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P. M. Barlow

Publications and source records attributed to P. M. Barlow.

10 recordsLinked to original sources
USGS2012

Simulating the effects of ground-water withdrawals on streamflow in a precipitation-runoff model

Precipitation-runoff models are used to assess the effects of water use and management alternatives on streamflow. Often, ground-water withdrawals are a major water-use component that affect streamflow, but the ability of surface-water models to simulate ground-water withdrawals is limited. As part of a Hydrologic Simulation Program-FORTRAN (HSPF) precipitation-runoff model developed to analyze the effect of ground-water and surface-water withdrawals on streamflow in the Ipswich River in northeastern Massachusetts, an analytical technique (STRMDEPL) was developed for calculating the effects of pumped wells on streamflow. STRMDEPL is a FORTRAN program based on two analytical solutions that solve equations for ground-water flow to a well completed in a semi-infinite, homogeneous, and isotropic aquifer in direct hydraulic connection to a fully penetrating stream. One analytical method calculates unimpeded flow at the stream-aquifer boundary and the other method calculates the resistance to flow caused by semipervious streambed and streambank material. The principle of superposition is used with these analytical equations to calculate time-varying streamflow depletions due to daily pumping. The HSPF model can readily incorporate streamflow depletions caused by a well or surface-water withdrawal, or by multiple wells or surface-water withdrawals, or both, as a combined time-varying outflow demand from affected channel reaches. These demands are stored as a time series in the Watershed Data Management (WDM) file. This time-series data is read into the model as an external source used to specify flow from the first outflow gate in the reach where these withdrawals are located. Although the STRMDEPL program can be run independently of the HSPF model, an extension was developed to run this program within GenScn, a scenario generator and graphical user interface developed for use with the HSPF model. This extension requires that actual pumping rates for each well be stored in a unique WDM dataset identified by an attribute that associates each well with the model reach from which water is withdrawn. Other attributes identify the type and characteristics of the data. The interface allows users to easily add new pumping wells, delete exiting pumping wells, or change properties of the simulated aquifer or well. Development of this application enhanced the ability of the HSPF model to simulate complex water-use conditions in the Ipswich River Basin. The STRMDEPL program and the GenScn extension provide a valuable tool for water managers to evaluate the effects of pumped wells on streamflow and to test alternative water-use scenarios. Copyright ASCE 2004.

Conference Paper↗
USGS2003

Conjunctive-management models for sustained yield of stream-aquifer systems

Conjunctive-management models that couple numerical simulation with linear optimization were developed to evaluate trade-offs between groundwater withdrawals and streamflow depletions for alluvial-valley stream-aquifer systems representative of those of the northeastern United States. A conjunctive-management model developed for a hypothetical stream-aquifer system was used to assess the effect of interannual hydrologic variability on minimum monthly streamflow requirements. The conjunctive-management model was applied to the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system of central Rhode Island. Results show that it is possible to increase the amount of current withdrawal from the aquifer by as much as 50% by modifying current withdrawal schedules, modifying the number and configuration of wells in the supply-well network, or allowing increased streamflow depletion in the Annaquatucket and Pettaquamscutt rivers. Alternatively, it is possible to reduce current rates of streamflow depletion in the Hunt River by as much as 35% during the summer, but such reductions would result increases in groundwater withdrawals.

Journal of Water Resources Planning and Management↗
USGS2000

Aquifer response to stream-stage and recharge variations. II. Convolution method and applications

In this second of two papers, analytical step-response functions, developed in the companion paper for several cases of transient hydraulic interaction between a fully penetrating stream and a confined, leaky, or water-table aquifer, are used in the convolution integral to calculate aquifer heads, streambank seepage rates, and bank storage that occur in response to streamstage fluctuations and basinwide recharge or evapotranspiration. Two computer programs developed on the basis of these step-response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream-aquifer systems in the northeastern and central United States. These applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank hydraulic properties, recharge rates, streambank seepage rates, and bank storage. Analysis of the water-table aquifer adjacent to the Blackstone River in Massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer (negligible specific yield). This finding is consistent with previous studies that have shown that the effective specific yield of an unconfined aquifer approaches zero when the capillary fringe, where sediment pores are saturated by tension, extends to land surface. Under this condition, the aquifer's response is determined by elastic storage only. Estimates of horizontal and vertical hydraulic conductivity, specific yield, specific storage, and recharge for a water-table aquifer adjacent to the Cedar River in eastern Iowa, determined by the use of analytical methods, are in close agreement with those estimated by use of a more complex, multilayer numerical model of the aquifer. Streambank leakance of the semipervious streambank materials also was estimated for the site. The streambank-leakance parameter may be considered to be a general (or lumped) parameter that accounts not only for the resistance of flow at the river-aquifer boundary, but also for the effects of partial penetration of the river and other near-stream flow phenomena not included in the theoretical development of the step-response functions.Analytical step-response functions, developed for several cases of transient hydraulic interaction between a fully penetrating stream and a confined, leaky, or water-table aquifer, are used in the convolution integral to calculate aquifer heads, streambank seepage rates, and bank storage that occur in response to stream-stage fluctuations and basinwide recharge or evapotranspiration. Two computer programs developed on the basis of these step-response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream-aquifer systems. These applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank seepage rates and bank storage.

Journal of Hydrology↗
USGS1996

Geohydrology and conceptual model of a ground-water-flow system near a Superfund site in Cheshire, Connecticut

Degradation of ground-water quality has been identified in an area of the north-central part of the town of Cheshire, Connecticut. An investigation by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, was done during 1994-95 to characterize the unconsolidated glacial deposits and the sedimentary bedrock, integrate the local geohydrologic conditions with the regional geohydrologic system, and develop a conceptual understanding of ground-water flow in the study area. A regional ground-water-flow model developed for the region near the study area indicates that perennial streams, including Judd Brook and the Tenmile River, form hydrologic divides that separate the larger region into hydraulically independent flow systems. In the local study area, synoptic water-level measurements made in June 1995 indicate that ground water near the water table flows west and southwestward from the low hill on the eastern side of the area toward the pond and wetlands along Judd Brook. Water-level data indicate that there is good hydraulic connection between the unconsolidated materials and underlying fractured bedrock. Unconsolidated materials in the study area consist principally of glacial stratified deposits that are fine sand, silt, and clay of glaci- olacustrine origin; locally these overlie thin glacial till. The glacial sediments range in thickness from a few feet to about 25 ft in the eastern part of the study area and are as much as 100 ft thick in the western and southern part of the study area beneath the Judd Brook and Tenmile River valleys. Fluvial redbeds of the New Haven Arkose underlie the glacial deposits in the region; in the study area, the redbeds consist of (1) channel sandstone units, which are coarse sandstone to fine conglomerate, generally in 6- to 15-ft- thick sequences; and (2) overbank mudstone units, which are siltstone and silty sandstone with some fine sandstone, generally in 6- to 50-ft-thick sequences. Thin-bedded zones of siltstone that are particularly fissile are present locally within the mudstone units. Rock units strike northward and dip eastward at about 20. The eastward-dipping strata are cut by a consistent set of west to west-northwest dipping, high-angle fractures. These fractures are oriented perpendicular to bedding and are present mostly in the channel sandstone units, but locally extend into the mudstone units as well. Borehole-geophysical logging indicates that ground water flows along bedding planes in fissile zones and between fissile zones in high-angle fractures, which are perpendicular to bedding. The combined fracture types form an aquifer system in which ground water follows a stair-step flowpath, flowing horizontally through fissile zones and vertically through high-angle fractures. Heat-pulse flow meter measurements and borehole fluid-conductivity and temperature logs indicate that only a small subset of the fissile zones and some high-angle fractures are hydraulically significant. A generalized local-scale ground-water flow model based on a nonspecific, but realistic, rock and fracture geometry was developed for the study area. Simulations show that under nonpumping conditions at a hypothetical well located in the middle of the model, ground-water flow was separated into upper and lower zones in which flow paths differed but were generally from northeast to southwest. Several short-duration aquifer tests conducted in the study area indicate that there is good hydraulic connection in the fractures between the pumping well (CS-221) and two bedrock wells located approximately 100 ft to the north and south along bedding strike. During the short duration of the aquifer tests, there was no hydraulic connection in bedrock wells located to the east, perpendicular to the strike. A range of transmissivity of 27 to 46 ft2/d was calculated from the aquifer-test data for the fractured-bedrock aquifer at CS-221 and TH-2. Individual fracture zones identified by bo

Open-File Report↗
USGS1995

Water-quality and hydrologic conditions at a site of ground-water contamination by volatile organic compounds, South Grafton, Massachusetts, September and October 1994

Ground-water quality and hydrologic data were collected at a site contaminated by volatile organic compounds (VOCs) in South Grafton, Massachusetts, during September and October 1994. The VOCs have formed a plume of contaminated ground water at an abandoned textile mill adjacent to the Blackstone River. Concentrations of total VOCs in the plume ranged from less than 1 to more than 40,000 micrograms per liter. Trichloroethylene (TCE) was the primary chlorinated contaminant, comprising as much as 98 percent of the total VOCs. The highest concentration, 43,000 micrograms per liter, was higher than any previously measured concentration at the site; however, the maximum extent and distribution of concentrations in the VOC plume in September 1994 was similar to that found in July 1993 and in earlier rounds of sampling. In addition to TCE, 1,2-dichloroethene (1,2-DCE) and vinyl chloride were detected at most sites. Spatial and temporal changes in concentrations of TCE, 1,2-DCE, and vinyl chloride are consistent with the hypothesis that TCE biodegradation was the source of 1,2-DCE and vinyl chloride. Ground water at the site contained low to moderately high concentrations of dissolved solids (44 to 406 milligrams per liter), had a moderately high specific conductance (155 to 670 microsiemens per centimeter at 25 degrees Celsius), and was slightly acidic (pH=5.9 to 7.0). Concentrations of the major ions-calcium, sodium, chloride, and sulfate-were not related to VOC concentrations. Dissolved-oxygen concentrations were low (0 to 2 milligrams per liter) throughout most of the aquifer. Distribution of nitrogen species, iron, and manganese indicates that zones of varying oxidation-reduction potential were present in the aquifer. Concentrations of trace metals other than iron or manganese, including arsenic, cadmium, chromium, and copper, generally were less than analytical detection limits. Stream stage in the Blackstone River at the site during September and October 1994 fluctuated by about 1 to 2 feet within 24-hour periods. These rapid fluctuations resulted from sudden release of impounded water at a hydroelectric-generating facility downstream from the site. In addition to the daily fluctuations, rapid small changes in stream stage also occurred that were related to storms. Fluctuations in ground-water levels in four observation wells at the site were similar in amplitude and timing to the rapid fluctuations in stream stage; the daily fluctuations of ground-water levels were greatest in an observation well within 100 feet of the river and least in an observation well about 300 feet from the river. Because ground- water levels at the study site seem to be affected by fluctuations in stage of the Blackstone River, transport of the VOC plume in ground water also is likely to be affected by the fluctuations in stage.

Open-File Report↗
USGS1994

Particle-tracking analysis of contributing areas of public-supply wells in simple and complex flow systems, Cape Cod, Massachusetts

Steady-state, two-and three-dimensional, ground-water flow models coupled with a particle- tracking program were evaluated to determine their effectiveness in delineating contributing areas of existing and hypothetical public-supply wells pumping from two contrasting stratified-drift aquifers of Cape Cod, Mass. Several of the contri- buting areas delineated by use of the three- dimensional models do not conform to simple ellipsoidal shapes that are typically delineated by use of a two-dimensional analytical and numerical modeling techniques, include dis- continuous areas of the water table, and do not surround the wells. Because two-dimensional areal models do not account for vertical flow, they cannot adequately represent many of the hydro- geologic and well-design variables that were shown to complicate the delineation of contributing areas in these flow systems, including the presence of discrete lenses of 1ow hydraulic conductivity, large ratios of horizontal to ver- tical hydraulic conductivity, shallow streams, partially penetrating supply wells, and 1ow pumping rates (less than 0.1 million gallons per day). Nevertheless, contributing areas delineated for two wells in the simpler of the two flow systems--a thin (less than 100 feet), single- layer, uniform aquifer with near-ideal boundary conditions--were not significantly different for the two- or three-dimensional models of the natural system, for a pumping rate of 0.5 million gallons per day. Use of particle tracking helped identify the source of water to simulated wells, which included precipitation recharge, wastewater return flow, and pond water. Pond water and wastewater return flow accounted for as much as 73 and 40 percent, respectively, of the water captured by simulated wells.

Massachusetts↗
USGS1993

Simulated hydrologic responses of the Quashnet River stream-aquifer system to proposed ground-water withdrawals, Cape Cod, Massachusetts

An investigation of the Quashnet River stream- aquifer system on Cape Cod was initiated in response to concern over possible streamflow reduction and degradation of the sea-run brown trout habitat of the river resulting from proposed ground-water withdrawals. A two-layer finite-difference ground-water-flow model was developed to simulate the stream-aquifer system. Steady-state pumping rates of 0.5, 1.0, and 2.0 million gallons per day were simulated at three well sites 1,500 to 2,500 feet west of the river. No infiltration of water from the river to the aquifer was induced in any of the simulations. Maximum streamflow depletion along the river for the scenarios tested ranged from 3 to 15 percent of calculated steady-state prepumping streamflow. Mean monthly streamflow depletions determined by use of the transient model, for a constant withdrawal of 1.0 million gallons per day from a site 1,500 feet west of the river, range from 6 to 8 percent of the mean monthly streamflows measured at a gage located 0.3 miles from the mouth of the river. A particle-tracking postprocessor to the steady-state model was used to delineate contributing areas of the river and the proposed withdrawal sites. Although the simulated cone of depression produced by pumping extends beyond the river, the contributing area of the well does not include the river under any of the withdrawal schemes simulated.

Water-Resources Investigations Report↗