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Scott C. Christenson

Publications and source records attributed to Scott C. Christenson.

17 recordsLinked to original sources
USGS2012

Hydrogeology, water chemistry, and transport processes in the zone of contribution of a public-supply well in Albuquerque, New Mexico, 2007-9

The National Water-Quality Assessment Program (NAWQA) of the U.S. Geological Survey began a series of groundwater studies in 2001 in representative aquifers across the Nation in order to increase understanding of the factors that affect transport of anthropogenic and natural contaminants (TANC) to public-supply wells. One of 10 regional-scale TANC studies was conducted in the Middle Rio Grande Basin (MRGB) in New Mexico, where a more detailed local-scale study subsequently investigated the hydrogeology, water chemistry, and factors affecting the transport of contaminants in the zone of contribution of one 363-meter (m) deep public-supply well in Albuquerque. During 2007 through 2009, samples were collected for the local-scale study from 22 monitoring wells and 3 public-supply (supply) wells for analysis of major and trace elements, arsenic speciation, nutrients, dissolved organic carbon, volatile organic compounds (VOCs), dissolved gases, stable isotopes, and tracers of young and old water. To study groundwater chemistry and ages at various depths within the aquifer, the monitoring wells were divided into three categories: (1) each shallow well was screened across the water table or had a screen midpoint within 18.3 m of the water level in the well; (2) each intermediate well had a screen midpoint between about 27.1 and 79.6 m below the water level in the well; and (3) each deep well had a screen midpoint about 185 m or more below the water level in the well. The 24-square-kilometer study area surrounding the "studied supply well" (SSW), one of the three supply wells, consists of primarily urban land within the MRGB, a deep alluvial basin with an aquifer composed of unconsolidated to moderately consolidated deposits of sand, gravel, silt, and clay. Conditions generally are unconfined, but are semiconfined at depth. Groundwater withdrawals for public supply have substantially changed the primary direction of flow from northeast to southwest under predevelopment conditions, to west to east under modern conditions. Analysis of age tracers indicates that groundwater from most sampled wells is dominated by old (pre-1950) water, ranging in mean age from about 4,000 years to more than 22,000 years, but includes a fraction of young (post-1950) recharge. Patterns in chemical and isotopic data are consistent with the conclusions that shallow groundwater in the area typically includes a fraction that evaporated prior to recharge and (or) flushed accumulated solutes out of the unsaturated zone during recharge, and that shallow groundwater has mixed to deeper parts of the aquifer, which receives recharge mainly by seepage from the Rio Grande. Among shallow and intermediate wells that produced water with a fraction of young recharge, that fraction ranged between 1.5 and 46 percent. Samples from the two deep wells had groundwater ages exceeding 18,000 years, with no fraction of young recharge. Two supply wells (including the SSW) had a fraction of young recharge, which ranged between about 3 and 11 percent, despite mean groundwater ages exceeding 10,000 years. The fraction of young recharge to the SSW varied seasonally, probably because seasonal pumping patterns affected local hydraulic gradients and (or) because of flow through the well bore when the SSW is not pumping. Well-bore flow data collected during winter (low-pumping season) indicated that about 61 percent of the water pumped from the SSW entered the well from the intermediate part of the aquifer, and that the remaining 39 percent entered from the deep part of the aquifer. Volatile organic compounds (VOCs) were detected in samples from most shallow and intermediate monitoring wells and from two of three supply wells, including the SSW. Detected VOCs were primarily chlorinated solvents or their degradation products. Many of the wells in which most of these VOCs were detected are located near known sites of solvent contamination that were targeted for sampling because trichloroethylene (TCE) and cis-1,2-dichloroethylene had been detected in the SSW, and several of these wells may have become contaminated at least partly because of enhanced vertical migration associated with the pumping of and (or) direct migration down deep well bores. Except for TCE in the sample from a shallow monitoring well, all detections of VOCs were at concentrations below Maximum Contaminant Levels (MCLs) set by the U.S. Environmental Protection Agency. Concentrations of all VOCs detected in the supply wells were less than one-tenth of the corresponding MCLs. However, the presence of VOCs in all but deep groundwater, including the detection of chloroform (a chlorination byproduct) in several shallow wells, indicates that groundwater in the study area commonly is affected by human activities, even to substantial depths. The only natural contaminant detected at concentrations near or above its MCL was arsenic, which has been detected at elevated concentrations across broad areas of the MRGB. Concentrations of arsenic, present primarily as arsenate, exceeded the MCL of 10 micrograms per liter (μg/L) in water from the two deep wells (one of which had the highest concentration, 35 μg/L), from one intermediate well, and from two supply wells, including the SSW. Water-quality and solid-phase data from this study are consistent with elevated arsenic concentrations in groundwater being related to pH-dependent desorption of arsenic from ferric oxyhydroxides in sediments in deep parts of the aquifer. Concentrations of nitrate ranged between 1.3 and 5.4 milligrams per liter (mg/L) in water from shallow wells screened across the water table, but were less than 0.9 mg/L in water from all but one deeper well. Nitrogen isotopes and chloride/bromide ratios for shallow wells were consistent with natural soil nitrogen. Nitrate concentrations and nitrogen isotopes indicated that denitrification is occurring at intermediate aquifer depths, and that the progress of the denitrification reaction typically is greatest for wells that include a fraction of groundwater associated with particular recharge sources or with known sites of contamination contributing organic compounds that can provide a carbon source for microbial respiration. Overall, hydrologic and chemical data from the study area indicate that young recharge is reaching the aquifer across broad areas and is migrating from shallow to intermediate depths of the aquifer as a result of mixing that is associated with human development of groundwater. Consequently, groundwater that human activities in the urban study area have affected is present at depths that are within the screened intervals of public-supply wells, resulting in detections of VOCs and implying greater vulnerability to anthropogenic contamination than might be assumed based on the dominantly old age of the regional groundwater. However, the fractions of old groundwater that public-supply wells produce substantially dilute the anthropogenic contaminants, while contributing natural contaminants (primarily arsenic) to the wells. Based on data from the SSW, vulnerability of public-supply wells to natural and anthropogenic contaminants in the area changes through time, including with seasonal changes in pumping stresses that alter the fractions of young and old water being contributed to wells.

New Mexico↗
USGS2011

Selected approaches to estimate water-budget components of the High Plains, 1940 through 1949 and 2000 through 2009

The High Plains aquifer, underlying almost 112 million acres in the central United States, is one of the largest aquifers in the Nation. It is the primary water supply for drinking water, irrigation, animal production, and industry in the region. Expansion of irrigated agriculture throughout the past 60 years has helped make the High Plains one of the most productive agricultural regions in the Nation. Extensive withdrawals of groundwater for irrigation have caused water-level declines in many parts of the aquifer and increased concerns about the long-term sustainability of the aquifer. Quantification of water-budget components is a prerequisite for effective water-resources management. Components analyzed as part of this study were precipitation, evapotranspiration, recharge, surface runoff, groundwater discharge to streams, groundwater fluxes to and from adjacent geologic units, irrigation, and groundwater in storage. These components were assessed for 1940 through 1949 (representing conditions prior to substantial groundwater development and referred to as "pregroundwater development" throughout this report) and 2000 through 2009. Because no single method can perfectly quantify the magnitude of any part of a water budget at a regional scale, results from several methods and previously published work were compiled and compared for this study when feasible. Results varied among the several methods applied, as indicated by the range of average annual volumes given for each component listed in the following paragraphs. Precipitation was derived from three sources: the Parameter-Elevation Regressions on Independent Slopes Model, data developed using Next Generation Weather Radar and measured precipitation from weather stations by the Office of Hydrologic Development at the National Weather Service for the Sacramento-Soil Moisture Accounting model, and precipitation measured at weather stations and spatially distributed using an inverse-distance-weighted interpolation method. Precipitation estimates using these sources, as a 10-year average annual total volume for the High Plains, ranged from 192 to 199 million acre-feet (acre-ft) for 1940 through 1949 and from 185 to 199 million acre-ft for 2000 through 2009. Evapotranspiration was obtained from three sources: the National Weather Service Sacramento-Soil Moisture Accounting model, the Simplified-Surface-Energy-Balance model using remotely sensed data, and the Soil-Water-Balance model. Average annual total evapotranspiration estimated using these sources was 148 million acre-ft for 1940 through 1949 and ranged from 154 to 193 million acre-ft for 2000 through 2009. The maximum amount of shallow groundwater lost to evapotranspiration was approximated for areas where the water table was within 5 feet of land surface. The average annual total volume of evapotranspiration from shallow groundwater was 9.0 million acre-ft for 1940 through 1949 and ranged from 9.6 to 12.6 million acre-ft for 2000 through 2009. Recharge was estimated using two soil-water-balance models as well as previously published studies for various locations across the High Plains region. Average annual total recharge ranged from 8.3 to 13.2 million acre-ft for 1940 through 1949 and from 15.9 to 35.0 million acre-ft for 2000 through 2009. Surface runoff and groundwater discharge to streams were determined using discharge records from streamflow-gaging stations near the edges of the High Plains and the Base-Flow Index program. For 1940 through 1949, the average annual net surface runoff leaving the High Plains was 1.9 million acre-ft, and the net loss from the High Plains aquifer by groundwater discharge to streams was 3.1 million acre-ft. For 2000 through 2009, the average annual net surface runoff leaving the High Plains region was 1.3 million acre-ft and the net loss by groundwater discharge to streams was 3.9 million acre-ft. For 2000 through 2009, the average annual total estimated groundwater pumpage volume from two soil-water-balance models ranged from 8.7 to 16.2 million acre-ft. Average annual irrigation application rates for the High Plains ranged from 8.4 to 16.2 inches per year. The USGS Water-Use Program published estimated total annual pumpage from the High Plains aquifer for 2000 and 2005. Those volumes were greater than those estimated from the two soil-water-balance models. Total groundwater in storage in the High Plains aquifer was estimated as 3,173 million acre-ft prior to groundwater development and 2,907 million acre-ft in 2007. The average annual decrease of groundwater in storage between 2000 and 2007 was 10 million acre-ft per year.

High Plains Aquifer↗
USGS2008

Results of the chemical and isotopic analyses of sediment and ground water from alluvium of the Canadian River near a closed municipal landfill, Norman, Oklahoma, part 2

Analytical results on sediment and associated ground water from the Canadian River alluvium collected subsequent to those described in Breit and others (2005) are presented in this report. The data presented herein were collected primarily to evaluate the iron and sulfur species within the sediment at well sites IC 36, IC 54, and IC South located at the USGS Norman Landfill study site. Cored sediment and water samples were collected during October 2004 and April 2005. The 52 sediment samples collected by coring were analyzed to determine grain size, the abundance of extractable iron species, and the abundance of sulfur forms and their isotopic compositions. Ground water was collected from cluster wells that sampled ground water from 11 to 15 screened intervals at each of the three sites. The depth range of the wells overlapped the interval of cored sediment. Concentrations of major ions, dissolved organic carbon (DOC), ammonium, and iron are reported with pH, specific conductance, and the isotopic composition of the water for the 75 water samples analyzed. Dissolved sulfate in selected water samples was analyzed to determine its sulfur and oxygen isotope composition.

Oklahoma↗
USGS2007

Pharmaceuticals and other organic wastewater contaminants within a leachate plume downgradient of a municipal landfill

Ground water samples collected from the Norman Landfill research site in central Oklahoma were analyzed as part of the U.S. Geological Survey (USGS) Toxic Substances Hydrology Program's national reconnaissance of pharmaceuticals and other organic waste water contaminants (OWCs) in ground water. Five sites, four of which are located downgradient of the landfill, were sampled in 2000 and analyzed for 76 OWCs using four research methods developed by the USGS. OWCs were detected in water samples from all of the sites sampled, with 22 of the 76 OWCs being detected at least once. Cholesterol (a plant and animal steroid), was detected at all five sites and was the only compound detected in a well upgradient of the landfill. N,Ndiethyltoluamide (DEET used in insect repellent) and tri(2-chloroethyl) phosphate (fire-retardant) were detected in water samples from all four sites located within the landfill-derived leachate plume. The sites closest to the landfill had more detections and greater concentrations of each of the detected compounds than sites located farther away. Detection of multiple OWCs occurred in the four sites located within the leachate plume, with a minimum of four and a maximum of 17 OWCs detected. Because the landfill was established in the 1920s and closed in 1985, many compounds detected in the leachate plume were likely disposed of decades ago. These results indicate the potential for long-term persistence and transport of some OWCs in ground water.

Oklahoma↗
USGS2005

Results of chemical and isotopic analyses of sediment and water from alluvium of the Canadian River near a closed municipal landfill, Norman, Oklahoma

Results of physical and chemical analyses of sediment and water collected near a closed municipal landfill at Norman, Oklahoma are presented in this report. Sediment analyses are from 40 samples obtained by freeze-shoe coring at 5 sites, and 14 shallow (depth <1.3 m) sediment samples. The sediment was analyzed to determine grain size, the abundance of extractable iron species and the abundances and isotopic compositions of forms of sulfur. Water samples included pore water from the freeze-shoe core, ground water, and surface water. Pore water from 23 intervals of the core was collected and analyzed for major and trace dissolved species. Thirteen ground-water samples obtained from wells within a few meters of the freeze-shoe core sites and one from the landfill were analyzed for major and trace elements as well as the sulfur and oxygen isotope composition of dissolved sulfate. Samples of surface water were collected at 10 sites along the Canadian River from New Mexico to central Oklahoma. These river-water samples were analyzed for major elements, trace elements, and the isotopic composition of dissolved sulfate.

Oklahoma↗
USGS2001

Relation of shallow water quality in the Central Oklahoma Aquifer to geology, soils, and land use

The purpose of this report is to identify, describe, and explain relations between natural and land-use factors and ground-water quality in the Central Oklahoma aquifer NAWQA study unit. Natural factors compared to water quality included the geologic unit in which the sampled wells were completed and the properties of soils in the areas surrounding the wells. Land-use factors included types of land use and population densities surrounding sampled wells. Ground-water quality was characterized by concentrations of inorganic constituents, and by frequencies of detection of volatile organic compounds and pesticides. Water-quality data were from samples collected from wells 91 meters (300 feet) or less in depth as part of Permian and Quaternary geologic unit survey networks and from an urban survey network. Concentrations of many inorganic constituents were significantly related to geology. In addition, concentrations of many inorganic constituents were greater in water from wells from the Oklahoma City urban sampling network than in water from wells from low-density survey networks designed to evaluate ambient water quality in the Central Oklahoma aquifer study unit. However, sampling bias may have been induced by differences in hydrogeologic factors between sampling networks, limiting the ability to determine land-use effects on concentrations of inorganic constituents. Frequencies of detection of pesticide and volatile organic compounds (VOC's) in ground-water samples were related to land use and population density, with these compounds being more frequently detected in densely-populated areas. Geology and soil properties were not significantly correlated to pesticide or VOC occurrence in ground water. Lesser frequencies of detection of pesticides in water from wells in rural areas may be due to low to moderate use of those compounds on agricultural lands in the study unit, with livestock production being the primary agricultural activity. There are many possible sources of pesticides and VOC's in the urban areas of Central Oklahoma. Because only existing water-supply wells were sampled, it is not clear from the data collected whether pesticides and VOC's: (1) occur in low concentrations throughout upper portions of the aquifer in urban areas, or (2) are present in ground water only in the immediate vicinity of the wells due to back-flow of those chemicals into the wells or to inflow around cement seals and through gravel packs surrounding well casings of surface runoff containing those compounds.

Oklahoma↗
USGS1998

Spatial variation in hydraulic conductivity determined by slug tests in the Canadian River alluvium near the Norman Landfill, Norman, Oklahoma

Slug tests were used to characterize hydraulic conductivity variations at a spatial scale on the order of meters in the alluvial aquifer downgradient of the Norman Landfill. Forty hydraulic conductivity measurements were made, most along a 215-meter flow path transect. Measured hydraulic conductivity, excluding clayey layers, ranged from 8.4 x 10 -7 to 2.8 x 10 -4 meters per second, with a median value of 6.6 x 10 -5 meters per second. The hydraulic conductivity measurements yield a preliminary concept of the permeability structure of the aquifer along this transect. A low hydraulic conductivity silt-clay layer at about 4 meters below the water table and a high hydraulic conductivity layer at the base of the aquifer appear to have the most potential to affect contaminant transport. Specific conductance measurements show the leachate plume along this transect becomes attenuated between 150 and 200 meters downgradient of the landfill, except at the base of the aquifer, where it extends at least 225 meters downgradient of the landfill.

Oklahoma↗
USGS1998

Ground-water-quality assessment of the Central Oklahoma aquifer, Oklahoma: Results of investigations

This is a collection of five papers intended to summarize the results of an assessment of the ground-water quality of the Central Oklahoma Aquifer. The papers include a summary of investigations, the diagenetic history of Permian rocks in the aquifer, a geochemical characterization of solid-phase materials, a summary of geochemical and geohydrologic investigations of the Central Oklahoma Aquifer, and a summary on naturally occurring trace substances that contaminated many wells completed in the aquifer.

Oklahoma↗
USGS1996

Ground-water-quality assessment of the central Oklahoma Aquifer, Oklahoma — Geochemical and geohydrologic investigations

Ground-water samples, core samples, and hydrologic measurements were obtained in the Central Oklahoma Aquifer as part of the pilot National Water-Quality Assessment Program. This report examines ground-water recharge and discharge, the potentiometric surface, the chemical and isotopic composition of ground water, and the abundances and textures of minerals in core materials to determine the rates and directions of ground-water flow and the geochemical reactions occurring within the aquifer.

Oklahoma↗
USGS1995

Contamination of wells completed in the Roubidoux aquifer by abandoned zinc and lead mines, Ottawa County, Oklahoma

The Roubidoux aquifer in Ottawa County Oklahoma is used extensively as a source of water for public supplies, commerce, industry, and rural water districts. Water in the Roubidoux aquifer in eastern Ottawa County has relatively low dissolved-solids concentrations (less than 200 mg/L) with calcium, magnesium, and bicarbonate as the major ions. The Boone Formation is stratigraphically above the Roubidoux aquifer and is the host rock for zinc and lead sulfide ores, with the richest deposits located in the vicinity of the City of Picher. Mining in what became known as the Picher mining district began in the early 1900's and continued until about 1970. The water in the abandoned zinc and lead mines contains high concentrations of calcium, magnesium, bicarbonate, sulfate, fluoride, cadmium, copper, iron, lead, manganese, nickel, and zinc. Water from the abandoned mines is a potential source of contamination to the Roubidoux aquifer and to wells completed in the Roubidoux aquifer. Water samples were collected from wells completed in the Roubidoux aquifer in the Picher mining district and from wells outside the mining district to determine if 10 public supply wells in the mining district are contaminated. The chemical analyses indicate that at least 7 of the 10 public supply wells in the Picher mining district are contaminated by mine water. Application of the Mann-Whitney test indicated that the concentrations of some chemical constituents that are indicators of mine-water contamination are different in water samples from wells in the mining area as compared to wells outside the mining area. Application of the Wilcoxon signed-rank test showed that the concentrations of some chemical constituents that are indicators of mine-water contamination were higher in current (1992-93) data than in historic (1981-83) data, except for pH, which was lower in current than in historic data. pH and sulfate, alkalinity, bicarbonate, magnesium, iron, and tritium concentrations consistently indicate that the Cardin, Commerce 1, Commerce 3, Picher 2, Picher 3, Picher 4, and Quapaw 2 wells are contaminated.

Oklahoma↗
USGS1992

Hydrogeologic maps of the central Oklahoma aquifer, Oklahoma

This report presents hydrogeologic maps of the Central Oklahoma aquifer. The maps were prepared by measuring water levels in wells during the winder of 1986 and 1987; examination of geophysical logs to determine the altitudes of the top of selected geologic units and the base of fresh ground water; and compilation of existing information on the stratigraphy of selected geologic units and the base of fresh ground water.

Oklahoma↗
USGS1989

Ground-water quality assessment of the central Oklahoma aquifer, Oklahoma - Analysis of available water-quality data through 1987

Beginning in 1986, the Congress annually has appropriated funds for the U.S. Geological Survey to test and refine concepts for a National Water-Quality Assessment (NAWQA) Program. The long-term goals of a full-scale program would be to: Provide a nationally consistent description of current water-quality conditions for a large part of the Nation's surface- and ground-water resources; Define long-term trends (or lack of trends) in water quality; and Identify, describe, and explain, as possible, the major factors that affect the observed water-quality conditions and trends. The results of the NAWQA Program will be made available to water managers, policy makers, and the public, and will provide an improved scientific basis for evaluating the effectiveness of water-quality management programs. At present (1988), the assessment program is in a pilot phase in seven project areas throughout the country that represent diverse hydrologic environments and water-quality conditions. The Central Oklahoma aquifer project is one of three pilot ground-water projects. One of the initial activities performed by each pilot project was to compile, screen, and interpret the large amount of water-quality data available within each study unit. The purpose of this report is to assess the water quality of the Central Oklahoma aquifer using the information available through 1987. The scope of the work includes compiling data from Federal, State, and local agencies; evaluating the suitability of the information for conducting a regional water-quality assessment; mapping regional variations in major-ion chemistry; calculating summary statistics of the available water-quality data; producing maps to show the location and number of samples that exceeded water-quality standards; and performing contingency-table analyses to determine the relation of geologic unit and depth to the occurrence of chemical constituents that exceed water-quality standards. This report provides an initial description of water-quality conditions in the Central Oklahoma aquifer study unit. No attempt was made in this report to determine the causes for regional variations in major-ion chemistry or to examine the reasons that some chemical constituents exceed water-quality standards.

Oklahoma↗
USGS1988

Geologic logs for selected deep wells in parts of Oklahoma, Texas, and New Mexico

A computerized data base of geologic logs for selected deep wells in parts of Oklahoma, Texas, and New Mexico was prepared by the U.S. Geological Survey as part of the Central Midwest Regional Aquifer-System Analysis. At least one well per county in the study area was selected, and the geologic logs for the wells were entered into the data base. Summaries of the geologic logs are presented in this report. Geophysical logs were used for interpretation of the geologic logs, and a list of these geophysical logs also is presented. These geophysical logs are available for inspection at the U.S. Geological Survey office in Oklahoma City, Oklahoma.

Open-File Report↗