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USGS1997

Hydrogeology and simulation of ground-water flow in the thick regolith-fractured crystalline rock aquifer system of Indian Creek basin, North Carolina

The Indian Creek Basin in the southwestern Piedmont of North Carolina is one of five type areas studied as part of the Appalachian Valleys-Piedmont Regional Aquifer-System analysis. Detailed studies of selected type areas were used to quantify ground-water flow characteristics in various conceptual hydrogeologic terranes. The conceptual hydrogeologic terranes are considered representative of ground-water conditions beneath large areas of the three physiographic provinces--Valley and Ridge, Blue Ridge, and Piedmont--that compose the Appalachian Valleys-Piedmont Regional Aquifer-System Analysis area. The Appalachian Valleys-Piedmont Regional Aquifer-System Analysis study area extends over approximately 142,000 square miles in 11 states and the District of Columbia in the Appalachian highlands of the Eastern United States. The Indian Creek type area is typical of ground-water conditions in a single hydrogeologic terrane that underlies perhaps as much as 40 percent of the Piedmont physiographic province. The hydrogeologic terrane of the Indian Creek model area is one of massive and foliated crystalline rocks mantled by thick regolith. The area lies almost entirely within the Inner Piedmont geologic belt. Five hydrogeologic units occupy major portions of the model area, but statistical tests on well yields, specific capacities, and other hydrologic characteristics show that the five hydrogeologic units can be treated as one unit for purposes of modeling ground-water flow. The 146-square-mile Indian Creek model area includes the Indian Creek Basin, which has a surface drainage area of about 69 square miles. The Indian Creek Basin lies in parts of Catawba, Lincoln, and Gaston Counties, North Carolina. The larger model area is based on boundary conditions established for digital simulation of ground-water flow within the smaller Indian Creek Basin. The ground-water flow model of the Indian Creek Basin is based on the U.S. Geological Survey?s modular finite-difference ground-water flow model. The model area is divided into a uniformly spaced grid having 196 rows and 140 columns. The grid spacing is 500 feet. The model grid is oriented to coincide with fabric elements such that rows are oriented parallel to fractures (N. 72° E.) and columns are oriented parallel to foliation (N. 18° W.). The model is discretized vertically into 11 layers; the top layer represents the soil and saprolite of the regolith, and the lower 10 layers represent bedrock. The base of the model is 850 feet below land surface. The top bedrock layer, which is only 25 feet thick, represents the transition zone between saprolite and unweathered bedrock. The assignment of different values of transmissivity to the bedrock according to the topographic setting of model cells and depth results in inherent lateral and vertical anisotropy in the model with zones of high transmissivity in bedrock coinciding with valleys and draws, and zones of low transmissivity in bedrock coinciding with hills and ridges. Lateral anisotropy tends to be most pronounced in the north-northwest to south-southeast direction. Transmissivities decrease nonlineraly with depth. At 850 feet, depending on topographic setting, transmissivities have decreased to about 1 to 4 percent of the value of transmissivity immediately below the regolith-bedrock interface. The model boundaries are, for the most part, specified-flux boundaries that coincide with streams that surround the Indian Creek Basin. The area of active model nodes within the boundaries is about 146 square miles and has about 17,400 active cells. The numerical model is designed not as a predictive tool, but as an interpretive one. The model is designed to help gain insight into flow-system dynamics. Predictive capabilities of the numerical model are limited by the constraints placed on the flow system by specified fluxes and recharge distribution.

North Carolina↗

USGS1980

Ground water of coal deposits, Bay County, Michigan

A coal deposit in Bay County, Mich., typical of Pennsylvanian-coal deposits in the State, was studied to determine the degree to which hydrologic factors might affect future coal mining. The coal deposit, which averages about 0.5 meters in thickness, lies 50 meters below land surface. It is part of a multi-layered aquifer system that contains sandstone, shale, sand and gravel, and clay units in addition to beds of coal. Hydrologic characteristics (hydraulic conductivity and storage coefficient) of each unit were evaluated by analyses of aquifer tests and a finite-difference groundwater flow model. A model simulating groundwater flow to a hypothetical mine was developed. Results of the study indicate that seepage will probably not be great enough to preclude mining coal. Also, pumping water to keep the mine dry will have little effect on heads in aquifers outside the mine during the first decade of mining. Although coal was mined in Michigan during 1860-1950, significant reserves remain. These deposits, part of the Saginaw Formation of Pennsylvanian age, are near the industrialized parts of the State. The quantity of pumped water needed to keep mines dry and the effect of pumping on aquifers surrounding the mines is a major factor in determining the feasibility of opening new mines.

Michigan↗

USGS2007

Climate change: Potential impacts and interactions in wetlands of the United States

Wetlands exist in a transition zone between aquatic and terrestrial environments which can be altered by subtle changes in hydrology. Twentieth century climate records show that the United States is generally experiencing a trend towards a wetter, warmer climate; some climate models suggest that his trend will continue and possibly intensify over the next 100 years. Wetlands that are most likely to be affected by these and other potential changes (e.g., sea-level rise) associated with atmospheric carbon enrichment include permafrost wetlands, coastal and estuarine wetlands, peatlands, alpine wetlands, and prairie pothote wetlands. Potential impacts range from changes in community structure to changes in ecological function, and from extirpation to enhancement. Wetlands (particularly boreal peatlands) play an important role in the global carbon cycle, generally sequestering carbon in the form of biomass, methane, dissolved organic material and organic sediment. Wetlands that are drained or partially dried can become a net source of methane and carbon dioxide to the atmosphere, serving as a positive biotic feedback to global warming. Policy options for minimizing the adverse impacts of climate change on wetland ecosystems include the reduction of current anthropogenic stresses, allowing for inland migration of coastal wetlands as sea-level rises, active management to preserve wetland hydrology, and a wide range of other management and restoration options.

Journal of the American Water Resources Associatio↗

USGS2021

Hydrology of annual winter water level drawdown regimes in recreational lakes of Massachusetts, United States

Annual winter water level drawdown (WD) is a common lake management strategy to maintain recreational value by controlling nuisance macrophytes and preventing ice damage to shoreline infrastructure in lakes of the northeastern United States. The state of Massachusetts provides general guidelines for lake managers to implement and practice WDs. However, WD management reporting is not required and as such empirical water level records are scarce, making it difficult to assess guideline adherence and link these management actions to littoral habitat conditions. We monitored water levels bihourly in 18 lakes with ongoing WD regimes and 3 non-drawdown lakes over 3–4 yr. Our results show an interlake drawdown magnitude gradient of 0.07–2.66 m with intralake consistency across years. Corresponding WD magnitudes generated exposure of 1.3–37.6% for entire lakebeds and 9.2–71.1% for littoral zones. WD durations averaged 171 d and ranged widely from 5 to 246 d. Longer recession and refill phase durations and faster recession rates were moderately to strongly correlated with drawdown magnitudes. WDs were predominantly initiated prior to the state of Massachusetts 1 November starting guideline (83.1%) and refilled to summer reference levels after the recommended date of 1 April (70.6%). To minimize ecological impacts while still meeting recreational goals, WD performance guidelines may require a more fine-scale approach that integrates local hydrogeomorphic features and the presence of WD-sensitive littoral biotic assemblages. However, climate change model projections of warmer and wetter winters in the Northeast indicate increasing uncertainty for WD as an effective and worthwhile macrophyte control tool.

Massachusetts↗

USGS2012

Integrated watershed-scale response to climate change for selected basins across the United States

A study by the U.S. Geological Survey (USGS) evaluated the hydrologic response to different projected carbon emission scenarios of the 21st century using a hydrologic simulation model. This study involved five major steps: (1) setup, calibrate and evaluated the Precipitation Runoff Modeling System (PRMS) model in 14 basins across the United States by local USGS personnel; (2) acquire selected simulated carbon emission scenarios from the World Climate Research Programme's Coupled Model Intercomparison Project; (3) statistical downscaling of these scenarios to create PRMS input files which reflect the future climatic conditions of these scenarios; (4) generate PRMS projections for the carbon emission scenarios for the 14 basins; and (5) analyze the modeled hydrologic response. This report presents an overview of this study, details of the methodology, results from the 14 basin simulations, and interpretation of these results. A key finding is that the hydrological response of the different geographical regions of the United States to potential climate change may be different, depending on the dominant physical processes of that particular region. Also considered is the tremendous amount of uncertainty present in the carbon emission scenarios and how this uncertainty propagates through the hydrologic simulations.

Scientific Investigations Report↗

USGS1994

Great Salt Lake basins study unit

In 1991, the U.S. Geological Survey (USGS) began implementing a full-scale National Water-Quality Assessment (NAWQA) Program. The long-term goals of the NAWQA Program are to describe the status and trends in the quality of a large, representative part of the Nation’s surface- and ground-water resources and to provide a sound, scientific understanding of the primary natural and human factors that affect the quality of these resources. In meeting these goals, the program will produce a wealth of water-quality information that will be useful to policy makers and managers at Federal, State, and local levels. A major design feature of the NAWQA Program will enable water-quality information at different areal scales to be integrated. A major component of the program is study-unit investigations, which ae the principal building blocks of the program upon which national-level assessment activities will be based. The 60 study-unit investigations that make up the program are hydrologic systems that include principal river basins and aquifer systems throughout the Nation. These study units cover areas from less than 1.000 to greater than 60,000 mi 2 and incorporate from about 60 to 70 percent of the Nation’s water use and population served by public water supply. In 1993, assessment activities began in the Great Salt Lake Basins NAWQA study unit.

Idaho, Utah, Wyoming↗

USGS1991

National water-quality assessment program : the Albemarle- Pamlico drainage

In 1991, the U.S. Geological Survey (USGS) began to implement a full-scale National Water-Quality Assessment (NAWQA) program. Long-term goals of the NAWQA program are to describe the status and trends in the quality of a large, representative part of the Nation's surface- and ground-water resources and to provide a sound, scientific understanding of the primary natural and human factors affecting the quality of these resources. In meeting these goals, the program will produce a wealth of water quality information that will be useful to policy makers and managers at the national, State, and local levels. Study-unit investigations constitute a major component of the NAWQA program, forming the principal building blocks on which national-level assessment activities are based. The 60 study-unit investigations that make up the program are hydrologic systems that include parts of most major river basins and aquifer systems. These study units cover areas of 1,200 to more than 65,000 square miles and incorporate about 60 to 70 percent of the Nation's water use and population served by public water supply. In 1991, the Albemarle-Pamlico drainage was among the first 20 NAWQA study units selected for study under the full-scale implementation plan. The Albemarle-Pamlico drainage study will examine the physical, chemical, and biological aspects of water quality issues in a coordinated investigation of surface water and ground water in the Albemarle-Pamlico drainage basin. The quantity and quality of discharge from the Albemarle-Pamlico drainage basin contribute to some water quality problems in the biologically sensitive waters of Albemarle and Pamlico Sounds. A retrospective analysis of existing water quality data will precede a 3-year period of intensive data-collection and analysis activities. The data resulting from this study and the improved understanding of important processes and issues in the upstream part of the study unit will enhance understanding of the quality of water in Albemarle-Pamlico Sounds, the second largest estuarine system in the United States.

Open-File Report↗

USGS1971

Suggested criteria for hydrologic design of storm-drainage facilities in the San Francisco Bay Region, California

This report presents basic criteria, in the form of tables and graphs, for each of the four methods of hydrologic design most commonly used in the San Francisco Bay region--flood-frequency analysis, Rational Method, unit-hydrograph method, and runoff simulation by means of hydrologic basin modeling. The term "hydrologic design" as used in this report refers to the computation of either design values of peak discharge or design hydrographs of storm runoff. The hydraulics of open-channel and pipeline flow and the actual design of appurtenances for conveying the runoff are not discussed in this paper. Use of the suggested criteria results in fairly close agreement between peak discharges computed by the flood-frequency and unit-hydrograph methods. Those peak discharges are not directly comparable with discharges computed by the Rational Method, in part because the results obtained by the Rational Method are affected by the values assigned to parameters for overland and channel flow. Those parameters are additional to the ones used in the flood-frequency and unit-hydrograph methods. A demonstration of runoff simulation by use of a hydrologic basin model is beyond the scope of this paper--such demonstrations are found in the appropriate references cited. However, this report does present an original technique for transposing storm rainfall in the region, storm transposition being commonly required to obtain the precipitation input used with hydrologic basin models.

California↗

USGS1985

Effects of surface coal mining and reclamation on ground water in small watersheds in the Allegheny Plateau, Ohio

The hydrologic effects of surface coal mining in unlimited areas is difficult to predict, partly because of a lack of adequate data collected before and after mining and reclamation. In order to help provide data to assess the effects of surface mining on the hydrology of small basins in the coal fields of the eastern United States, the U.S. Bureau of Mines sponsored a comprehensive hydrologic study at three sites in the Ohio part of the Eastern Coal Province. These sites are within the unqlaciated part of the Allegheny Plateau, and are representative of similar coal-producing areas in Kentucky, West Virginia, and Pennsylvania. The U.S. Geological Survey was responsible for the ground-water phase of the study. The aquifer system at each watershed consisted of two localized perched aquifers (top and middle) above a deeper, more regional aquifer. The premining top aquifer was destroyed by mining in each case, and was replaced by spoils during reclamation. The spoils formed new top aquifers that were slowly becoming resaturated at the end of the study period. Water levels in the aquifers were about the same after reclamation as before mining, although levels rose in a few places. It appears that the underclay at the base of the new top aquifers at all three sites prevents significant downward leakage from the top aquifers to lower except in places where the layer may have been damaged during mining. Water in the top aquifers is a calcium sulfate type, whereas calcium bicarbonate type water predominated before mining. The median specific conductance of water in the new top aquifers was about 5 times greater than that of the original top aquifers in two of the watersheds, and 1 1/2 times the level of the original top aquifers in the third. Concentrations of dissolved sulfate, iron, and manganese in the top aquifers before mining generally did not exceed U.S. and Ohio Environmental Protection Agency drinking-water limits, but generally exceeded these limits after reclamation. Water-quality changes in the middle aquifers were minor by comparison. Water levels and water quality in the deeper, regional aquifers were unaffected by mining.

Water-Resources Investigations Report↗

USGS2017

The U.S. Geological Survey Monthly Water Balance Model Futures Portal

The U.S. Geological Survey Monthly Water Balance Model Futures Portal ( https://my.usgs.gov/mows/ ) is a user-friendly interface that summarizes monthly historical and simulated future conditions for seven hydrologic and meteorological variables (actual evapotranspiration, potential evapotranspiration, precipitation, runoff, snow water equivalent, atmospheric temperature, and streamflow) at locations across the conterminous United States (CONUS). The estimates of these hydrologic and meteorological variables were derived using a Monthly Water Balance Model (MWBM), a modular system that simulates monthly estimates of components of the hydrologic cycle using monthly precipitation and atmospheric temperature inputs. Precipitation and atmospheric temperature from 222 climate datasets spanning historical conditions (1952 through 2005) and simulated future conditions (2020 through 2099) were summarized for hydrographic features and used to drive the MWBM for the CONUS. The MWBM input and output variables were organized into an open-access database. An Open Geospatial Consortium, Inc., Web Feature Service allows the querying and identification of hydrographic features across the CONUS. To connect the Web Feature Service to the open-access database, a user interface—the Monthly Water Balance Model Futures Portal—was developed to allow the dynamic generation of summary files and plots based on plot type, geographic location, specific climate datasets, period of record, MWBM variable, and other options. Both the plots and the data files are made available to the user for download

Open-File Report↗

USGS1986

Hydrogeology of the eastern part of the Salt River Valley area, Maricopa and Pinal Counties, Arizona

The Salt River Valley is a major agricultural and metropolitan area in semiarid south-central Arizona. Groundwater in the permeable sedimentary deposits underlying the area is a major water supply for agricultural, municipal, and industrial users. Groundwater levels have declined as much as 400 ft in recent years. Management of the remaining groundwater resources and their protection from contamination will require knowledge of the hydrogeologic framework and the water-bearing characteristics of the sedimentary units in the groundwater system. The rocks in the eastern part of the Salt River Valley are divided into six units--crystalline rocks, extrusive rocks, red units, lower unit, middle unit, and upper unit. The crystalline and extrusive rocks underlie the basin and form virtually impermeable hydrologic boundaries. The red, lower, middle and upper sedimentary units contain most of the groundwater. The red unit contains usable quantities of ground water, principally near Scottsdale, where it yields as much as 1 ,000 gallons/min (gpm) of water to wells. The lower unit, which makes up the largest volume of sedimentary deposits, consists mostly of mudstone, clay, silt, and evaporite deposits that may be as much as 10,000 ft thick in the central part of the basin. Wells tapping the mudstone, clay, silt yield 50 (gpm) or less but the conglomerate and the sand and gravel may yield as much as 3,500 gpm. The middle unit is the principal water-bearing unit in the basin and consists mostly of silt, siltstone, and silty sand and gravel. The unit is as much as 1,000 ft thick in the central part of the basin and as much as 700 ft is saturated. The unit will yield as much as 1,000 gpm where the saturated thickness is at least 500 ft. Locally, north of Mesa, the unit yields as much as 4,000 gpm. The upper unit is gravel, sand, and silt and is saturated only in a small area in the southwestern part of the basin. Where saturated, the unit may yield as much as 4,500 gpm. The upper unit transmits recharge derived from sheet flow, from flood flow in ephemeral streams, and from irrigation to the water table. (Author 's abstract)

Water-Resources Investigations Report↗

USGS1989

Geology and water resources of Owens Valley, California

Owens Valley, a long, narrow valley located along the east flank of the Sierra Nevada in east-central California, is the main source of water for the city of Los Angeles. The city diverts most of the surface water in the valley into the Owens River-Los Angeles Aqueduct system, which transports the water more than 200 miles south to areas of distribution and use. Additionally, ground water is pumped or flows from wells to supplement the surface-water diversions to the river-aqueduct system. Pumpage from wells needed to supplement water export has increased since 1970, when a second aqueduct was put into service, and local concerns have been expressed that the increased pumpage may have had a detrimental effect on the environment and the indigenous alkaline scrub and meadow plant communities in the valley. The scrub and meadow communities depend on soil moisture derived from precipitation and the unconfined part of a multilayered aquifer system. This report, which describes the hydrogeology of the aquifer system and the water resources of the valley, is one in a series designed to (1) evaluate the effects that ground-water pumping has on scrub and meadow communities and (2) appraise alternative strategies to mitigate any adverse effects caused by pumping. Two principal topographic features are the surface expression of the geologic framework--the high, prominent mountains on the east and west sides of the valley and the long, narrow intermountain valley floor. The mountains are composed of sedimentary, granitic, and metamorphic rocks, mantled in part by volcanic rocks as well as by glacial, talus, and fluvial deposits. The valley floor is underlain by valley fill that consists of unconsolidated to moderately consolidated alluvial fan, glacial and talus, and fluvial and lacustrine deposits. The valley fill also includes interlayered recent volcanic flows and pyroclastic rocks. The bedrock surface beneath the valley fill is a narrow, steep-sided graben that is structurally separated into the Bishop Basin to the north and the Owens Lake Basin to the south. These two structural basins are separated by (1) a bedrock high that is the upper bedrock block of an east-west normal fault, (2) a horst block of bedrock (the Poverty Hills), and (3) Quaternary basalt flows and cinder cones that intercalate and intrude the sedimentary deposits of the valley fill. The resulting structural separation of the basins allowed separate development of fluvial and lacustrine depositional systems in each basin. Nearly all the ground water in Owens Valley flows through and is stored in the saturated valley fill. The bedrock, which surrounds and underlies the valley fill, is virtually impermeable. Three hydrogeologic units compose the valley-fill aquifer system, a defined subdivision of the ground-water system, and a fourth represents the valley fill below the aquifer system and above the bedrock. The aquifer system is divided into horizontal hydrogeologic units on the basis of either (1) uniform hydrologic characteristics of a specific lithologic layer or (2) distribution of the vertical hydraulic head. Hydrogeologic unit 1 is the upper unit and represents the unconfined part of the system, hydrogeologic unit 2 represents the confining unit (or units), and hydrogeologic unit 3 represents the confined part of the aquifer system. Hydrogeologic unit 4 represents the deep part of the ground-water system and lies below the aquifer system. Hydrogeologic unit 4 transmits or stores much less water than hydrogeologic unit 3 and represents either a moderately consolidated valley fill or a geologic unit in the valley fill defined on the basis of geophysical data. Nearly all the recharge to the aquifer system is from infiltration of runoff from snowmelt and rainfall on the Sierra Nevada. In contrast, little recharge occurs to the system by runoff from the White and Inyo Mountains or from direct precipitation on the valley floor. Ground water flows from the margins of the valley towards the center of the valley; the ground water then flows south to the terminus of the system at Owens (dry) Lake. Ground water flows south from Bishop Basin to Owens Lake Basin through the narrows that constrict the flow opposite Poverty Hills. The aquifer system in the northern half of Owens Lake Basin is divided into east and west halves by the barrier effect caused by the Owens Valley fault. Discharge from the aquifer system is primarily by pumpage and evapotranspiration, and to a lesser extent by flowing wells, springs, underflow, and leakage to the Owens River-Los Angeles aqueduct system. Withdrawals from pumped or flowing wells is the largest component of discharge and accounts for about 50 percent of the outflow from the system. Transpiration by scrub and meadow plant communities, and to a lesser extent by irrigated alfalfa pasture, accounts for about 40 percent of the system's discharge. Natural hydraulic conductivity ranges from less than 400 to about 12,000 feet per day in the basalt flows, the more permeable material in the aquifer system. Where the basalts are fractured by explosives and drilling techniques, actual transmissivities can be greater than 1,000,000 feet squared per day. Hydraulic conductivities in sedimentary deposits of the aquifer system range from less than a few feet per day in lacustrine clays to more than 300 feet per day in gravel stringers and beach deposits in the transition zone between alluvial fan deposits and fluvial and lacustrine deposits. Degree of confinement in the aquifer system generally increases to the south and east in both the Bishop and Owens Lake Basins. The vertical hydraulic gradient across hydrogeologic unit 2 and confining beds in hydrogeologic units 1 and 3 is a function of (1) the asymmetric recharge and hydraulic head created by the dominant recharge from Sierra Nevada runoff and (2) the areal extent and thickness of the confining beds. Although most of the pumpage is from hydrogeologic unit 3, some coincident drawdown has been recorded in nonpumped wells that tap unit 1. Drawdown in hydrogeologic unit 1 is a function of changes in (1) lateral flow through hydrogeologic unit 1, (2) upward flow of ground water through the confining beds, (3) downward leakage of water from hydrogeologic unit 1 to unit 3 through wells, (4) direct withdrawal from well intervals open to hydrogeologic unit 1, and (5) increased evapotranspiration. The water in the aquifer system is generally of excellent quality for public supply and irrigation, with the exception of water stored in thick sequences of lacustrine silts and clays near Owens Lake. The water is principally a calcium bicarbonate type and dissolved-solids concentrations range from approximately 104 to 325 milligrams per liter. Water in the lacustrine sediments of Owens (dry) Lake is a sodium bicarbonate type and dissolved-solids concentrations are about 5,400 milligrams per liter.

California↗

USGS1991

Geology and water resources of Owens Valley, California

Water Supply Paper↗

USGS2025

Characterizing water-quality response after the 2020 Cameron Peak Fire using a novel application of the Weighted Regressions on Time, Discharge, and Season method

The frequency and severity of wildfire activity in the western United States emphasises the utility of hydrologic models to predict water-quality response. This study presents a novel application of the Weighted Regressions on Time, Discharge and Season (WRTDS) method to assess potential changes in water quality in two watersheds draining the North Fork Big Thompson River and Buckhorn Creek in Larimer County, Colorado that were affected by the 2020 Cameron Peak Fire. WRTDS models were developed using 12 years of pre-fire data and used to estimate the expected constituent concentrations for each sample collected in the post-fire record. The predicted constituent concentrations modelled in this manner are representative of conditions in the absence of fire and allow pre-fire and post-fire stream chemistry to be quantitatively compared. Nitrate and total phosphorus concentrations showed the greatest differences between the observed and predicted concentrations, which were up to 153% greater than expected. We linked changes in source inputs and elevation as likely controls on the difference in magnitude and timing of response between the two watersheds. Post-fire arsenic and manganese concentrations were greater than the predicted concentrations in both watersheds, with arsenic up to 42% greater and manganese up to 85% greater than the model predictions. Post-fire calcium, magnesium, chloride and sulphate concentrations were greater than model predictions at the North Fork and less than the predictions at Buckhorn. We argue that greater burn severity at Buckhorn likely reduced soil–water infiltration and led to bypassed subsurface flow paths through a major lithologic source of these constituents. Post-fire changes in total organic carbon and dissolved iron concentrations were weakly supported by the model results, as observed concentrations were largely within the bounds of expected values calculated from the pre-fire model. The novel approach to WRTDS presented in this study could be a useful tool for water-quality assessments after land disturbances in the western United States.

Colorado↗

USGS2004

Regional hydrology and simulation of flow of stratified-drift aquifers in the glaciated northeastern United States

No abstract available.

Connecticut, Maine, Massachusetts, New Hampshire, ↗

USGS2014

Evaluation of statistically downscaled GCM output as input for hydrological and stream temperature simulation in the Apalachicola–Chattahoochee–Flint River Basin (1961–99)

The accuracy of statistically downscaled general circulation model (GCM) simulations of daily surface climate for historical conditions (1961–99) and the implications when they are used to drive hydrologic and stream temperature models were assessed for the Apalachicola–Chattahoochee–Flint River basin (ACFB). The ACFB is a 50 000 km 2 basin located in the southeastern United States. Three GCMs were statistically downscaled, using an asynchronous regional regression model (ARRM), to ⅛° grids of daily precipitation and minimum and maximum air temperature. These ARRM-based climate datasets were used as input to the Precipitation-Runoff Modeling System (PRMS), a deterministic, distributed-parameter, physical-process watershed model used to simulate and evaluate the effects of various combinations of climate and land use on watershed response. The ACFB was divided into 258 hydrologic response units (HRUs) in which the components of flow (groundwater, subsurface, and surface) are computed in response to climate, land surface, and subsurface characteristics of the basin. Daily simulations of flow components from PRMS were used with the climate to simulate in-stream water temperatures using the Stream Network Temperature (SNTemp) model, a mechanistic, one-dimensional heat transport model for branched stream networks. The climate, hydrology, and stream temperature for historical conditions were evaluated by comparing model outputs produced from historical climate forcings developed from gridded station data (GSD) versus those produced from the three statistically downscaled GCMs using the ARRM methodology. The PRMS and SNTemp models were forced with the GSD and the outputs produced were treated as “truth.” This allowed for a spatial comparison by HRU of the GSD-based output with ARRM-based output. Distributional similarities between GSD- and ARRM-based model outputs were compared using the two-sample Kolmogorov–Smirnov (KS) test in combination with descriptive metrics such as the mean and variance and an evaluation of rare and sustained events. In general, precipitation and streamflow quantities were negatively biased in the downscaled GCM outputs, and results indicate that the downscaled GCM simulations consistently underestimate the largest precipitation events relative to the GSD. The KS test results indicate that ARRM-based air temperatures are similar to GSD at the daily time step for the majority of the ACFB, with perhaps subweekly averaging for stream temperature. Depending on GCM and spatial location, ARRM-based precipitation and streamflow requires averaging of up to 30 days to become similar to the GSD-based output. Evaluation of the model skill for historical conditions suggests some guidelines for use of future projections; while it seems correct to place greater confidence in evaluation metrics which perform well historically, this does not necessarily mean those metrics will accurately reflect model outputs for future climatic conditions. Results from this study indicate no “best” overall model, but the breadth of analysis can be used to give the product users an indication of the applicability of the results to address their particular problem. Since results for historical conditions indicate that model outputs can have significant biases associated with them, the range in future projections examined in terms of change relative to historical conditions for each individual GCM may be more appropriate.

Florida, Georgia↗

USGS1991

Geohydrology of Mesozoic rocks in the upper Colorado River basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

The purpose of this report is to provide a quantitative analysis of the occurrence, movement, and quality of water and the hydrologic characteristics of aquifers and confining units in the Mesozoic rocks of the Upper Colorado River Basin. The analysis is regional in scope and, hence, does not address site-specific problems caused by intricate localized quality, lithologic, or structural discontinuities. The report is intended to answer questions about the lateral flow of ground water from recharge to discharge areas, its vertical movement between aquifer systems, and the general water-yielding properties of aquifers. Because the investigation was regional in scope, analyses of recharge, ground-water movement, discharge, and storage were based on data and interpretations from the results of previous investigations and existing files from government and private sources. Analyses of hydrologic properties and water quality were based largely on the same sources but were supplemented with a small quantity of newly collected data for areas for which this type of information was lacking.

Arizona, Colorado, New Mexico, Utah, Wyoming↗

USGS2012

Hydrogeologic characteristics and water quality of a confined sand unit in the surficial aquifer system, Hunter Army Airfield, Chatham County, Georgia

An 80-foot-deep well (36Q397, U.S. Geological Survey site identification 320146081073701) was constructed at Hunter Army Airfield to assess the potential of using the surficial aquifer system as a water source to irrigate a ballfield complex. A 300-foot-deep test hole was drilled beneath the ballfield complex to characterize the lithology and water-bearing characteristics of sediments above the Upper Floridan aquifer. The test hole was then completed as well 36Q397 open to a 19-foot-thick shallow, confined sand unit contained within the surficial aquifer system. A single-well, 24-hour aquifer test was performed by pumping well 36Q397 at a rate of 50 gallons per minute during July 13-14, 2011, to characterize the hydrologic properties of the shallow, confined sand unit. Two pumping events prior to the aquifer test affected water levels. Drawdown during all three pumping events and residual drawdown during recovery periods were simulated using the Theis formula on multiple changes in discharge rate. Simulated drawdown and residual drawdown match well with measured drawdown and residual drawdown using values of horizontal hydraulic conductivity and specific storage, which are typical for a confined sand aquifer. Based on the hydrologic parameters used to match simulated drawdown and residual drawdown to measured drawdown and residual drawdown, the transmissivity of the sand was determined to be about 400 feet squared per day. The horizontal hydraulic conductivity of the sand was determined to be about 20 feet per day. Analysis of a water-quality sample indicated that the water is suitable for irrigation. Sample analysis indicated a calcium-carbonate type water having a total dissolved solids concentration of 39 milligrams per liter. Specific conductance and concentrations of all analyzed constituents were below those that would be a concern for irrigation, and were below primary and secondary water-quality criteria levels.

Georgia↗