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At least 541 records · Page 30Linked to original sources
USGS2004

Occurrence of human pharmaceuticals in water resources of the United States: A review

The widespread environmental presence of some pharmaceuticals and other organic wastewater compounds has been documented globally (e.g. Buser et al. 1998; Ternes 1998; Stumpf et al.1999; Heberer et al. 2001; Kümmerer 2001; Ternes et al. 2001; Scheytt et al. 2001; Golet et al. 2002; Kolpin et al. 2002; Boyd et al. 2003; Metcalf et al. 2003). Recently, there have been several literature reviews and summary studies of the occurrence, fate, transport, and treatment of targeted human pharmaceuticals in wastewater effluent and associated environmental waters across the globe (e.g. Daughton and Ternes 1999; Sedlak et al. 2000; Suter and Giger 2000; Daughton and Jones-Lepp 2001; Jones et al. 2001; Heberer 2002; and Drewes et al. 2002). The occurrence of pharmaceutical compounds in water resources is explained by their ubiquitous use, excretion of large percentages of the mass consumed, and incomplete removal during wastewater treatment (Stumpf et al.1999). The recent increase in detection of trace concentrations (typically less than a part per billion) of pharmaceuticals in water resources across the globe reflects improvements in laboratory analytical methods (Sedlak et al. 2000) and the associated increases in field surveys. The detection of pharmaceutical compounds in large rivers in Europe and in the North Sea (Buser et al. 1998; Ternes 1998; Stumpf et al. 1999) highlighted the fact that highly soluble, trace organic compounds, such as pharmaceuticals, may escape removal in wastewater treatment, and the mixing and concentration of wastewaters through conventional wastewater treatment processes could provide a means of delivering these chemicals to environmental waters in a manner that would contaminate water resources on a large scale at trace levels (Richardson and Bowron 1985). In the United States, some of the first detections of a limited number of pharmaceutically active compounds or their transformation products were found in waters associated with landfill leachates or sewage effluent (Tabak and Bunch 1970; Garrison et al. 1976; Hignite and Azarnoff 1977; Bouwer et al. 1982; Eckel et al. 1991) decades ago. At the time of these studies, other industrial contaminants were the focus of regulatory and scientific interest; therefore, further studies on the environmental occurrence and transport of pharmaceutical compounds were rare.

Book chapter↗
USGS2016

Application of decision science to resilience management in Jamaica Bay

This book highlights the growing interest in management interventions designed to enhance the resilience of the Jamaica Bay socio-ecological system. Effective management, whether the focus is on managing biological processes or human behavior or (most likely) both, requires decision makers to anticipate how the managed system will respond to interventions (i.e., via predictions or projections). In systems characterized by many interacting components and high uncertainty, making probabilistic predictions is often difficult and requires careful thinking not only about system dynamics, but also about how management objectives are specified and the analytic method used to select the preferred action(s). Developing a clear statement of the problem(s) and articulation of management objectives is often best achieved by including input from managers, scientists and other stakeholders affected by the decision through a process of joint problem framing (Marcot and others 2012; Keeney and others 1990). Using a deliberate, coherent and transparent framework for deciding among management alternatives to best meet these objectives then ensures a greater likelihood for successful intervention. Decision science provides the theoretical and practical basis for developing this framework and applying decision analysis methods for making complex decisions under uncertainty and risk.

Book chapter↗
USGS2002

Design and performance of limestone drains to increase pH and remove metals from acidic mine drainage, Chapter 2

Data on the construction characteristics and the composition of influent and effluent at 13 underground, limestone-filled drains in Pennsylvania and Maryland are reported to evaluate the design and performance of limestone drains for the attenuation of acidity and dissolved metals in acidic mine drainage. On the basis of the initial mass of limestone, dimensions of the drains, and average flow rates, the initial porosity and average detention time for each drain were computed. Calculated porosity ranged from 0.12 to 0.50 with corresponding detention times at average flow from 1.3 to 33 h. The effectiveness of treatment was dependent on influent chemistry, detention time, and limestone purity. At two sites where influent contained elevated dissolved Al (>5 mg/liter), drain performance declined rapidly; elsewhere the drains consistently produced near-neutral effluent, even when influent contained small concentrations of dissolved Fe^+ ( <5 mg/liter). Rates of limestone dissolution computed on the basis of average long-term Ca ion flux normalized by initial mass and purity of limestone at each of the drains ranged from 0.008 to 0.079 year -1 . Data for alkalinity concentration and flux during 11-day closed-container tests using an initial mass of 4kg crushed limestone and a solution volume of 2.3 liter yielded dissolution rate constants that were comparable to these long-term field rates. An analytical method is proposed using closed-container test data to evaluate long-term performance (longevity) or to estimate the mass of limestone needed for a limestone treatment. This method condisers flow rate, influent alkalinity, steady-state alkalinity of effluent, and desired effluent alkalinity or detention time at a future time(s) and aplies first-order rate laws for limestone dissolution (continuous) and production of alkalinity (bounded).

Book chapter↗
USGS2018

Estimating freshwater productivity, overwinter survival, and migration patterns of Klamath River Coho Salmon

An area of great importance to resource management and conservation biology in the Klamath Basin is balancing water usage against the life history requirements of threatened Coho Salmon. One tool for addressing this topic is a freshwater dynamics model to forecast Coho Salmon productivity based on environmental inputs. Constructing such a forecasting tool requires local data to quantify the unique life history processes of Coho Salmon inhabiting this region. Here, we describe analytical methods for estimating a series of sub-models, each capturing a different life history process, which will eventually be synchronized as part of a freshwater dynamics model for Klamath River Coho Salmon. Specifically, we draw upon extensive population monitoring data collected in the basin to estimate models of freshwater productivity, overwinter survival, and migration patterns. Our models of freshwater productivity indicated that high summer temperatures and high winter flows can both adversely affect smolt production and that such relationships are more likely in tributaries with naturally regulated flows due to substantial intraannual environmental variation. Our models of overwinter survival demonstrated extensive variability in survival among years, but not among rearing locations, and demonstrated that a substantial proportion (~ 20%) of age-0+ fish emigrate from some rearing sites in the winter. Our models of migration patterns indicated that many age-0+ fish redistribute in the basin during the summer and winter. Further, we observed that these redistributions can entail long migrations in the mainstem where environmental stressors likely play a role in cueing refuge entry. Finally, our models of migration patterns indicated that changes in discharge are important in cueing the seaward migration of smolts, but that the nature of this behavioral response can differ dramatically between tributaries with naturally and artificially regulated flows. Collectively, these analyses demonstrate that environmental variation interacts with most phases of the freshwater life history of Klamath River Coho Salmon and that anthropogenic environmental variation can have a particularly large bearing on productivity.

Arcata Fisheries Technical Report↗
USGS2020

Technical memorandum: Compound specific isotope analysis, Oak Grove Village well site OU1, Franklin County, Missouri

A study involving Compound Specific Isotope Analysis (CSIA) of trichloroethene (TCE) in groundwater at the Oak Grove Village (OGV) Well Site was conducted by the U.S. Environmental Protection Agency (EPA) in 2014 in an effort to fingerprint the source(s). This technical memorandum, written as a joint effort between HydroGeoLogic, Inc. (HGL) and the U.S. Geological Survey (USGS) Central Midwest Water Science Center (Schumacher, 2019), documents the procedures and analysis of the CSIA investigation. CSIA is an analytical method that measures the isotopic ratios of naturally occurring stable isotopes in specific chemical compounds in environmental samples. CSIA using primarily the ratio of carbon 13 C/ 12 C (δ 13 C), known as 1-D CSIA, has been used for decades in evaluating degradation pathways of organic compounds, including chlorinated solvents such as TCE. Ratios of stable chlorine isotopes 37 Cl/ 35 Cl (δ 37 Cl) also have been used with carbon isotopes, collectively known as 2-D CSIA, and most recently isotopes of hydrogen 2 H/ 1 H (δ 2 H) have been added, collectively known as 3-D CSIA, in attempts to further determine source, transport, and fate of compounds such as TCE (Ertl et al., 1998; Hunkeler et al., 2011; Kuder et al., 2013; McHugh et al., 2011; Shouakar-Stash et al., 2003; EPA, 2008; and van Warmerdam et al., 1995.

Missouri↗
USGS1977

Mercury in oil shale from the mahogany zone of the Green River formation, eastern Utah and western Colorado

Mercury has been reported in concentrations as high as 4 parts per million from oil shale in the Green River Formation near the Federal oil-shale prototype lease-tracts U-a and U-b in eastern Utah. This high concentration of mercury if present throughout a minable zone, would be of concern in commercial oil-shale operations processing large volumes of shale. Using an improved analytical method, surface samples from eastern Utah previously reported to contain high concentrations of mercury were reanalyzed, and an additional 183 drill core samples from the Mahogany zone and adjacent beds were analyzed. The reanalyzed samples averaged slightly more than 0.35 ppm mercury and the drill-core samples averaged 0.37 ppm. The products from a Fischer assay of 100-gram sample of oil shale, found to yield 35 gallons pier ton of oil and 43 ppm of mercury, were analyzed for their mercury content. The spent shale contained only 2 percent of the total mercury in the assay products and the gas fraction contained about 58 percent.

Colorado, Utah↗
USGS2023

Sediment sources and connectivity linked to hydrologic pathways and geomorphic processes: A conceptual model to specify sediment sources and pathways through space and time

Sediment connectivity is a framework for transfer and storage of sediment among different geomorphic compartments across upland and channel network of the catchment sediment cascade. Sediment connectivity and dysconnectivity (i.e., source delivery and storage processes) are linked to the water cycle and hydrologic systems with the associated multiscale interactions with climate, soil, topography, ecology, and landuse/landcover under natural variability and human intervention. We review the sediment connectivity concept and frameworks developed in the last few decades to examine and quantify water and sediment transfer in catchment systems. Past conceptual models of connectivity have attempted to integrate multiple processes into sediment domain, including geomorphic, hydrologic, and ecological processes (i.e., “holistic approach to connectivity”). In particular, multiple studies highlight the importance of sediment and water interaction in defining landscape connectivity. There are also efforts to quantify the topographic controls on sediment connectivity, in the advent of increasingly high-resolution digital terrain models. More recent modeling efforts have integrated structural and functional connectivity through coupling topographic information with hydrologic simulation models. Though this recent modeling development is encouraging, a comprehensive sediment connectivity framework that integrates geomorphic and hydrologic processes across spatiotemporal scales is yet to be conceived. Such an effort will require understanding the governing hydrologic and geomorphic processes that control sediment source, storage, and transport. A conceptual model is proposed to describe dominant hydrologic-sediment connectivity regimes through spatial-temporal feedbacks between hydrologic processes (rainfall, flow routing, and water residence time) and geomorphic drivers (upland soil erosion and deposition, and geomorphic channel erosion and deposition response). Recent advancements in landscape monitoring techniques using geochemical tracers, remote-sensing, increasing availability of hydrologic monitoring data, and the integration of various analytic methods (e.g., isotopic hydrograph separation, stormflow concentration-discharge, hysteretic behavior analysis) have the potential to broaden the spatial and temporal scales of geomorphic observations and understanding of landscape sediment connectivity. Using the conceptual model as a “thinking” space, we examine sediment and hydrologic interactions in real world examples of watershed studies using multiple lines of evidence and modeling techniques.

Conference Paper↗
USGS2025

A framework for guiding management decisions for amphibians in an uncertain future

Managing species in a rapidly changing climate requires knowledge of how species will respond to climate change and other threats while simultaneously developing management actions to reduce threats. Amphibians are one of the most threatened taxa on earth and often serve as the ‘canary in the coalmine’ for the health of ecosystems that countless other species and humans rely on. To understand the status of and guide management for the boreal toad (Anaxyrus boreas boreas), an imperiled amphibian species in the North Central region, we coproduced several products with the Boreal Toad Conservation Team. These products included 1) reconstructed seasonal hydrology patterns for historical boreal toad breeding wetlands and high elevation watersheds in the Southern Rocky Mountain Region (SRMR) from remotely sensed data, 2) current and future predictions of drying rates for historical breeding wetlands, 3) current and future predictions on the status of the boreal toad in the SRMR, and 4) a web tool to guide management actions. While the boreal toad is considered a ‘data rich’ species given data collection efforts that span multiple decades, many amphibian species are considered ‘data poor’, meaning managers lack data on the biology, ecology, or status of the species needed to make sound decisions. To address this knowledge gap, we also quantified drying patterns across watersheds for two ‘data poor’ species in the North Central region at risk from climate change: the Great Basin spadefoot toad ( Spea intermontana ) and the wood frog ( Lithobates sylvaticus ). These new data can guide management decisions for these species by allowing managers to understand habitat changes with respect to water availability, a crucial element for amphibian survival and persistence. Together, these products demonstrate how cutting-edge technology and analytical methods can produce a range of useful information to support amphibian conservation.

Colorado, New Mexico, Wyoming↗
USGS2011

CRMS vegetation analytical team framework: Methods for collection, development, and use of vegetation response variables

This document identifies the main objectives of the Coastwide Reference Monitoring System (CRMS) vegetation analytical team, which are to provide (1) collection and development methods for vegetation response variables and (2) the ways in which these response variables will be used to evaluate restoration project effectiveness. The vegetation parameters (that is, response variables) collected in CRMS and other coastal restoration projects funded under the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA) are identified, and the field collection methods for these parameters are summarized. Existing knowledge on community and plant responses to changes in environmental drivers (for example, flooding and salinity) from published literature and from the CRMS and CWPPRA monitoring dataset are used to develop a suite of indices to assess wetland condition in coastal Louisiana. Two indices, the floristic quality index (FQI) and a productivity index, are described for herbaceous and forested vegetation. The FQI for herbaceous vegetation is tested with a long-term dataset from a CWPPRA marsh creation project. Example graphics for this index are provided and discussed. The other indices, an FQI for forest vegetation (that is, trees and shrubs) and productivity indices for herbaceous and forest vegetation, are proposed but not tested. New response variables may be added or current response variables removed as data become available and as our understanding of restoration success indicators develops. Once indices are fully developed, each will be used by the vegetation analytical team to assess and evaluate CRMS/CWPPRA project and program effectiveness. The vegetation analytical teams plan to summarize their results in the form of written reports and/or graphics and present these items to CRMS Federal and State sponsors, restoration project managers, landowners, and other data users for their input.

Open-File Report↗
USGS1990

Evaluation of selected methods for determining streamflow during periods of ice effect

Seventeen methods for estimating ice-affected streamflow are evaluated for potential use for the U.S. Geological Survey streamflow-gaging station network. The methods evaluated were identified by written responses from U.S. Geological Survey field offices and by a comprehensive literature search. The methods selected and techniques used for applying the methods are described in the report. The methods are evaluated by comparing estimated results to data collected at three streamflow-gaging stations in Iowa during the winter of 1987-88. Discharge measurements were obtained at 1- to 5-day intervals during the ice-affected periods at the three stations to define an accurate baseline record. Discharge records were compiled for each method based on data available assuming a 6-week field schedule. The methods are classified into two general categories, subjective and analytical, depending on whether individual judgement is necessary for method application. On the basis of results of the evaluation for the three Iowa stations, two of the subjective methods (discharge ratio and hydrographic-and-climatic comparison) were more accurate than the other subjective methods, and approximately as accurate as the best analytical method. Three of the analytical methods (index velocity, adjusted rating curve, and uniform flow) could potentially be used for streamflow-gaging stations where the need for accurate ice-affected discharge estimates justifies the expense of collecting additional field data. One analytical method (ice adjustment factor) may be appropriate for use for stations with extremely stable stage-discharge ratings and measuring sections. Further research is needed to refine the analytical methods. The discharge ratio and multiple regression methods produce estimates of streamflow for varying ice conditions using information obtained from the existing U.S. Geological Survey streamflow-gaging network.

Iowa↗
USGS1992

Evaluation of selected methods for determining streamflow during periods of ice effect

Seventeen methods for estimating ice-affected streamflow are evaluated for potential use with the U.S. Geological Survey streamflow-gaging station network. The methods evaluated were identified by written responses from U.S. Geological Survey field offices and by a comprehensive literature search. The methods selected and techniques used for applying the methods are described in this report. The methods are evaluated by comparing estimated results with data collected at three streamflow-gaging stations in Iowa during the winter of 1987-88. Discharge measurements were obtained at 1- to 5-day intervals during the ice-affected periods at the three stations to define an accurate baseline record. Discharge records were compiled for each method based on data available, assuming a 6-week field schedule. The methods are classified into two general categories-subjective and analytical--depending on whether individual judgment is necessary for method application. On the basis of results of the evaluation for the three Iowa stations, two of the subjective methods (discharge ratio and hydrographic-and-climatic comparison) were more accurate than the other subjective methods and approximately as accurate as the best analytical method. Three of the analytical methods (index velocity, adjusted rating curve, and uniform flow) could potentially be used at streamflow-gaging stations, where the need for accurate ice-affected discharge estimates justifies the expense of collecting additional field data. One analytical method (ice-adjustment factor) may be appropriate for use at stations with extremely stable stage-discharge ratings and measuring sections. Further research is needed to refine the analytical methods. The discharge-ratio and multiple-regression methods produce estimates of streamflow for varying ice conditions using information obtained from the existing U.S. Geological Survey streamflow-gaging network.

Iowa↗
USGS2003

Probabilistic assessment methodology for continuous-type petroleum accumulations

The analytic resource assessment method, called ACCESS (Analytic Cell-based Continuous Energy Spreadsheet System), was developed to calculate estimates of petroleum resources for the geologic assessment model, called FORSPAN, in continuous-type petroleum accumulations. The ACCESS method is based upon mathematical equations derived from probability theory in the form of a computer spreadsheet system. ?? 2003 Elsevier B.V. All rights reserved.

International Journal of Coal Geology↗
USGS1997

Computation of the time-varying flow rate from an artesian well in central Dade County, Florida, by analytical and numerical simulation methods

Simulation of the development of a plume of brackish water in a surficial aquifer caused by discharge from a flowing artesian well required an accurate estimate of the rate of flow during a 40-year period. The rate of flow from the well, constructed with 12-inch casing in 1944, was measured to be 2,350 gallons per minute 2 months after completion and 1,170 gallons per minute in 1964, 1965, and 1969. The rates measured 20 years apart appeared to be mutually inconsistent unless the difference could be explained by the: (1) drawdown of the aquifer over time, (2) raising of the altitude at which the water was discharged, (3) installation of 80 feet of 8-inch liner, or (4) deterioration of the condition of the well over time. The latter possibility implies losses of flows through holes in the casing and increased friction losses. Application of an analytical solution relating the time-varying rate of flow to a constant opposing head (a rewriting of the "constant drawdown" formula) failed to reconcile the measured rates, though estimates provided by use of the formula differed by only about 15 percent. Numerical simulation techniques were also used to estimate the rate of artesian flow from the source aquifer, a permeable zone at about 1,200 feet below land surface, near the top of the Upper Floridan aquifer in southeastern Florida. The selected simulation code contained a well-riser model that was used to account for friction losses in the well. Construction of a highly generalized model of the Floridan aquifer system for the flow-rate analysis, and the determination of a set of predevelopment head values for use as an initial condition, permitted simulation of the effects of recharge through leaky confining layers or from aquifer boundaries at a finite distance from the well. The conceptual model supported by the calibration of the model of the Floridan aquifer system is that a hydraulically uniform Lower Floridan aquifer ("Boulder Zone") provides recharge to the Upper Floridan aquifer through a leaky middle confining unit, and head variations in the Upper Floridan aquifer are related to variations in the thickness of the zone of fresh and brackish water extending downward into the confining unit. Results of the flow-rate analysis indicated that the flow rate should reach equilibrium after about 1 week because the Upper Floridan aquifer received recharge from the Boulder Zone through the intervening middle confining unit. The well modifications probably only decreased the rate of flow by 18 to 19 percent. A sensitivity analysis indicated that variation in the roughness coefficient of a degree that could represent severe deterioration of the well casing decreased the estimated flow rate by about 17.5 percent. Another sensitivity analysis indicated that installation of 80 feet of 8-inch liner had only a slight effect on the flow rate. The flow-rate inconsistency was not fully resolved by the analysis, but could be explained as a combination of the result of well modification, deterioration of the condition of the well, and other factors not amenable to analysis (inaccuracy in one or more of the flow-rate measurements or greater than estimated losses through the casing). The transmissivity of the source aquifer was estimated to be 11,125 feet squared per day at the well site. Besides the construction of a generalized model of the Floridan aquifer system, the most significant result of the analysis was the demonstration of a simulation approach for accurately showing the relation between aquifer characteristics and the rate of flow from artesian wells. However, this approach requires considerably more analytical effort and data describing aquifer properties than does application of the constant drawdown formula.

Florida↗
USGS2017

High pressure size exclusion chromatography (HPSEC) determination of dissolved organic matter molecular weight revisited: Accounting for changes in stationary phases, analytical standards, and isolation methods

We reassessed the molecular weight of dissolved organic matter (DOM) determined by high pressure size exclusion chromatography (HPSEC) using measurements made with different columns and various generations of polystyrenesulfonate (PSS) molecular weight standards. Molecular weight measurements made with a newer generation HPSEC column and PSS standards from more recent lots are roughly 200 to 400 Da lower than initial measurements made in the early 1990s. These updated numbers match DOM molecular weights measured by colligative methods and fall within a range of values calculated from hydroxyl radical kinetics. These changes suggest improved accuracy of HPSEC molecular weight measurements that we attribute to improved accuracy of PSS standards and changes in the column packing. We also isolated DOM from wetlands in the Prairie Pothole Region (PPR) using XAD-8, a cation exchange resin, and PPL, a styrene-divinylbenzene media, and observed little difference in molecular weight and specific UV absorbance at 280 nm (SUVA 280 ) between the two solid phase extraction resins, suggesting they capture similar DOM moieties. PPR DOM also showed lower SUVA 280 at similar weights compared to DOM isolates from a global range of environments, which we attribute to oxidized sulfur in PPR DOM that would increase molecular weight without affecting SUVA 280 .

Environmental Science & Technology↗
USGS1995

Computation of the time-varying flow rate from an artesian well in central Dade County, Florida, by analytical and numerical simulation methods

To construct a digital simulation of a plume of brackish water in the surficial Biscayne aquifer of central Dade County, Florida, that originated from a flowing artesian well, it was necessary to quantify the rate of spillage and the consequent point-source loading of the aquifer. However, a flow-rate measurement (2,350 gallons per minute) made 2 months after drilling of the well in 1944 was inconsistent with later measurements (1,170 gallons per minute) in 1964, 1965, and 1969. Possible explanations were the: (1) drawdown of the aquifer over time; (2) raising of the altitude at which the water was discharged; (3) installation of 80 feet of 8-inch liner; (4) an increase in the density of the flowing water; and (5) gradual deterioration of the well casing. The first approach to reconciling the measured flow rates was to apply a form of the equation for constant-drawdown analysis often used to estimate aquifer transmissivity. Next, a numerical simulation analysis was made that provided the means to account for friction loss in the well and recharge across vertically adjacent confining layers and from lateral boundaries. The numerical analysis required the construction of a generalized model of the subsurface from the surficial Biscayne aquifer to the cavernous, dolomitic Boulder Zone at a depth of 3,000 feet. Calibration of the generalized flow model required that the moddle confining unit of the Floridan aquifer system separating the artesian flow zone in the Upper Floridan aquifer from the Lower Floridan aquifer (the Boulder Zone) have a vertical hydraulic conductivity of at least 1 foot per day. The intermediate confining unit separating the flow zone from the surficial Biscayne aquifer was assigned a much lower hydraulic conductivity (0.01 foot per day or less). The model indicated that the observed mounding of Upper Floridan aquifer heads along the axis of the Florida Peninsula was related to the variable depth of the freshwater and brackish-water zone overlying deeper saline water. The analyses only partly reconciled the two rates. The second rate was accepted as representative of the conditions prevailing at the time of its measurement. On the basis of flowmeter logging, it was assumed that an additional 230 gallons per minute escaped through the corroded casing at that time. Factors not amenable to analysis, such as the inherent inaccuracy of the method of estimating flow from the well and possible error in estimating losses through the casing, could easily account for the remainder of the difference between the two measured rates.

Florida↗
USGS2012

Simulation of groundwater conditions and streamflow depletion to evaluate water availability in a Freeport, Maine, watershed

In order to evaluate water availability in the State of Maine, the U.S. Geological Survey (USGS) and the Maine Geological Survey began a cooperative investigation to provide the first rigorous evaluation of watersheds deemed "at risk" because of the combination of instream flow requirements and proportionally large water withdrawals. The study area for this investigation includes the Harvey and Merrill Brook watersheds and the Freeport aquifer in the towns of Freeport, Pownal, and Yarmouth, Maine. A numerical groundwater- flow model was used to evaluate groundwater withdrawals, groundwater-surface-water interactions, and the effect of water-management practices on streamflow. The water budget illustrates the effect that groundwater withdrawals have on streamflow and the movement of water within the system. Streamflow measurements were made following standard USGS techniques, from May through September 2009 at one site in the Merrill Brook watershed and four sites in the Harvey Brook watershed. A record-extension technique was applied to estimate long-term monthly streamflows at each of the five sites. The conceptual model of the groundwater system consists of a deep, confined aquifer (the Freeport aquifer) in a buried valley that trends through the middle of the study area, covered by a discontinuous confining unit, and topped by a thin upper saturated zone that is a mixture of sandy units, till, and weathered clay. Harvey and Merrill Brooks flow southward through the study area, and receive groundwater discharge from the upper saturated zone and from the deep aquifer through previously unknown discontinuities in the confining unit. The Freeport aquifer gets most of its recharge from local seepage around the edges of the confining unit, the remainder is received as inflow from the north within the buried valley. Groundwater withdrawals from the Freeport aquifer in the study area were obtained from the local water utility and estimated for other categories. Overall, the public-supply withdrawals (105.5 million gallons per year (Mgal/yr)) were much greater than those for any other category, being almost 7 times greater than all domestic well withdrawals (15.3 Mgal/yr). Industrial withdrawals in the study area (2.0 Mgal/yr) are mostly by a company that withdraws from an aquifer at the edge of the Merrill Brook watershed. Commercial withdrawals are very small (1.0 Mgal/yr), and no irrigation or other agricultural withdrawals were identified in this study area. A three-dimensional, steady-state groundwater-flow model was developed to evaluate stream-aquifer interactions and streamflow depletion from pumping, to help refine the conceptual model, and to predict changes in streamflow resulting from changes in pumping and recharge. Groundwater levels and flow in the Freeport aquifer study area were simulated with the three-dimensional, finite-difference groundwater-flow modeling code, MODFLOW-2005. Study area hydrology was simulated with a 3-layer model, under steady-state conditions. The groundwater model was used to evaluate changes that could occur in the water budgets of three parts of the local hydrologic system (the Harvey Brook watershed, the Merrill Brook watershed, and the buried aquifer from which pumping occurs) under several different climatic and pumping scenarios. The scenarios were (1) no pumping well withdrawals; (2) current (2009) pumping, but simulated drought conditions (20-percent reduction in recharge); (3) current (2009) recharge, but a 50-percent increase in pumping well withdrawals for public supply; and (4) drought conditions and increased pumping combined. In simulated drought situations, the overall recharge to the buried valley is about 15 percent less and the total amount of streamflow in the model area is reduced by about 19 percent. Without pumping, infiltration to the buried valley aquifer around the confining unit decreased by a small amount (0.05 million gallons per day (Mgal/d)), and discharge to the streams increased by about 8 percent (0.3 Mgal/d). A 50-percent increase in pumping resulted in a simulated decrease in streamflow discharge of about 4 percent (0.14 Mgal/d). Streamflow depletion in Harvey Brook was evaluated by use of the numerical groundwater-flow model and an analytical model. The analytical model estimated negligible depletion from Harvey Brook under current (2009) pumping conditions, whereas the numerical model estimated that flow to Harvey Brook decreased 0.38 cubic feet per second (ft 3 /s) because of the pumping well withdrawals. A sensitivity analysis of the analytical model method showed that conducting a cursory evaluation using an analytical model of streamflow depletion using available information may result in a very wide range in results, depending on how well the hydraulic conductivity variables and aquifer geometry of the system are known, and how well the aquifer fits the assumptions of the model. Using the analytical model to evaluate the streamflow depletion with an incomplete understanding of the hydrologic system gave results that seem unlikely to reflect actual streamflow depletion in the Freeport aquifer study area. In contrast, the groundwater-flow model was a more robust method of evaluating the amount of streamflow depletion that results from withdrawals in the Freeport aquifer, and could be used to evaluate streamflow depletion in both streams. Simulations of streamflow without pumping for each measurement site were compared to the calibratedmodel streamflow (with pumping), the difference in the total being streamflow depletion. Simulations without pumping resulted in a simulated increase in the steady-state flow rate of 0.38 ft 3 /s in Harvey Brook and 0.01 ft 3 /s in Merrill Brook. This translates into a streamflow-depletion amount equal to about 8.5 percent of the steady-state base flow in Harvey Brook, and an unmeasurable amount of depletion in Merrill Brook. If pumping was increased by 50 percent and recharge reduced by 20 percent, the amount of streamflow depletion in Harvey Brook could reach 1.41 ft 3 /s.

Maine↗