvents, such as sulfate-reducers, methanotrophs, and ammonia-oxidizers, were identified from karst-aquifer water using the RNA-hybridization technique. Results from microcosms using raw karst-aquifer water found that aerobic cometabolism and anaerobic reductive-dechlorination degradation processes were possible when appropriate conditions were established in the microcosms. These chemical and biological results provide circumstantial evidence that several biodegradation processes are active in the aquifer. Additional site hydrologic information was developed to determine if appropriate conditions persist long enough in the karst aquifer for these biodegradation processes to be significant. Continuous monitoring devices placed in four wells during the spring of 1998 indicated that pH, specific conductance, dissolved oxygen, and oxidation-reduction potentials changed very little in areas isolated from active ground-water flow paths. These stable areas in the karst aquifer had geochemical conditions and bacteria conducive to reductive dechlorination of chlorinated ethenes. Other areas of the karst aquifer were associated with active ground-water flow paths and fluctuated between anaerobic and aerobic conditions in response to rain events. Associated with this dynamic environment were bacteria and geochemical conditions conducive to cometabolism. In summary, multiple lines of evidence developed from chemical, biological, and hydrologic data demonstrate that a variety of biodegradation processes are active in this karst aquifer.

Tennessee↗