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Seabed maps showing topography, ruggedness, backscatter intensity, sediment mobility, and the distribution of geologic substrates in Quadrangle 6 of the Stellwagen Bank National Marine Sanctuary Region offshore of Boston, Massachusetts

The U.S. Geological Survey (USGS), in cooperation with the National Oceanic and Atmospheric Administration's National Marine Sanctuary Program, has conducted seabed mapping and related research in the Stellwagen Bank National Marine Sanctuary (SBNMS) region since 1993. The area is approximately 3,700 square kilometers (km 2 ) and is subdivided into 18 quadrangles. Seven maps, at a scale of 1:25,000, of quadrangle 6 (211 km 2 ) depict seabed topography, backscatter, ruggedness, geology, substrate mobility, mud content, and areas dominated by fine-grained or coarse-grained sand. Interpretations of bathymetric and seabed backscatter imagery, photographs, video, and grain-size analyses were used to create the geology-based maps. In all, data from 420 stations were analyzed, including sediment samples from 325 locations. The seabed geology map shows the distribution of 10 substrate types ranging from boulder ridges to immobile, muddy sand to mobile, rippled sand. Mapped substrate types are defined on the basis of sediment grain-size composition, surface morphology, sediment layering, the mobility or immobility of substrate surfaces, and water depth range. This map series is intended to portray the major geological elements (substrates, topographic features, processes) of environments within quadrangle 6. Additionally, these maps will be the basis for the study of the ecological requirements of invertebrate and vertebrate species that utilize these substrates and guide seabed management in the region.

Massachusetts↗

Streamflow and water-quality conditions including geologic sources and processes affecting selenium loading in the Toll Gate Creek watershed, Aurora, Arapahoe County, Colorado, 2007

Toll Gate Creek is a perennial stream draining a suburban area in Aurora, Colorado, where selenium concentrations have consistently exceeded the State of Colorado aquatic-life standard for selenium of 4.6 micrograms per liter since the early 2000s. In cooperation with the City of Aurora, Colorado, Utilities Department, a synoptic water-quality study was performed along an 18-kilometer reach of Toll Gate Creek extending from downstream from Quincy Reservoir to the confluence with Sand Creek to develop a detailed understanding of streamflow and concentrations and loads of selenium in Toll Gate Creek. Streamflow and surface-water quality were characterized for summer low-flow conditions (July–August 2007) using four spatially overlapping synoptic-sampling subreaches. Mass-balance methods were applied to the synoptic-sampling and tracer-injection results to estimate streamflow and develop spatial profiles of concentration and load for selenium and other chemical constituents in Toll Gate Creek surface water. Concurrent groundwater sampling determined concentrations of selenium and other chemical constituents in groundwater in areas surrounding the Toll Gate Creek study reaches. Multivariate principal-component analysis was used to group samples and to suggest common sources for dissolved selenium and major ions. Hydrogen and oxygen stable-isotope ratios, groundwater-age interpretations, and chemical analysis of water-soluble paste extractions from core samples are presented, and interpretation of the hydrologic and geochemical data support conclusions regarding geologic sources of selenium and the processes affecting selenium loading in the Toll Gate Creek watershed.

Colorado↗

Perchlorate, metals, organic compounds, and lead isotopes in groundwater, surface water, shallow groundwater, and soil within and near the Middleton Municipal Airport–Morey Field (C29), Middleton, Wisconsin, 2022

The Middleton Municipal Airport–Morey Field (C29) is in the City of Middleton and adjacent to the towns of Middleton and Springfield, Wisconsin. Nearby homes in the towns rely on private drinking water wells, and residents are concerned about the potential contamination of groundwater and surface water by airport activities, including flights by small aircraft that use leaded aviation fuel and a fireworks display in July 2021. The U.S. Geological Survey, in cooperation with the Town of Middleton, completed a study in 2022 to characterize the occurrence and sources of perchlorate, metals (including lead), and organic compounds in samples of groundwater, surface water, shallow groundwater, and soils within and near the airport. Lead isotopes were also measured to determine sources of lead by comparing samples to environmental references. Magnitudes of concentrations from samples of water and soil collected in 2022, and their spatial patterns across site locations, indicate the fireworks display in July 2021 was a likely source of perchlorate and metals in the airport study area. The highest perchlorate concentration was measured in surface water at the southeastern corner of the airport near the fireworks launch site; the highest concentrations of fireworks-associated metals were measured in shallow groundwater near the same location. Fireworks were not the only possible source of perchlorate and metals in the airport study area because both were also detected upgradient and away from the fireworks launch site. Ratios of lead isotopes indicate that lead measured in water and soil within the airport study area was primarily sourced from background atmospheric lead deposition or Wisconsin galena lead ore. However, two groundwater samples (one upgradient and one downgradient from the airport; both with concentrations less than 1 microgram per liter) had isotopic signatures matching leaded aviation fuel sold at the airport.

Wisconsin↗

Stratigraphy and hydrologic conditions at the Brookhaven National Laboratory and vicinity, Suffolk County, New York, 1994-97

Brookhaven National Laboratory (BNL) has installed many test borings as part of an effort to delineate the extent of ground-water contamination at the site. In 1994, the U.S. Geological Survey began a study in cooperation with BNL to define the stratigraphy in the 28-square-mile area encompassing BNL, and to monitor ground-water levels in the 300 squaremile area of central Suffolk County that surrounds BNL. The uppermost geologic units at BNL are of Pleistocene age. These sediments are underlain unconformably by the Matawan Group-Magothy Formation, undifferentiated (referred to as the Magothy Formation), of Cretaceous age, which typically consists of light- to dark-gray, variably sorted sand interbedded with light- to dark-gray clay layers; it also contains beds of grayish-brown to brownish-gray sand. Bed thicknesses differ substantially within each boring and tend to be laterally discontinuous as a result of their terrestrial deltaic depositional environment, although a prominent clay unit, referred to as the ?grayish-brown clay? in this report, was encountered at many borings. Pollen-sample analyses confirm that this unit is of Cretaceous age and is the uppermost unit of Cretaceous sediments in several parts of the study area. The upper surface of the Cretaceous deposits is irregular within the 28-square-mile study area and has relief of about 120 feet. Several prominent channels and ridges in the surface are aligned generally northwest-southeast. The Cretaceous surface beneath BNL is characterized more by local erosional features than by the regional cuesta shape that was suggested by previous authors. The overlying Pleistocene-aged units include (1) a sand layer overlain by the Gardiners Clay, (2) the Gardiners Clay, and (3) upper Pleistocene deposits, which include the Upton unit, glacial outwash, glaciolacustrine deposits, and terminal moraine deposits. The sand unit below the Gardiners Clay was the first Pleistocene unit to be deposited atop the irregular surface of the Cretaceous deposits in this area. The Gardiners Clay was deposited during a major rise in sea level as the sea encroached into parts of the present-day BNL study area. The shallow part of the upper Pleistocene deposits generally consists of light-brown sand and gravel but overlies green to grayish-green, variably sorted sand, silt, and clay at altitudes of 50 to 70 feet below sea level in some parts of the study area. This lower part of the upper Pleistocene deposits in the study area was referred to by previous investigators as the unidentified unit and has been designated as the Upton unit in this report. The discharge of ground water to the Peconic and Carmans Rivers locally affects the water-table configuration. The main ground-water divide on Long Island is about 0.5 miles north of the site; a secondary divide originates near the start of flow of the Peconic River and extends east-southeastward toward the South Fork. The water-table configuration on the BNL site is affected by pumping from supply wells and remediation wells, by infiltration of the water through recharge basins, by discharge from the sewage-treatment plant, and by local near-surface clay units. The horizontal hydraulic gradient at BNL typically is 0.001 foot per foot but can steepen near recharge basins and pumping wells. Vertical flow gradients within the upper Pleistocene deposits (upper glacial aquifer) were as large as 0.007 foot per foot (downward) in the northern part of BNL and were negligible in the southern part. Downward vertical gradients between the lower part of the upper glacial aquifer and the upper part of the Magothy Formation (Magothy aquifer) were about 0.018 foot per foot throughout the site.

Water-Resources Investigations Report↗

Computation of bromide concentrations at the Kansas River at De Soto, Kansas, January 2021 through October 2023

The Kansas River is an essential water resource that provides drinking water to more than 950,000 people in northeastern Kansas. Water suppliers that rely on the Kansas River as a water-supply source use physical and chemical water-treatment strategies to remove contaminants before distribution. Water District No. 1 of Johnson County, Kansas (WaterOne), is the largest water supplier in the State and uses the Kansas and Missouri Rivers as water-supply sources to provide drinking water to the Kansas City metropolitan area. WaterOne has been using ozone disinfection as a primary water-treatment strategy since the summer of 2020. Water suppliers that rely on ozone disinfection have become increasingly concerned with the presence of elevated dissolved bromide (the negatively charged form of bromine; hereafter referred to as “bromide”) concentrations in their water-supply source. Ozone disinfection of source water containing elevated concentrations of bromide can lead to the formation of bromate, a regulated disinfection byproduct and probable carcinogen. Real-time computations of bromide concentrations upstream from the WaterOne source-water intake in the Kansas River can be used to assist WaterOne with proactive adjustment of water-treatment strategies. These computations can also be used to advance understanding of hydrologic processes affecting ozone disinfection and formation of bromate. This report documents the development of the surrogate-regression model that computes bromide concentrations in real time at De Soto, Kansas, and characterizes daily and monthly bromide concentrations at this location during the study period. The U.S. Geological Survey (USGS), in cooperation with WaterOne, collected specific conductance and discrete bromide sample data at the USGS streamgage Kansas River at De Soto, Kans. (06892350; hereafter referred to as “De Soto”), during January 2021 through October 2023 to develop a surrogate-regression model using ordinary least-squares regression that computes bromide concentrations at De Soto, which is about 15 miles upstream from the WaterOne source-water intake in the Kansas River. Specific conductance explained about 85 percent of the variance in bromide concentrations at De Soto during the study period. The surrogate-regression model documented in this report estimated that bromide concentrations at De Soto were likely to exceed the WaterOne water-treatment level of concern (150 micrograms per liter [μg/L]) when specific conductance was greater than or equal to about 930 microsiemens per centimeter at 25 degrees Celsius. Surrogate-regression model computations of bromide concentrations documented in this report are available at the USGS National Real-Time Water-Quality website ( https://nrtwq.usgs.gov/ ). Bromide concentrations in discrete samples ranged from 31.9 to 251 μg/L and exceeded the water-treatment level of concern in about 34 percent of the 41 samples collected at De Soto during January 2021 through October 2023. Computed daily bromide concentrations ranged from 38.2 to 277 μg/L and exceeded the water-treatment level of concern about 46 percent of the time during January 2021 through October 2023. Generally, an inverse relation was observed between bromide and streamflow during the study period. Higher bromide concentrations were observed during September through February, and lower bromide concentrations were observed during March through August. Seasonal median bromide concentrations were significantly different in all pairwise seasonal combinations, except for summer versus spring. Computed median bromide concentrations were highest during winter, followed by fall, then spring and summer.

Kansas↗

Occurrence and distribution of trace elements in snow, streams, and streambed sediments, Cape Krusenstern National Monument, Alaska, 2002-2003

Cape Krusenstern National Monument is located in Northwest Alaska. In 1985, an exchange of lands and interests in lands between the Northwest Alaska Native Association and the United States resulted in a 100-year transportation system easement for 19,747 acres in the monument. A road was then constructed along the easement from the Red Dog Mine, a large zinc concentrate producer and located northeast of the monument, through the monument to the coast and a port facility. Each year approximately 1.3 million tonnes of zinc and lead concentrate are transported from the Red Dog Mine via this access road. Concern about the possible deposition of cadmium, lead, zinc and other trace elements in the monument was the basis of a cooperative project with the National Park Service. Concentrations of dissolved cadmium, dissolved lead, and dissolved zinc from 28 snow samples from a 28 mile by 16 mile grid were below drinking water standards. In the particulate phase, approximately 25 percent of the samples analyzed for these trace elements were higher than the typical range found in Alaska soils. Boxplots of concentrations of these trace elements, both in the dissolved and particulate phase, indicate higher concentrations north of the access road, most likely due to the prevailing southeast wind. The waters of four streams sampled in Cape Krusenstern National Monument are classified as calcium bicarbonate. Trace-element concentrations from these streams were below drinking water standards. Median concentrations of 39 trace elements from streambed sediments collected from 29 sites are similar to the median concentrations of trace elements from the U.S. Geological Survey?s National Water-Quality Assessment database. Statistical differences were noted between trace-element concentrations of cadmium, lead, and zinc at sites along the access road and sites north and south of the access road; concentrations along the access road being higher than north or south of the road. When normalized to 1 percent organic carbon, the concentrations of these trace elements are not expected to be toxic to aquatic life when compared to criteria established by the Canadian government and other recent research.

Scientific Investigations Report↗

Emergent sandbar dynamics in the lower Platte River in eastern Nebraska: methods and results of pilot study, 2011

The lower Platte River corridor provides important habitats for two State- and federally listed bird species: the interior least tern (terns; Sternula antillarum athallassos) and the piping plover (plovers; Charadrius melodus). However, many of the natural morphological and hydrological characteristics of the Platte River have been altered substantially by water development, channelization, hydropower operations, and invasive vegetation encroachment, which have decreased the abundance of high-quality nesting and foraging habitat for terns and plovers. The lower Platte River (LPR), defined as 103 miles (mi) of the Platte River between its confluence with the Loup River and its confluence with the Missouri River, has narrowed since the late-19th and early-20th centuries, yet it partially retains many geomorphologic and hydrologic characteristics important to terns and plovers. These birds nest on the sandbars in the river and along shorelines at sand- and gravel-pit lakes in the adjacent valley. The need to balance continued economic, infrastructure, and resource development with the conservation of important physical and aquatic habitat resources requires increased understanding of the physical and biological dynamics of the lower Platte River. Spatially and temporally rich datasets for emergent sandbar habitats are necessary to quantify emergent sandbar dynamics relative to hypothesized controls and stressors. In cooperation with the Lower Platte South Natural Resources District, the U.S. Geological Survey initiated a pilot study of emergent sandbar dynamics along a 22-mi segment of the LPR downstream from its confluence with Salt Creek, near Ashland, Nebraska. The purposes of the study were to: (1) develop methods to rapidly assess sandbar geometries and locations in a wide, sand-bed river, and (2) apply and validate the method to assess emergent sandbar dynamics over three seasons in 2011. An examination of the height of sandbars relative to the local stage of the formative discharge event, and how subsequent river discharges, of both high and low magnitude, alter sandbar geometries and abundance within the LPR was of particular interest. A “rapid-assessment” method was developed with the goal of characterizing the spatial distribution and habitat-relevant geometries of the complete population of sandbars along the study segment. Three primary measures were used to assess emergent sandbar dynamics in the study segment: sandbar area, sandbar height, and sandbar location. Data to derive these measures were collected during three, week-long survey periods in 2011, herein named “spring survey period,” “summer survey period,” and “fall survey period.” Emergent sandbars were grouped into one of three generalized types: (1) bank-attached, (2) island-attached, and (3) mid-channel.

Nebraska↗

A pilot study for delineation of areas contributing water to wellfields at Jackson, Tennessee

The U.S. Geological Survey, in cooperation with the Tennessee Department of Health and Environment, Division of Groundwater Protection, and the Jackson Utility Division, conducted a pilot study to determine data needs and the applicability of four methods for the delineation of wellhead protection areas. Jackson Utility Division in Jackson, Madison County, Tennessee, pumps about 9 million gallons of ground water daily from two municipal wellfields that tap an unconfined sand aquifer. Under natural hydraulic gradients, ground waterflows southward toward the South Wellfield at approximately 2 to 3 feet per day; natural flow toward the North Wellfield from the east at 1 to 2 feet per day. Water quality generally is suitable for most uses. Concentrations of dissolved solids are low, and excessive iron is the only significant naturally occurring water-quality problem. However, trace concentrations of volatile organic compounds have been detected in water pumps from the South Wellfield; the highest concentration of a single compound has been 23 micrograms per liter of tetrachloroethylene. Potential sources of ground-water contamination in the Jackson area include a hazardous-waste site, municipal and industrial landfill, and underground-storage tanks. Some of the four method for delineating wellhead protection areas did not adequately describe zones contributing flow to the wellfields. Calculations based on a uniform flow equation provided a preliminary delineation of zones of contribution for the wellfields and ground-water time-of-travel contours. Limitations of the applied methods motivated the design of a more rigorous hydrogeologic investigation.

Tennessee↗

Estimated 2016 groundwater level and drawdown from predevelopment to 2016 in the Santa Fe Group Aquifer System in the Albuquerque Area, Central New Mexico

The U.S. Geological Survey, in cooperation with the Albuquerque Bernalillo County Water Utility Authority (ABCWUA), has developed a series of maps and associated reports to document changes in the groundwater level in the production zone of the Santa Fe Group aquifer system in the Albuquerque, New Mexico, area. The current map and associated report document the construction of contours representing the groundwater-level surface of winter (November to March) conditions for water year 2016 and estimated net groundwater-level declines (called drawdown) since widespread groundwater pumping began in the early 1960s (called predevelopment conditions). Prior to 2008, groundwater withdrawal from the Santa Fe Group aquifer system was the principal water supply for the study area. The large quantity of withdrawal relative to recharge resulted in drawdown throughout the Albuquerque area. In response, the ABCWUA implemented a strategy for sustainable development of its water resources, including the diversion of surface water as part of the San Juan-Chama Drinking Water Project in 2008. The 2016 groundwater-level contours indicate that the general direction of groundwater flow is towards clusters of production wells in the eastern and northwestern parts of the study area. Drawdown from predevelopment to 2016 is greatest along the eastern margin of the study area and in the northwestern part of the study area, likely correlated with groundwater withdrawals and potentially compounded by proximity to faults. Comparing drawdown in water year 2016 to that of water years 2002, 2008, and 2012 shows a reduction in drawdown (groundwater-level rebound) in the study area since 2008, which corresponds with the timing of reductions in groundwater withdrawals as a result of the ABCWUA’s San Juan-Chama Drinking Water Project. Time-series analysis of groundwater-level measurements in piezometers within the study area also indicates the recent groundwater-level rebound since 2008.

New Mexico↗

Ground-water investigations of the Project Gnome area, Eddy and Lea Counties, New Mexico

The U.S. Atomic Energy Commission, through the Office of Test Operations, Albuquerque Operations Office, plans to detonate a nuclear device in a massive salt bed 1,200 feet beneath the land surface. The project, known as Project Gnome, is an element of the Plowshare program--a study of peacetime applications of nuclear fission. The location of the proposed underground shot is in a sparsely-populated area in southeastern Eddy County, N. Mex., east of the Pecos River and about 25 miles southeast of the city of Carlsbad. The area is arid to Semiarid and ground water is a vital factor in the economic utilization of the land, which is primarily used for stock raising. An investigation of the Project Gnome site and surrounding area for the purposes of evaluating the ground-water resources and the possible effect upon them from the detonation of the nuclear shot was desired by the Commission. This report describes work done by the U.S. Geological Survey on behalf of the Commission and presents results of the investigation of the ground-water resources and geology of the area. The most intensive investigations were made within a 15-mile radius of the site of Project Gnome and mainly on the east side of the Pecos River. The total area of study of over 1,200 square miles includes parts of Eddy and Lea Counties, N. Mex. The Project Gnome site is in the sedimentary Delaware Basin. It is underlain by about 18,000 feet of sedimentary rocks ranging in age from Ordovician to Recent. Upper Permian evaporitic rocks, which contain the principal source of potash available in the United States, are worked in nearby mines. The potash minerals are found in a massive salt bed about 1,400 feet thick in the Salado Formation of Permian age. The land surface of the area is covered mostly by a wind-blown sand and caliche; however, rocks of the Rustler Formation of Permian age and younger rocks of Permian, Triassic, Pleistocene(?) and Recent age crop out at several localities. Solution by ground water of salt at the top of the Salado Formation and of anhydrite within the Rustler Formation has removed thick sections of these rocks. A subsequent lowering of the land surface and differential collapse of the Rustler has formed many sinkholes and has created a karst topography over much of the western part of the area. Ground water is obtained from rocks of Permian, Triassic, Tertiary, and Quaternary age in the general region. However, the only aquifer at the Gnome site is the Culebra Dolomite Member of the Rustler Formation of Permian age. The aquifer is about 500 feet beneath the surface at the site and is about 30 feet thick. An aquifer, immediately above the top of the salt, contains a brine solution in Nash Draw, a few miles west of the Gnome site. This aquifer discharges into the Pecos River and is a major source of contamination of the river water. No potable water is known to be present in the area below the top of the salt of the Salado Formation. The ground water in the area is generally under artesian pressure. The general direction of ground-water movement is toward the Pecos River both east and west of the river. At the Gnome site the artesian head of the water in the Culebra Dolomite Member is about 7.5 feet. The water moves westward through the aquifer at a rate of about ? foot per day. The most widespread utilization of ground water east of the river is for stock use. Irrigation usage west of the Pecos River accounts for the largest withdrawal of water. Wells range in depth from a few tens of feet to nearly 800 feet. Water levels range from a few feet to about 500 feet below the surface. A test well at the Gnome site drawing water from the Culebra Dolomite Member was pumped at a rate of 100 gpm (gallons per minute); however, most wells east of the river yield only a few gpm. Irrigation wells west of the river yield as much as 3,500 gpm. Most of the water in the area is highly mineralized and is suitable only for use by livest

Open-File Report↗

Geology and hydrogeology of the Yucaipa groundwater subbasin, San Bernardino and Riverside Counties, California

The Yucaipa groundwater subbasin (referred to in this report as the Yucaipa subbasin) is located about 75 miles (mi) east of of Los Angeles and about 12 mi southeast of the City of San Bernardino. In the Yucaipa subbasin, as in much of southern California, limited annual rainfall and large water demands can strain existing water supplies; therefore, understanding local surface water and groundwater conditions is essential for managing these resources. To better understand the hydrogeology and water resources in the Yucaipa subbasin, especially groundwater, the San Bernardino Valley Municipal Water District and the U.S. Geological Survey initiated a cooperative study to evaluate the hydrogeologic system of the Yucaipa subbasin and the encompassing Yucaipa Valley watershed. Previous studies of the area provided information on general geologic and hydrologic conditions, but this study provides the first comprehensive definition of the hydrogeology of the subsurface throughout the entire subbasin. The Yucaipa subbasin is located between the northwest trending San Andreas fault zone and San Jacinto fault. Several northeast-trending dip-slip faults dissect the Yucaipa subbasin, providing the mechanism for structural relief within the sediment-filled subbasin and between the subbasin and surrounding mountains and highlands. Several of these dip-slip faults have been previously identified as potential barriers to groundwater flow. This report provides a synthesis of previous studies and a discussion of the geologic interpretations that were used as the foundation for hydrogeologic classification of the Yucaipa subbasin. Notably, this report (1) adopts the recently named and classified sedimentary deposits of Live Oak Canyon geologic formation and extends the mapped distribution of the formation into the Yucaipa subbasin, and (2) adopts the interpretation that activity along the Banning fault predates the deposition of most basin-fill sedimentary materials in the Yucaipa subbasin. Four hydrogeologic units were classified in the Yucaipa subbasin: (1) crystalline basement, (2) consolidated sedimentary materials, (3) unconsolidated sediment, and (4) surficial materials. The crystalline basement unit forms the bottom boundary of the aquifer system, and the three other units comprise the basin-fill aquifer system. The four hydrogeologic units vary in extent, thickness, and structural relief across the subbasin, with the unconsolidated sediment unit serving as the primary aquifer unit. A three-dimensional hydrogeologic framework model was developed for the Yucaipa subbasin and surrounding area to characterize the thickness, extent, and hydrogeologic variability of the aquifer system. Geologic maps, borehole geophysical logs, drillers’ lithology logs, and depth-to-basement gravity data were used to map and interpolate the subsurface extent and structure of the hydrogeologic units within the subbasin. Faults and structures of geologic and (or) hydrogeologic importance were included in the model for future evaluation of their potential effects on groundwater flow. The resulting hydrogeologic framework is consistent with existing geologic concepts and the tectonic and structural history of the Yucaipa subbasin and surrounding area. The framework is also suitable for use in basin-scale hydrogeologic investigations.

California↗

Hydrogeology and ground-water quality in the Black Belt area of west-central Alabama, and estimated water use for aquaculture, 1990

Commercial production of catfish in west-central Alabama began about 1970, and by 1991 catfish ponds covered about 16,000 acres in the Black Belt area of the State. The rapid increase in catfish farming or aquaculture and the associated demand for ground water led the U.S. Geological Survey in cooperation with other Federal and State agencies in 1990 to initiate a study to better define the ground-water resources in the Black Belt area. The major aquifers in the study area are sand and gravel beds in the Eutaw, Gordo, and Coker Formations. Recharge to these aquifers occurs primarily in areas where those formations crop out. The average recharge to the major aquifers in the study area, as estimated from baseflow analysis of streams in the outcrop area, is 11.4 inches per year. Water from the major aquifers in the study area generally is of good quality and suitable for most uses. Water from the Eutaw aquifer, however, contains chloride in concentrations greater than 500 milligrams per liter in central Greene County and in downdip areas in Marengo and Wilcox Counties and is not suitable for public water supply. Some ground water with elevated chloride concentrations is used for catfish farming in these areas, however. The total estimated water use for aquaculture in the study area in 1990 was 21.83 million gallons per day, 16.08 million gallons per day from ground-water sources, and 5.75 million gallons per day from surface water sources. About 13.54 million gallons per day of water was used for filling catfish ponds and an additional 8.29 million gallons per day was used to replace evaporation losses.

Alabama↗

Peak-flow frequency for tributaries of the Colorado River downstream of Austin, Texas

A procedure to estimate the peak discharge associated with large floods is needed for tributaries of the Colorado River downstream of Austin, Texas, so that appropriate peak discharges can be used to estimate floodplain boundaries and used for the design of bridges and other structures. The U.S. Geological Survey, in cooperation with the Lower Colorado River Authority, studied flood peaks for streams in all or parts of 22 counties in that part of the Colorado River Basin extending downstream of Town Lake in Austin to the Gulf of Mexico. The study area was selected because the streams in this area either are tributaries to the Colorado River or have flood characteristics similar to those tributaries. Peak-flow frequency for 38 stations with at least 8 years of data in natural (unregulated and nonurbanized) basins was estimated on the basis of annual peak-streamflow data through water year 1995. Peak-flow frequency represents the peak discharges for recurrence intervals of 2, 5, 10, 25, 50, 100, 250, and 500 years. The peak-flow frequency and drainage basin characteristics for the stations were used to develop two sets of regression equations to estimate peak-flow frequency for tributaries of the Colorado River in the study area. One set of equations was developed for contributing drainage areas less than 32 square miles, and another set was developed for contributing drainage areas greater than 32 square miles. A procedure is presented to estimate the peak discharge at sites where both sets of equations are considered applicable. Additionally, procedures are presented to compute the 50-, 67-, and 90-percent prediction interval for any estimation from the equations.

Texas↗

Development of a Flood-Warning System and Flood-Inundation Mapping for the Blanchard River in Findlay, Ohio

Digital flood-inundation maps of the Blanchard River in Findlay, Ohio, were created by the U.S. Geological Survey (USGS) in cooperation with the City of Findlay, Ohio. The maps, which correspond to water levels at the USGS streamgage at Findlay (04189000), were provided to the National Weather Service (NWS) for incorporation into a Web-based flood-warning system that can be used in conjunction with NWS flood-forecast data to show areas of predicted flood inundation associated with forecasted flood-peak stages. The USGS reestablished one streamgage and added another on the Blanchard River upstream of Findlay. Additionally, the USGS established one streamgage each on Eagle and Lye Creeks, tributaries to the Blanchard River. The stream-gage sites were equipped with rain gages and multiple forms of telemetry. Data from these gages can be used by emergency management personnel to determine a course of action when flooding is imminent. Flood profiles computed by means of a step-backwater model were prepared and calibrated to a recent flood with a return period exceeding 100 years. The hydraulic model was then used to determine water-surface-elevation profiles for 11 flood stages with corresponding streamflows ranging from approximately 2 to 100 years in recurrence interval. The simulated flood profiles were used in combination with digital elevation data to delineate the flood-inundation areas. Maps of Findlay showing flood-inundation areas overlain on digital orthophotographs are presented for the selected floods.

Scientific Investigations Report↗

Occurrence of fecal coliform bacteria in selected streams in Wyoming, 1990-99

The U.S. Geological Survey (USGS), in cooperation with the Wyoming Department of Environmental Quality (WDEQ), is collecting water samples for analysis of fecal coliform bacteria at 18 stream sites as part of a statewide network. Contamination by bacteria of fecal origin in streams where contact recreation is a designated water use is a concern because of potential public-health risk from the presence of enteric pathogens. Fecal coliform concentrations are temporally and spatially variable in Wyoming streams-concentrations ranged from less than 1 to 45,000 colonies per 100 milliliters of water during 1990-99. Fecal coliform concentrations were less than the water-quality criterion of 400 colonies per 100 milliliters in 83 percent of the samples, indicating fecal coliform contamination is not a widespread problem in these Wyoming streams. However, 14 of the 18 monitoring sites had at least one sample in which the fecal coliform concentration exceeded 400 colonies per 100 milliliters at some time during the 10-year period. Fecal coliform concentrations generally are higher during April through September than during October through March. The higher concentrations coincide with the time period when the public-health risk is higher because summer months are when contact recreation use is more likely occurring. Fecal coliform concentrations were positively correlated with discharge and stream temperature and generally were negatively correlated with pH, specific conductance, and dissolved oxygen.

Wyoming↗

Hydrogeology of, and ground-water flow in, a valley-fill and carbonate-rock aquifer system near Long Valley in the New Jersey Highlands

The hydrogeology of and ground-water flow in a valley-fill and carbonate-rock aquifer system were evaluated by using numerical-modeling techniques and geochemical interpretations to address concerns about the adequacy of the aquifer system to meet increasing demand for water. The study was conducted during 1987-90 by the U.S. Geological Survey, in cooperation with the New Jersey Department of Environmental Protection and Energy. The effects of recent and anticipated ground-water withdrawals on water levels, stream base flows, and water budgets were estimated. Simulation results indicate that recent withdrawals of 4.7 million gallons per day have resulted in water-level declines of up to 35 feet. Under conditions of increases in withdrawals of 121 percent, water levels would decline up to an additional 28 feet. The magnitude of predicted average base-flow depletion, when compared with historic low flows, indicates that projected increases in withdrawals may substantially deplete seasonal low flow of Drakes Brook and South Branch Raritan River. Results of a water-budget analysis indicate that the sources of water to additional supply wells would include leakage from the overlying valley-fill aquifer and induced leakage of surface water into the aquifer system. Results of water-quality analyses indicate that human activities are affecting the quality of the ground water. With the exception of an elevated iron concentration in water from one well, concentrations of inorganic constituents in water from 75 wells did not exceed New Jersey primary or secondary drinking-water regulations. Volatile organic compounds were detected in water from several wells; in two samples, concentrations of specific compounds exceeded drinking-water regulations.

Water-Resources Investigations Report↗

Geological, geochemical, and geophysical studies by the U.S. Geological Survey in Big Bend National Park, Texas

Big Bend National Park (BBNP), Tex., covers 801,163 acres (3,242 km 2 ) and was established in 1944 through a transfer of land from the State of Texas to the United States. The park is located along a 118-mile (190-km) stretch of the Rio Grande at the United States-Mexico border. The park is in the Chihuahuan Desert, an ecosystem with high mountain ranges and basin environments containing a wide variety of native plants and animals, including more than 1,200 species of plants, more than 450 species of birds, 56 species of reptiles, and 75 species of mammals. In addition, the geology of BBNP, which varies widely from high mountains to broad open lowland basins, also enhances the beauty of the park. For example, the park contains the Chisos Mountains, which are dominantly composed of thick outcrops of Tertiary extrusive and intrusive igneous rocks that reach an altitude of 7,832 ft (2,387 m) and are considered the southernmost mountain range in the United States. Geologic features in BBNP provide opportunities to study the formation of mineral deposits and their environmental effects; the origin and formation of sedimentary and igneous rocks; Paleozoic, Mesozoic, and Cenozoic fossils; and surface and ground water resources. Mineral deposits in and around BBNP contain commodities such as mercury (Hg), uranium (U), and fluorine (F), but of these, the only significant mining has been for Hg. Because of the biological and geological diversity of BBNP, more than 350,000 tourists visit the park each year. The U.S. Geological Survey (USGS) has been investigating a number of broad and diverse geologic, geochemical, and geophysical topics in BBNP to provide fundamental information needed by the National Park Service (NPS) to address resource management goals in this park. Scientists from the USGS Mineral Resources and National Cooperative Geologic Mapping Programs have been working cooperatively with the NPS and several universities on several research studies within BBNP. Because the last geologic map of the entire BBNP was published in the 1960s, one of the primary goals of the USGS is to provide a new geologic map of BBNP at a scale 1:100,000; this work is ongoing among the USGS, NPS, the Texas Bureau of Economic Geology, and university scientists. This USGS Circular summarizes eight studies funded and primarily carried out by the USGS, but it is not intended to be a comprehensive reference of work conducted in BBNP. This Circular describes topical research of the recently completed interdisciplinary USGS project, which has provided information leading to a more complete understanding of the following topics in BBNP: Tectonic and geologic history (Chapters 1, 2, and 3), Age and formation processes of a skarn mineral deposit (Chapter 4), Geoenvironmental effects of abandoned mercury mines (Chapter 5), Age, source, and geochemistry of surface and subsurface water resources (Chapter 6), Isotopic tracing of food sources of bears (Chapter 7), and Geophysical characteristics of surface and subsurface geology (Chapter 8). Additional information and the geochemical and geophysical data of the USGS studies in BBNP are available on line at http://minerals.cr.usgs.gov/projects/big_bend/index.html.

Texas↗

Regional hydraulic geometry characteristics of stream channels in the Boston Mountains in Arkansas

Many stream-channel infrastructure, habitat enhancement, and restoration projects are undertaken on streams throughout Arkansas by Federal, State, and local agencies as well as by private organizations and businesses with limited data on local geomorphology and streamflow conditions. Equations that relate drainage area above stable stream reaches to the basin characteristics, bankfull streamflow, and the associated channel dimensions can be used to estimate stream conditions. These equations, along with streambed material particle information, provide information that can be used to improve stream-channel projects. The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, Little Rock District, completed a study to develop these equations for streams in the Boston Mountains in Arkansas. Fourteen U.S. Geological Survey streamgages and stream reaches located in the Boston Mountains were selected for analysis. Geomorphic parameters of streams, including the mean bankfull channel dimensions (cross-sectional area, top width, mean depth, and streamflow), and the contributing drainage areas were investigated. Streambed materials were collected at eight of these sites to develop descriptive statistics of the streambed particle-size distributions and percentages of substrate type. Stream reaches at each study site were classified to Rosgen level II stream type based on the averages of stream-channel metrics collected from site cross sections and profiles. Of the 14 selected Boston Mountain stream reaches, 7 were classified as B-type streams, and 7 were classified as C-type streams. For these streams, the significant differences in measured parameters between stream types were that the B-type streams had greater depth, hydraulic radii, and bar D50 and D85 particle sizes, while C-type streams had greater watershed slopes. Streambed material particle size decreased with mean drainage basin elevation and decreased with increasing entrenchment ratios. Bar sediment size exhibited decreasing size with increasing sinuosity. Regional hydraulic geometry curves were constructed for the streams in the Boston Mountains by plotting measured bankfull geometry dimensions from stable reaches and the associated bankfull streamflow against the contributing drainage area.

Arkansas, Oklahoma↗