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A. H. Welch

Publications and source records attributed to A. H. Welch.

9 recordsLinked to original sources
USGS2008

In situ arsenic removal in an alkaline clastic aquifer

In situ removal of As from ground water used for water supply has been accomplished elsewhere in circum-neutral ground water containing high dissolved Fe(II) concentrations. The objective of this study was to evaluate in situ As ground-water treatment approaches in alkaline ground-water (pH > 8) that contains low dissolved Fe (<a few tens of μg/L). The low dissolved Fe content limits development of significant Fe-oxide and the high-pH limits As adsorption onto Fe-oxide. The chemistries of ground water in the two aquifers studied are similar except for the inorganic As species. Although total inorganic As concentrations were similar, one aquifer has dominantly aqueous As(III) and the other has mostly As(V). Dissolved O 2 , Fe(II), and HCl were added to water and injected into the two aquifers to form Fe-oxide and lower the pH to remove As. Cycles of injection and withdrawal involved varying Fe(II) concentrations in the injectate. The As concentrations in water withdrawn from the two aquifers were as low as 1 and 6 μg/L, with greater As removal from the aquifer containing As(V). However, Fe and Mn concentrations increased to levels greater than US drinking water standards during some of the withdrawal periods. A balance between As removal and maintenance of low Fe and Mn concentrations may be a design consideration if this approach is used for public-supply systems. The ability to lower As concentrations in situ in high-pH ground water should have broad applicability because similar high-As ground water is present in many parts of the world.

Applied Geochemistry↗
USGS2003

Arsenic in ground water: Geochemistry and occurrence

Interest in arsenic in ground water has greatly increased in the past decade because of the increased awareness of human health effects and the costs of avoidance or treatment of ground water supplies used for consumption. The goal of this book is to provide a description of the basic processes that affect arsenic occurrence and transport by providing sufficient background information on arsenic geochemistry and descriptions of hi- arsenic ground water, both affected and unaffected by human activity. An understanding of thermodynamics, adsorption, and the speciation of arsenic in solid phases, which are described in first three chapters, is needed to predict the fate of arsenic in ground water systems. Large-scale and deep movement of ground water can and has redistributed arsenic in the near surface environment, as described in the next two chapters. These large-scale systems can affect large volumes of both ground water and surface water, such as in the Yellowstone system, and can produce mineralised zones that subsequently release arsenic to ground water supplies. Regional identification of high-arsenic ground water and its consumption as described in the next three chapters clearly demonstrates a need for increased wat- quality monitoring, particularly in south and southeast Asia. Chapters 9-11 provide examples of high arsenic ground water associated with sulfide mineral oxidation and alkaline conditions. Finally, smaller scale studies of the effects of human activities that have produced high-arsenic ground water and methods for attenuation of ground water are presented

Book↗
USGS1996

Geochemistry and isotope hydrology of representative aquifers in the Great Basin region of Nevada, Utah, and adjacent states

This report briefly describes the general quality and chemical character of the ground water, discusses in detail the geochemical and hydrologic processes that produce the chemical and isotopic compositions of water in the two principal types of aquifers (basin fill and carbonate rock), delineates flow systems in carbonate-rock aquifers of southern Nevada, and discusses ground-water ages and flow velocities within the carbonate-rock systems.

Professional Paper↗
USGS1989

Ground-water-quality assessment of the Carson River basin, Nevada and California: Analysis of available water-quality data through 1987

Data on groundwater quality, hydrogeology, and land and water use for the Carson River basin, Nevada and California were analyzed as part of the U. S. Geological Survey National Water-Quality Assessment program. The basin consists of six hydrographic areas--a mountainous headwaters area and five downstream areas interconnected by the Carson River. Each valley contains one or more basin-fill aquifers. The data on groundwater quality came from several agencies and were screened to verify site location and to avoid analyses of treated water. The screened data are stored in the U. S. Geological Survey National Water Information System data base. Differences in sample-collection and preservation procedures among some of the data-collection agencies restrict use of the data to a descriptive analysis. Drinking water standards were employed as the basis for evaluating reported concentrations. Frequencies with which primary or secondary standards are exceeded increase from upstream parts of the basin to downstream parts. Primary standards commonly exceeded are fluoride in upstream areas and arsenic and fluoride in downstream areas. Secondary standards commonly exceeded are iron and manganese in upstream areas and chloride, dissolved solids, iron, manganese, and sulfate in downstream areas. The poorer-quality groundwater generally is a result of natural geochemical reactions, rather than the introduction of chemicals by man. Limited data indicate, however , that manmade organic compounds are present, mostly at or near urban land.

California, Nevada↗
USGS1987

Water-quality assessment of the Carson River ground-water basin, Nevada and California; project description

In April 1986, the U.S. Geological Survey began a pilot program to assess the quality of the nation 's surface water and groundwater resources. This program, called the National Water-Quality Assessment (NAWQA) program, is designed to acquire and interpret information about a wide range of water quality issues. The program is in its early stages and consists of four surface water and three groundwater pilot projects. The objectives of the Carson River basin NAWQA project are described in the context of the national program, the study area and its associated water quality issues, and a proposed study approach. The objectives of the Carson River basin NAWQA project are to: (1) investigate regional groundwater quality; (2) describe relations of groundwater quality to land use, geohydrology, and other pertinent factors; (3) provide a general description of the location, nature and possible causes of selected widespread water quality problems in the project area; and (4) develop new techniques for characterizing regional groundwater quality, especially in arid alluvial basins. There are to be three major phases of the Carson River basin project. The first will consist of compilation and analysis of existing data. The second phase will consist of a regional water quality survey that will produce a consistent set of data that can be used to: (1) define regional quality of groundwater within the Carson River basin; and (2) compare that water quality with other aquifers in the Nation. The third phase will include topical studies that will define groundwater quality in the Carson River basin with respect to certain constituents, either basin wide or within specific areas of concern. (Lantz-PTT)

Open-File Report↗
USGS1986

Shallow subsurface temperature surveys in the Basin and Range province, U.S.A.-I. Review and evaluation

Temperature surveys at depths of 1–2 m have had varying success in geothermal exploration in the Basin and Range province. The most successful surveys have identified patterns of near-surface thermal-fluid flow within areas of less than 2 km 2 . Results have been less consistent in larger areas where zones of hydrothermal upflow are less well known, nongeothermal perturbing factors are significant and lateral variations in shallow subsurface temperature are small. Nongeothermal perturbations can be minimized by use of mean annual temperatures instead of synoptic temperatures, by physically based simulation of ground temperatures or by statistical modeling.

Geothermics↗
USGS1984

Geohydrology, aqueous geochemistry, and thermal regime of the Soda Lakes and Upsal Hogback geothermal systems, Churchill County, Nevada

A flow-routing model of the upper Schoharie Creek basin, New York, was developed and used to simulate high flows at the inlet of the Blenheim-Gilboa Reservoir. The flows from Schoharie Creek at Prattsville, the primary source of flow data in the basin, and tributary flows from the six minor basins downstream, are combined and routed along the 9.7 mile reach of the Schoharie Creek between Prattsville and the reservoir inlet. Data from five historic floods were used for model calibration and four for verification. The accuracy of the model as measured by the difference between simulated and observed total flow volumes, is within 14 percent. Results indicate that inflows to the Blenheim-Gilboa Reservoir can be predicted approximately 2 hours in advance. One of the historical floods was chosen for additional model testing to assess a hypothetical real-time model application. Total flow-volume errors ranged from 30.2 percent to -9.2 percent. Alternative methods of obtaining hydrologic data for model input are presented for use in the event that standard forms of hydrologic data are unavailable. (USGS)

Water-Resources Investigations Report↗