USGS Science⌕ Search

SEARCH · USGS Science

Results for “Water Research”

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

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76Linked to original sources
USGS2010

Accuracy of an estuarine hydrodynamic model using smooth elements

A finite element model which uses triangular, isoparametric elements with quadratic basis functions for the two velocity components and linear basis functions for water surface elevation is used in the computation of shallow water wave motions. Specifically addressed are two common uncertainties in this class of two-dimensional hydrodynamic models: the treatment of the boundary conditions at open boundaries and the treatment of lateral boundary conditions. The accuracy of the models is tested with a set of numerical experiments in rectangular and curvilinear channels with constant and variable depth. The results indicate that errors in velocity at the open boundary can be significant when boundary conditions for water surface elevation are specified. Methods are suggested for minimizing these errors. The results also show that continuity is better maintained within the spatial domain of interest when ‘smooth’ curve-sided elements are used at shoreline boundaries than when piecewise linear boundaries are used. Finally, a method for network development is described which is based upon a continuity criterion to gauge accuracy. A finite element network for San Francisco Bay, California, is used as an example.

California↗
USGS2010

Quantile estimation with more or less floodlike distributions

The desirable properties of an estimator relative to a hypothetical population may be irrelevant in practice unless the population at issue more or less resembles the hypothetical population. Evidence that floods are distributed with long, stretched upper tails suggests that use of the more common distributions results in a rather precise underestimation of the extreme quantiles and thereby in the underdesign of flood protection measures.

Water Resources Research↗
USGS2010

Flood risks and the willingness to purchase flood insurance

Computer simulation experiments were conducted to determine the effects of alternative sources of uncertainty on the willingness to pay for flood insurance. Two alternative insurance protection schemes were investigated: coinsurance and fixed coverage. The question investigated here is to what extent does the insurance scheme influence how purchasers respond to flood risks? Floods were assumed to be log normally distributed and the effects on the purchase of insurance of uncertainties in the parameters of the distribution were explored using response surface analysis. Results indicate that fixed coverage insurance provisions shift most of the uncertainty in the physical parameters governing natural disaster occurrences away from the insuree and onto the insurer. The results also show that the form of the damage function has little effect on the demand for flood insurance.

Water Resources Research↗
USGS2010

A model to forecast short-term snowmelt runoff using synoptic observations of streamflow, temperature, and precipitation

Snowmelt runoff is forecast with a statistical model that utilizes daily values of stream discharge, gaged precipitation, and maximum and minimum observations of air temperature. Synoptic observations of these variables are made at existing low- and medium-altitude weather stations, thus eliminating the difficulties and expense of new, high-altitude installations. Four model development steps are used to demonstrate the influence on prediction accuracy of basin storage, a preforecast test season, air temperature (to estimate ablation), and a prediction based on storage. Daily ablation is determined by a technique that employs both mean temperature and a radiative index. Radiation (both long- and short-wave components) is approximated by using the range in daily temperature, which is shown to be closely related to mean cloud cover. A technique based on the relationship between prediction error and prediction season weather utilizes short-term forecasts of precipitation and temperature to improve the final prediction. Verification of the model is accomplished by a split sampling technique for the 1960–1977 period. Short- term (5–15 days) predictions of runoff throughout the main snowmelt season are demonstrated for mountain drainages in western Washington, south-central Arizona, western Montana, and central California. The coefficient of prediction ( C p ) based on actual, short-term predictions for 18 years is for Thunder Creek (Washington), 0.69; for South Fork Flathead River (Montana), 0.45; for the Black River (Arizona), 0.80; and for the Kings River (California), 0.80.

Water Resources Research↗
USGS2010

Faulting caused by groundwater level declines, San Joaquin Valley, California

Approximately 230 mm of aseismic vertical offset of the land surface across the Pond-Poso Creek fault in the San Joaquin Valley, California, probably is related to groundwater withdrawal for crop irrigation. The scarp is approximately 3.4 km long and occurs in an area where the land subsided more than 1.5 m from 1926 to 1970. Modern faulting postdates the beginning of water level declines and associated subsidence. Movement detected by precise leveling surveys from February 1977 to March 1979 was seasonal, occurring during periods of water level decline. Fault offset was greater in the year with the lower seasonal low water level. The modern movement probably is caused by localized differential compaction induced by differential water level declines across the preexisting fault.

California↗
USGS2010

Measurement and computation of bed-material discharge in a shallow sand-bed stream, Muddy Creek, Wyoming

Both the measurement and computation of the bed-material discharge of a stream involve large uncertainties because of the difficulties in determining bedload discharge. Measurements of bedload discharge are rare and frequently of unknown accuracy because no bedload sampler has been extensively tested and calibrated over a wide range of hydraulic conditions. Bed-material discharge equations have been derived primarily from laboratory flume data where the effects of channel pattern, alluvial banks, sediment availability, sediment sorting, and unsteady flow upon the sediment discharge of a natural stream have not been simulated. Bed-material discharge equations generally are applicable only within the range of flow conditions and sediment sizes for which the equations were derived. To compare the relative value of measuring versus computing bed-material discharges, the bed-material discharge of Muddy Creek, a shallow sand-bed stream in southwestern Wyoming, was determined on 35 occasions for water discharges ranging from 0.15 to 1.57 m 3 /s by separately sampling the suspended- and bedload-sediment discharges. Measured bed-material discharges were statistically indistinguishable, at an 0.02 level of significance, from flume data collected under the same flow conditions. This agreement indicates that the measured bed-material discharges are reasonable estimates of the true values. Bed-material discharges computed by Engelund-Hansen, Yang, Shen-Hung, and Ackers-White equations were compared with the measured values and found to be in good agreement. These equations predicted bed-material discharges of between 0.5 to 2 times the observed rates 60% to 79% of the time.

Wyoming↗
USGS2010

Flow through fractures

Flow through fractures is often idealized as flow between two parallel plates (plane Poiseuille flow). The opening or aperture between parallel plates is unambiguous and its relation to flowrate is well known. However, fractures in rock have uneven walls and a variable aperture. A model for flow in a fracture is proposed wherein the fracture is represented by a set of parallel plate openings with different apertures. The model leads to a modified Poiseuille equation for flow which includes an aperture frequency distribution for the fracture. Any arbitrary aperture distribution can be used; in order to simplify computation and demonstrate the properties of the model a log normal form of distribution is assumed. Even when an analytical form of the distribution is assumed, two parameters, rather than a single value representing ‘aperture size’ are required to determine flowrate. Models of aperture change for a fracture undergoing compression (fracture walls deforming) and extension (fracture walls separating) are developed which constrain the additional parameter and allow calculation of flowrate as a function of mean aperture. The theoretical relationships developed between mean aperture and flowrate can be used to interpret published laboratory data for single fractures.

Water Resources Research↗
USGS2010

Earth fissures and localized differential subsidence

Long linear tension cracks associated with declining groundwater levels at four sites in subsiding areas in south-central Arizona, Fremont Valley, California, and Las Vegas Valley, Nevada, occur near points of maximum convex-upward curvature in subsidence profiles oriented perpendicular to the cracks. Profiles are based on repeated precise vertical control surveys of lines of closely spaced bench marks. Association of these fissures with zones of localized differential subsidence indicates that linear earth fissures are caused by horizontal tensile strains probably resulting from localized differential compaction. Horizontal tensile strains across the fissures at the point of maximum convex-upward curvature, ranging from approximately 100 to 700 microstrains (0.01 to 0.07% per year), were indicated based on measurements with a tape or electronic distance meter.

Arizona, California, Idaho, Nevada, Utah↗
USGS2010

The effect of snowmelt on the water quality of Filson Creek and Omaday Lake, northeastern Minnesota

Sulfate concentration and p H were determined in surface water, groundwater, and precipitation samples collected in the Filson Creek watershed to evaluate the sources of sulfate in Filson Creek. During and immediately after snowmelt, sulfate concentrations in Filson Creek increased from about 2 to 14 mg/l. Concurrently, H + ion activity increased from an average of 10 −6.6 to 10 −5.5 . These changes suggest that sulfate acidity is concentrated in the snowpack at snowmelt, which is similar to changes reported in Scandinavia in areas subject to acid precipitation. Mass balance calculations indicate that the sulfate contribution from groundwater during snowmelt was minimal in comparison to that from snow. During base flow, sulfate did not appreciably increase from the headwaters of Filson Creek to the mouth, even though sulfate was as high as 58 mg/l in groundwater discharging to the creek from surficial materials overlying a sulfide-bearing mineralized zone in the lower third of the watershed. Approximately 10.6 kg of sulfate per hectare per year was retained in 1977.

Minnesota↗
USGS2010

A numerical inversion of the Laplace transform solution to radial dispersion in a porous medium

A special form of the numerical inversion of the Laplace transform described by Stehfest (1970) is applied to the transformed solution of dispersion in a radial flow system in a porous medium. The inversion is extremely simple to use because the weighting coefficients depend only on the number of terms used in the computation and not upon the transform solution as required by most numerical inversion techniques. The result obtained by use of this approximate inversion of the radial dispersion problem reproduced the curves obtained previously by Hoopes and Harleman (1967) with a finite difference scheme.

Water Resources Research↗
USGS2010

Hydromythology and ethnohydrology in the New World

From mythology, archeology, and chronicles of early explorers we can learn how early Americans viewed the cause and effect relations of hydrologic phenomena. Hopes and fears are the basis of religion, and it was through religion that water management was first practiced. Early people used their water resources to develop diverse civilizations in various parts of the western hemisphere. Not only was the rise of these earlier civilizations hydrologically influenced, but also the downfall of some was related to natural or man-made hydrological crises in which gods and mythology continued to play a role.

Water Resources Research↗
USGS2010

Preconsolidation stress of aquifer systems in areas of induced land subsidence

Aquifer systems in the Eloy-Picacho area, Arizona, the Houston-Galveston area, Texas, and the Tulare-Wasco area and Santa Clara Valley, California, appear to have been overconsolidated by an amount that ranged approximately from 1.6 to 6.2 bars (16 to 63 m of water) before man began to withdraw groundwater from them. The relation between land subsidence and water level decline in these areas, consists of two linear segments. In these areas, subsidence per unit water level decline was approximately constant until water levels had declined an amount that ranged from 16 to 63 m. When water levels declined past these values, subsidence per unit water level decline increased to larger constant values. Although slow drainage from aquitards may have contributed to this response, it is interpreted here to be caused primarily by natural overconsolidation of the compacting part of the aquifer system. The water level decline at which the ratio of subsidence to unit water level decline changed indicates approximately the amount by which the preconsolidation stress exceeded the overburden stress on the aquifer system that existed before groundwater withdrawals began.

Arizona, California, Texas↗
USGS2010

Estimation of impervious-area washoff parameters

In recent years many models have been developed which simulate the quality of rainfall runoff from urban areas. Common to many of these models is the use of an exponential washoff equation. This washoff equation is often modified by an availability equation to account for the effects of runoff intensity on constituent washoff. Optimization techniques for estimating the values of coefficients used in these equations have been developed. Application of these techniques to a small urban watershed in south Florida demonstrated considerable variability in the optimized parameter values among different storms and among different constituents.

Water Resources Research↗
USGS2010

Estimation of accumulation parameters for urban runoff quality modeling

Many recently developed watershed models utilize accumulation and washoff equations to simulate the quality of runofffrom urban impervious areas. These models often have been calibrated by trial and error and with little understanding of model sensitivity to the various parameters. Methodologies for estimating best fit values of the washoff parameters commonly used in these models have been presented previously. In this paper, parameter identification techniques for estimating the accumulation parameters from measured runoff quality data are presented along with a sensitivity analysis of the parameters. Results from application of the techniques and the sensitivity analysis suggest a need for data quantifying the magnitude and identifying the shape of constituent accumulation curves. An exponential accumulation curve is shown to be more general than the linear accumulation curves used in most urban runoff quality models. When determining accumulation rates, attention needs to be given to the effects of residual amounts of constituents remaining after the previous period of storm runoff or street sweeping.

Water Resources Research↗
USGS2010

Optimal dynamic management of groundwater pollutant sources

The linear programing-superposition method is presented for managing multiple sources of groundwater pollution over time. The method uses any linear solute transport simulation model to generate a unit source-concentration response matrix that is incorporated into a management model. This series of constraints indicates local solute concentration histories that will result from any series of waste injection schedules. The linear program operates on the matrix to arrive at optimal disposal schedules. An example demonstrates application of the method to maximizing groundwater waste disposal while maintaining water quality of local water supplies within desired limits. Flow field variations associated with waste injection are ignored as an approximation. Parametric programing is shown to be an important tool in evaluating waste disposal trade-offs at various injection sites over time. Mixed-integer programing permits restrictions to be placed upon the number of injection wells which may operate during given management periods.

Water Resources Research↗
USGS2010

Techniques of trend analysis for monthly water quality data

Some of the characteristics that complicate the analysis of water quality time series are non-normal distributions, seasonality, flow relatedness, missing values, values below the limit of detection, and serial correlation. Presented here are techniques that are suitable in the face of the complications listed above for the exploratory analysis of monthly water quality data for monotonie trends. The first procedure described is a nonparametric test for trend applicable to data sets with seasonality, missing values, or values reported as ‘less than’: the seasonal Kendall test. Under realistic stochastic processes (exhibiting seasonality, skewness, and serial correlation), it is robust in comparison to parametric alternatives, although neither the seasonal Kendall test nor the alternatives can be considered an exact test in the presence of serial correlation. The second procedure, the seasonal Kendall slope estimator, is an estimator of trend magnitude. It is an unbiased estimator of the slope of a linear trend and has considerably higher precision than a regression estimator where data are highly skewed but somewhat lower precision where the data are normal. The third procedure provides a means for testing for change over time in the relationship between constituent concentration and flow, thus avoiding the problem of identifying trends in water quality that are artifacts of the particular sequence of discharges observed (e.g., drought effects). In this method a flow-adjusted concentration is defined as the residual (actual minus conditional expectation) based on a regression of concentration on some function of discharge. These flow-adjusted concentrations, which may also be seasonal and non-normal, can then be tested for trend by using the seasonal Kendall test.

Water Resources Research↗
USGS2010

On conducting the modified ‘Slug’ test in tight formations

The method introduced by Bredehoeft and Papadopulos (1980) for conducting a modified ‘slug’ test in tight formations does not assure the condition of approximate equilibrium necessary at the start of the test. In addition, compressibility in the shut-in well can be significantly larger than the compressibility of water, which Bredehoeft and Papadopulos indicate should be used in the calculations. Errors that may result from using the original test procedure are discussed, and a modified procedure and testing arrangement are presented.

Water Resources Research↗
USGS2010

Stability of βMnOOH and manganese oxide deposition from springwater

Beta MnOOH is precipitated preferentially (with respect to Mn 3 O 4 ) at temperatures near O°C when Mn 2+ is oxidized in aerated aqueous solutions. Upon aging in solutions open to the atmosphere a slurry of βMnOOH tends to disproportionate to form MnO 2 and Mn 2+ . In such aged solutions, Mn 2+ and H + activities can be constant, and both the oxidation reaction Mn 2+ +¼O 2 (aq) + 3/2H 2 O → βMnOOH (c) + 2H + and the disproportionate reaction 2βMnOOH (c) + 2H + → MnO 2 (c) + Mn 2+ + 2H 2 O can have positive reaction affinities. It is not possible for both reactions to be in thermodynamic equilibrium in the same system unless oxygen is almost completely absent. A value for Δ G f 0 of −129.8±0.6 kcal/mol was obtained for βMnOOH from experimental data by assuming that the reaction affinity for the oxidation reaction is equal to that for the disproportionation. A value for Δ G f 0 for βMnOOH of −129.8±0.5 kcal/mol was determined by measuring the redox potentials for the postulated half-reaction MnO 2 (c) + H + + e − → βMnOOH (c) at 0°, 5°, and 15°C and extrapolating to 25°C. Both these values are consistent with laboratory observations that βMnOOH is less stable than γMnOOH or Mn 3 O 4 at 25°C. Analytical data for manganese-depositing springwater samples are consistent with a nonequilibrium model involving disproportionation of either βMnOOH or Mn 3 O 4 .

Water Resources Research↗