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Chloride and nitrate were coinjected into the surface waters of a third—order stream for 20 d to examine solute retention, and the fate of nitrate during subsurface transport. A series of wells (shallow pits) 0.5—10 m from the adjacent channel were sampled to estimate the lateral interflow of water. Two...

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The paper presents a prioritized list of research issues related to structural marsh management developed by a multidisciplinary panel of regulatory agency representatives, landowners, and scientists. More than 75 issues were identified concerning landscape changes, influence on ecological processes (i.e., hydrologic, biologic, and edaphic factors), habitat quality, cumulative impacts, and...

Organic liquids inadvertently spilled and then distributed in the unsaturated zone can pose a long-term threat to ground water. Many of these substances have significant volatility, and thereby establish a premise for contaminant removal from the unsaturated zone by inducing advective air-phase transport...

Between the Potomac and Susquehanna Rivers and from the Blue Ridge to the Fall Zone, landscapes of the Piedmont are illustrated for times in the Holocene, Late Wisconsin, Early Miocene, Early Cretaceous, Late Triassic, and Permian. Landscape evolution took place in tectonic settings marked by major plate collisions (Permian), arching...

A late Quaternary paleolimnological history from the Mexican highlands has been obtained by diatom analysis of short cores and stratigraphic sections of lake and marsh sediments from the Cuenca de México, the large, endorheic, graben basin that holds Mexico City. The records, dated by radiocarbon and tephrochronologic methods, extend...

Problems include: a) definition of the spatial and temporal distribution of model input; b) measurement or estimation of snow accumulation, snowmelt, and runoff process parameters for a range of applications and scales; and c) development of accurate short term and long term snowmelt runoff forecasts. Procedures being investigated to solve...

A pH perturbation experiment was conducted in an acidic, metal-enriched, mountain stream to identify relative rates of chemical and hydrologic processes as they influence iron transport. During the experiment the pH was lowered from 4.2 to 3.2 for three hours by injection of sulfuric acid. Amorphous iron oxides are abundant...

Sediment samples from nearshore sites in south San Francisco Bay and from streams flowing into that section of the Bay have been characterized in terms of their content of biogenic and anthropogenic molecular marker compounds. The distributions, input sources, and applicability of these compounds in determining sediment movement are discussed....

The Thornthwaite water balance and combinations of temperature and precipitation changes representing climate change were used to estimate changes in seasonal soil-moisture and runoff in the Delaware River basin. Winter warming may cause a greater proportion of precipitation in the northern part of the basin to fall as rain, which...

The U.S. Geological Survey, like other Federal agencies, uses Hydrology Subcommittee Bulletin 17 for guidance in statistical frequency analysis of flood records. This paper describes the formal statistical and computational aspects of the Bulletin 17 methodology. The methodology includes provisions for dealing with high and low out-liers, historic peaks, and...

Transport of indigenous bacteria through sandy aquifer sediments was investigated in forced- and natural-gradient tracer teste. A diverse population of bacteria was collected and concentrated from groundwater at the site, stained with a DNA-specific fluorochrome, and injected back into the aquifer. Included with the injectate were a conservative tracer (Br-...

In small limestone islands, the depositional history and subsequent chemical interactions between ground water and the aquifer host rock play critical roles in the occurrence, movement, and chemical quality of ground water. The hydrogeochemistry of the Laura fresh-water lens, Majuro atoll, Marshall Islands, is an example of these relations.Laura is...

A simultaneous calorimetric and potentiometric technique has been developed for measuring the thermodynamics of proton binding to mineral oxides in the presence of a supporting electrolyte. Modifications made to a commercial titration calorimeter to add a combination pH electrode and maintain an inert atmosphere in the calorimeter reaction vessel are...

Appraisal of ground water contaminated by organic substances raises problems of difficult sample collection and timely chemical analysis. High-performance liquid chromatography was evaluated for on-site determination of specific organic contaminants in ground water samples and was used at three study sites. Organic solutes were determined directly in water samples, with...

We investigate optimal predictors of the peak (S) and distance to peak (T) of the width function of drainage networks under the assumption that the networks are topologically random with independent and exponentially distributed link lengths. Analytical results are derived using the fact that, under these assumptions, the width function...

Preliminary results from New York, New Jersey, Connecticut, Florida, Nebraska, and Colorado indicate that regional ground-water quality has been affected by human activities. The frequencies of detection of volatile organic compounds and some trace elements were larger in ground water underlying urban or industrial areas in comparison to undeveloped areas....

A rainfall-runoff model is used in conjunction with a probabilistic description of the input to this model to obtain simple regression-like relations for basin runoff in terms of basin and storm characteristics. These relations, similar to those sought in regionalization studies, are computed by evaluating the conditional distribution of model...

Chemical hydrogeology, including organic and inorganic aspects, has contributed to an increased understanding of groundwater flow systems, geologic processes, and stressed environments. Most of the basic principles of inorganic-chemical hydrogeology were first established by investigations of organic-free, regional-scale systems for which simplifying assumptions could be made. The problems of groundwater...

A comparison involving both field and laboratory trials was performed to evaluate the utility of two continuous-flow centrifuges and a tangential-flow filtration system for dewatering suspended sediments for subsequent trace element analysis. Although recovery efficiencies for the various devices differ, the analytical results from the...

During 1983 and 1984, wet precipitation was primarily a solution of dilute sulphuric acid, whereas calcium and bicarbonate were the major ions in springs and ground water in two small watersheds with a deciduous forest cover in central Maryland. Dominant ions in soil water were...

Thermodynamic models of aqueous solutions have indicated that the mixing of seawater and calcite-saturated fresh groundwater can produce a water that is undersaturated with respect to calcite. Mixing of such waters in coastal carbonate aquifers could lead to significant amounts of limestone dissolution. The potential for such dissolution in coastal...

Spatial distributions of copper (Cu), zinc (Zn) and cadmium (Cd) were followed along a longitudinal gradient of dissolved organic carbon (DOC) in South San Francisco Bay (herein referred to as the South Bay). Dissolved Cu, Zn and Cd concentrations ranged from 24 to...

A Laplace transform solution was obtained for the injection of a tracer in a well situated in a homogeneous aquifer where steady, horizontal, radially convergent flow has been established due to pumping at a second well. The standard advection-dispersion equation for mass transfer was used as the controlling equation. For...

The hydrologic response to development of three of the most heavily pumped sedimentary aquifer systems in the United States is similar in some aspects and different in others. In the semiarid West, an unconfined sand aquifer and a confined sand and clay aquifer system have...