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At least 1,243 records · Page 69Linked to original sources

USGS1976

Hydrologic data for urban studies in the San Antonio, Texas metropolitan area, 1976

Hydrologic investigations of urban watersheds in Texas were begun by the U.S. Geological Survey in 1954. These studies are now in progress in Austin, Dallas, Dallas County, Fort Worth, Houston, and San Antonio. The Geological Survey, in cooperation with the Texas Department of Water Resources, expanded the existing streamflow network in the San Antonio metropolitan area in May 1968 to begin urban hydrology studies in this area. In September 1968, the program was further expanded to include the collection of water-quality data.

Texas↗

USGS1995

Hydrology and simulation of ground-water flow in the Aguadilla to Rio Camuy area, Puerto Rico

The aquifers of the Aguadilla to Rio Camuy area, in the northwestern part of Puerto Rico, are the least developed of those on the north coast, and relatively little information is available concerning the ground-water system. The present study, which was part of a comprehensive appraisal of the ground-water resources of the North Coast Province, attempts to interpret the hydrology of the area within the constraints of available data. The study area consists of an uplifted rolling plain that is 200 to 400 feet above sea level and a heavily forested, karst upland. The only major streams in the area are the Rfo Camuy and the Rio Guajataca. Most water used in the area is obtained from Lago de Guajataca, just south of the study area, and ground-water use is minimal (less than 5 million gallons per day). Sedimentary rocks of Tertiary age, mainly limestone and calcareous clays, comprise the aquifers of the Aguadilla to Rio Camuy area. The rocks generally dip from 4 to 7 degrees to the north, and the total sedimentary rock sequence may be as much as 6,000 feet thick near the Atlantic coast. Baseflows for the Rio Camuy are 58 cubic feet per second near Bayaney and 72 cubic feet per second near Hatillo. The ground-water discharge to the Rio Camuy between these stations is estimated to be 15 cubic feet per second, or 2.6 cubic feet per second per linear mile. The flow of the Rio Guajataca is regulated by the Guajataca Dam at Lago de Guajataca. Ground-water discharge to the Rio Guajataca between the dam and the coast is estimated to be about 17 cubic feet per.second, based on the average ground-water discharge per linear mile estimated for the Rio Camuy. Both water-table and artesian aquifers are present in the Aguadilla to Rio Camuy area; how-ever, most ground water occurs within the watertable aquifer, which was the primary focus of this study. The top of the confining unit, below the water-table aquifer, generally is within the unnamed upper member of the Cibao Formation; however, it is within the Los Puertos Formation in the eastern part of the study area. The water-table aquifer primarily is composed of rocks of the Aymam6n Limestone and the Los Puertos Formation. The estimated saturated thickness of the water-table aquifer ranges from zero at the southern limit of the aquifer to more than 600 feet south of Isabela. Hydraulic conductivity of the Aymam6n Limestone, based on specific-capacity test data for seven wells, ranges from about 1 to about 25 feet per day and averages 7.5 feet per day. Hydraulic conductivity of the Los Puertos Formation, based on specific-capacity test data for four wells, generally was less than 7 feet. per day. The average hydraulic-conductivity value for both the Aymam6n Limestone and the Los Puertos Formation, based on specific-capacity test data, is estimated to be about 6.0 feet per day. These hydraulic-conductivity values are much less than average values for the water-table aquifer reported for other parts of the North Coast Province. Transmissivity values, based on the average hydraulic-conductivity value for the aquifer derived from specific-capacity tests, range from zero to about 4,000 feet squared per day; however, these values were adjusted upward during model calibration. Ground water generally moves from the highlands in the south toward the sea to the north and west, and locally, to streams. A major groundwater divide extends from the southeastern corner of the study area to the northwest, and separates flow north and east into the study area from flow to the southwest toward the Rio Culebrinas. Nearly all recharge to the aquifer is from infiltration of rainfall into the karst uplands. Discharge from the aquifer primarily occurs as leakage to streams and to the sea, and to a lesser degree as flow to wells. A two-layer, three-dimensional, steady-state, numerical model was constructed to simulateground-water flow in the water-table aquifer between Aguadilla and the R/o Camuy area. A basic a

Water-Resources Investigations Report↗

USGS2013

Flood-inundation maps for the Flatrock River at Columbus, Indiana, 2012

Digital flood-inundation maps for a 5-mile reach of the Flatrock River on the western side of Columbus, Indiana, from County Road 400N to the river mouth at the confluence with Driftwood River, were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Department of Transportation. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/ and the Federal Flood Inundation Mapper Web site at http://wim.usgs.gov/FIMI/FloodInundationMapper.html, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage on the Flatrock River at Columbus (station number 03363900). Near-real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at http://waterdata.usgs.gov/ or the National Weather Service (NWS) Advanced Hydrologic Prediction Service, which also presents the USGS data, at http:/water.weather.gov/ahps/. Flood profiles were computed for the stream reach by means of a one-dimensional step-backwater model. The model was calibrated by using the most current stage-discharge relation at the Flatrock River streamgage, high-water marks that were surveyed following the flood of June 7, 2008, and water-surface profiles from the current flood-insurance study for the City of Columbus. The hydraulic model was then used to compute 12 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum and ranging from 9 ft or near bankfull to 20 ft, which exceeds the stages that correspond to both the estimated 0.2-percent annual exceedance probability flood (500-year recurrence interval flood) and the maximum recorded peak flow. The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from Light Detection and Ranging (LiDAR) data having a 0.37 ft vertical accuracy and 3.9 ft horizontal resolution) to delineate the area flooded at each water level. The availability of these maps on the USGS Federal Flood Inundation Mapper Web site, along with Internet information regarding current stage from the USGS streamgage, will provide emergency management personnel and residents with information that is critical for flood response activities, such as evacuations and road closures, as well as for post-flood recovery efforts.

Indiana↗

USGS2001

Water Resources Data, Georgia, 2001, Volume 1: Continuous water-level, streamflow, water-quality data, and periodic water-quality data, Water Year 2001

Water resources data for the 2001 water year for Georgia consists of records of stage, discharge, and water quality of streams; and the stage and contents of lakes and reservoirs published in two volumes in a digital format on a CD-ROM. Volume one of this report contains water resources data for Georgia collected during water year 2001, including: discharge records of 133 gaging stations; stage for 144 gaging stations; precipitation for 58 gaging stations; information for 19 lakes and reservoirs; continuous water-quality records for 17 stations; the annual peak stage and annual peak discharge for 76 crest-stage partial-record stations; and miscellaneous streamflow measurements at 27 stations, and miscellaneous water-quality data recorded by the NAWQA program in Georgia. Volume two of this report contains water resources data for Georgia collected during calendar year 2001, including continuous water-level records of 159 ground-water wells and periodic records at 138 water-quality stations. These data represent that part of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in Georgia. Note: Historically, this report was published as a paper report. For the 1999 and subsequent water-year reports, the Water Resources Data for Georgia changed to a new, more informative and functional format on CD-ROM. The format is based on a geographic information system (GIS) user interface that allows the user to view map locations of the hydrologic monitoring stations and networks within respective river basins.

Georgia↗

USGS2003

Application of artificial neural networks to complex groundwater management problems

As water quantity and quality problems become increasingly severe, accurate prediction and effective management of scarcer water resources will become critical. In this paper, the successful application of artificial neural network (ANN) technology is described for three types of groundwater prediction and management problems. In the first example, an ANN was trained with simulation data from a physically based numerical model to predict head (groundwater elevation) at locations of interest under variable pumping and climate conditions. The ANN achieved a high degree of predictive accuracy, and its derived state-transition equations were embedded into a multiobjective optimization formulation and solved to generate a trade-off curve depicting water supply in relation to contamination risk. In the second and third examples, ANNs were developed with real-world hydrologic and climate data for different hydrogeologic environments. For the second problem, an ANN was developed using data collected for a 5-year, 8-month period to predict heads in a multilayered surficial and limestone aquifer system under variable pumping, state, and climate conditions. Using weekly stress periods, the ANN substantially outperformed a well-calibrated numerical flow model for the 71-day validation period, and provided insights into the effects of climate and pumping on water levels. For the third problem, an ANN was developed with data collected automatically over a 6-week period to predict hourly heads in 11 high-capacity public supply wells tapping a semiconfined bedrock aquifer and subject to large well-interference effects. Using hourly stress periods, the ANN accurately predicted heads for 24-hour periods in all public supply wells. These test cases demonstrate that the ANN technology can solve a variety of complex groundwater management problems and overcome many of the problems and limitations associated with traditional physically based flow models.

Natural Resources Research↗

USGS2001

Selected hydrologic data for Little Cottonwood Creek, Salt Lake County, Utah, September 1998

Metals enter Little Cottonwood Creek in Salt Lake County, Utah, in drainage water that discharges from inactive mines in the watershed (fig. 1). As part of a study to evaluate the effects of this mine drainage on water quality, a sodium chloride tracer was injected into Little Cottonwood Creek during September 17-18, 1998. The purpose of the injection was to quantify stream discharge; to identify inflows, both those observable and those dispersed in the subsurface; and ultimately, to determine which areas within the watershed contribute the most metals to Little Cottonwood Creek. The purpose of this report is to make these data available to agencies responsible for managing the area’ s water resources and to supplement interpretive reports for this study.

Utah↗

USGS2011

Hydrogeomorphic processes of thermokarst lakes with grounded-ice and floating-ice regimes on the Arctic coastal plain, Alaska

Thermokarst lakes cover > 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded ice) and deeper lakes maintaining perennial liquid water (floating ice). Thus, lake depth relative to maximum ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum ice thickness by analysing remotely sensed, water quality, and climatic data over a 35-year period. Shoreline erosion rates due to permafrost degradation ranged from < 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P − E L ) with periods of full and nearly dry basins. Shorter-term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long-term record for only shallow lakes. Our analysis suggests that grounded-ice lakes are ice-free on average 37 days longer than floating-ice lakes resulting in a longer period of evaporative loss and more frequent negative P − E L . These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum ice thickness in ACP lakes.

Alaska↗

USGS2018

Episodic master recession evaluation of groundwater and streamflow hydrographs for water-resource estimation

Hydrograph analysis tools using a master recession curve (MRC) can produce many types of hydrologically important watershed-response quantifications, including aquifer recharge and stormflow characterization. An MRC is the relation between the value of a measured response R and its rate of change with time, d R /d t , occurring on the falling limb when there is no infiltration or other water input. We have developed MRC and episodic hydrograph-evaluation methods for multiple purposes, utilizing both water table and streamflow data. The determination of a parameterized MRC through a structured procedure provides a basis for quantification of hydrologic variables and characteristics that can be validly compared among different events, sites, and periods of time. Application of the MRC to needed hydrologic quantifications is done with our revised episodic master recession (EMR) method. Expert-guided iterative procedures are used to quantify parameters needed in applying the MRC and EMR methods to a given site. Hydrologic judgments such as the significance threshold for response magnitude, and the time window within which the precipitation is assumed to be the cause of an observed response, inherently involve some elements of subjectivity. Our structured iterative approach, however, affords much flexibility in formulating expert judgments and serves to confine them to statements and procedures that can be quantified and documented. Parallel application to streamflow and water table hydrographs can produce new hydrologic insights and understanding, not least in the role of unsaturated zone processes in controlling exchanges among components of the water cycle.

Vadose Zone Journal↗

USGS1995

Water-related scientific activities of the U.S. Geological Survey in Nevada, fiscal years 1993-94

The U.S. Geological Survey has been collecting water-resources data in Nevada since 1890. Most of the projects that constitute the current Nevada District program can be classified as either basic- data acquisition (about 25 percent) or hydrologic interpretation (about 75 percent). About 39 percent of the activities are supported by cooperative agreements with State and local agencies. Technical projects supported by other Federal agencies make up about 32 percent of the program, and the re- maining 29 percent consists of USGS data collection, interpretive projects, and research. Water con- ditions in most of Nevada during fiscal years 1993 and 1994 continued to be dry, a continuation of drought conditions since late 1986. The major water-resource issues in Nevada include: water allocation in the Truckee River and Carson River Basins; water-supply needs of Las Vegas and the Reno/Sparks area, including water-importation plans; hydrologic effects of weapons testing at the Nevada Test Site; assessment of potential long-term effects of the proposed Yucca Mountain Nuclear Waste Repository; and drought. Future water-resources issues in Nevada are likely to center on water supply for, and environmental effects of, the rapidly growing population centers at Las Vegas, Reno, and Elko; impacts of operations at the Nevada Test Site; management of interstate rivers such as the Truckee, Carson, Walker, and Colorado Rivers; hydrologic and environmental impacts at heavily mined areas; and water-quality management in the Lake Tahoe Basin.

Open-File Report↗

USGS1997

Hydrologic investigations in the Mammoth Corridor, Yellowstone National Park and vicinity, U.S.A.

The Mammoth Corridor in and adjacent to Yellowstone National Park encompasses a N-S alignment of geothermal features that extends from the Norris Geyser Basin adjacent to the Yellowstone caldera through Mammoth Hot Springs to the Corwin Springs Known Geothermal Resources Area (KGRA). Thermal springs in this region discharge water that ranges from NaKCl, silica-depositing type to CaNaHC0 3 SO 4 , travertine-depositing type. Although only a few relatively shallow wells have been drilled in the corridor, the region is of special interest because of the environmental issues associated with potential geothermal development adjacent to Yellowstone National Park. The U.S. Geological Survey conducted an intensive hydrogeologic study of this region during 1988–1990 and continued to collect hydrologic and geophysical data until 1994. The results of these investigations document the rates of discharge of thermal water and heat within the corridor, evidence for a magmatic heat source beneath the Mammoth Hot Springs area, and evidence for separate geothermal systems associated with Mammoth Hot Springs and with thermal waters discharging in the KGRA in the vicinity of La Duke Hot Springs. These investigations also indicate that limited development of the 70°C geothermal resource in the La Duke area would not affect thermal springs in Yellowstone National Park.

Geothermics↗

USGS2009

Groundwater availability of the Central Valley Aquifer, California

California's Central Valley covers about 20,000 square miles and is one of the most productive agricultural regions in the world. More than 250 different crops are grown in the Central Valley with an estimated value of $17 billion per year. This irrigated agriculture relies heavily on surface-water diversions and groundwater pumpage. Approximately one-sixth of the Nation's irrigated land is in the Central Valley, and about one-fifth of the Nation's groundwater demand is supplied from its aquifers. The Central Valley also is rapidly becoming an important area for California's expanding urban population. Since 1980, the population of the Central Valley has nearly doubled from 2 million to 3.8 million people. The Census Bureau projects that the Central Valley's population will increase to 6 million people by 2020. This surge in population has increased the competition for water resources within the Central Valley and statewide, which likely will be exacerbated by anticipated reductions in deliveries of Colorado River water to southern California. In response to this competition for water, a number of water-related issues have gained prominence: conservation of agricultural land, conjunctive use, artificial recharge, hydrologic implications of land-use change, and effects of climate variability. To provide information to stakeholders addressing these issues, the USGS Groundwater Resources Program made a detailed assessment of groundwater availability of the Central Valley aquifer system, that includes: (1) the present status of groundwater resources; (2) how these resources have changed over time; and (3) tools to assess system responses to stresses from future human uses and climate variability and change. This effort builds on previous investigations, such as the USGS Central Valley Regional Aquifer System and Analysis (CV-RASA) project and several other groundwater studies in the Valley completed by Federal, State and local agencies at differing scales. The principal product of this new assessment is a tool referred to as the Central Valley Hydrologic Model (CVHM) that accounts for integrated, variable water supply and demand, and simulates surface-water and groundwater-flow across the entire Central Valley system. The development of the CVHM comprised four major elements: (1) a comprehensive Geographic Information System (GIS) to compile, analyze and visualize data; (2) a texture model to characterize the aquifer system;(3) estimates of water-budget components by numerically modeling the hydrologic system with the Farm Process (FMP); and (4) simulations to assess and quantify hydrologic conditions.

Professional Paper↗

USGS2007

Marl prairie vegetation response to 20th century hydrologic change

We conducted geochronologic and pollen analyses from sediment cores collected in solution holes within marl prairies of Big Cypress National Preserve to reconstruct vegetation patterns of the last few centuries and evaluate the stability and longevity of marl prairies within the greater Everglades ecosystem. Based on radiocarbon dating and pollen biostratigraphy, these cores contain sediments deposited during the last ~300 years and provide evidence for plant community composition before and after 20th century water management practices altered flow patterns throughout the Everglades. Pollen evidence indicates that pre-20th century vegetation at the sites consisted of sawgrass marshes in a peat-accumulating environment; these assemblages indicate moderate hydroperiods and water depths, comparable to those in modern sawgrass marshes of Everglades National Park. During the 20th century, vegetation changed to grass-dominated marl prairies, and calcitic sediments were deposited, indicating shortening of hydroperiods and occurrence of extended dry periods at the site. These data suggest that the presence of marl prairies at these sites is a 20th century phenomenon, resulting from hydrologic changes associated with water management practices.

Florida↗

USGS2019

Hydrologic balance, water quality, chemical-mass balance, and geochemical modeling of hyperalkaline ponds at Big Marsh, Chicago, Illinois, 2016–17

Hyperalkaline (pH greater than 12) ponds and groundwater exist at Big Marsh near Lake Calumet, Chicago, Illinois, a site used by the steel industry during the mid-1900s to deposit steel- and iron-making waste, in particular, slag. The hyperalkaline ponds may pose a hazard to human health and the environment. The U.S. Geological Survey (USGS), in cooperation with the Environmental Protection Agency (EPA) and in collaboration with the City of Chicago’s Park District, completed a study to evaluate the hydrologic balance, water quality, and chemical-mass balance of hyperalkaline ponds at Big Marsh and geochemical modeling used to evaluate remediation options for water quality at the site based on data collected in 2016–17. Synoptic measurements of surface-water and groundwater elevations were used to determine flow directions and to enable a preliminary estimate of the hydrologic balance for the ponds. Water-quality samples also were collected and analyzed for selected constituents including major anions and cations, nutrients, metals, and trace elements. The results of the water-quality analyses were used to develop a geochemical model to evaluate concentrations, factors affecting pH, and the state of equilibrium between surface waters and atmospheric carbon dioxide. The geochemical model was used to evaluate remediation scenarios using riprap, spillways, or active aeration. The results indicate that active aeration will decrease the pH to near 7.5 in about 8 hours, the fastest rate of the scenarios. Passive aeration, such as riprap or spillways, also can be effective at decreasing the pH in about 45 hours, but spatial obstacles limit their implementation. Seasonal variations in temperature also affect the rate of equilibration, where colder temperatures may have a lower pH than warmer temperatures and may affect the timing and frequency of remediation.

Illinois↗

USGS2019

Use of a Numerical Model to Simulate the Hydrologic System and Transport of Contaminants Near Joint Base Cape Cod, Western Cape Cod, Massachusetts

Historical training and operational activities at Joint Base Cape Cod (JBCC) on western Cape Cod, Massachusetts, have resulted in the release of contaminants into an underlying glacial aquifer that is the sole source of water to the surrounding communities. Remedial systems have been installed to contain and remove contamination from the aquifer. Groundwater withdrawals for public supply are expected to increase as the region continues to urbanize. Increases in water-supply withdrawals and wastewater return flow likely will affect the hydrologic system around JBCC and could affect the transport of any contamination that may remain in the aquifer following remediation of contamination from the JBCC. The U.S. Geological Survey, in cooperation with the Air Force Civil Engineer Center, developed a numerical, steady-state regional model of the Sagamore flow lens on western Cape Cod and evaluated the potential effects of future (2030) groundwater withdrawals on water levels, streamflows, hydraulic gradients, and advective transport near the JBCC. The aquifer consists generally of sandy sediments underlain by impermeable bedrock and is bounded laterally by a freshwater/saltwater interface. Data on the altitude of the bedrock surface, position of the freshwater/saltwater interface, lithology of the aquifer, spatial distribution of recharge, and hydrologic boundaries were incorporated into the three-dimensional, finite-difference groundwater flow model. Some inputs into the numerical model—aquifer properties, leakances, and recharge—are represented as parameters to facilitate estimation of optimal parameter values in an inverse calibration. A hybrid parameterization scheme, with both zones of piecewise constancy and pilot points, is used to represent hydraulic conductivity; other adjustable parameters include recharge, boundary leakance, and porosity. Data on water levels, the distribution of subsurface contamination, and groundwater ages were compiled, evaluated, and used to develop observations of long-term average hydraulic gradients and advective-transport patterns. These observations of steady-state hydrologic conditions were combined with the parameterized groundwater model in an inverse calibration to estimate model parameters that best fit the observations. Current (2010) and future (2030) conditions were simulated in the calibrated model to characterize the groundwater flow system and to determine potential effects of increased groundwater withdrawals on advective-transport patterns at the JBCC. Groundwater flow and advective transport are radially outward from a water-table divide in the northern part of the JBCC; flow diverges from the divide toward all points of the compass. Most groundwater flow and contaminant transport occur in shallow parts of the aquifer. On average, about one-half of the groundwater flux occurs in the shallowest 20 percent of the saturated thickness; shallow flow is even more predominant near streams and lakes. Projected (2030) increases in groundwater withdrawals decrease water levels by a maximum of about 1.2 feet in the northern part of the JBCC; drawdowns exceeding 1 foot generally are limited to areas near the largest increases in withdrawals, such as in the northern part of the JBCC, near Long Pond in Falmouth, and in eastern Barnstable. Streamflow decreases average about 6 percent; the largest decreases are in areas with the largest drawdowns. Changes in hydraulic-gradient directions at the water table exceed 1 degree in about 13 percent of the aquifer, generally near groundwater divides where gradient magnitudes are small and near large groundwater withdrawals. Predictions of advective transport from randomly selected locations at the water table are similar for current (2010) and future (2030) groundwater withdrawals. The results indicate that projected increases in groundwater withdrawals affect water levels and streamflows, but effects on hydraulic gradients and advective transport at the JBCC likely are small. Several underlying assumptions inherent in the model, including observations and weights used in the calibration, representation of local-scale heterogeneity, and simulation of the freshwater/saltwater interface, could affect model calibration and predictions; these assumptions were evaluated with alternative models and alternative inverse calibrations. Eight alternative calibrations were performed in which different, but reasonable, observations and weights were used. The preferred calibrated model had the best overall fit to the observations. Fine-grained silty sediments occur in many parts of the aquifer, and silt lenses can locally affect hydraulic gradients. A set of alternative models in which silts were represented with different correlation distances and hydraulic conductivities indicated that explicitly representing silt lenses could affect model calibration but that the implicit representation of local-scale heterogeneity may be sufficient at the regional scale to represent regional-scale hydraulic gradients. For the coastal boundary, two alternative models representing silty and sandy seabeds and their associated interface positions were developed to test the importance of the assumed coastal-boundary condition. The two alternative models resulted in different predictions of streamflow—streamflows increase with smaller (silty) seabed leakances. However, predictions of advective transport, particularly near the JBCC, generally were similar between the alternative and preferred calibrated models, indicating that the seabed leakance and associated interface position at the coastal boundary does not affect simulations of advective transport in inland parts of the aquifer.

Massachusetts↗

USGS2004

Observed and simulated ground motions in the San Bernardino basin region for the Hector Mine, California, earthquake

During the MW 7.1 Hector Mine earthquake, peak ground velocities recorded at sites in the central San Bernardino basin region were up to 2 times larger and had significantly longer durations of strong shaking than sites just outside the basin. To better understand the effects of 3D structure on the long-period ground-motion response in this region, we have performed finite-difference simulations for this earthquake. The simulations are numerically accurate for periods of 2 sec and longer and incorporate the detailed spatial and temporal heterogeneity of source rupture, as well as complex 3D basin structure. Here, we analyze three models of the San Bernardino basin: model A (with structural constraints from gravity and seismic reflection data), model F (water well and seismic refraction data), and the Southern California Earthquake Center version 3 model (hydrologic and seismic refraction data). Models A and F are characterized by a gradual increase in sediment thickness toward the south with an abrupt step-up in the basement surface across the San Jacinto fault. The basin structure in the SCEC version 3 model has a nearly uniform sediment thickness of 1 km with little basement topography along the San Jacinto fault. In models A and F, we impose a layered velocity structure within the sediments based on the seismic refraction data and an assumed depth-dependent Vp/Vs ratio. Sediment velocities within the SCEC version 3 model are given by a smoothly varying rule-based function that is calibrated to the seismic refraction measurements. Due to computational limitations, the minimum shear-wave velocity is fixed at 600 m/sec in all of the models. Ground-motion simulations for both models A and F provide a reasonably good match to the amplitude and waveform characteristics of the recorded motions. In these models, surface waves are generated as energy enters the basin through the gradually sloping northern margin. Due to the basement step along the San Jacinto fault, the surface wave energy is confined to the region north of this structure, consistent with the observations. The SCEC version 3 model, lacking the basin geometry complexity present in the other two models, fails to provide a satisfactory match to the characteristics of the observed motions. Our study demonstrates the importance of using detailed and accurate basin geometry for predicting ground motions and also highlights the utility of integrating geological, geophysical, and seismological observations in the development and validation of 3D velocity models.

California↗

USGS2015

Sustainable groundwater management in California

The U.S. Geological Survey (USGS) uses data collection, modeling tools, and scientific analysis to help water managers plan for, and assess, hydrologic issues that can cause “undesirable results” associated with groundwater use. This information helps managers understand trends and investigate and predict effects of different groundwater-management strategies.

California↗

USGS2004

Surface- and Ground-Water Monitoring and Mapping of Selected Features at the Blue Ridge Parkway Mt. Pisgah Campground, Haywood County, North Carolina, 2002

During 2002, a baseline study of hydrologic conditions was conducted, and selected features were mapped within the Mt. Pisgah campground on the Blue Ridge Parkway in Haywood County, North Carolina. Field surveys were performed by using global positioning system equipment one time (January 2002) during the study to locate hydrologic and other types of features in the study area. Water-level and streamflow data and seasonal water-quality samples were collected from a stream that receives all surface-water drainage from the campground area. During 2002, water levels (stage) in the stream ranged from 1.09 to 1.89 feet above gage datum (4,838.06 to 4,838.86 feet above mean sea level). Flow in the stream ranged from 0.05 to 9.7 cubic feet per second. Annual daily mean flow for calendar year 2002 was approximately 0.35 cubic foot per second (about 226,000 gallons per day). Samples collected from the stream had low concentrations of all constituents measured. Four compounds associated with human activity (camphor, N,N-diethyl-meta-toluamide (the insect repellent DEET), tributylphosphate, and methylsalicylate) were detected in the stream samples; however, concentrations were less than detection levels. Stream samples collected in April and September and analyzed for fecal coliform bacteria had densities of 76 and 110 colonies per 100 milliliters of water, respectively. No violations of water-quality standards were noted for any constituent measured in the stream samples. Seven shallow ground-water wells were installed near a natural area in the center of the campground. Ground-water levels measured periodically in these wells and in two existing shallow piezometers generally were highest in the spring and lowest in the fall. Water temperature, pH, and specific conductance were measured in samples collected from the shallow wells in April and September 2002. Measured pH values were consistently lowest in samples from two wells on the west side of the natural area and highest in samples from the well located near the center of the natural area. Specific-conductance values measured in samples from wells on the east side of the natural area were lower than those measured in samples from the other wells. Specific-conductance values measured in samples from two wells on the west side and from one well near the center of the natural area generally were two to three times higher than the specific-conductance values measured in samples from wells on the east side of the natural area. Samples for fecal coliform bacteria were collected from six wells on September 11, 2002. The fecal coliform densities in samples from most of the wells were less than or equal to 8 colonies per 100 milliliters. Samples from two of the three wells on the west side of the natural area had coliform densities of 16 and 480 colonies per 100 milliliters. Other ground-water samples collected on September 11 and September 24 were analyzed with a spectrophotometer in the U.S. Geological Survey (USGS) North Carolina District Office for nitrate concentrations only. From the samples collected on September 11, estimated nitrate concentrations of 1 milligram per liter or less were detected in three wells, two on the west side and one on the east side of the natural area. Nitrate was not detected with a spectrophotometer in any of the ground-water samples collected on September 24. Indicator test strips also were used in the field to screen for nitrate and nitrite in ground-water samples collected on September 24. Nitrate was detected by test strips in one well on the west side of the natural area, with estimated concentrations of 1 milligram per liter or less indicated. Nitrite was not detected by the test strips in samples collected from any of the wells.

North Carolina↗

USGS2008

U.S. Geological Survey Science Support Strategy for Biscayne National Park and Surrounding Areas in Southeastern Florida

The U.S. Geological Survey conducts a wide range of research in and around the Biscayne National Park region of southern Florida. This research encompasses the biologic, ecologic, meteorologic, geologic, and hydrologic components of the system, including water-quality analyses, ground-water modeling, hydrogeologic-data collection, ecologic-habitat evaluations, wetlands characterizations, biogeochemistry of ecosystems, and paleo-ecologic analyses. Relevant information is provided herein for researchers and managers interested in the Biscayne Bay area and about current U.S. Geological Survey efforts that address important resource protection and management issues. Specifically, managers and scientists are provided with information on current and recently completed U.S. Geological Survey projects and a sample listing of potential U.S. Geological Survey research projects addressing relevant issues that face the study area.

Open-File Report↗