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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 775 records · Page 43Linked to original sources
USGS1998

Evaluating the source and residence times of groundwater seepage to streams, New Jersey Coastal Plain

A conceptual model of the patterns and residence times of groundwater seepage to gaining streams indicates that groundwater seepage originates from sources that are both near and far from the stream. Consequently, the age of groundwater seepage across a stream-channel transect increases from its banks to its center and becomes progressively older with distance downstream. A groundwater flow model and particle-tracking analysis of the Cohansey River Basin in the New Jersey Coastal Plain supports this conceptual model and demonstrates that the orientation of the stream channels with respect to the regional groundwater flow direction, and the heterogeneities of the aquifer and stream-channel patterns, can shift source area locations and distributions of groundwater residence time from those expected. Groundwater samples collected from stream transects were analyzed for nitrogen, representative of widespread agricultural land use in the basin in recent decades, and for chlorofluorocarbons, used to estimate groundwater ages. The patterns of nitrogen concentration and the age of groundwater entering the stream channel corroborate model inferences. The conceptual model of groundwater seepage to streams presented herein is relevant to unconfined aquifer systems with gaining streams and demonstrates how nonpoint-source contaminants are transported to streams by groundwater. Results are useful for the design of programs needed to monitor stream-water quality.

New Jersey↗
USGS1998

A note on conservative transport in anisotropic, heterogeneous porous media in the presence of small-amplitude transients

The late-time macrodispersion coefficients are obtained for the case of flow in the presence of a small-scale deterministic transient in a three-dimensional anisotropic, heterogeneous medium. The transient is assumed to affect only the velocity component transverse to the mean flow direction and to take the form of a periodic function. For the case of a highly stratified medium, these late-time macrodispersion coefficients behave largely as the standard coefficients used in the transport equation. Only in the event that the medium is isotropic is it probable that significant deviations from the standard coefficients would occur.

Water Resources Research↗
USGS1999

Practical Scheffe‐type credibility intervals for variables of a groundwater model

Simultaneous Scheffé‐type credibility intervals (the Bayesian version of confidence intervals) for variables of a groundwater flow model calibrated using a Bayesian maximum a posteriori procedure were derived by Cooley [1993b]. It was assumed that variances reflecting the expected differences between observed and model‐computed quantities used to calibrate the model are known, whereas they would often be unknown for an actual model. In this study the variances are regarded as unknown, and variance variability from observation to observation is approximated by grouping the data so that each group is characterized by a uniform variance. The credibility intervals are calculated from the posterior distribution, which was developed by considering each group variance to be a random variable about which nothing is known a priori, then eliminating it by integration. Numerical experiments using two test problems illustrate some characteristics of the credibility intervals. Nonlinearity of the statistical model greatly affected some of the credibility intervals, indicating that credibility intervals computed using the standard linear model approximation may often be inadequate to characterize uncertainty for actual field problems. The parameter characterizing the probability level for the credibility intervals was, however, accurately computed using a linear model approximation, as compared with values calculated using second‐order and fully nonlinear formulations. This allows the credibility intervals to be computed very efficiently.

Water Resources Research↗
USGS2010

Solute erosion and chloride balance in selected river basins of the western conterminous United States

The estimated average rates of annual solute erosion in 11 important western river basins range from 180 tons per square mile (Willamette basin) to 4.2 tons per square mile (Gila basin). An average rate of 58 tons per square mile is indicated for the entire 545,000‐square‐mile area drained by the 11 rivers. The wide range in tonnage is the result of a complex of causes, among which differences in geology, gross climatic environments, and activities of man are the most important. Rates of solute erosion are highest in areas of abundant precipitation and runoff, in contrast to rates of suspended‐sediment removal, which are characteristically highest in basins subjected to only 10–15 inches of effective annual precipitation. Tonnages of chloride brought into the 11 river basins by rain and snow make up an equivalent of about 1.6 to about 17% of the chloride removed in runoff during an average year. The range of percentages reflects differences in the relative importance of oceanic and continental solute contributions. This paper is not subject to U.S. copyright. Published in 1965 by the American Geophysical Union.

Water Resources Research↗
USGS2010

Glacier mass budget measurements by hydrologic means

Ice storage changes for the South Cascade Glacier drainage basin were determined for the 1957–1964 period using basin runoff and precipitation measurements. Measurements indicate that evaporation and condensation are negligible compared with the large runoff and precipitation values. Runoff, measured by a stream discharge station, averaged 4.04 m/yr; precipitation, determined by snow accumulation measurements at a central point on the glacier and by storage gages, averaged 3.82 m/yr, resulting in a basin net loss of about 0.22 m/yr. During the same period, South Cascade Glacier net budgets were determined by ablation stakes, snow density-depth profiles, and maps. The average glacier net budget for the period was −0.61sol;yr of water. This amount is equivalent to −0.26 m of water when averaged over the drainage basin (43% glacier-covered), which is in fair agreement with the net storage change measured by hydrologic methods. Agreement between the two methods for individual years is slightly less perfect.

Washington↗
USGS2010

Geohydrologic use of lithofacies maps in glaciated areas

Subsurface conditions may differ considerably from conditions indicated by surficial geologic maps, particularly in glaciated areas. Therefore, it is advantageous to use a series of lithofacies maps as a sequence of overlays plotted on transparent paper. Such maps permit direct visual determination of the lithology and areal extent of aquifers and indicate areas of possible stream losses or gains. They indicate areas and boundaries of confining layers and, in some places, they may be used to delineate areas of water-table and artesian conditions. They are especially useful in determining buried channels in glaciated areas. The porosity of rock units making up an aquifer may be plotted on a lithofacies map, and the product of the volume of each lithologic type and the porosity provides an estimate of the total water in storage. In addition, if the water-bearing properties are known, the quantity of water moving through an aquifer and the amount available to wells may be determined. Lithofacies maps also aid in the explanation of complex changes in water quality.

Water Resources Research↗
USGS2010

Applications of factor analysis in study of chemistry of groundwater quality, Mojave River Valley, California

Factor analysis is applied to results of chemical analyses of 103 water samples from wells in the Upper and Middle Mojave River valley, San Bernardino County, California. Chemical analyses showed that there are three principal chemical types of water, calcium bicarbonate, sodium sulfate, and sodium chloride, as well as many mixtures of the three. Data were studied by factor analysis to learn the relative importance of each principal ion in determining the variations among the samples, and to examine the possibility of chemical equilibrium between aqueous and solid phases in the aquifers. Most of the covariance in the system may be accounted for by variances of Ca +2 , Mg +2 , Na +1 , SO 4 −2 , and Cl −1 . There is almost identical loading on the constituents Na +1 and Cl −1 . The variance in chemical composition of the hydrochemical system is governed largely by sources of sodium chloride. None of the components is controlled by equilibrium between ions in the water and minerals in the aquifers. Concentrations of NO 3 −1 and F −1 vary independently of other constituents. Geographic distribution of statistical loadings of the principal constituents at individual wells does not reveal sources of the constituents, which must be deduced from geologic and hydrologic evidence. Factor analysis, however, furnished the critical information on chemical relationships basic to the deduction.

California↗
USGS2010

On the quantitative inventory of the riverscape

In the vicinity of Berkeley, California, 24 minor valleys were described in terms of factors chosen to represent aspects of the river landscape. A total of 28 factors were evaluated at each site. Some were directly measurable, others were estimated, but each observation was assigned to one of five categories for that factor. Each factor for each site was then expressed as a uniqueness ratio, which depended on the number of sites being in the same category. The uniqueness ratio is believed to represent one way the scarcity of a given riverscape can be ranked quantitatively without bias based on notions of good or bad, and without assigning monetary value.

California↗
USGS2010

Ground-water flow related to streamflow and water quality

A ground-water flow system in southwestern Minnesota illustrates water movement between geologic units and between the land surface and the subsurface. The flow patterns indicate numerous zones of ground-water recharge and discharge controlled by topography, varying thicknesses of geologic units, variation in permeabilities, and the configuration of the basement rock surface. Variations in streamflow along a reach of the Yellow Medicine River agree with the subsurface flow system. Increases and decreases in runoff per square mile correspond, apparently, to ground-water discharge and recharge zones. Ground-water quality variations between calcium sulfate waters typical of the Quaternary drift and sodium chloride waters typical of the Cretaceous rocks are caused by mixing of the two water types. The zones of mixing are in agreement with ground-water flow patterns along the hydrologic section.

Water Resources Research↗
USGS2010

The linear decision rule in reservoir management and design: 1, Development of the stochastic model

With the aid of a linear decision rule, reservoir management and design problems often can be formulated as easily solved linear programing problems. The linear decision rule specifies the release during any period of reservoir operation as the difference between the storage at the beginning of the period and a decision parameter for the period. The decision parameters for the entire study horizon are determined by solving the linear programing problem. Problems may be formulated in either the deterministic or the stochastic environment.

Water Resources Research↗
USGS2010

Effect of rainfall variability on streamflow simulation

Three recording rain gages in a 9.7‐square‐mile basin in southern California were used with a deterministic rainfall‐runoff model to simulate flood hydrographs and peaks and to assess the effects of data errors on simulation results. Bias in the estimation of effective basin rainfall seemed to result in curve fitting parameter adjustments which compensated for the bias. The combined effects for a storm of both difference in the time distribution of rainfall at different points and spatial variability of rainfall volume over the basin limit the possible accuracy of simulation results. The use of a single rain gage on a basin with this hydrology can at best be expected to predict peak discharge with a standard error of estimate on the order of 20%.

California↗
USGS2010

A graphic presentation of stream gain or loss as an aid in understanding streamflow characteristics

A graphic presentation of cumulative monthly stream gain or loss on a given stream reach is used as a tool to show whether the stream gain or loss is apparent or real, and to determine the magnitude, time, and cause of the gain or loss. The graphic method could also be used to determine how much of the base flow is ground-water discharge. Interpretations of the cumulative gain or loss graph are described for three reaches on the James River in northeastern South Dakota and southeastern North Dakota.

North Dakota, South Dakota↗
USGS2010

Reply

No abstract available.

Water Resources Research↗
USGS2010

An improved method for size distribution of stream bed gravel

Random sampling of surface rocks on a gravel bar is biased toward larger sizes which, because of their area, are more likely to be picked up. Weighting can eliminate this bias. Data on average weight of a single rock are used to change numbers of rocks to weights, thus yielding size frequency data in general agreement with a sieved and weighed sample. The question of what to sample depends on the use to which the data are to be put, and is not treated in detail in this paper.

Water Resources Research↗
USGS2010

Saline groundwater resources of the conterminous United States

Saline water is arbitrarily defined as water containing more than 1000 milligrams per liter of dissolved solids. Saline ground water is known to underlie about two‐thirds of the 48 states. Locally, aquifers yield saline ground water in profuse quantities, some of which is used by industry, particularly for cooling. Generally, however, saline water has been considered a nuisance. In this report it is dealt with as a resource, especially for the future. Forty chemical types of mineralized ground water were recognized, but sodium chloride dominates the occurrences and is almost the only type found where concentrations exceed about 20,000 mg/l. The occurrence and hydrologic properties of saline water aquifers deserve much more study than they have had. Copyright 1970 by the American Geophysical Union.

Water Resources Research↗
USGS2010

An approach to the design of statewide or regional ground water information systems

The design of water information or basic data systems must be flexible enough to provide information and data for a broad range of interests from national to local. The system must satisfy the need for information for accounting, surveillance, and areal synthesis purposes. The network is designed by identifying specific needs in terms of maps, analyses, and studies that will provide the basic knowledge for understanding each particular phase of the groundwater system. Each specific need is then analyzed with respect to whether it will provide information on accounting, surveillance, or areal synthesis. If a particular type of map, analysis, or observation can serve any of these three functions, a network of data collection or a program of studies is outlined in detail that will provide the information needed. The method of design necessitates the establishment of accuracy levels for maps, the density of data points, confidence limits, and so forth. The information system should be under the general guidance of a single agency, but much of the work and responsibility to carry out the details of the system must be shared by a number of agencies.

Water Resources Research↗
USGS2010

New tritium data on movement of groundwater in western Fresno County, California

Well waters along two traverse lines were sampled in 1963 and tested for tritium concentration. Haskell et al . [1966] estimated from the apparent thermonuclear tritium concentrations that groundwater had moved westward in the lower water‐bearing zone at a maximum velocity of 14–16.5 mi (23–27 km) in 9 yr. The maximum velocities and permeabilities estimated from the 1963 sampling were about an order of magnitude greater than the velocities and permeabilities suggested by prior hydrologic and geologic evidence. Consequently, in 1966–1970 the U.S. Geological Survey sampled and tested the tritium concentrations of well waters along the same two traverses but also extended the sampling eastward. On the basis of these analyses it is concluded that (1) thermonuclear tritium had not invaded the lower zone by 1970 within the extent of the 1963 sampling and (2) although the maximum westward movement of groundwater in the lower zone from 1955 to 1970 is indeterminate, it has been less than 4 mi (6.5 km) from the recharge area in 15 yr.

California↗
USGS2010

Economic basis of resource information systems: The case of streamflow network design

A general method for the economic design of natural resource information systems is presented for a certain class of natural phenomena. The system design is determined by the interaction of the technical input‐output relationship, i.e., the production function, the set of resource constraints, and an economic loss function defined in terms of parameter uncertainty. An application of the proposed method to streamflow network design is presented. Results of this analysis indicate that the method is fairly robust with respect to the assumptions. Observations are made which suggest extensions to flood measurement networks, long‐term precipitation networks, and seismic observation network design.

Water Resources Research↗