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D.W. Clark

Publications and source records attributed to D.W. Clark.

10 recordsLinked to original sources
USGS2007

Groundwater chemistry and occurrence of arsenic in the Meghna floodplain aquifer, southeastern Bangladesh

Dissolved major ions and important heavy metals including total arsenic and iron were measured in groundwater from shallow (25-33 m) and deep (191-318 m) tube-wells in southeastern Bangladesh. These analyses are intended to help describe geochemical processes active in the aquifers and the source and release mechanism of arsenic in sediments for the Meghna Floodplain aquifer. The elevated Cl- and higher proportions of Na+ relative to Ca2+, Mg2+, and K+ in groundwater suggest the influence by a source of Na+ and Cl-. Use of chemical fertilizers may cause higher concentrations of NH 4+ and PO 43- in shallow well samples. In general, most ions are positively correlated with Cl-, with Na+ showing an especially strong correlation with Cl-, indicating that these ions are derived from the same source of saline waters. The relationship between Cl-/HCO 3- ratios and Cl- also shows mixing of fresh groundwater and seawater. Concentrations of dissolved HCO 3- reflect the degree of water-rock interaction in groundwater systems and integrated microbial degradation of organic matter. Mn and Fe-oxyhydroxides are prominent in the clayey subsurface sediment and well known to be strong adsorbents of heavy metals including arsenic. All five shallow well samples had high arsenic concentration that exceeded WHO recommended limit for drinking water. Very low concentrations of SO 42- and NO 3- and high concentrations of dissolved Fe and PO 43- and NH 4+ ions support the reducing condition of subsurface aquifer. Arsenic concentrations demonstrate negative co-relation with the concentrations of SO 42- and NO 3- but correlate weakly with Mo, Fe concentrations and positively with those of P, PO 43- and NH 4+ ions. ?? 2007 Springer-Verlag.

Environmental Geology↗
USGS1995

Geochemical processes in ground water resulting from surface mining of coal at the Big Sky and West Decker Mine areas, southeastern Montana

A potential hydrologic effect of surface mining of coal in southeastern Montana is a change in the quality of ground water. Dissolved-solids concen- trations in water in spoils aquifers generally are larger than concentrations in water in the coal aquifers they replaced; however, laboratory experiments have indicated that concentrations can decrease if ground water flows from coal-mine spoils to coal. This study was conducted to determine if decreases in concentrations occur onsite and, if so, which geochemical processes caused the decreases. Solid-phase core samples of spoils, unmined over- burden, and coal, and ground-water samples were collected from 16 observation wells at two mine areas. In the Big Sky Mine area, changes in ground- water chemistry along a flow path from an upgradient coal aquifer to a spoils aquifer probably were a result of dedolomitization. Dissolved-solids concentrations were unchanged as water flowed from a spoils aquifer to a downgradient coal aquifer. In the West Decker Mine area, dissolved-solids concentrations apparently decreased from about 4,100 to 2,100 milligrams per liter as water moved along an inferred flow path from a spoils aquifer to a downgradient coal aquifer. Geochemical models were used to analyze changes in water chemistry on the basis of results of solid-phase and aqueous geochemical characteristics. Geochemical processes postulated to result in the apparent decrease in dissolved-solids concentrations along this inferred flow path include bacterial reduction of sulfate, reverse cation exchange within the coal, and precipitation of carbonate and iron-sulfide minerals.

Montana↗
USGS1990

Pesticides in soils and ground water in selected irrigated agricultural areas near Havre, Ronan, and Huntley, Montana

Three areas in Montana representing a range of agricultural practices and applied pesticides, were studied to document whether agricultural pesticides are being transported into the soil and shallow groundwater in irrigated areas. Analytical scans for triazine herbicides, organic-acid herbicides, and carbamate insecticides were performed on soil and shallow groundwater samples. The results indicate pesticide residue in both types of samples. The concentrations of pesticides in the groundwater were less than Federal health-advisory limits. At the Havre Agricultural Experiment Station, eight wells were installed at two sites. All four soil samples and two of four water samples collected after application of pesticides contained detectable concentrations of atrazine or dicamba. In an area where seed potatoes are grown near Ronan, eight wells were installed at two sites. Pesticides were not detected after initial application of pesticides and irrigation water. The site was resampled after irrigation water was reapplied, and aldicarb metabolities were detected in four of five soil samples and one of five water samples. At the Huntley Agricultural Experiment Station, five wells were installed in a no-tillage corn field where atrazine was applied in 1987. Soil and water samples were collected in June and July 1988; pesticides were not detected in any samples. Results indicate residue of two pesticides in soil samples and three soluble pesticides in groundwater samples. Therefore, irrigated agricultural areas in Montana might be susceptible to transport of soluble pesticides through permeable soil to the shallow groundwater system. (USGS)

Water-Resources Investigations Report↗
USGS1987

Seepage studies of the Weber River and the Davis-Weber and Ogden Valley canals Davis and Weber Counties, Utah, 1985

Studies of selected reaches of the Weber River, Davis-Weber Canal, and the Ogden Valley Canal in Davis and Weber Counties, Utah, were made to determine gains or losses of flow in those reaches. Three to five sets of seepage measurements were made on the river and each canal during 1985. Adjustments for fluctuations in flow were made from information obtained from water-stage recorders operated at selected locations during the time of each set of seepage measurements. The studies indicated a loss of 20.0 cubic feet per second in the upstream reach of the Weber River and a gain of 17.0 cubic feet per second in the downstream reaches or a net loss of 3.0 cubic feet per second. Study results also indicated a net loss of 17.0 cubic feet per second in the Davis-Weber Canal and a net loss of 4.0 cubic feet per second in the Ogden Valley Canal.

Utah↗
USGS1985

Ground-water resources of northern Utah Valley, Utah

An evaluation was made of the ground-water resources of northern Utah Valley, Utah, to describe the ground-water system and to document changes in ground-water conditions since 1963. The principal ground-water reservoir is in basin-fill deposits. It consists of three major confined aquifers and an unconfined aquifer in pre-Lake Bonneville deposits along the mountains that adjoin the valley. The principal ground-water reservoir contains about 10 million acre-feet of recoverable water.

Utah↗
USGS1984

The ground-water system and simulated effects of ground-water withdrawals in northern Utah Valley, Utah

The effects of withdrawals from the principal ground-water reservoir in northern Utah Valley, Utah, were projected by means of a three-dimensional, finite-difference, digital-computer model, which was constructed to study and simulate the ground-water system. The model was calibrated against (1) water levels measured in 1947, which were assumed to represent steady-state conditions; (2) observed water-level changes from 1947-83 for transient-state conditions; and (3) the results of an aquifer test. The calibrated model was used to simulate varying quantities of ground-water withdrawal and recharge and to estimate water-level changes for 1980-2000. The average annual rate of recharge for the area is assumed to be 190,000 acre-feet per year, and the average annual discharge from wells at the end of transient-state calibration was assumed to be 50 ,100 acre-feet per year. Water-level declines of as much as 25 feet are projected for the 20-year period if the average recharge rate is assumed and the discharge from wells is as much as 91,400 acre-feet per year. During transient-state calibration , changes in recharge to the principal ground-water reservoir were shown to be a major cause of the variations in water levels. (USGS)

Water-Resources Investigations Report↗