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 847 records · Page 47Linked to original sources
USGS2005

Effects of urban development in the Puget Lowland, Washington, on interannual streamflow patterns: Consequences for channel form and streambed disturbance

Recovery and protection of streams in urban areas depend on a comprehensive understanding of how human activities affect stream ecosystems. The hydrologic effects of urban development and the consequences for stream channel form and streambed stability were examined in 16 streams in the Puget Lowland, Washington, using three streamflow metrics that integrate storm‐scale effects of urban development over annual to decadal timescales: the fraction of time that streamflow exceeds the mean streamflow (T Qmean ), the coefficient of variation of annual maximum streamflow (CV AMF ), and the fraction of time that streamflow exceeds the 0.5‐year flood (T 0.5 ). Urban streams had low interannual variability in annual maximum streamflow and brief duration of frequent high flows, as indicated by significant correlations between road density and both CV AMF and T 0.5 . The broader distribution of streamflow indicated by T Qmean may be affected by urban development, but differences in T Qmean between streams are also likely a result of other physiographic factors. The increase in the magnitude of frequent high flows due to urban development but not their cumulative duration has important consequences for channel form and bed stability in gravel bed streams because geomorphic equilibrium depends on moderate duration streamflow (e.g., exceeded 10% of the time). Streams with low values of T Qmean and T 0.5 are narrower than expected from hydraulic geometry. Dimensionless boundary shear stress (t*) for the 0.5‐year flood was inversely related to T 0.5 among the streams, indicating frequent and extensive bed disturbance in streams with low values of T 0.5 . Although stream channels expand and the size of bed material increases in response to urban streamflow patterns, these adjustments may be insufficient to reestablish the disturbance regime in urban streams because of the differential increase in the magnitude of frequent high flows causing disturbance relative to any changes in longer duration, moderate flows that establish a stable channel.

Water Resources Research↗
USGS2005

An integrated environmental tracer approach to characterizing groundwater circulation in a mountain block

The subsurface transfer of water from a mountain block to an adjacent basin (mountain block recharge (MBR)) is a commonly invoked mechanism of recharge to intermountain basins. However, MBR estimates are highly uncertain. We present an approach to characterize bulk fluid circulation in a mountain block and thus MBR that utilizes environmental tracers from the basin aquifer. Noble gas recharge temperatures, groundwater ages, and temperature data combined with heat and fluid flow modeling are used to identify clearly improbable flow regimes in the southeastern Salt Lake Valley, Utah, and adjacent Wasatch Mountains. The range of possible MBR rates is reduced by 70%. Derived MBR rates (5.5–12.6 × 10 4 m 3 d −1 ) are on the same order of magnitude as previous large estimates, indicating that significant MBR to intermountain basins is plausible. However, derived rates are 50–100% of the lowest previous estimate, meaning total recharge is probably less than previously thought.

Water Resources Research↗
USGS2006

Longitudinal hydraulic analysis of river‐aquifer exchanges

A longitudinal analysis of transient flow between a river and an underlying aquifer is developed to calculate flow rates between the river and the aquifer and the location of groundwater seepage into the river as it changes over time. Two flow domains are defined in the analysis: an upstream domain of fluvial recharge, where water flows vertically from the river into the unsaturated portion of the aquifer and horizontally in saturated parts of the aquifer, and a downstream domain of groundwater seepage to the river, where groundwater flows parallel to the underlying impermeable base. The river does not necessarily penetrate completely through the aquifer. A one‐dimensional, unsteady flow equation is derived from mass conservation, Darcy's law, and the geometry of the river‐aquifer system to calculate the water table position and the groundwater seepage rate into the river. Models based on numerical and analytical solutions of the flow equation were applied to a reach of the Methow River in north central Washington. The calibrated models simulated groundwater seepage with a root‐mean‐square error less than 5% of the mean groundwater seepage rates for three low‐flow evaluation periods. The analytical model provides a theoretical basis for a nonlinear exponential base flow recession generated by a draining aquifer, but not an explicit functional form for the recession. Unlike cross‐sectional approaches, the longitudinal approach allows the analysis of the length and location of groundwater seepage to a river, which have important ecological implications in many rivers. In the numerical simulations, the length of the groundwater seepage varied seasonally by about 4 km and the upstream boundary of groundwater seepage was within 689 m of its location at a stream gage on 9 September 2001 and within 91 m of its location on 6 October 2002. To demonstrate its utility in ecological applications, the numerical model was used to calculate differences in length of groundwater seepage to the Methow River under an early runoff scenario and the timing of those differences with respect to life stages of chinook salmon.

Water Resources Research↗
USGS2005

Effective discharge analysis of ecological processes in streams

Discharge is a master variable that controls many processes in stream ecosystems. However, there is uncertainty of which discharges are most important for driving particular ecological processes and thus how flow regime may influence entire stream ecosystems. Here the analytical method of effective discharge from fluvial geomorphology is used to analyze the interaction between frequency and magnitude of discharge events that drive organic matter transport, algal growth, nutrient retention, macroinvertebrate disturbance, and habitat availability. We quantify the ecological effective discharge using a synthesis of previously published studies and modeling from a range of study sites. An analytical expression is then developed for a particular case of ecological effective discharge and is used to explore how effective discharge varies within variable hydrologic regimes. Our results suggest that a range of discharges is important for different ecological processes in an individual stream. Discharges are not equally important; instead, effective discharge values exist that correspond to near modal flows and moderate floods for the variable sets examined. We suggest four types of ecological response to discharge variability: discharge as a transport mechanism, regulator of habitat, process modulator, and disturbance. Effective discharge analysis will perform well when there is a unique, essentially instantaneous relationship between discharge and an ecological process and poorly when effects of discharge are delayed or confounded by legacy effects. Despite some limitations the conceptual and analytical utility of the effective discharge analysis allows exploring general questions about how hydrologic variability influences various ecological processes in streams.

Water Resources Research↗
USGS2006

Partitioning evapotranspiration in sparsely vegetated rangeland using a portable chamber

A portable chamber was used to separate evapotranspiration ( ET ) from a sparse, mixed‐species shrub canopy in southeastern Arizona, United States, into vegetation and soil components. Chamber measurements were made of ET from the five dominant species, and from bare soil, on 3 days during the monsoon season when the soil surface was dry. The chamber measurements were assembled into landscape ET using a simple geometric model of the vegetated land surface. Chamber estimates of landscape ET were well correlated with, but about 26% greater than, simultaneous eddy‐correlation measurements. Excessive air speed inside the chamber appears to be the primary cause of the overestimate. Overall, transpiration accounted for 84% of landscape ET , and bare soil evaporation for 16%. Desert zinnia, a small (∼0.1 m high) but abundant species, was the greatest water user, both per unit area of shrub and of landscape. Partitioning of ET into components varied as a function of air temperature and shallow soil moisture. Transpiration from shorter species was more highly correlated with air temperature whereas transpiration from taller species was more highly correlated with shallow soil moisture. Application of these results to a full drying cycle between rainfalls at a similar site suggests that during the monsoon, ET at such sites may be about equally partitioned between transpiration and bare soil evaporation.

Water Resources Research↗
USGS2006

Flow resistance dynamics in step‐pool stream channels: 1. Large woody debris and controls on total resistance

Flow resistance dynamics in step‐pool channels were investigated through physical modeling using a laboratory flume. Variables contributing to flow resistance in step‐pool channels were manipulated in order to measure the effects of various large woody debris (LWD) configurations, steps, grains, discharge, and slope on total flow resistance. This entailed nearly 400 flume runs, organized into a series of factorial experiments. Factorial analyses of variance indicated significant two‐way and three‐way interaction effects between steps, grains, and LWD, illustrating the complexity of flow resistance in these channels. Interactions between steps and LWD resulted in substantially greater flow resistance for steps with LWD than for steps lacking LWD. LWD position contributed to these interactions, whereby LWD pieces located near the lip of steps, analogous to step‐forming debris in natural channels, increased the effective height of steps and created substantially higher flow resistance than pieces located farther upstream on step treads. Step geometry and LWD density and orientation also had highly significant effects on flow resistance. Flow resistance dynamics and the resistance effect of bed roughness configurations were strongly discharge‐dependent; discharge had both highly significant main effects on resistance and highly significant interactions with all other variables.

Water Resources Research↗
USGS2006

Flow resistance dynamics in step‐pool channels: 2. Partitioning between grain, spill, and woody debris resistance

In step‐pool stream channels, flow resistance is created primarily by bed sediments, spill over step‐pool bed forms, and large woody debris (LWD). In order to measure resistance partitioning between grains, steps, and LWD in step‐pool channels we completed laboratory flume runs in which total resistance was measured with and without grains and steps, with various LWD configurations, and at multiple slopes and discharges. Tests of additive approaches to resistance partitioning found that partitioning estimates are highly sensitive to the order in which components are calculated and that such approaches inflate the values of difficult‐to‐measure components that are calculated by subtraction from measured components. This effect is especially significant where interactions between roughness features create synergistic increases in resistance such that total resistance measured for combinations of resistance components greatly exceeds the sum of those components measured separately. LWD contributes large proportions of total resistance by creating form drag on individual pieces and by increasing the spill resistance effect of steps. The combined effect of LWD and spill over steps was found to dominate total resistance, whereas grain roughness on step treads was a small component of total resistance. The relative contributions of grain, spill, and woody debris resistance were strongly influenced by discharge and to a lesser extent by LWD density. Grain resistance values based on published formulas and debris resistance values calculated using a cylinder drag approach typically underestimated analogous flume‐derived values, further illustrating sources of error in partitioning methods and the importance of accounting for interaction effects between resistance components.

Water Resources Research↗
USGS2006

Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies

Ammonium (NH 4 + ) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH 4 + movement in a treated wastewater plume were studied by a combination of techniques including large‐scale monitoring of NH 4 + distribution; isotopic analyses of coexisting aqueous NH 4 + , NO 3 − , N 2 , and sorbed NH 4 + ; and in situ natural gradient 15 NH 4 + tracer tests with numerical simulations of 15 NH 4 + , 15 NO 3 − , and 15 N 2 breakthrough data. Combined results indicate that the main mass of NH 4 + was moving downgradient at a rate about 0.25 times the groundwater velocity. Retardation factors and groundwater ages indicate that much of the NH 4 + in the plume was recharged early in the history of the wastewater disposal. NO 3 − and excess N 2 gas, which were related to each other by denitrification near the plume source, were moving downgradient more rapidly and were largely unrelated to coexisting NH 4 + . The δ 15 N data indicate areas of the plume affected by nitrification (substantial isotope fractionation) and sorption (no isotope fractionation). There was no conclusive evidence for NH 4 + ‐consuming reactions (nitrification or anammox) in the anoxic core of the plume. Nitrification occurred along the upper boundary of the plume but was limited by a low rate of transverse dispersive mixing of wastewater NH 4 + and O 2 from overlying uncontaminated groundwater. Without induced vertical mixing or displacement of plume water with oxic groundwater from upgradient sources, the main mass of NH 4 + could reach a discharge area without substantial reaction long after the more mobile wastewater constituents are gone. Multiple approaches including in situ isotopic tracers and fractionation studies provided critical information about processes affecting NH 4 + movement and N speciation.

Water Resources Research↗
USGS2006

Mountain hydrology of the western United States

Climate change and climate variability, population growth, and land use change drive the need for new hydrologic knowledge and understanding. In the mountainous West and other similar areas worldwide, three pressing hydrologic needs stand out: first, to better understand the processes controlling the partitioning of energy and water fluxes within and out from these systems; second, to better understand feedbacks between hydrological fluxes and biogeochemical and ecological processes; and, third, to enhance our physical and empirical understanding with integrated measurement strategies and information systems. We envision an integrative approach to monitoring, modeling, and sensing the mountain environment that will improve understanding and prediction of hydrologic fluxes and processes. Here extensive monitoring of energy fluxes and hydrologic states are needed to supplement existing measurements, which are largely limited to streamflow and snow water equivalent. Ground‐based observing systems must be explicitly designed for integration with remotely sensed data and for scaling up to basins and whole ranges.

Water Resources Research↗
USGS2006

Storage and transit time of chemicals in thick unsaturated zones under rangeland and irrigated cropland, High Plains, United States

In 2000-2002, three rangeland and six irrigated sites were instrumented to assess the storage and transit time of chemicals in thick (15 to 50 m) unsaturated zones (UZ) in the High Plains. These processes are likely to influence relations between land use and groundwater quality, yet they have not been documented systematically in the High Plains. Land use and climate were important controls on the size of subsoil chloride, nitrate, and pesticide compound reservoirs. The reservoirs under irrigated cropland generally were larger than those under rangeland because more chemicals were applied to cropland than to rangeland. In some cases, chloride and nitrate reservoirs under rangeland were larger than those under cropland, presumably because of long‐term evaporative concentration near the base of the root zone. Natural salts mobilized by irrigation return flow accounted for as much as 60 and 80% of the nitrate and chloride reservoirs, respectively, under some cropland, as indicated by detailed chemical profiles and isotopic tracers ( 15 N, 18 O in nitrate and 2 H, 3 H, 18 O in water). Advective chemical transit times in the UZ under cropland ranged from about 50 to 375 years, longer than any of the instrumented fields had been irrigated, yet agrichemicals were detected at the water table at four of the six sites. The data provide evidence for the existence of slow and fast paths for water movement in the UZ, with larger subsoil chemical reservoirs occurring in areas dominated by slow paths. Implications of these findings with respect to water quality in the aquifer are significant because they indicate that the amount of chemical mass reaching the aquifer could increase with time as chemicals that still reside under irrigated fields reach the water table.

Water Resources Research↗
USGS2006

Use of radars to monitor stream discharge by noncontact methods

Conventional measurements of river flows are costly, time‐consuming, and frequently dangerous. This report evaluates the use of a continuous wave microwave radar, a monostatic UHF Doppler radar, a pulsed Doppler microwave radar, and a ground‐penetrating radar to measure river flows continuously over long periods and without touching the water with any instruments. The experiments duplicate the flow records from conventional stream gauging stations on the San Joaquin River in California and the Cowlitz River in Washington. The purpose of the experiments was to directly measure the parameters necessary to compute flow: surface velocity (converted to mean velocity) and cross‐sectional area, thereby avoiding the uncertainty, complexity, and cost of maintaining rating curves. River channel cross sections were measured by ground‐penetrating radar suspended above the river. River surface water velocity was obtained by Bragg scattering of microwave and UHF Doppler radars, and the surface velocity data were converted to mean velocity on the basis of detailed velocity profiles measured by current meters and hydroacoustic instruments. Experiments using these radars to acquire a continuous record of flow were conducted for 4 weeks on the San Joaquin River and for 16 weeks on the Cowlitz River. At the San Joaquin River the radar noncontact measurements produced discharges more than 20% higher than the other independent measurements in the early part of the experiment. After the first 3 days, the noncontact radar discharge measurements were within 5% of the rating values. On the Cowlitz River at Castle Rock, correlation coefficients between the USGS stream gauging station rating curve discharge and discharge computed from three different Doppler radar systems and GPR data over the 16 week experiment were 0.883, 0.969, and 0.992. Noncontact radar results were within a few percent of discharge values obtained by gauging station, current meter, and hydroacoustic methods. Time series of surface velocity obtained by different radars in the Cowlitz River experiment also show small‐amplitude pulsations not found in stage records that reflect tidal energy at the gauging station. Noncontact discharge measurements made during a flood on 30 January 2004 agreed with the rated discharge to within 5%. Measurement at both field sites confirm that lognormal velocity profiles exist for a wide range of flows in these rivers, and mean velocity is approximately 0.85 times measured surface velocity. Noncontact methods of flow measurement appear to (1) be as accurate as conventional methods, (2) obtain data when standard contact methods are dangerous or cannot be obtained, and (3) provide insight into flow dynamics not available from detailed stage records alone.

Water Resources Research↗
USGS2006

Evaluating uncertainty in predicting spatially variable representative elementary scales in fractured aquifers, with application to Turkey Creek Basin, Colorado

Computational limitations and sparse field data often mandate use of continuum representation for modeling hydrologic processes in large‐scale fractured aquifers. Selecting appropriate element size is of primary importance because continuum approximation is not valid for all scales. The traditional approach is to select elements by identifying a single representative elementary scale (RES) for the region of interest. Recent advances indicate RES may be spatially variable, prompting unanswered questions regarding the ability of sparse data to spatially resolve continuum equivalents in fractured aquifers. We address this uncertainty of estimating RES using two techniques. In one technique we employ data‐conditioned realizations generated by sequential Gaussian simulation. For the other we develop a new approach using conditioned random walks and nonparametric bootstrapping (CRWN). We evaluate the effectiveness of each method under three fracture densities, three data sets, and two groups of RES analysis parameters. In sum, 18 separate RES analyses are evaluated, which indicate RES magnitudes may be reasonably bounded using uncertainty analysis, even for limited data sets and complex fracture structure. In addition, we conduct a field study to estimate RES magnitudes and resulting uncertainty for Turkey Creek Basin, a crystalline fractured rock aquifer located 30 km southwest of Denver, Colorado. Analyses indicate RES does not correlate to rock type or local relief in several instances but is generally lower within incised creek valleys and higher along mountain fronts. Results of this study suggest that (1) CRWN is an effective and computationally efficient method to estimate uncertainty, (2) RES predictions are well constrained using uncertainty analysis, and (3) for aquifers such as Turkey Creek Basin, spatial variability of RES is significant and complex.

Water Resources Research↗
USGS2006

Updated streamflow reconstructions for the Upper Colorado River Basin

Updated proxy reconstructions of water year (October–September) streamflow for four key gauges in the Upper Colorado River Basin were generated using an expanded tree ring network and longer calibration records than in previous efforts. Reconstructed gauges include the Green River at Green River, Utah; Colorado near Cisco, Utah; San Juan near Bluff, Utah; and Colorado at Lees Ferry, Arizona. The reconstructions explain 72–81% of the variance in the gauge records, and results are robust across several reconstruction approaches. Time series plots as well as results of cross‐spectral analysis indicate strong spatial coherence in runoff variations across the subbasins. The Lees Ferry reconstruction suggests a higher long‐term mean than previous reconstructions but strongly supports earlier findings that Colorado River allocations were based on one of the wettest periods in the past 5 centuries and that droughts more severe than any 20th to 21st century event occurred in the past.

Upper Colorado River Basin↗
USGS2006

Beaver dams and overbank floods influence groundwater-surface water interactions of a Rocky Mountain riparian area

Overbank flooding is recognized by hydrologists as a key process that drives hydrogeomorphic and ecological dynamics in mountain valleys. Beaver create dams that some ecologists have assumed may also drive riparian hydrologic processes, but empirical evidence is lacking. We examined the influence of two in‐channel beaver dams and a 10 year flood event on surface inundation, groundwater levels, and flow patterns in a broad alluvial valley during the summers of 2002–2005. We studied a 1.5 km reach of the fourth‐order Colorado River in Rocky Mountain National Park (RMNP), Colorado, USA. The beaver dams and ponds greatly enhanced the depth, extent, and duration of inundation associated with floods; they also elevate the water table during both high and low flows. Unlike previous studies we found the main effects of beaver on hydrologic processes occurred downstream of the dam rather than being confined to the near‐pond area. Beaver dams on the Colorado River caused river water to move around them as surface runoff and groundwater seepage during both high‐ and low‐flow periods. The beaver dams attenuated the expected water table decline in the drier summer months for 9 and 12 ha of the 58 ha study area. Thus we provide empirical evidence that beaver can influence hydrologic processes during the peak flow and low‐flow periods on some streams, suggesting that beaver can create and maintain hydrologic regimes suitable for the formation and persistence of wetlands.

Water Resources Research↗
USGS2006

Hydrogeophysical tracking of three‐dimensional tracer migration: The concept and application of apparent petrophysical relations

Direct estimation of groundwater solute concentrations from geophysical tomograms has been only moderately successful because (1) reconstructed tomograms are often highly uncertain and subject to inversion artifacts, (2) the range of subsurface conditions represented in data sets is incomplete because of the paucity of colocated well or core data and aquifer heterogeneity, and (3) geophysical methods exhibit spatially variable sensitivity. We show that electrical resistivity tomography (ERT) can be used to estimate groundwater solute concentrations if a relation between concentration and inverted resistivity is used to deal quantitatively with these issues. We use numerical simulation of solute transport and electrical current flow to develop these relations, which we call “apparent” petrophysical relations. They provide the connection between concentration, or local resistivity, and inverted resistivity, which is measured at the field scale based on ERT for media containing ionic solute. The apparent petrophysical relations are applied to tomograms of electrical resistivity obtained from field measurements of resistance from cross‐well ERT to create maps of tracer concentration. On the basis of synthetic and field cases we demonstrate that tracer mass and concentration estimates obtained using these apparent petrophysical relations are far better than those obtained using direct application of Archie's law applied to three‐dimensional tomograms from ERT, which gives severe underestimates.

Water Resources Research↗
USGS2006

Reply to comment by F. Molz et al. on “Investigating the Macrodispersion Experiment (MADE) site in Columbus, Mississippi, using a three‐dimensional inverse flow and transport model”

W e are pleased to have the opportunity to discuss further what we think are important met hods and results presented by Barlebo et al. [2004] . W e are especially pleased to enter into a public discussion with four scientists who we regard with such high esteem concerning an important topic of mutual interest.

Georgia↗
USGS2007

A field investigation of phreatophyte‐induced fluctuations in the water table

Hydrographs from shallow wells in vegetated riparian zones frequently display a distinctive pattern of diurnal water table fluctuations produced by variations in plant water use. A multisite investigation assessed the major controls on these fluctuations and the ecohydrologic insights that can be gleaned from them. Spatial and temporal variations in the amplitude of the fluctuations are primarily a function of variations in (1) the meteorological drivers of plant water use, (2) vegetation density, type, and vitality, and (3) the specific yield of sediments in the vicinity of the water table. Past hydrologic conditions experienced by the riparian zone vegetation, either in previous years or earlier within the same growing season, are also an important control. Diurnal water table fluctuations can be considered a diagnostic indicator of groundwater consumption by phreatophytes at most sites, so the information embedded within these fluctuations should be more widely exploited in ecohydrologic studies.

Water Resources Research↗
USGS2006

Climate model biases in seasonality of continental water storage revealed by satellite gravimetry

Satellite gravimetric observations of monthly changes in continental water storage are compared with outputs from five climate models. All models qualitatively reproduce the global pattern of annual storage amplitude, and the seasonal cycle of global average storage is reproduced well, consistent with earlier studies. However, global average agreements mask systematic model biases in low latitudes. Seasonal extrema of low‐latitude, hemispheric storage generally occur too early in the models, and model‐specific errors in amplitude of the low‐latitude annual variations are substantial. These errors are potentially explicable in terms of neglected or suboptimally parameterized water stores in the land models and precipitation biases in the climate models.

Water Resources Research↗