East St. Louis Creek drains 8 km2 of alpine and subalpine terrain in the Colorado Rocky Mountains. Mean annual peak discharges of approximately 0.6 m3/s occur during the summer, when the majority of the sand- to cobble-size bedload is transported along the steep channel. Repeat sampling of depth, velocity, and suspended and bedload sediment at 12 cross sections indicated significant correlations between both suspended and bedload sediment movement, and discharge, although sediment movement was highly variable at equivalent discharges. Correlations between sediment movement and velocity were not significant. Sediment entrainment relations suggest that present peak flows generate bed shear stress values close to critical threshold values for the D84 of the bed-surface layer. The majority of the sampled bedload was finer grained than the bed sediments. This may be explained by the presence of either a censored layer (which does not require mobilization of the coarse fabric), or a pavement, from which only a few coarse particles are entrained at any instant. It is hypothesized that East St. Louis Creek has a pavement. The lack of correlation between shear stress values and sediment movement indicates either that the use of hydraulic variables averaged across the entire cross section is insufficient to differentiate incipient motion, or that cross-sectional flow characteristics are not as important as reach-scale controls on sediment movement. Bedload appears to come primarily from valley-bottom and in-channel sources, particularly when the bed is disturbed by the movement of woody debris. Woody debris in the channel traps and stores bedload and acts as a major local control on temporal and spatial patterns of bedload movement.
To study the effect of various factors on the reduction of hexavalent chromium in groundwater, batch experiments were carried out using material collected from the sub-oxic zone of a shallow sand-and-gravel aquifer, where the groundwater was depleted in oxygen and showed an increase in manganese content, but conditions were not sufficiently reducing to reduce iron. Reduction of hexavalent chromium in this material was heterogeneous and occurred principally on ferrous-bearing mineral. The fine fraction of the sediment (less than 64 mm diameter) dominated chromium reduction because of its greater reactivity and surface area. Reduction of chromium increased with decrease in pH value and with increase in the initial concentration of hexavalent chromium. The most consistent description of the rate data was achieved by assuming that intraparticle differsion limited the observed rate of reduction.
As a result of the so-called greenhouse effect, projected increases in the levels of carbon dioxide in the atmosphere were widely expected to induce global warming, which could in turn give rise to changes in precipitation patterns, rates of evapotranspiration and an increase in sea level. This report describes the reasoning behind these predicted changes, and discusses the problems and uncertainties associated with the prediction and effects of climate change. It also presents the results of sensitivity analyses showing how climate change might effect water resources and related hydrological characteristics, including aquifer storage in the Delaware river basin, together with the possible rise in sea level and extent of coastal inundation along the southern shore of New Jersey where the coastal swamps were vulnerable to intrusion from the sea.
Sixty-three water samples collected during June to October 1982 from the Leviathan/Bryant Creek drainage basin were originally analyzed by simultaneous multielement direct-current plasma (DCP) atomic-emission spectrometry, flame atomic-absorption spectrometry, graphite-furnace atomic-absorption spectrometry (GFAAS) (thallium only), ultraviolet-visible spectrometry, and hydride-generation atomic-absorption spectrometry.Determinations were made for the following metallic and semi-metallic constituents: AI, As, B, Ba, Be, Bi, Cd, Ca, Cr, Co, Cu, Fe(II), Fe(total), Li, Pb, Mg, Mn, Mo, Ni, K, Sb, Se, Si, Na, Sr, TI, V, and Zn. These samples were re-analyzed later by simultaneous multielement inductively coupled plasma (ICP) atomic-emission spectrometry and Zeeman-corrected GFAAS to determine the concentrations of many of the same constituents with improved accuracy, precision, and sensitivity. The result of this analysis has been the generation of comparative concentration values for a significant subset of the solute constituents. Many of the more recently determined values replace less-than-detection values for the trace metals; others constitute duplicate analyses for the major constituents. The multiple determinations have yielded a more complete, accurate, and precise set of analytical data. They also have resulted in an opportunity to compare the performance of the plasma-emission instruments operated in their respective simultaneous multielement modes.
Flame atomic-absorption spectrometry was judged best for Na and K and hydride-generation atomic-absorption spectrometry was judged best for As because of their lower detection limit and relative freedom from interelement spectral effects. Colorimetric determination using ferrozine as the color agent was judged most accurate, precise, and sensitive for Fe. Cadmium, lead, and vanadium concentrations were too low in this set of samples to enable a determination of whether ICP or DCP is a more suitable technique. Of the remaining elements, Ba, Be, Ca, Cr, Mg, Mn, Sr, and Zn have roughly equivalent accuracy, precision, and detection limit by ICP and DCP. Cobalt and Ni were determined to be better analyzed by ICP, because of lower detection limits; B, Cu, Mo, and Si were determined to be better analyzed by DCP, because of relative freedom from interferences. The determination oral by DCP was far more sensitive, owing to the use of a more sensitive wavelength, compared with the ICP. However, there is a very serious potential interference from a strong Ca emission line near the 396.15 nanometer DCP wavelength. Thus, there is no clear choice between the plasma techniques tested, for the determination oral. The ICP and DCP detection limits are typically between 0.001 and 0.5 milligrams per liter in acid mine waters. For those metals best analyzed by ICP and/or DCP, but below these limits, GFAAS is the method of choice because of its relatively greater sensitivity and specificity. Six of the elements were not determined by DCP, ICP or Zeeman-corrected GFAAS, and are not discussed in this report. These elements are: Bi, Fe(II), Li, Sb, Se, and TI.
Sorption of tetra- and pentachlorobenzene by sediment from a glacial outwash aquifer on Cape Cod, MA, was evaluated. Particle size and mineralogical fractions (separated based on paramagnetic susceptibility) were characterized with respect to sediment organic carbon (SOC), mineralogy, surface area, metal oxide coatings, and spatial variability. SOC increases by a factor of 10 as particle size decreases from 500-1000 to <63 mm. Magnetic mineral abundance is a function of particle size and increases from <5% in the 500-1000-mm fraction to >25% in the <63- mm fraction, and SOC is preferentially associated with the magnetic minerals. Sorption increases with decreasing particle size and the magnetic mineral fraction has greater sorption than the bulk or nonmagnetic fractions. Removal of SOC decreases sorption proportional to the decrease in SOC and results in a nonlinear isotherm.
The d18O content of streamflow discharge entering Pyramid Lake is a simple mixture of isotopically enriched Lake Tahoe discharge and isotopically depleted snowmelt. The d18O value of Pyramid Lake water varies continuously, as isotopically depleted water enters the lake as streamflow discharge and on-lake precipitation. In a normal water year, the d18O of Pyramid Lake surface water varies seasonally because the components of the hydrologic balance in the Pyramid Lake system are seasonally shifted. The problem of isotopic and thermal heterogeneity can be minimized by analyzing carbonates that integrate the annual variance in d18O, form in an environment in which temperature is relatively invariant, and are not subject to recrystallization after deposition.
During 1988 and 1989, a series of water-vapor extractions were conducted in the Pyramid Lake basin to determine the source of moisture that overlies the lake. Calculations of the isotopic and water-vapor balances were made from isotopic and meteorological data from the Pyramid Lake and Reno, Nevada, areas. The results indicate that in the warm season, most of the moisture that overlies the lake is derived from evaporation as opposed to advected moisture. Isotopic fluxes at the lake surface can be approximated by climatic data from the lake site, which simplifies the calculation of this input in numerical simulations of the isotopic evolution of the lake.
Abstract Tertiary-treated wastewater currently (1991) is being injected into the Hueco bolson aquifer at a site in northeastern El Paso, Texas, to supplement the quantity of available freshwater. Hydrologic data were compiled and water-quality and bacterial data were collected from existing wells near the Hueco Bolson Recharge Project (HBRP) in August and September 1990 and 1991. Borehole tracer tests indicated upward ground-water flow in nearly all tested intervals of several observation wells. The cumulative volume of injected water was less than the volume produced from wells adjacent to the HBRP area. Water levels in three production wells, located more than 1.5 miles from the injection wells, declined at rates comparable to those observed before injection operations. Water levels in wells located within 0.75 mile of the injection-well pipeline declined at a slower rate after HBRP injection operations had begun. Between 1985 and 1991, water levels in observation wells located within 700 feet of an injection well either did not appreciably decline, or declined at smaller rates than water levels in more distant production wells. Trihalomethane compounds were detected in water from 8 of the 16 observation and production wells sampled in 1990 and in 10 of the 17 wells sampled in 1991. Concentrations trihalomethane compounds in these samples ranged from 0.05 to 1.9 mg/L in 1990 and from 0.05 to 1.4 mg/L in 1991. Concentrations of trihalomethane compounds in samples of injected water from two wells were 27.8 and 34.6 mg/L respectively, in 1991. Dibromomethane and dichloromethane were detected in water from injection wells and from observation wells within about 700 feet of the injection wells. Aerobic bacteria were determined to be the only bacteria type present in ground water except for samples from two wells, which also contained denitrifying bacteria. The populations of aerobic bacteria determined in ground water ranged from 80 to more than 160,000 most probable number of organisms per milliliter of sample.
Water samples were collected in the San Francisco Bay estuary during 22 cruises from January through December 1993. Conductivity, temperature, light attenuation, turbidity, oxygen, and in-vivo fluorescence were measured 1ongitudinally and vertically in the main channel of the estuary from south of the Dumbarton Bridge in the southern part of the bay to Rio Vista on the Sacramento River. Discrete water samples were analyzed for chlorophyll a, phaeopigments, suspended particulate matter, and dissolved oxygen. Water density was calculated from values for salinity, temperature, and pressure (depth), and is included in the data summaries. Photosynthetic parameters, water column respiration, and phytoplankton species abundance and cell volume were determined at selected stations every other month.
Long-term changes in biomass, species composition, and distribution of submersed aquatic macrophytes have been documented and studied at two sites in the mid-Atlantic region: the tidal Potomac River and Estuary in Maryland, Virginia, and the District of Columbia, and the Currituck Sound-Back Bay system in Virginia and North Carolina. Additional information based on a shorter time period is available for the Pamlico River Estuary in North Carolina. This paper briefly describes the study areas, summarizes the history of declines and increases in each area and factors implicated in these changes, and discusses the factors influencing invasion/establishment success and the current status of submersed macrophytes in the three areas.
Weather and water-quality data from 1980 to 1989 were correlated with fluctuations in submersed macrophyte populations in the tidal Potomac River near Washington, D.C., to elucidate causal relationships and explain population dynamics. Both reaches were unvegetated in 1980 when mean growing-season Secchi depths were <0.60 m. Macrophyte resurgence in the upper tidal river in 1983 was associated with a growing-season Secchi depth of 0.86 m, total suspended solids (TSS) of 17.7 mg/l, chlorophyll a concentrations of 15.2 mg/l, significantly higher than average percent available sunshine, and significantly lower than average wind speed. From 1983 to 1989, mean seasonal Secchi depths <0.65 m were associated with decrease in plant coverage and mean seasonal Secchi depths >0.65 were associated with increases in plant coverage. Changes in mean seasonal Secchi depth were related to changes in mean seasonal TSS and chlorophyll a concentration; mean Secchi depths >0.65 generally occur when seasonal mean TSS is <19 mg/l and seasonal mean chlorophyll a concentration is less than or equal to 15 mg/l. Secchi depth is highly correlated with plant growth in the upper tidal river and chlorophyll a and TSS with plant growth in the lower tidal river. Wind speed is an important influence on plant growth in both reaches.
Behavior of regional precipitation and temperature over the West Coast of the United States was examined in a long perpetual winter simulation from a simplified global general circulation model. The model, a simplified version of the U.S. National Weather Service global operational forecast model, was run over a series of 568 winters, complete with geopotential, precipitation, and near-surface temperature. In spite of the fixed climatological boundary conditions, the simulated winter-mean precipitation and temperature anomalies have a fairly realistic low-frequency regional variability. Both synoptic-scale events and seasonal average behavior are produced quite realistically by the model. Like observations, the regional surface variations can be related to the large-scale low-frequency circulation. Four regional temperature/precipitation extremes-namely, warm/dry, cool/wet, cool/dry, and warm/wet-can be identified from the simulated winter-mean time series over the West Coast. Associated with these four regional extremes, model Northern Hemisphere 500-mb height composites exhibit distinct planetary-scale circulation patterns. An empirical orthogonal function analysis further reveals that the first and third modes of the 500-mb height anomalies are primary contributors to these four regional extremes. The first mode largely governs the regional temperature variation, whereas the third mode largely determines the precipitation variation.
High-pressure size exclusion chromatography (HPSEC) was used to measure the number- and weight-averaged molecular weights of aquatic fulvic acids from the U.S.A. and Antarctica, a commercial humic acid and unfractionated organic matter from the Suwannee river, Ga.. The spectroscopic properties of the humic samples were studied. The molecular weights obtained using HPSEC were in general agreement with those obtained by other methods. Aquatic humic substances were smaller and less polydisperse than previously believed. There was a strong correlation between molar absorptivity, total aromaticity, and the weight average molecular weights of all the humic substances, suggesting that bulk spectroscopic properties can be used to estimate the size and aromatic contents of humic substances.
Discrete red patches of water were observed in South San Francisco Bay (USA) on 30 April 1993, and examination of live samples showed that this red tide was caused by surface accumulations of the pigmented ciliate Mesodinium rubrum. Vertical profiles showed strong salinity and temperature stratification in the upper 5 m, peak chlorophyll fluorescence in the upper meter, and differences in the small-scale density structure and fluorescence distribution among red patches. Events preceding this Mesodinium red tide included: 1} heavy precipitation and run-off, allowing for strong salinity stratification; 2} a spring diatom bloom where the chlorophyll a concentration reached 50 mg m-3; 3} depletions of dissolved inorganic N and Si in the photic zone; and 4) several days of rapid warming and stabilization of the upper surface layer. These conditions may be general prerequisites for M. rubrum blooms in temperate estuaries.
The geochemical evolution of low-molecular-weight organic acids in groundwater downgradient from a crude-oil spill near Bemidji, Minnesota, was studied over a five year period (1986-90). The organic acids are metabolic intermediates of the degradation of components of the crude oil and are structurally related to hydrocarbon precursors. The concentrations of organic acids, particularly aliphatic acids, increase as the microbial alteration of hydrocarbons progresses. The organic-acid pool changes in composition and concentration over time and in space as the degradation processes shift from Fe(III) reduction to methanogenesis. Over time, the aquifer system evolves into one in which the groundwater contains more oxidized products of hydrocarbon degradation and the reduced forms of iron, manganese, and nitrogen. Laboratory microcosm experiments with aquifer material support the hypothesis that organic acids observed in the groundwater originate from the microbial degradation of aromatic hydrocarbons under anoxic conditions. The geochemistry of two other shallow aquifers in coastal plain sediments, one contaminated with creosote waste and the other with gasoline, were compared to the Bemidji site. The geochemical evolution of the low-molecular-weight organic acid pool in these systems is controlled, in part, by the presence of electron acceptors available for microbially mediated electron-transfer reactions. The depletion of electron acceptors in aquifers leads to the accumulation of aliphatic organic acids in anoxic groundwater.
The genetic population structure of the recently introduced Asian clam, Potamocorbula amurensis, in San Francisco Bay was described using starch gel electrophoresis at eight presumptive loci. Specimens were taken from five environmentally distinct sites located throughout the bay. The population maintains a high degree of genetic variation, with a mean heterozygosity of 0.295, a mean polymorphism of 0.75, and an average of 3.70 alleles per locus. The population is genetically homogeneous, as evidenced from genetic distance values and F-statistics. However, heterogeneity of populations was indicated from a contingency chi-square test. Significant deviations from Hardy-Weinberg equilibrium and heterozygote deficiencies were found at the Lap-1 locus for all populations and at the Lap-2 locus for a single population. High levels of variability could represent a universal characteristic of invading species, the levels of variability in the source population(s), and/or the dynamics of the introduction. Lack of differentiation between subpopulations may be due to the immaturity of the San Francisco Bay population, the "general purpose" phenotype genetic strategy of the species, high rates of gene flow in the population, and/or the selective neutrality of the loci investigated.
As the United States and the world seek relatively nonpolluting sources of energy to power industrial economies and rapid developing nations, alternatives to the traditional fossil fuels are considered. Geothermal energy is environmentally benign relative to fossil-fuel energy sources. Geothermal energy is already harnessed to generate electricity as well as contribute heat directly to many industrial processes in the United States and several other nations. Geothermal energy now supplies only a small part of national and world energy demand, although appropriate research and development could increase this supply manyfold.
The detection of many organic contaminants in water is often hindered by their transient nature and low concentration. However, these contaminants can represent a significant environmental hazard to biota and humans through bioconcentration. Traditional methods of analyzing aquatic biota are complicated by the limited availability of suitable biota; intraspecies variations such as sex, age, and health; and interspecies variations due to differences in behavioral patterns, metabolism and lipid composition. A new sampling device attempts to resolve some of these problems by mimicking bioconcentration using a semipermeable-membrane (low-density polyethylene) tube containing pure synthetic lipid (triolein). These sampling devices were deployed at 10 sites along the upper Mississippi River; and for comparison, caged fish were located at three of these sites. The devices and caged fish were exposed for 28 days, and indigenous fish were collected from the sites at the end of the study. Target compounds (27 pesticides, herbicides, and PCB's) were readily extracted from the sampling devices by dialysis into an appropriate solvent, and samples were analyzed by gas-chromatography negative chemical-ionization mass spectrometry. Data from the sampling devices were used to predict water and fish concentrations. Mean values for measured and predicted water and fish concentrations were found to be statistically equivalent. The high degree of variability in the data may account for this finding, and the fact that no functional relationship was found between measured and predicted values.
Specific anomalous atmospheric circulation conditions over the North Pacific are conducive to the occurrence of the largest winter floods ( less than or equal to 10-yr return period) on rivers in six hydroclimatic subregions of Arizona and southern Utah, Nevada, and California. Composite maps of anomalies in daily 700-mb heights indicate that floods in all of the subregions are associated with a low pressure anomaly off the California coast and a high-pressure anomaly in the vicinity of either Alaska or the Aleutian Islands. Of these two major circulation features, the presence of the low is the controlling factor in determining whether large floods will occur. Shifts in the locations of the low and high pressure anomalies over the North Pacific appear to control which subregions experience floods, with high-elevation topographic features and proximity to air masses forming a major influence over the specific atmospheric circulation conditions that generate large floods in each hydroclimatic region. Concerning the interannual variability of flooding in the Southwest, there is an increased frequency of large winter floods during multiple-year periods dominated by negative SOI and a virtual absence of large floods during the intervening periods. This suggests that global-scale climatic anomalies exert a strong influence on the occurrence of severe regional winter floods.
The catastrophic release of gas from Lake Nyos, Cameroon, in 1986 caused substantial but incomplete mixing of the stratified water column. The post-release evolution of water-column structure has been monitored through April 1992. Changes began immediately after the event as rainfall and inflow brought dilute fluid into the surface layer. Inflow and surface mixing have gradually deepened the chemocline.
Boreholes were drilled in South Cascade Glacier to investigate the hydraulics of subglacial water flow. Results indicate that subglacial water pressures are generally close to local ice-overburden pressures and that a subglacial debris layer probably exists. Calculations indicate that the range of hydraulic conductivity of this layer is 10-7-10-4 m/s. The borehole water levels generally increased during the ablation season and may caused by a seasonal evolution in the permeability of the debris layer. Water in the debris layer drains to a subglacial conduit, the existence of which is inferred by large diurnal variations in the water level of one borehole. These levels commonly reached the bottom of the glacier, indicating near-atmospheric pressures in the conduit.
Major- and minor-element concentrations are pre- sented for streambed and suspended sediment, filtered- and unfiltered-water, and aquatic-biota samples collected during 1987-91 from the Yakima River Basin in south-central Washington. The samples were collected as part of the U.S. Geological Survey's National Water-quality Assessment (NAWQA) program which is designed to provide results that are useful in understanding and managing the Nation's water resources. This report includes the sampling approach, field collection and processing techniques, and methods of chemical analysis, as well as a compilation of chemical data, statistical summaries, and quality- control data. These data may be used by scientists and resource managers to describe (1) spatial distribution of selected major and minor elements in sediment, water, and aquatic biota of the Yakima River Basin; (2) temporal variation for element concentrations in filtered water and in suspended sediment at selected sites; (3) suita- bility of surface water for preservation of aquatic life and protection of human health; and (4) major natural and anthropogenic sources of major and minor elements in the Yakima River Basin that affect observed water-quality conditions. Streambed-sediment samples were collected once from 27 sites in the basin during 1987-91. Suspended-sediment and filtered-water samples were collected monthly and during hydrologic events (including snowmelt and winter rainstorms) at seven sites, and filtered-water samples were collected at least once at an additional 37 sites during synoptic samplings. Unfiltered-water samples were collected at seven sites on a quarterly basis during 1987 only. Samples of aquatic plants were collected once in 1989, and aquatic insects, fish, and clams were collected from 34 sites three times during 1989-90.
Balkan endemic nephropathy (BEN) is a disease of interstitial nephropathy leading to end-stage renal failure. The disease occurs in persons living in villages on alluvial valleys of streams tributary to the Danube River in Rumania, Bulgaria and former Yugoslavia. The etiologic agent is not known, but a contaminant in shallow groundwater has become suspect. In this study, samples of drinking water from endemic and non-endemic village water supplies were analyzed by excitation/emission matrix (EEM) fluorescence spectroscopy. Spectra characteristic of groundwater from BEN households show elongated teardrop shapes in the fluorescence excitation/emission matrix. A sharp rise occurs in fluorescence emission between 380 and 400 nanometers (nm) and a trailing emission intensity from 400 to 550 nm. Spectra of groundwater samples from some BEN households have an additional excitation maxima at 300 nm, which further contributes to the emission intensity at 400 nm. Spectra of water samples from non-BEN households located in endemic villages show characteristics of BEN household waters, exhibiting the 250-nm excitation peak, even though the fluorophoric intensity is much less than that in samples from BEN household waters. Samples from non-endemic villages do not show the characteristic EEM spectra described as "teardrop shaped". The non-BEN households have lower concentrations of these fluorophores in the drinking water than the endemic households; hence, one of the factors in contracting the disease may be the concentration of these fluorescent materials in drinking water.
Quantitative modeling of magmatic-hydrothermal systems has been hampered by the lack of publicly available , documented computer models for multiphase, high-temperature flow. This report documents HYDROTHERM, a finite-difference model for three-dimensional, multiphase flow of pure water and heat over a temperature range of 0 to 1,200 degrees Celsius and a pressure range of 0.5 *0 10,000 bars. HYDROTHERM solves numerical approximations to mass- and energy-balance equations that are posed in terms of pressure and enthalpy. Major assumptions are that the rock matrix can be treated as a porous medium; that water and rock are in thermal equilibrium; and that capillary pressure is negligible.
Aquatic humic substances (AHS) were isolated from peatbog water by adsorption (1) on diethylaminoethyl cellulose (DEAE-C) and (2) on Amberlite XAD-2 (XAD) to compare yields of the methods and the composition of the isolated AHS. To provide a detailed comparison, the isolates were fractionated using size-exclusion and hydrophobic-interaction chromatography on Sephadex G-50. The fractions were characterized by ultraviolet-visible, infrared and super(13)C-nuclear magnetic spectroscopies and analyzed for elemental, functional-group, carbohydrate and amino acid compositions. More AHS adsorbed onto DEAE-C than onto XAD-2 (94 and 74%, respectively). However, only 76% of the AHS adsorbed onto DEAE-C was recovered using 0.1 M NaOH, whereas 98% of the AHS adsorbed onto XAD was released by consecutive elution with 1 M NH4OH (91%) and methanol (7%). Four main fractions of different composition were obtained from each of the alkali-desorbed AHS samples by Sephadex-gel chromatography. General agreement was found in relative amounts, spectroscopic characteristics and composition of corresponding fractions of both isolates except nitrogen content, which was significantly higher in AHS isolated with XAD, apparently due to the reaction of AHS with NH4OH used for the desorption from the resin.
Controlled laboratory redox titration experiments were performed on samples of surface flow and groundwater taken near the head of perennial flow in Pinal creek, Ariz., to elucidate processes involved in the formation of manganese-bearing precipitates in the stream bed and in parts of the subsurface. The underlying groundwater had been contaminated by low-pH metal-enriched mining and ore-processing wastewaters. The thermodynamic feasibilities of 8 potential chemical reactions forming solid phases of interest were evaluated by calculating reaction affinities attained during titration and ageing. The results were in general agreement with those of X-ray and electron diffraction.
A physically based model of variations in d18O and d2H in Pyramid Lake is presented. For inputs, the model uses measurements of liquid water inflows and outflows and their associated isotopic compositions and a set of meteorological data (radiative fluxes, air temperature, relative humidity, and windspeed). The model simulates change of lake volume, thermal and isotopic stratification, evaporation, and the isotopic composition of evaporation. A validation of the model for 1987-1989 and 1991 indicates that it can reproduce measured intra- and interannual variations of d18O and d2H. Three applications of the model demonstrate its ability to simulate longer term responses of d18O to change in the hydrologic balance and hydrologic characteristics (opening and closing) of the lake.
The effects of ionic strength on the determination of DOC by low temperature wet chemical methods was studied on freshwater sources adjusted up to 0.7 M with a defined seawater-type medium. The low temperature method involved acidification and pumping to remove inorganic carbon dioxide before injection into a reaction vessel containing persulphate and oxygen exposed to UV. Mercury compounds were included to suppress chloride effects. Evolved carbon dioxide was determined by infra-red detector. No significant effects were noted as ionic strengths increased, probably because the methodology of injecting into a reaction vessel was superior to conventional ampoule methods.
The geologic and hydrologic settings are described and geologic, geochemical, and geophysical data are interpreted in terms of the characteristics of the hydrothermal systems. Numerical simulation methods are used to investigate two alternate conceptual models of the deep thermal structure. The study area includes a 135-km-long section of the arc between latitudes 44 degrees 00' and 45 degrees 15'N. It lies generally southeast of Portland, northeast of Eugene, and northwest of Bend, and includes parts of the Cascade Range, Deschutes-Umatilla Plateau, and High Lava Plains physiographic provinces.
Large areas of the Australian continent contain scattered saline lakes underlain by shallow saline groundwaters of regional extent and debated origin. The normative salt composition of subsurface pore fluids extracted by squeezing cores collected during deep drilling at Piangil West 2 in the central Murray Basin in southeastern Australia, and of surface and shallow subsurface brines produced by subaerial evaporation in the nearby Lake Tyrrell systems, helps constrain interpretation of the origin of dissolved solutes in the groundwaters of this part of the continent. Although regional sedimentation in the Murray Basin has been dominantly continental except for a marine transgression in Oligocene-Pliocene time, most of the solutes in saline surface and subsurface waters in the central Murray Basin have a distinctly marine character. Some of the Tyrrell waters, to the southwest of Piangil West 2, show the increase in NaCl and decrease in sulfate salts expected with evaporative concentration and gypsum precipitation in an ephemeral saline lake or playa environment. The salt norms for most of the subsurface saline waters at Piangil West 2 are compatible with the dilution of variably fractionated marine bitterns slightly depleted in sodium salts, similar to the more evolved brines at Lake Tyrrell, which have recharged downward after evaporation at the surface and then dissolved a variable amount of gypsum at depth. Apparently over the last 0.5 Ma significant quantities of marine salt have been blown into the Murray Basin as aerosols which have subsequently been leached into shallow regional groundwater systems basin-wide, and have been transported laterally into areas of large evaporative loss in the central part of the basin. This origin for the solutes helps explain why the isotopic compositions of most of the subsurface saline waters at Piangil West 2 have a strong meteoric signature, whereas the dissolved salts in these waters appear similar to a marine assemblage.
A survey of the hydraulic properties of the rock formations beneath the Lee valley basin, a 2.25 square mile catchment about 18 miles east of San Diego, California, is reported. Wells were drilled at selected points and pumping tests performed to determine potential yields from formations at different depths. The yields were characteristic of fractured-rock aquifers with a high degree of heterogeneity. They were generally low (median value 15 U.S. gallons per minute) although a few higher-yielding wells (more than 100 U.S. gallons per minute) were located. There was no discernible spatial correlation for yields from wells at different points, although some evidence of increased yields near fault lines was observed. Recharge originated primarily as infiltration of rainfall, and could be either greater of less than the normal rate of discharge in any one year. Increased rates of abstraction, if combined with a succession of years with below average rainfall, could result in severe depletion of reserves within an interval of about 10 years.
The fractal scaling of river networks has been described in the context of both thin and fat fractals. Whereas the thin-fractal characterization is presented as a fractal dimension, D, derived from the length properties of the river channels, a fat-fractal characterization is given as a scaling exponent, beta , derived from the behavior of river-channel area. Several authors have related D to the bifurcation ratio, Rb, and length ratio, Rl, of idealized Hortonian-network trees. Here, for these types of trees, we asymptotically relate beta to Rb, Rl, and to a diameter exponent, Delta, which governs the downstream channel-widening process. Using this result, we present a linkage of D to beta and discuss the implications of the relative values of Rb, Rl, and Delta on this linkage and on network channel behavior. Finally, we illustrate bias in the estimation of beta from preasymptotic trees.
A geohydrologic investigation was performed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to determine the distribution of volatile organic compounds in a fractured-rock aquifer near the Southeast Rockford Groundwater Contamination Site in Rockford, Ill. The geologic units of concern are the St. Peter Sandstone and Glenwood Formation; the dolomites of the Platteville and Galena Groups of Ordovician age; and the sands, gravels, silts, and clays of Quaternary age. The hydraulic units of concern are the unconsolidated aquifer, composed of sand and gravel; the fractured- dolomite aquifer, composed of the Galena and Platteville Groups and the dolomitic sections of the Glenwood Formation; and the sandstone aquifer, composed of the St. Peter Sandstone and the sandstone beds in the Glenwood Formation. The dolomite aquifer is well connected hydraulically to the overlying unconsolidated aquifer and the underlying sandstone aquifer. Caliper and acoustic-televiewer logs show several subhorizontal fractures in the dolomite that can be correlated throughout the study area. Comparison of televiewer and flowmeter logs indicates that most of the flow in the dolomite aquifer is through these fractures. Ground-water flow through two of the fractures can be correlated over large parts of the study area. Volatile organic compounds, in concentrations exceeding 2,000 micrograms per liter, were detected within the entire thickness of the dolomite aquifer where flow is measurable. Volatile organic compounds were detected in an area of the aquifer where they were thought to be absent in previous investigations.
The discharge and residence time in a 1497 m reach of a stream receiving acid mine drainage were determined with a lithium chloride tracer. The transport of metals from inputs of acidic metal-rich water was evaluated on the basis of synoptic samples of metal concentrations and hydrological characteristics. Transport of sulphate and manganese was generally conservative, but in the sub-reaches most affected by acidic inflows it was reactive. Iron in all forms was reactive over most of the stream reach. High concentrations of aluminium partitioned onto particles. The steady-state profiles of sulphate, manganese, iron and aluminium were simulated by first order reactions. Several processes occurring on a stream-reach scale were incorporated into the calculated rate constants for net removal. Chemical reactions were only important over short distances in the stream near the acidic inflows where they occurred on a timescale comparable with hydrological transport.
The authors studied the dynamic response in aqueous concentrations of metals and sulfate to an experimental increase of pH in a mountain stream affected by acidic mine drainage. Downstream from mine spoils in St. Kevin Gulch, Colorado, U.S.A., ambient pH was 3.5; filtered concentrations of Al, Cu, Fe, and SO42- were 3.1, 0.18, 1.1, and 128 mg/L, respectively. Injection of Na2CO3 caused pH to increase to 4.2 and eventually to 5.9 at a site 24 meters downstream from the injection. Filtered Al decreased to 0.07 mg/L; Cu, to 0.12 mg/L; Fe, to 0.41 mg/L; and SO42- to 122 mg/L. Particulate metal concentrations increased as filtered concentrations decreased, indicating processes of partitioning. Measured concentrations compared favorably with concentrations calculated by a geochemical equilibrium model that simulated precipitation of amorphous Fe and Al hydroxysulfates and sorption of Cu to the precipitating Fe phase. Differences between measured values and concentrations simulated with a conservative solute transport model indicated the substantial buffering capacity of streambed sediments. Particulate concentrations of Al, Cu, and Fe decreased downstream because of sedimentation to the bed. After the injection, concentrations of filtered Al and Cu exceeded background levels. At a site 24 meters downstream, 100 percent of the particulate Al that had settled from the water column was returned after the injection; 53 percent of the Cu was returned, but only 19 percent of the Fe was returned. These observations are attributed to dissociation of the settled polynuclear complexes of Al and to desorption of Cu from the settled Fe phases.
The U.S. Geological Survey computer model to simulate two-dimensional solute transport and dispersion in ground water (Konikow and Bredehoeft, 1978; Goode and Konikow, 1989) has been modified to improve management of input and output data and to provide progressive run-time information. All opening and closing of files are now done automatically by the program. Names of input data files are entered either interactively or using a batch-mode script file. Names of output files, created automatically by the program, are based on the name of the input file. In the interactive mode, messages are written to the screen during execution to allow the user to monitor the status and progress of the simulation and to anticipate total running time. Information reported and updated during a simulation include the current pumping period and time step, number of particle moves, and percentage completion of the current time step. The batch mode enables a user to run a series of simulations consecutively, without additional control. A report of the model's activity in the batch mode is written to a separate output file, allowing later review. The user has several options for creating separate output files for different types of data. The formats are compatible with many commercially available applications, which facilitates graphical postprocessing of model results. Geohydrology and Evaluation of Stream-Aquifer Relations in the Apalachicola-Chattahoochee-Flint River Basin, Southeastern Alabama, Northwestern Florida, and Southwestern Georgia.
The unsaturated zone at Yucca Mountain, Nevada, is being investigated as a potential location for a high-level nuclear waste repository. Characterization of the liquid water flux and its spatial distribution under natural conditions provides estimates of the amount of water that could potentially contact the waste canisters and transport soluble radionuclides to the accessible environment. Estimates of ambient water flux may affect design requirements by indicating the degree to which reliance must be placed on engineered barriers or the waste-generated heat to keep the waste canisters dry.
Water, bed sediment, and biota were sampled in streams from Butte to below Missoula as part of a program to characterize aquatic resources in the upper Clark Fork basin of western Montana. Water-quality data were obtained periodically at 16 stations during October 1992 through September 1993 (water year 1993); daily suspended-sediment data were obtained at six of these stations. Bed-sediment and biological data were obtained at 11 stations in August 1993. Sampling stations were located on the Clark Fork and major tributaries. The primary constituents analyzed were trace elements associated with mine tailings from historic mining and smelting activities. Water-quality data include concentra- tions of major ions, trace elements, and suspended sediment in samples collected periodically during water year 1993. A statistical summary of water- quality data is provided for the period of record at each station since 1985. Daily values of streamflow, suspended-sediment concentration, and suspended-sediment discharge are given for six stations. Bed-sediment data include trace- element concentrations in the fine and bulk fractions. Biological data include trace-element concentrations in whole-body tissue of aquatic benthic insects. Quality-assurance data are reported for analytical results of water, bed sediment, and biota.
The hydrodynamic effects in the Port Royal sound, N.C., estuarine system of highway-crossing embankments were evaluated using the 2-dimensional, depth-averaged, finite-difference Surface-Water, Integrated, Flow and Transport model (SWIFT20). A 1-year extensive data-collection programme provided prototype information including water-surface elevations, tidal cycle discharge, flooding and dewatering and bathymetric data. The original 183 m global model of the entire system was used to compute boundary-value data for a finer-scale submodel with a grid size of 63 m that was implemented for a subregion in which extensive tidal flats adjoined deep, narrow channels. Numerical experiments showed that in the presence of highway embankments, there was a net reduction of mass transport into and out of upper Battery creek on the Beaufort river (a principal tidal subchannel). Computed particle trajectories demonstrated that the embankments also altered circulation patterns within Battery creek. The SWIFT20 model provided an investigative and design tool for evaluating the effects of civil engineering projects on flow and mass transport in complex water bodies.
Recent investigations provide new insight on the structural chemistry of dissolved organic matter (DOM) in freshwater environments and the role of these structures in contaminant binding. Molecular models of DOM derived from allochthonous and autochthonous sources show that short-chain, branched, and alicyclic structures are terminated by carboxyl or methyl groups in DOM from both sources. Allochthonous DOM, however, had aromatic structures indicative of tannin and lignin residues, whereas the autochthonous DOM was characterized by aliphatic alicyclic structures indicative of lipid hydrocarbons as the source. DOM isolated from different morphoclimatic regions had minor structural differences.
The potential for using concentrations of dissolved H2 to determine the distribution of redox processes in anoxic groundwaters was evaluated. In pristine aquifers in which standard geochemical measurements indicated that Fe-(III) reduction, sulfate reduction, or methanogenesis was the terminal electron accepting process (TEAP), the H2 concentrations were similar to the H2 concentrations that have previously been reported for aquatic sediments with the same TEAPs. In two aquifers contaminated with petroleum products, it was impossible with standard geochemical analyses to determine which TEAPs predominated in specific locations. However, the TEAPs predicted from measurements of dissolved H2 were the same as those determined directly through measurements of microbial processes in incubated aquifer material. These results suggest that H2 concentrations may be a useful tool for analyzing the redox chemistry of nonequilibrium groundwaters.
Washed cell suspensions of Desulfovibrio vulgaris reduced chromium(VI) to chromium(III) with hydrogen as the electron donor. The c3 cytochrome functioned as a chromium(VI) reductase.
A chemical budget analysis for Williams Lake, Minnesota, tracks the seasonal progression of carbon inputs and outputs. CO2 exchanges with the atmosphere reverse seasonally, with uptake by the lake in summer preceded and followed by larger losses to the atmosphere. Calcium bicarbonate-rich groundwaters seep steadily into the lake, augmented by remobilization of lacustrine marls. Most of the carbon used in summer photosynthesis nevertheless derives from depletion of lake carbon stores, facilitated significantly by plant calcification. Calcification in summer reduces alkalinity and calcium inventories by 15 and 25%, respectively, while generating equal molar quantities of CO2. Marl precipitates mainly on submersed macrophytes, several of which calcify in 1:1 ratio to photosynthesis when incubated in Ca-supplemented lake water. Despite calcite supersaturation within the epilimnion, there is little authigenic calcification.
The Upper Floridan aquifer is the sole source of water supply for the city of Valdosta, Ga., and much of the surrounding area. Users and water-resources managers and developers are concerned about the quality of water in the aquifer. The water quality of a large part of the Upper Floridan aquifer in the Valdosta area is affected by direct recharge of water from the Withlacoochee River to the aquifer through sinkholes in the river channel north of Valdosta. Furthermore, because the Withlacoochee River receives little filtration as it recharges the aquifer in this area, ground water might be vulnerable to contamination as a result of human activities within the Withlacoochee River basin. Stream-discharge and water-quality data from 17 surface-water sites and ground-water-quality dam from 111 wells in the vicinity of Valdosta, Ga., are presented for the period 1961-93. Also, ground- water-level data for the Upper Floridan aquifer in the Valdosta area are presented in a series of potentiometric-surface maps. The water-resources data were collected mostly in Lowndes County in the vicinity of Valdosta and lesser amounts were collected in surrounding Berrien, Brooks, Cook, Echols, and Lanier Counties.
We isolated fulvic acids from two antarctic coastal ponds by means of preparative scale column chromatography with XAD-8 resin. Both ponds are on Ross Island. Pony Lake at Cape Royds has abundant phytoplankton populations, and Feather Pond at Cape Bird has a luxuriant benthic algal mat. Neither site has higher plants in the watershed. The dissolved organic carbon (DOC) concentration in Pony Lake was very high, but the percentage of DOC accounted for by fulvic acid was low, as has been observed for other lakes with algal-derived DOC sources. Fulvic acid from Pony Lake was more enriched in nitrogen than fulvic acid from Feather Pond, with a C:N atomic ratio of 13 in Pony Lake and a C:N ratio of 24 in Feather Pond. The [13C]NMR spectra for the coastal pond samples showed that the content of sp2-hybridized carbon atoms (aromatic or olefinic) was only 16.5% of the total spectral area for Pony Lake and only 20.1% for Feather Pond.
Debris flows occur in 529 tributaries of the Colorado River in Grand Canyon between Lees Ferry and Diamond Creek, Arizona (river miles 0 to 225). An episodic type of flash flood, debris flows transport poorly-sorted sediment ranging in size from clay to boulders into the Colorado River. Debris flows create and maintain debris fans and the hundreds of associated riffles and rapids that control the geomorphic framework of the Colorado River downstream from Glen Canyon Dam. Between 1984 and 1994, debris flows created 4 new rapids and enlarged 17 existing rapids and riffles.
Debris flows in Grand Canyon are initiated by slope failures that occur during intense rainfall. Three of these mechanisms of slope failure are documented. Failures in weathered bedrock, particularly in the Hermit Shale and Supai Group, have initiated many historic debris flows in Grand Canyon. A second mechanism, termed the fire-hose effect, occurs when runoff pours over cliffs onto unconsolidated colluvial wedges, triggering a failure. A third initiation mechanism occurs when intense precipitation causes failures in colluvium overlying bedrock. Multiple source areas and extreme topographic relief in Grand Canyon commonly result in combinations of these three initiation mechanisms. Interpretation of 1,107 historical photographs spanning 120 years, supplemented with aerial photography made between 1935 and 1994, yielded information on the frequency of debris flows in 168 of the 529 tributaries (32 percent) of the Colorado River in Grand Canyon. Of the 168 tributaries, 96 contain evidence of debris flows that have occurred since 1872, whereas 72 tributaries have not had a debris flow during the last century. The oldest debris flow we have documented in Grand Canyon occurred 5,400 years ago in an unnamed tributary at river mile 63.3-R. Our results indicate that the frequency of debris flows ranges from one every 10 to 15 years in certain eastern tributaries, to less than one per century in other drainage basins. On average, debris flows may recur approximately every 30 to 50 years in individual tributaries, although adjacent tributaries may have considerably different histories.
Peak discharges were estimated in 18 drainages for debris flows that occurred between 1939 and 1994. Typically, discharges range from about 100 to 300 cubic meters per second (m3/s). The largest debris flow in Grand Canyon during the last century, which occurred in Prospect Canyon in 1939, had a peak discharge of about 1,000 m3/s. Debris-flow deposits generally contain 15 to 30 percent sand-and-finer sediment; however, the variability of sand-and-finer sediment contained by recent debris flows is large. Reconstitution of debris-flow samples indicates a range in water content of 10 to 25 percent by weight;.
Before flow regulation of the Colorado River began, debris fans aggraded by debris flows were periodically reworked by large river floods that may have been as large as 11,000 m3/s.
Impoundment of the river by Glen Canyon Dam in 1963, and subsequent operation of the reservoir have reduced the magnitude of these floods. Flow releases from the dam since 1963 have only partly reworked recently-aggraded debris fans. Significant reworking of new debris-flow deposits now occurs only during river discharges higher than typical power plant releases, which currently range between 142 and 510 m3/s.
Tritium records were used to study hydrologic processes associated with irrigation and drainage in the Imperial Valley, a 2000-km2 agricultural area in the southeastern California desert. Tritium was analyzed in surface water, ground water, soil-pore water and drain water, and the results were compared to the historical record of tritium in the Colorado River. The Colorado River record was reconstructed using a simple reservoir model and precipitation data in the Colorado River Basin for the period prior to 1965, and from continuous measurements in the river for 1965-1988. This historical record is especially useful in the arid Imperial Valley because recent agricultural development has been entirely dependent on irrigation water diverted from the Colorado River and local recharge is negligible. Results indicate that it takes about 5 a for irrigation drainage to move through the soil to a depth of 2-3 m. Drainwaters have a wide range in tritium concentrations because of varying degrees of influence from ground-water intrusion, and from rapid percolation of irrigation through preferred pathways. The net result is that drainwater from about 40 fields had a range in tritium concentration similar to that of the Colorado River over the last 9 a (1980-1988), a period during which tritium concentration was declining about 15% annually in the river.
This paper describes the development and testing of the hypothesis that the long-term water balance is determined only by the local interaction of fluctuating water supply (precipitation) and demand (potential evapotranspiration), mediated by water storage in the soil. Adoption of this hypothesis, together with idealized representations of relevant input variabilities in time and space, yields a simple model of the water balance of a finite area having uniform climate. The partitioning of average annual precipitation into evapotranspiration and runoff depends on seven dimensionless numbers--the ratio of average annual potential evapotranspiration to average annual precipitation (index of dryness); the ratio of the spatial average plant-available water-holding capacity of the soil to the annual average precipitation amount; the mean number of precipitation events per year; the shape parameter of the gamma distribution describing spatial variability of storage capacity; and simple measures of the seasonality of mean precipitation intensity, storm arrival rate, and potential evapotrans- piration. The hypothesis is tested in an application of the model to the United States east of the Rocky Mountains, with no calibration. Study-area averages of runoff and evapotranspiration, based on observations, are 263 mm and 728 mm; the model yields corresponding estimates of 250 mm and 741 mm, and explains 88 percent of the geographical variance of observed runoff within the study region. The differences between modeled and observed runoff can be explained by uncertainties in the model inputs and in the observed runoff. In the humid (index of dryness less than 1) parts of the study area, the dominant factor producing runoff is the excess of annual precipitation over annual potential evapotranspiration, but runoff caused by variability of supply and demand over time is also significant; in the arid (index of dryness greater than 1) parts, all of the runoff is caused by variability of forcing over time. Contributions to model runoff attributable to small-scale spatial variability of storage capacity are insignificant throughout the study area. The consistency of the model with observational data is supportive of the supply- demand-storage hypothesis, which neglects infiltration-excess runoff and other finite- permeability effects on the soil water balance.
The effects of annual totals and seasonal variations of precipitation and potential evaporation on the annual water balance are explored. It is assumed that the only other factor of significance to annual water balance is a simple process of water storage, and that the relevant storage capacity is the plant-available water-holding capacity of the soil. Under the assumption that precipitation and potential evaporation vary sinusoidally through the year, it is possible to derive an analytic solution of the storage problem, and this yields an expression for the fraction of precipitation that evaporates (and the fraction that runs off) as a function of three dimensionless numbers: the ratio of annual potential evaporation to annual precipitation (index of dryness), an index of the seasonality of the difference between precipitation and potential evaporation, and the ratio of plant- available water-holding capacity to annual precipitation. The solution is applied to the area of the United States east of 105 W, using published information on precipitation, potential evaporation, and plant-available water-holding capacity as inputs, and using an independent analysis of observed river runoff for model evaluation. The model generates an areal mean annual runoff of only 187 mm, which is about 30 percent less than the observed runoff (263 mm). The discrepancy is suggestive of the importance of runoff-generating mechanisms neglected in the model. These include intraseasonal variability (storminess) of precipitation, spatial variability of storage capacity, and finite infiltration capacity of land.
The sensitivity of the global water cycle to the water-holding capacity of the plant-root zone of continental soils is estimated by simulations using a mathematical model of the general circulation of the atmosphere, with prescribed ocean-surface temperatures and prescribed cloud. With an increase of the globally constant storage capacity, evaporation from the continents rises and runoff falls, because a high storage capacity enhances the ability of the soil to store water from periods of excess for later evaporation during periods of shortage. In addition to this direct effect, atmospheric feedbacks associated with the resulting higher precipitation and lower potential evaporation drive further changes in evaporation and runoff. Most of the changes in evaporation and runoff occur in the tropics and in the northern middle-latitude rainbelts. Global evaporation from land increases by about 7 cm for each doubling of storage capacity in the range from less than 1 cm to almost 60 cm. Sensitivity is negligible for capacity above 60 cm. In the tropics and in the extratropics, the increased continental evaporation is split, in approximately equal parts, between increased continental precipitation and decreased convergence of atmospheric water vapor from ocean to land. In the tropics, this partitioning is strongly affected by induced circulation changes, which are themselves forced by changes in latent heating. The increased availability of water at the continental surfaces leads to an intensification of the Hadley circulation and a weakening of the monsoonal circulations. In the northern middle and high latitudes, the increased continental evaporation moistens the atmosphere. This change in humidity of the atmosphere is greater above the continents than above the oceans, and the resulting reduction in the sea-land humidity gradient causes a decreased onshore transport of water vapor by transient eddies. Results established here may have implications for certain problems in global hydrology and climate dynamics, including the effects of water resource development on global precipitation, climatic control of plant rooting characteristics, climatic effects of tropical deforestation, and climate-model errors induced by errors in land-surface hydrologic parameterizations.
Type-curve analysis of water-table aquifer pumping-test data has often resulted in values of specific yield that are unrealistically low when compared with values obtained by volume-balance calculations. It has been suggested that such values are the result of inadequate representation of drainage processes in the unsaturated zone. The commonly used analytical solution developed by Neuman for a homogeneous, water-table aquifer assumes that the drainage of pores in the zone above the water table due to lowering of the water table occurs instantaneously. Published pumping-test data from three relatively homogeneous, unconsolidated, granular aquifers with significantly different hydraulic conductivities are used to show that type-curve analysis based on the Neuman model will result in estimates of specific yield that agree with volume-balance calculations, provided that established procedures are followed. These involve the use of composite plots of drawdown observed at more than one location and inclusion of effects of partial penetration. Noninstantaneous drainage of pores in the unsaturated zone accounts for the finding that both type-curve analysis and volume-balance calculations yield values of specific yield that are slightly less than those obtained from laboratory column-drainage experiments. It may also account for a slight underestimation of vertical hydraulic conductivity as obtained by type-curve analysis.
A method for collecting suspended sediment samples has been developed that pumps a discharge-weighted volume of water from fixed depths at four to 40 locations across a river and separates the suspended sediment in the sample using a continuous-flow centrifuge. The efficacy of the method is evaluated by comparing the particle size distributions of sediment collected by the discharge-weighted pumping method with the particle size distributions of sediment collected by depth integration and separated by gravitational settling. The pumping method was found to undersample the suspended sand sized particles (> 63 mm) but to collect a representative sample of the suspended silt and clay sized particles (< 63 mm). The centrifuge separated the silt and clay sized particles (< 63 mm) into three fractions. Based on the average results of processing 17 samples from the Mississippi River and several of its large tributaries in 1990, about 10% of the silt and clay sized material was trapped in a centrifuge bowl-bottom sealing unit containing the nozzle and consisted of mostly medium and coarse silt from 16 to 63 mm. About 74% was retained on a Teflon liner in the centrifuge bowl and consisted of sizes from 0.1 to 63 mm. About 9% was discharged from the centrifuge in the effluent and was finer than 0.1 mu m. About 7% was lost during the processes of removing the wet sediment fractions from the centrifuge, drying and weighing. The success of the discharge-weighted pumping method depends on how homogeneously the silt and clay sized particles (< 63 mm) are distributed in the vertical direction in the river. The degree of homogeneity depends on the composition and degree of aggregation of the suspended sediment particles.
One hundred samples were collected from the surface of the Upper Fremont Glacier at equally spaced intervals defined by an 8,100 m2 snow grid to assess the significance of lateral variability in major-ion concentrations and d18O values. For the major ions, the largest concentration range within the snow grid was sodium (0.5056 mg/l) and the smallest concentration range was sulfate (0.125 mg/l). d18O values showed a range of 7.45 per mil. Comparison of the observed variability of each chemical constituent to the variability expected by measurement error indicated substantial lateral variability within the surface-snow layer. Results of the nested ANOVA indicate most of the variance for every constituent is in the values grouped at the two smaller geographic scales (between 506 m2 and within 506 m2 sections). Calcium and sodium concentrations and d18O values displayed the largest amount of variance at the largest geographic scale (between 2,025 m2 sections) within the grid and ranged from 14 to 26 per cent of the total variance. The variance data from the snow grid were used to develop equations to evaluate the significance of both positive and negative concentration/value peaks of nitrate and d18O with depth, in a 160 m ice core. Solving the equations indicates that both the nitrate and d18O ice-core profiles have concentration/value trends that exceed the limits expected from lateral variability. Values of d18O in the section from 110-150 m below the surface consistently vary outside the expected limits and possibly represents cooler temperatures during the Little Ice Age from about 1810 to 1725 A.D.
The feasibility and practicality of using the steady-state centrifuge method to determine recharge rates were studied. Core samples were obtained from a part of the unsaturated zone where the matric potential was known or estimated to be uniform. Unsaturated hydraulic conductivity values were then obtained at the in-situ water content, indicating the long-term average recharge rate at that point. Results from a site in the San Joaquin valley, Calif., showed that a better knowledge of matric pressure profiles was needed before a recharge rate could be determined. Fine-textured cores from a site in Washington state showed the need for new apparatus and procedures to ensure minimal compaction of samples.
Several species of flagellates (genera Bodo, Cercomonas, Cryptaulax, Cyathomonas, Goniomonas, Spumella) have been identified in cultures from a plume of organic contamination (treated sewage effluent) within an aquifer on Cape Cod, Massachusetts. Amoebae and numerous unidentifiable 2- to 3- mu m flagellates have also been observed. As a rule, flagellates were associated with solid surfaces, or were capable of temporary surface attachment, corroborating earlier observations from in situ and column transport experiments suggesting that protists in the Massachusetts aquifer have a high propensity for association with sediment grain surfaces. Based on the fact that cultures from the uncontaminated part of the aquifer yielded only a few species of protists, it is hypothesized that the greater abundance and variety of food sources in the contaminant plume is capable of supporting a greater number of protistan species.
Several species of flagellates (genera Bodo, Cercomonas, Cryptaulax, Cyathomonas, Goniomonas, Spumella) have been identified in cultures from a plume of organic contamination (treated sewage effluent) within an aquifer on Cape Cod, Massachusetts. Amoebae and numerous unidentifiable 2- to 3- mu m flagellates have also been observed. As a rule, flagellates were associated with solid surfaces, or were capable of temporary surface attachment, corroborating earlier observations from in situ and column transport experiments suggesting that protists in the Massachusetts aquifer have a high propensity for association with sediment grain surfaces. Based on the fact that cultures from the uncontaminated part of the aquifer yielded only a few species of protists, it is hypothesized that the greater abundance and variety of food sources in the contaminant plume is capable of supporting a greater number of protistan species.
Average-annual volumes of runoff, evapotranspiration, channel loss, upland (interchannel) recharge, and total recharge were estimated for watersheds of 53 channel sites in the Amargosa River basin above Shoshone, California. Estimates were based on a water-balance approach combining field techniques for determining streamflow with distributed-parameter simulation models to calculate transmission losses of ephemeral streamflow and upland recharge resulting from high-magnitude, low-frequency precipitation events. Application of the water-balance models to the Amargosa River basin, Nevada and California, including part of the Nevada Test Site, suggests that about 20.5 million cubic meters of water recharges the ground-water reservoir above Shoshone annually. About 1.6 percent of precipitation becomes recharge basinwide. About 90 percent of the recharge is by transmission loss in channels, and the remainder occurs when infrequent storms yield sufficient precipitation that soil water percolates beyond the rooting zone and reaches the zone of saturation from interchannel areas. Highest rates of recharge are in headwaters of the Amargosa River and Fortymile Wash; the least recharge occurs in areas of relatively low precipitation in the lowermost Amargosa River watershed.
Results of accelerated erosion on certain constructed surfaces in southeastern Arizona appear similar to those described by Bryan (1940) as gully gravure. Twenty cross-section excavations in eight rills incised into silt-rich lacustrine and fluvial deposits reveal partial filling of the rills by debris derived from overlying fluvial sand, gravel, and cobbles. Interstices of the coarse material gradually fill with fine-grained erosion products, decreasing permeability of the fill and deflecting subsequent runoff to the margins of the fill. Rills and rill fillings thus increase in width with time, and complete veneering of the surface by coarse debris ultimately may occur. Through incision, filling, lateral planation, and armoring, channels of the dissected surface heal and the new hillslope approaches an equilibrium condition. Natural hillslopes in the area with similar geologic conditions have inclinations of 16 degrees to 22 degrees , have generally unbroken veneers of coarse debris, and appear subject to the same erosional processes identified at constructed hillslopes. Field measurements and the revised universal soil loss equation (RUSLE) were used to estimate soil loss on natural and constructed hillslopes. Results suggest that erosion may be almost three orders of magnitude greater on steep, nonveneered, nonvegetated constructed surfaces than on natural hillslopes. Attributes of stable natural hillslopes provide criteria for the design of stable constructed hillslopes.
The most extensive data base for fractured bedrock aquifers consists of drilling reports maintained by various state agencies. We investigated the accuracy and reliability of such reports by comparing a representative set of reports for nine wells drilled by conventional air percussion methods in granite with a suite of geophysical logs for the same wells designed to identify the depths of fractures intersecting the well bore which may have produced water during aquifer tests. Production estimates reported by the driller ranged from less than 1 to almost 10 gallons per minute. The moderate drawdowns maintained during subsequent production tests were associated with approximately the same flows as those measured when boreholes were dewatered during air percussion drilling. We believe the estimates of production during drilling and drawdown tests were similar because partial fracture zone dewatering during drilling prevented larger inflows otherwise expected from the steeper drawdowns during drilling. The fractures and fracture zones indicated on the drilling report and the amounts of water produced by these fractures during drilling generally agree with those identified from the geophysical log analysis. Most water production occurred from two fractured and weathered zones which are separated by an interval of unweathered granite. The fractures identified in the drilling reports show various depth discrepancies in comparison to the geophysical logs, which are subject to much better depth control. However, the depths of the fractures associated with water production on the drilling report are comparable to the depths of the fractures shown to be the source of water inflow in the geophysical log analysis. Other differences in the relative contribution of flow from fracture zones may be attributed to the differences between the hydraulic conditions during drilling, which represent large, prolonged drawdowns, and pumping tests, which consisted of smaller drawdowns maintained over shorter periods. We conclude that drilling reports filed by experienced well drillers contain useful information about the depth, thickness, degree of weathering, and production capacity of fracture zones supplying typical domestic water wells. The accuracy of this information could be improved if relatively simple and inexpensive geophysical well logs such as gamma, caliper, and normal resistivity logs were routinely run in conjunction with bedrock drilling projects.
A suite of geophysical logs designed to identify and characterize fractures and water production in fractures was run in six bedrock boreholes at a ground-water contamination site near the towns of Millville and Uxbridge in south-central Massachusetts. The geophysical logs used in this study included conventional gamma, single-point resistance, borehole fluid resistivity, caliper, spontaneous potential, and temperature; and the borehole televiewer and heat-pulse flowmeter, which are not usually used to log bedrock water-supply wells. Downward flow under ambient hydraulic-head conditions was measured in three of the boreholes at the site, and the profile of fluid column resistivity inferred from the logs indicated downward flow in all six boreholes. Steady injection tests at about 1.0 gallon per minute were used to identify fractures capable of conducting flow under test conditions. Sixteen of 157 fractures identified on the televiewer logs and interpreted as permeable fractures in the data analysis were determined to conduct flow under ambient hydraulic-head conditions or during injection. Hydraulic-head monitoring in the bedrock boreholes indicated a consistent head difference between the upper and lower parts of the boreholes. This naturally occurring hydraulic-head condition may account, in part, for the transport of contaminants from the overlying soil into the bedrock aquifer. The downward flow may also account for the decrease in contaminant concentrations found in some boreholes after routine use of the boreholes as water-supply wells was discontinued.
Hydraulic fracture-stimulation procedures typical of those provided by contractors in the water-well industry were applied to two boreholes in basaltic and gabbroic rocks near Grand Portage, Minnesota.These boreholes were considered incapable of supplying adequate ground water for even a single household although geophysical logs showed both boreholes were intersected by many apparently permeable fractures. Tests made before and after stimulation indicated that the two boreholes would produce about 0.05 and 0.25 gallon per minute before stimulation, and about 1.5 and 1.2 gallons per minute after stimulation. These increases would be enough to obtain adequate domestic water supplies from the two boreholes but would not furnish enough water for more than a single household from either borehole. Profiles of high-resolution flow made during pumping after stimulation indicated that the stimulation enhanced previously small inflows or stimulated new inflow from seven fractures or fracture zones in one borehole and from six fractures or fracture zones in the other.Geophysical logs obtained after stimulation showed no specific changes in these 13 fractures that could be related to stimulation other than the increases in flow indicated by the flowmeter logs. The results indicate that the stimulation has increased inflow to the two boreholes by improving the connectivity of favorably orientated fractures with larger scale flow zones in the surrounding rocks. Three of four possible diagnostics related to measured pressure and flow during the stimulation treatments were weakly correlated with the increases in production associated with each treatment interval. These correlations are not statistically significant on the basis of the limited sample of 16 treatment intervals in two boreholes, but the results indicate that significant correlations might be established from a much larger data set.
Sixteen years of annual surveys reveal how Powder River responds to varying discharges. During 1978, the second largest recorded daily mean discharge occurred. Cutbank migration, bed degradation, net bank erosion, and overbank deposition all contributed to increase the channel area at 12 cross sections by an average of 62%. During the ensuing years, the channel area decreased as sediment was stored in low-lying benches adjacent to the active bed of the channel. The survey data indicate that the balance between bank erosion and deposition varies with discharge. In years when the annual maximum daily mean discharge is <60 m3/s (a flow of 60 m3/s has a recurrence interval of approximately 1.1 yr), bank erosion and deposition are approximately equal. In years when the annual maximum daily mean discharge is between 60 and approximately 150 m3/s (a discharge of 150 m3/s has a recurrence interval of approximately 2.7 yr), bank deposition exceeds bank erosion, and the channel contracts, often by developing benches. In years with higher discharges, the channel expands through net bank erosion. These results demonstrate that the channel of Powder River is influenced by a wide variety of formative discharges. Powder River's recent history of expansion and contraction and the development of prominent benches cannot be explained by equilibrium models based on a single, channel-forming discharge.
NETPATH is an interactive Fortran 77 computer program used to interpret net geochemical mass-balance reactions between an initial and final water along a hydrologic flow path. Alternatively, NETPATH computes the mixing proportions of two to five initial waters and net geochemical reactions that can account for the observed composition of a final water. The program utilizes previously defined chemical and isotopic data for waters from a hydrochemical system. For a set of mineral and (or) gas phases hypothesized to be the reactive phases in the system, NETPATH calculates the mass transfers in every possible combination of the selected phases that accounts for the observed changes in the selected chemical and (or) isotopic compositions observed along the flow path. The calculations are of use in interpreting geochemical reactions, mixing proportions, evaporation and (or) dilution of waters, and mineral mass transfer in the chemical and isotopic evolution of natural and environmental waters. Rayleigh distillation calculations are applied to each mass-balance model that satisfies the constraints to predict carbon, sulfur, nitrogen, and strontium isotopic compositions at the end point, including radiocarbon dating. DB is an interactive Fortran 77 computer program used to enter analytical data into NETPATH, and calculate the distribution of species in aqueous solution. This report describes the types of problems that can be solved, the methods used to solve problems, and the features available in the program to facilitate these solutions. Examples are presented to demonstrate most of the applications and features of NETPATH. The codes DB and NETPATH can be executed in the UNIX or DOS1 environment. This report replaces U.S. Geological Survey Water-Resources Investigations Report 91-4078, by Plummer and others, which described the original release of NETPATH, version 1.0 (dated December, 1991), and documents revisions and enhancements that are included in version 2.0.
1 The use of trade, brand or product names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.
The distribution and transport of selected hydrophobic halogenated organic compounds on suspended sediment from the lower Mississippi River were determined using discharge-weighted sampling with concurrent discharge measurements. Trends in compound concentration from upstream to downstream and the effects of selected tributaries were determined. The compounds identified on the suspended sediment include pentachlorobenzene, hexachlorobenzene, pentachloroanisole, dacthal, chlordane (trans-), nonachlor (trans-), chlorthalonil, and penta-, hexa-, hepta- and octachlorobiphenyls. Loads of most of the compounds increased from upstream to downstream on the main stem of the Mississippi River. Of the tributaries studied, the Ohio River had the most significant effect on the loads.
Transient one-dimensional fluxes of soil water (liquid and vapor) and heat in response to 1 year of atmospheric forcing were simulated numerically for a site in the Chihuahuan Desert of Texas. The model was initialized and evaluated using the monitoring data presented in a companion paper (Scanlon, this issue). Soil hydraulic and thermal properties were estimated a priori from a combination of laboratory measurements, models, and other published information. In the first simulation, the main drying curves were used to describe soil water retention, and hysteresis was ignored. Remarkable consistency was found between computed and measured water potentials and temperatures. Attenuation and phase shift of the seasonal cycle of water potentials below the shallow subsurface active zone (0-0- 0.3-m depth) were similar to those of temperatures, suggesting that water potential fluctuations were driven primarily by temperature changes. Water fluxes in the upper 0.3 m of soil were dominated by downward and upward liquid fluxes that resulted from infiltration of rain and subsequent evaporation from the surface. Upward flux was vapor dominated only in the top several millimeters of the soil during periods of evaporation. Below a depth of 0.3 m, water fluxes varied slowly and were dominated by downward thermal vapor flux that decreased with depth, causing a net accumulation of water. In a second simulation, nonhysteretic water retention was instead described by the estimated main wetting curves; the resulting differences in fluxes were attributed to lower initial water contents (given fixed initial water potential) and unsaturated hydraulic conductivities that were lower than they were in the first simulation. Below a depth of 0.3 m, the thermal vapor fluxes dominated and were similar to those in the first simulation. Two other simulations were performed, differing from the first only in the prescription of different (wetter) initial water potentials. These three simulations yielded identical solutions in the upper 0.2 m of soil after infiltration of summer rain; however, the variuos initial water potentials were preserved throughout the year at depths greater than 0.2 m. Comparison of all four simulations showed that the predominantly upward liquid fluxes below a depth of 0.2 m were very sensitive to the differences in water retention functions and initial water potentials among simulations, because these factors strongly affected hydraulic conductivities. Comparison of numerical modeling results with chemical tracer data showed that values of downward vapor flux below the surface evaporation zone were of the same order of magnitude as those previously estimated by analysis of depth distributions of bomb 3H (volatile) and 36Cl (nonvolatile).
Ground water is the major source of freshwater supply in southern Cape May County, New Jersey. Withdrawals from the shallow aquifers provide about 50 percent of the freshwater used in the county. These withdrawals increased by 66 percent from 1956 to 1986, from 4.22 to 7.00 million gallons per day. Development of the shallow aquifers has modified the direction of ground-water flow, resulting in the contamination of many wells with saltwater. Prior to the development of the aquifers, ground water beneath the center of Cape May peninsula moved upward from the Cohansey aquifer to the estuarine sand aquifer and horizontally to the Delaware Bay and Atlantic Ocean, thus maintaining a substantial reservoir of fresh ground water beneath the peninsula. Water levels in the unconfined Holly Beach water-bearing zone did not change significantly from 1958 to 1987, but withdrawals of up to 7.00 million gallons per day caused heads in the confined Cohansey and estuarine sand aquifers to decline to as much as 24 feet below sea level, allowing saltwater to intrude into these aquifers. Chloride concentrations as high as 850 milligrams per liter have been measured in wells used for freshwater supply. A comparison between lines of equal chloride concentration in 1958 and 1984-87 indicates that saltwater has intruded into the estuarine sand and Cohansey aquifers and is migrating landward in the Cohansey aquifer in the southern and western parts of the peninsula.
Addition of hydrogen or formate significantly enhanced the rate of consumption of nitrate in slurried core samples obtained from an active zone of denitrification in a nitrate-contaminated sand and gravel aquifer (Cape Cod, Mass.). Nine strains of hydrogen-oxidizing denitrifying bacteria were subsequently isolated from the aquifer. Eight of the strains grew autotrophically on hydrogen with either oxygen or nitrate as the electron acceptor. One strain grew mixotrophically. All of the isolates were capable of heterotrophic growth, but none were similar to Paracoccus denitrificans, a well-characterized hydrogen-oxidizing denitrifier. The kinetics for hydrogen uptake during denitrification were determined for each isolate with substrate depletion progress curves. These results suggest that these organisms may have significant potential for in situ bioremediation of nitrate contamination in ground water.
In 1990, the State of Hawaii proposed the Hawaii Geothermal Project for the development of as much as 500 MW of electric power from the geothermal system in the East Rift Zone of Kilauea Volcano. This report uses data from 31 wells and 8 springs to describe the properties of the ground-water system in and adjacent to the East Rift Zone. Potential effects of this project on ground-water resources are also discussed. Data show differences in ground-water chemistry and heads within the study area that appear to be related to mixing of waters of different origins and ground-water impoundment by volcanic dikes. East of Pahoa, the ground-water system within the rift is highly transmissive and receives abundant recharge from precipitation; therefore, the pumping of freshwater to support geothermal development in that part of the rift zone would have a minimal effect on ground-water levels. To the southwest of Pahoa, dike impoundment reduces the transmissivity of the ground-water system to such an extent that wells might not be capable of supplying sufficient fresh water to support geothermal operations. Contamination of ground-water resources by accidental release of geothermal fluids into shallow aquifers is possible because of corrosive conditions in the geothermal wells, potential well blowouts, and high ground-water velocities in parts of the region. Hydrologic monitoring of water level, temperature, and chemistry in observation wells should continue throughout development of geothermal resources for the Hawaii Geothermal Project for early detection of leakage and migration of geothermal fluids within the groundwater system.
Measurements or estimates of heat loss were made at eight steam-heated thermal areas and one conduc- tively heated thermal area in Lassen Volcanic National Park during the period 1986-93. Total heat discharge at the steam-heated areas is assumed proportional to the rate of steam upflow from underlying reservoirs. The dominant mode of heat loss differs among the areas studied; at Bumpass Hell and Boiling Springs Lake evaporation from water surfaces dominates, whereas at Devils Kitchen and Little Hot Springs Valley most of the heat is lost by advection in streams, Heat loss from fumaroles, which discharge at temperatures of 93 degrees Celsius-157 degrees Celsius depending on the area, accounts for less than 30 percent of the total heat loss for all but the smallest thermal areas. Estimates of total heat loss from the eight steam-heated areas range from about 30 megawatts at Bumpass Hell and Boiling Springs Lake to less than 2 megawatts at Terminal Geyser, Pilot Pinnacle and Lassen Peak, and total about 120 megawatts. The corresponding rate of steam upflow required to supply this total heat loss is approximately 40 kg/s, with about half providing heat input to the five thermal areas situated on the flanks of Lassen Peak and the remainder supplying heat to thermal areas situated to the southeast of Lassen Peak along or near Hot Springs Creek. For the most part, heat-loss measurements were made during late summer and fall when stream- flows were relatively low. At several thermal areas, the rate of streamflow and assocaited rate of advective heat loss are greatest in the spring and early summer, relfecting depletion of stored heat by infiltrating cold water. The effect of such seasonal variations, along with errors in our heat- loss determinations combine to yield an uncertainty of approximately +20 percent in our estimates of total heat loss and steam upflow at all the Park's thermal areas.
Phytoplankton were collected over five austral summers (1987-1988 through 1991-1992) to examine seasonal and annual fluctuations in species composition and biovolume in Lake Fryxell, a perennially ice-covered lake located in the Dry Valleys of South Victoria Land, Antarctica. Lake Fryxell has perennial gradients of salinity, dissolved oxygen and nutrients. We found that algal species diversity was low (56 taxa were collected), confirming the results of previous short-term studies. The phytoplankton consisted primarily of cryptophyte and chlorophyte flagellates, and filamentous cyanobacteria. The presence of filamentous cyanobacteria, which have not been reported as abundant in this lake by previous workers, may represent a significant ecological change. Each austral summer, one dominant species contributed > 70% of the total biovolume; Chroomonas lacustris was dominant in 1987-1988, while Cryptomonas sp. dominated the phytoplankton in the remaining 4 years. No species succession occurred during the austral summer. Some common taxa were vertically stratified (Oscillatoria limnetica, Phormidium angustissimum, Pyramimonas sp., Oscillatoria sp.), while others showed no distinct vertical stratification (Chlamydomonas subcaudata, Cryptomonas sp.). The stratification of the phytoplankton reflects the gradients of nutrients and light, and the stability of the water column.
Acidic water from a copper-mining area has contaminated an alluvial aquifer and stream near Globe, Arizona. The most contaminated groundwater has a pH of 3.3, and contains about 100 mmol/l SO4, 50 mmol/l Fe, 11 mmol/L Al and 3 mmol/L Cu. Reactions between alluvium and acidic groundwater were first evaluated in laboratory column experiments. A geochemical model was developed and used in the equilibrium speciation program, MINTEQA2, to simulate breakthrough curves for different constituents from the column. The geochemical model was then used to simulate the measured changes in concentration of aqueous constituents along a flow path in the aquifer. The pH was predominantly controlled by reaction with carbonate minerals. Where carbonates had been dissolved, adsorption of H+ by iron oxides was used to simulate pH. Acidic groundwater contained little or no dissolved oxygen, and most aqueous Fe was present as Fe(II). In the anoxic core of the plume, Fe(II) was oxidized by MnO2 to Fe(III), which then precipitated as Fe(OH)3. Attenuation of aqueous Cu, Co, Mn, Ni and Zn was a function of pH and could be quantitatively modeled with the diffuse-layer, surface complexation model in MINTEQA2. Aluminum precipitated as amorphous Al(OH)3 at pH >4.7 and as AlOHSO4 at pH <4.7. Aqueous Ca and SO4 were close to equilibrium with gypsum. After the alluvium in the column had reached equilibrium with acidic groundwater, uncontaminated groundwater was eluted through the column to evaluate the effect of reactants on groundwater remediation. The concentration of Fe, Mn, Cu, Co, Ni and Zn rapidly decreased to the detection limits within a few pore volumes. All of the gypsum that had precipitated initially redissolved, resulting in elevated Ca and SO4 concentrations for about 5 pore volumes. Aluminum and pH exhibited the most potential for continued adverse effects on groundwater quality. As H+ desorbed from Fe(OH)3, pH remained below 4.5 for more than 20 pore volumes, resulting in dissolution of AlOHSO4 and elevated aqueous Al.
A PCR primer set and an internal probe that are specific for Pseudomonas sp. strain B13, a 3-chlorobenzoate-metabolizing strain, were developed. Using this primer set and probe, we were able to detect Pseudomonas sp. strain B13 DNA sequences in DNA extracted from aquifer samples 14.5 months after Pseudomonas sp. strain B13 had been injected into a sand and gravel aquifer. This primer set and probe were also used to analyze isolates from 3-chlorobenzoate enrichments of the aquifer samples by Southern blot analysis. Hybridization of Southern blots with the Pseudomonas sp. strain B13-specific probe and a catabolic probe in conjunction with restriction fragment length polymorphism (RFLP) analysis of ribosome genes was used to determine that viable Pseudomonas sp. strain B13 persisted in this environment. We isolated a new 3-chlorobenzoate-degrading strain from one of these enrichment cultures. The B13-specific probe does not hybridize to DNA from this isolate. The new strain could be the result of gene exchange between Pseudomonas sp. strain B13 and an indigenous bacterium. This speculation is based on an RFLP pattern of ribosome genes that differs from that of Pseudomonas sp. strain B13, the fact that identically sized restriction fragments hybridized to the catabolic gene probe, and the absence of any enrichable 3-chlorobenzoate-degrading strains in the aquifer prior to inoculation.
This study was undertaken to determine the effects of sewage-sludge disposal at the Lowry sewage-sludge-disposal area, near Denver, Colorado, on ground- and surface-water quality, to determine the fate of nitrates from sludge leachate, and to determine the source areas of leachate and the potential for additional leaching from the disposal area. Sewage-sludge disposal began in 1969. Two methods were used to apply the sludge: burial and plowing. Also, the sludge was applied both in liquid and cake forms. Data in this report represent the chemical composition of soil and streambed sediment from seven soil- and four streambed-sampling sites in 1986, chemical and bacterial composition of ground water from 28 wells from 1981 to 1987, and surface-water runoff from seven water-sampling sites from 1984 to 1987. Ground water samples were obtained from alluvial and bedrock aquifers. Samples of soil, streambed sediment, ground water and surface water were obtained for onsite measurement and chemical analysis. Measurements included determination of nitrogen compounds and major cations and anions, fecal-coliform and -streptococcus bacteria, specific conductance, and pH. Thirteen wells in the alluvial aquifer in Region 3 of the study area contain water that was probably affected by sewage-sludge leachate. The plots of concentration of nitrate with time show seasonal trends and trends caused by precipitation. In addition to yearly fluctuation, there were noticeable increases in ground-water concentrations of nitrate that coincided with increased precipitation. After 3 years of annual ground-water-quality monitoring and 4 years of a quarterly sampling program, it has been determined that leachate from the sewage-sludge-disposal area caused increased nitrite plus nitrate (as nitrogen) concentration in the alluvial ground water at the site. Soil analyses from the disposal area indicate that organic nitrogen was the dominant form of nitrogen in the soil.
Sediment (0.5 mm-2.0 mm grain size) was incubated in nylon bags (200 mu m mesh) below the water table in the channel and in two transects of shallow wells perpendicular to the banks (to 18 m) of a third-order stream during August, 1987. One transect of wells drained steep old-growth forest, and the other a steep 23 year-old clear-cut partially regenerated in alder. At approximately 6-week intervals between October, 1987, and June, 1988, bags were retrieved. Total exchangeable ammonium was determined on sediment, and dissolved oxygen, nitrate and ammonium were determined in stream and well water. Exchangeable ammonium ranged from 10meq/100 g of sediment in the stream where nitrification potential and subsurface exchange with stream water were high, to 115meq/100 g sediment 18 m inland where channel water-groundwater mixing and nitrification potential were both low. Sorbed ammonium was highest during summer/autumn base flow and lowest during winter storm flow. Both channel and well water contained measurable dissolved oxygen at all times. Ammonium concentration was typically < 10 mg-N/L in channel water, increased with distance inland, but did not exceed 365 mg-N/L at any site. Nitrate concentration was typically higher in well water than channel water. Nitrate levels increased dramatically in wells at the base of the clear-cut following the onset of autumn rains. The results indicate a potential for temporary storage of ammonium on riparian sediments which may influence biotic nitrogen cycling, and alter the timing and form of dissolved inorganic nitrogen transport from the watershed.
During the 1990-91 and 1991-92 field seasons in Antarctica, streamflow, water-temperature, and specific-conductance data were collected on the major streams draining into Lake Fryxell. Lake Fryxell is a permanently ice-covered, closed-basin lake with 13 tributary streams. Continuous streamflow data were collected at eight sites, and periodic streamflow measurements were made at three sites. Continuous water-temperature and specific- conductance data were collected at seven sites, and periodic water-temperature and specific-conductance data were collected at all sites. Streamflow for all streams measured ranged from 0 to 0.651 cubic meter per second. Water temperatures for all streams measured ranged from 0 to 14.3 degrees Celsius. Specific conductance for all streams measured ranged from 11 to 491 microsiemens per centimeter at 25 degrees Celsius. It is probable that stream- flow in the Lake Fryxell Basin during 1990-92 was greater than average. Examination of the 22-year streamflow record in the Onyx River in the Wright Valley revealed that in 1990 streamflow began earlier than for any previous year recorded and that the peak streamflow of record was exceeded. Similar high-flow conditions occurred during the 1991-92 field season. Thus, the data collected on streams draining into Lake Fryxell during 1990-92 are representative of greater than average stream- flow conditions.
Regional geohydrologic characterization of the flow field in the coastal stratified basalt aquifer of the Pearl Harbor area in southern Oahu, Hawaii, is provided by a synthesis of geochemical and isotopic information, collected in vertical profiles, and numerical simulation of the variable-density ground-water flow. The uppermost water layer, 75 m to 125 m thick, consists of water recharged from local rainfall and irrigation over the past few decades. Below this is the core of the freshwater lens, 100 m to 150 m thick, containing waters with an apparent carbon-14 age of 1800 years. The freshwater lens floats on a third saltwater layer that likely extends to the bottom of the aquifer. The apparent carbon-14 age of the saltwater is between 6000 years and 9000 years, and the difference in ages between an inland well and a coastal well suggests that before aquifer development began in the 1880s, saltwater flowed inland at a velocity of about 2 m/yr. Assuming a constant lateral velocity in the saltwater body, the saltwater recharge area may thus be estimated to be 11 km to 24 km from the observation wells, in an area located between 1 km and 14 km offshore of the southern Oahu coast. Post-bomb carbon-14 and tritium data indicate a residence time of water within the freshwater lens of no more than a few tens of years. If total recharge estimates assumed here are correct, the 1800-year apparent age of this water can only be explained by long residence time in recharge area compartments the central plateau of Oahu and the dike zone in the Koolau Mountains before entering the lens, although the storage volume is not sufficient to account for the entire delay. In addition, some of the great apparent freshwater age may be accounted for by a component of old organic carbon introduced in the ground-water recharge area. The simple geochemical reactions in this aquifer system allow clear interpretation of water chemistry and isotopic data. The chemical and stable isotope composition of all samples is well- explained by simple mixing of the three types of water. The major reaction in the saltwater is sodium-calcium exchange, which increases calcium concentration over that of seawater, but which has negligible effect on carbon-14 dating. There is no evidence of calcite dissolution affecting the freshwater. Extrapolated aquifer saltwater carbon-13 content is somewhat lighter than oceanic values, probably indicative of oxidation of organic carbon. Assuming this organic carbon was devoid of carbon-14, measured carbon-14 values for saltwater must be adjusted upward by at most a factor of 1.24. Thus, carbon-14 values with or without adjustment give similar absolute ages and travel times of water flow between measurement points. Unfortunately, a number of samples collected show a high degree of scatter suggesting the possibility of contamination by modern carbon-14 during handling or analysis, reducing the quantity of vertical age data available from profiling. The characterization of both the freshwater and saltwater flow field obtained from geochemical analysis is consistent with regional hydrologic behavior of the Pearl Harbor area represented by the cross-sectional variable-density flow and solute transport model of Voss and Souza (1993). This model was based only on analysis of hydraulic data and vertical salinity profiles through the freshwater lens and saltwater transition zone. Thus, the simply-structured numerical model, which included an estimate of regional effective porosity for flow (0.04) that could not be verified on the basis of data existing at that time, can explain all currently-available geochemical and hydraulic field information. This may be the first analysis in which it was possible to corroborate ground-water model-calculated density-driven saltwater velocities in a coastal aquifer with flow velocity determined from chemical and isotopic field data.
Episodic late Quaternary flooding is recorded by bouldery deposits and slackwater sediments along Arthurs Rock Gulch, an ephemeral stream west of Fort Collins, Colorado. Flood deposits consist of individual granodiorite and pegmatite boulders, boulder bars, and coarse overbank sediment that rest on erosional terrace segments along the channel. We identified evidence for at least five floods in the lower two thirds of the 1.84 km2 drainage basin. Flood deposits are differentiated by their position above the active channel, weathering characteristics, degree of boulder burial by colluvium, amount of lichen cover, and position with respect to terrace and colluvial deposits. Age estimates for the flood deposits are based on radiocarbon dating, tree-ring analyses, and relative-age criteria from four sites in the basin. At least two floods occurred in the last 300 years; a third flood is at least 5000 years old, but likely younger than 10,000 yr BP; and the two oldest floods occurred at least 40,000 years BP.
The Leviathan and Bryant Creek (LBC) drainage system, on the border of California and Nevada, flows through overburden and waste from a former open-pit sulfur mine. The drainage contains acid mine waters with high concentrations of several trace elements, including Cu, Zn, and As, derived from oxidative weathering of sulfides in the wastes and altered bedrock. In June and October, 1982, the mainstream and tributary flows of the LBC drainage were measured and the waters sampled and analyzed for major and trace elements. Empirical mass flow and metal attenuation rates were determined, and chemical models were used to examine mechanisms of trace element removal during downstream transport. In June the flow in the mainstream was 2-5 times greater than in October, and with higher contributions from the acid mine effluent. Seasonal variations in the attenuation rates of Cu, Zn, and As were directly related to this increase in acid mine-effluent production, and to the consequent increase in the acidity of the mainstream drainage. Although As concentrations immediately below the mine site were high in June, As was readily removed from solution by adsorption onto an assumed iron(III) oxyhydroxysulfate precipitate, whereas Cu was incompletely adsorbed and Zn remained unaffected by adsorption. In October, the smaller discharge of acidic LBC drainage waters were more readily diluted (and neutralized) by other regional tributaries. Arsenic concentrations remained low, and both Cu and Zn were removed from solution by adsorption onto iron(III) oxyhydroxysulfate in the lower regions of the LBC drainage system.
Dense nonaqueous phase liquids (DNAPLS) are important pollutants because of their widespread use as chemical and industrial solvents. An example of the pollution caused by the discharge of DNAPLs is found at the Picatinny Arsenal, New Jersey, where trichloroethylene (TCE) has been discharged directly into the unsaturated zone. This discharge has resulted in the formation of a plume of TCE-contaminated water in the aquifer downgradient of the discharge. A zone of dark-colored groundwater containing a high dissolved organic C content has been found near the point of discharge of the TCE. The colored-water plume extends from the point of discharge at least 30 m (100 feet) downgradient. Fulvic acids isolated from the colored-waters plume, from water from a background well that has not been affected by the discharge of chlorinated solvents, and from soil pore water collected in a lysimeter installed at an uncontaminated site upgradient of the study area have been compared. Nuclear magnetic resonance spectra of the fulvic acids from the colored waters and from the lysimeter are very similar, but are markedly different from the nuclear magnetic resonance spectrum of the fulvic acid from the background well. The three-dimensional fluorescence spectrum and the DOC fractionation profile of the colored groundwater and the soil pore water are very similar to each other, but quite different from those of the background water. It is proposed from these observations that this colored water is soil pore water that has been displaced by a separate DNAPL liquid phase downward to the saturated zone.
Recent societal shift in emphasis from water supply to aquifer contamination requires supplementing the classic regional approach to recharge of the Ogallala Formation initiated by C.V. Theis. Chemical techniques and methods are developed to define the spatial-temporal aspects of recharge required of the new paradigm. Contrary to anecdotal and published speculation, chemical and isotopic data on water from the saturated and unsaturated zone suggest that playa-lake floors are a major source of ground-water recharge to the Ogallala Formation underlying the Southern High Plains. Evaluation of tritium in the unsaturated zone beneath a representative playa- basin floor suggests that piston-flow recharge is approximately 77 mm/y (millimeters per year). Additional analysis suggest approximately half (4 to 5 mm/y) of the annual recharge (9 to 10 mm/y) to the Ogallala occurs through the playa floors that occupy approximately 6 percent of the area. Runoff to the lake floor at the test site has averaged 24 mm/y over the last 30 years, consistent with estimates obtained from physically-based water- balance measurements on experimental basins in the area.
The ionic tracers lithium, sodium, chloride and bromide were used to measure flow loss in a small stream. An injectate containing all four tracers was added continuously at five sites along a 507 m study reach of St Kevin Gulch, Lake County, Colorado to determine which sections of the stream were losing water to the stream bed and to ascertain how well the four tracers performed. The acidity of the stream (pH 3.6) made it possible for lithium and sodium, which are normally adsorbed by ion exchange with stream bed sediment, to be used as conservative tracers. Net flow losses as low as 8% of flow, were calculated between measuring sites. By comparing the results of simultaneous injection it was determined whether subsections of the study reach were influent or effluent. Evaluation of tracer concentrations along 116m of stream indicated that all four tracers behaved conservatively. Discharges measured by Parshall flumes were 4-18% greater than discharges measured by tracer dilution.
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