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At least 721 records · Page 40Linked to original sources

USGS2017

Systematic comparisons between PRISM version 1.0.0, BAP, and CSMIP ground-motion processing

A series of benchmark tests was run by comparing results of the Processing and Review Interface for Strong Motion data (PRISM) software version 1.0.0 to Basic Strong-Motion Accelerogram Processing Software (BAP; Converse and Brady, 1992), and to California Strong Motion Instrumentation Program (CSMIP) processing (Shakal and others, 2003, 2004). These tests were performed by using the MatLAB implementation of PRISM, which is equivalent to its public release version in Java language. Systematic comparisons were made in time and frequency domains of records processed in PRISM and BAP, and in CSMIP, by using a set of representative input motions with varying resolutions, frequency content, and amplitudes. Although the details of strong-motion records vary among the processing procedures, there are only minor differences among the waveforms for each component and within the frequency passband common to these procedures. A comprehensive statistical evaluation considering more than 1,800 ground-motion components demonstrates that differences in peak amplitudes of acceleration, velocity, and displacement time series obtained from PRISM and CSMIP processing are equal to or less than 4 percent for 99 percent of the data, and equal to or less than 2 percent for 96 percent of the data. Other statistical measures, including the Euclidian distance (L 2 norm) and the windowed root mean square level of processed time series, also indicate that both processing schemes produce statistically similar products.

Open-File Report↗

USGS2025

The importance of sampling design for unbiased estimation of survival using joint live-recapture and live resight models

Survival is a key life history parameter that can inform management decisions and basic life history research. Because true survival is often confounded with emigration from the study area, many studies are forced to estimate apparent survival (i.e., probability of surviving and remaining inside the study area), which can be much lower than true survival for highly mobile species. One method for estimating true survival is the Barker joint live-recapture/live-resight (JLRLR) model, which combines capture data from a study area (hereafter the ‘capture site’) with resighting data from a broader geographic area. This model assumes that live resights occur throughout the entire area where animals can disperse to and this assumption is often not met in practice. Here we use simulation to evaluate survival bias from a JLRLR model under study design scenarios that differ in the site selection for resights: global, random, fixed including the capture site, and fixed excluding the capture site. Simulation results indicate that fixed designs that included the capture site showed negative survival bias, whereas fixed designs that excluded the capture site exhibited positive survival bias. The magnitude of the bias was dependent on movement and survival, where scenarios with high survival and frequent movement had minimal bias. In an effort to help minimize bias, we developed a multistate version of the JLRLR and demonstrated reductions in survival bias compared to the single-state version for most designs. Our results suggest minimizing bias can be accomplished by: 1) using a random resight design when feasible if global sampling is not possible, 2) using the multistate JLRLR model when appropriate, 3) including the capture site in the resight sampling frame when possible, and 4) reporting survival as apparent survival if fixed sites are used for resight with the single state JLRLR model.

Peer Community 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↗

USGS2008

GAP Analysis Bulletin Number 15

The Mission of the Gap Analysis Project (GAP) <http://gapanalysis.nbii.gov> is to promote conservation by providing broad geographic information on biological diversity to resource managers, planners, and policy makers who can use the information to make informed decisions. As part of the National Biological Information Infrastructure (NBII) <http://www.nbii.gov>?a collaborative program to provide increased access to data and information on the nation?s biological resources--GAP data and analytical tools have been used in hundreds of applications: from basic research to comprehensive state wildlife plans; from educational projects in schools to ecoregional assessments of biodiversity. The challenge: keeping common species common means protecting them BEFORE they become threatened. To do this on a state or regional basis requires key information such as land cover descriptions, predicted distribution maps for native animals, and an assessment of the level of protection currently given to those plants and animals. GAP works cooperatively with Federal, state, and local natural resource professionals and academics to provide this kind of information. GAP activities focus on the creation of state and regional databases and maps that depict patterns of land management, land cover, and biodiversity. These data can be used to identify ?gaps? in conservation--instances where an animal or plant community is not adequately represented on the existing network of conservation lands. GAP is administered through the U.S. Geological Survey. Through building partnerships among disparate groups, GAP hopes to foster the kind of collaboration that is needed to address conservation issues on a broad scale. For more information, contact: John Mosesso National GAP Director 703-648-4079 Kevin Gergely National GAP Operations Manager 208-885-3565

GAP Bulletin↗

USGS1970

A proposed streamflow-data program for Idaho

A streamflow information system is proposed for Idaho. This proposal resulted from a study in which the basic steps were (1) definition of long-term program goals, (2) examination and evaluation of available data to determine which goals have been achieved, and (3) consideration of alternate programs and techniques for meeting the remaining goals. The following conclusions are drawn from the study. Goals have been achieved on many of the principal unregulated streams; operation of 11 new or reactivated gages on principal streams are needed to satisfy needs. However, the goals cannot be met on unregulated minor streams with present data and analytical techniques. Few of the goals can be achieved with the available data for major or minor streams which are regulated, which are fed by springs or receive significant return flows, or which are affected by extensive channel losses. These streams will require river-systems studies which necessitate collection of complete records of diversions, return flows, upstream storage, and information relative to exchange between surface flow and ground water. Noteworthy inadequacies include data to define floods at long recurrence intervals, such as 100 year floods, and to define the low-flow characteristics, especially in small streams and in channels affected by springs, return flows, seepage, regulation, or diversions. The proposed program consists of both data collection and analyses to efficiently provide the streamflow information required for (1) current water use and management, (2) planning and design, (3) determination of long-term trends, and (4) assessment of stream environment.

Idaho↗

USGS1984

Fluoride, Nitrate, and Dissolved-Solids Concentrations in Ground Waters of Washington

This study provides basic data on ground-water quality throughout the State. It is intended for uses in planning and management by agencies and individuals who have responsibility for or interest in, public health and welfare. It also provides a basis for directing future studies of ground-water quality toward areas where ground-water quality problems may already exist. The information presented is a compilation of existing data from numerous sources including: the Washington Departments of Ecology and Social and Health Services, the Environmental Protection Agency, as well as many other local, county, state and federal agencies and private corporations. Only data on fluoride, nitrate, and dissolved-solids concentrations in ground water are presented, as these constituents are among those commonly used to determine the suitability of water for drinking or other purposes. They also reflect both natural and man-imposed effects on water quality and are the most readily available water-quality data for the State of Washington. The percentage of wells with fluoride, nitrate, or dissolved-solids concentrations exceeding U.S. Environmental Protection Agency Primary and Secondary Drinking Water Regulations were about 1, about 3, and about 3, respectively. Most high concentrations occurred in widely separated wells. Two exceptions were: high concentrations of nitrate and dissolved solids in wells on the Hanford Department of Energy Facility and high concentrations of nitrate in the lower Yakima River basin. (USGS)

Open-File Report↗

USGS1994

Geohydrology and water quality of stratified-drift aquifers in the lower Connecticut River basin, southwestern New Hampshire

Stratified-drift aquifers discontinuously underlie 116 square miles of the Lower Connecticut River basin in southwestern New Hampshire, which has a total drainage area of 1,163 square miles. Saturated thicknesses of stratified drift within the study area are locally greater than 400 feet but generally are less. Transmissivities 1ocally exceeds 4,000 feet squared per day but are generally much less. The 20.8 square mile, or 1.8 percent, of the study area identified as having transmissivity greater than 1,000 feet squared per day represents a valuable resource. The geohydrology of stratified- drift aquifers was investigated by focusing on basic aquifer properties, including aquifer boundaries; recharge, discharge, and direction of ground-water flow; saturated thickness and storage; and transmissivity. Surficial geologic mapping assisted in the determination of aquifer boundaries. Data from more than 2,300 wells, test borings, and springs were used to produce maps of water-table altitude, saturated thickness, and transmissivity of-stratified drift. Seismic-refraction profiles were completed at 29 locations in the study area. These profiles aided in the construction of the water-table and saturated-thickness maps. Seismic- reflection data were also collected along 60 miles of the Connecticut River. A stratified-drift aquifer in southern Croydon and northern Newport was analyzed for aquifer yield using transient simulations and a two-dimensional, finite-difference ground-water-flow model. The objective was to estimate the yield after a 180-day period of pumping. Two hypothetical wells were pumped at 1.0 Mgal/d and 0.5 Mgal/d for 180 days respectively. The amount of water available for infiltration was the limiting factor. Results of analysis of water samples from 22 wells and 8 spring show that, with some exceptions, water in the stratified-drift aquifer generally meets the U.S. Environmental Protection Agency's primary and secondary drinking-water regulations.

Water-Resources Investigations Report↗

USGS1984

Fluoride, Nitrate, and Dissolved-Solids Concentrations in Ground Waters of Washington

Water-Resources Investigations Report↗

USGS2020

A guidebook to spatial datasets for conservation planning under climate change in the Pacific Northwest

This guidebook provides user-friendly overviews of a variety of spatial datasets relevant to conservation and management of natural resources in the face of climate change in the Pacific Northwest, United States. Each guidebook chapter was created using a standardized template to summarize a spatial dataset or a group of closely related datasets. Datasets were selected according to standardized criteria based on input through a collaborative process involving researchers and natural-resource managers throughout the Pacific Northwest region. In each chapter, basic spatial and temporal information is provided for the dataset, along with a conceptual overview, glossary of key terms, links to download data and supporting documentation, a brief methods summary describing how the dataset was created, guidelines for dataset interpretation, assessment of uncertainties along with evaluation of caveats and simplifying assumptions, and information about potential and actual conservation applications of the dataset. Collectively, this information provides natural-resource managers with “snapshots” of a variety of datasets representing diverse processes and conditions, including climate projections, changes in hydrologic conditions, vegetation and fire-regime shifts, animal habitat changes, species movements, and topographic and soil conditions relevant to climate change. Along with other types of data and site-specific information, the datasets described in this guidebook have the potential to inform management of valued natural resources throughout the Pacific Northwest region in the context of adaptation to changing climate conditions.

Idaho, Montana, Oregon, Washington↗

USGS1997

Level II scour analysis for Bridge 29 (PUTNTH00210029) on Town Highway 21, crossing East Putney Brook, Putney, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure PUTNTH00210029 on Town Highway 21 crossing East Putney Brook, Putney, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the New England Upland section of the New England physiographic province in southeastern Vermont. The 10.3-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover consists of pasture and forest. In the study area, East Putney Brook has an incised, sinuous channel with a slope of approximately 0.009 ft/ft, an average channel top width of 33 ft and an average bank height (channel depth) of 3 ft. The channel bed material is cobbles predominantly with a median grain size (D 50 ) of 80.7 mm (0.265 ft). The geomorphic assessment at the time of the Level I and Level II site visit on August 19, 1996, indicated that the reach was stable. The Town Highway 21 crossing of East Putney Brook is a 35-ft-long, one-lane bridge consisting of one 29-foot steel-beam span (Vermont Agency of Transportation, written communication, March 30, 1995). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 40 degrees to the opening. Historical records show an opening-skew-to-roadway of 10 degrees but 20 degrees was computed using field survey data and used in this study. The scour protection measures at the site were type-2 stone fill (less than 36 inches diameter) on each abutment wall, the upstream right wingwall and the upstream right bank, and type-3 stone fill (less than 48 inches diameter) on the left bank upstream, the upstream left wingwall, and the downstream right bank. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.0 to 0.9 feet. The worst-case contraction scour occurred at the incipient-overtopping discharge, which was less than the 100-year discharge. Abutment scour ranged from 6.1 to 18.4 feet. The worst-case abutment scour occurred at the 500-year discharge for the right abutment and the incipient overtopping discharge for the left abutment. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A crosssection of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS2000

Elk-effects vegetation monitoring program for Tomales Point Elk Range, Point Reyes National Seashore, California

The monitoring program for elk effects on Tomales Point vegetation is designed to provide information on how tule elk grazing affects plant communities and rare species. The basic objective of the program is to show whether the elk are driving the vegetation into an unacceptable state by their grazing. The expectation is that as elk numbers increase, grazing pressure will increase too, resulting in unacceptable levels of any or all of the following: low vegetation ground cover, poor nutritional quality for the elk, undesirable increases in weedy species, unacceptable loss of native plant biodiversity, population declines in rare plants, population declines in plants used for food and nectar by the endangered silverspot butterfly, and increased erosion. The monitoring program has 3 basic components designed to provide complementary information on different aspects of the elk-vegetation system. Long-term plant community monitoring along permanent transects will show how plant species composition and cover are changing since cattle removal in 1979, and it will show whether any of he undesirable traits listed above are developing in the vegetation. However, monitoring these transects alone will not tell us what the effects of continued grazing by elk are apart from changes the vegetation would be undergoing anyway. In order to tease apart the elk effects from change that is happening because of cattle removal, elk exclosures are needed. By sampling inside and outside exclosures, we will be able to see how elk are modifying the rates and directions of change in the vegetation that would be happening in their absence. In a sense, the exclosures serve as a “check” on elk effects. They will allow us to interpret how much of the change is due to elk and how much can be attributed to other processes such as natural succession or weather patterns. This information will allow us to analyze whether changing elk management will have a desirable effect on the vegetation. Finally, periodic mapping and counting of plants in rare plant populations will show whether plant population ranges are expanding and populations are stable or growing. If not, then management actions can be taken to improve habitat conditions for the plants. A general summary of the rationale and sample design for each of the 3 components of the elk-effects monitoring program follows. Field sampling for the entire program should require about 15 weeks for a 2 to 3- person team, and data processing, analysis, and report writing should require about 9 weeks. Time and labor estimates for this program are given in Table A-1. In addition to elk-effects monitoring, Point Reyes staff periodically monitor fire transects and residual dry matter plots on Tomales Point. They are not included as part of the elk-effects monitoring program and they are described elsewhere. Protocols for fire and residual dry matter sampling are not included in the time estimate for the elk- effects monitoring program.

Open-File Report↗

USGS1977

Magmatic behavior of Cu, S, Cl, F, and H 2 O in igneous rocks associated with the Ray porphyry copper deposit, Arizona

Porphyry copper deposits are the subject of a large volume of literature indicating that controversy still reigns as to which model or combination of models explains their origin, and yet, over 70 years ago we reached agreement that the well-documented space-time relationship between the deposits and calc-alkaline plutons indicates a genetic tie between them. This genetic tie is generally assumed to indicate a causitive role for an exposed or nearby hidden pluton. There are many variants, but the two end-member models that incorporate this causitive assumption are the meteoric water model and the orthomagmatic model. It is my opinion that the controversy originates from use of indirect data and variant models to explain new observational data and experimental studies that threaten the survival of the basic end-member models. One of many examples of this is the end-stage magmatic evolution of chlorine-rich water required of the orthomagmatic model. This evolution is required because the low copper content of calc-alkaline plutons demands a large source magma, that, because it generally is not visible, has to be buried. Additionally, much of the ore minerals in porphyry deposits is along fractures. Both conditions require transportation of the ore components from the magma, and to transport enough ore components, given the limited amount of water soluble in a melt and the low solubility of base-metal sulfides in water without benefit of chloride complexing, we required of the original Lindgren magmatic model that the source pluton produced chloride-rich water. However, we did not investigate the rocks associated with deposits to substantiate the hypothesis. We went to the laboratory and found that sufficient water and chlorine could be dissolved in silicate melt in a gold capsule in a high-pressure high-temperature bomb to allow postulation of sufficient water and chlorine in the stocks associated with porphyry deposits; in other words, we invested in indirect rather than direct studies.

Arizona↗

USGS1982

Assessment of undiscovered conventionally recoverable petroleum resources of the Arabian-Iranian Basin

The estimates of undiscovered conventionally recoverable petroleum resources in the Arabian-Iranian basin at probability levels of 95 percent, 5 percent, and statistical mean are for oil (in billions of barrels): 72, 337, and 174; and for gas (in trillions of cubic feet): 299, 1792, and 849. The occurrence of petroleum can be accounted for in five definitive geological settings or plays. The assessment of undiscovered resource potential assumes that the new discoveries will expand the occurrence of petroleum in these basic plays; no additional plays with significant petroleum potential were recognized. The five plays listed by geologic age are: (I) Upper Cretaceous and Tertiary, (II) Lower and Middle Cretaceous sandstone, (III) Lower and Middle Cretaceous limestone, (IV) Jurassic, and (V) Permian. The Permian play, located in the south-central Arabian Gulf region and extending northeast-southwest from southern Iran to the Ar Rub' al Khali in Saudi Arabia, accounts for over four-fifths of the mean estimate of undiscovered gas. The remainder of the gas is divided about equally among the other four plays. The Jurassic play, located on the south side of the Arabian Gulf, accounts for slightly less than one-third of the estimated undiscovered oil, which is split equally between Saudi Arabia and Iraq. The Lower and Middle Cretaceous limestone play is located in the southern Gulf region and accounts for about one-fifth of the undiscovered oil, most of which is located in Saudi Arabia and the remainder in the United Arab Emirates. The Lower and Middle Cretaceous sandstone play is centralized in Kuwait at the head of the Arabian Gulf with significant potential extending to the northwest in Iraq; the play accounts for about one-third of the undiscovered oil, the great majority of which is estimated to be in Iraq with the remainder divided between Saudi Arabia and Kuwait. The upper Cretaceous-Tertiary play is located in the Zagros fold belt of Iran and Iraq and accounts for about one-fifth of the undiscovered oil. Estimation of the resources in this vast area is hindered by lack of data from certain broad regions, abandoned wells, and several significant dry holes, but the regional geology is well enough reported that geologic projections can be made and inferences from selected wells can be drawn to permit estimation of the resource potential.

Circular↗

USGS1997

Level II scour analysis for Bridge 13 (PFRDTH00030013) on Town Highway 3, crossing Furnace Brook, Pittsford, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure PFRDTH00030013 on Town Highway 3 crossing Furnace Brook, Pittsford, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the Taconic section of the New England physiographic province in western Vermont. The 17.1-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is grass along the downstream right bank while the remaining banks are primarily forested. In the study area, Furnace Brook has an incised, sinuous channel with a slope of approximately 0.03 ft/ft, an average channel top width of 49 ft and an average channel depth of 4 ft. The predominant channel bed material ranges from gravel to bedrock with a median grain size (D 50 ) of 70.2 mm (0.230 ft). The geomorphic assessment at the time of the Level I and Level II site visit on June 20, 1995, indicated that the reach was stable. The Town Highway 3 crossing of Furnace Brook is a 75-ft-long, two-lane bridge consisting of one 72-ft-long steel stringer span (Vermont Agency of Transportation, written communication, March 14, 1995). The bridge is supported by vertical, concrete abutments with spill-through slopes. The channel is skewed approximately 20 degrees to the opening while the opening-skew-to-roadway is 35 degrees. The opening-skew-to-roadway was determined from surveyed data collected at the bridge although, information provided from the VTAOT files, indicates that the opening-skew-to-roadway is 30 degrees (Appendix D). The scour protection measures at the site included type-2 stone fill (less than 36 inches diameter) on the spill-through slope along each abutment. Type-2 stone fill scour protection was also found along the upstream left wingwall and downstream right wingwall. Type-1 (less than 12 inches diameter) stone fill scour protection was found along the upstream right wingwall and downstream left wingwall. No bank protection was observed downstream or upstream. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 1.2 to 2.0 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 7.8 to 13.1 ft. The worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution although, bedrock outcropping is apparent both upstream and downstream of this bridge. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1997

Water-quality assessment of south-central Texas: Occurrence and distribution of volatile organic compounds in surface water and ground water, 1983-94, and implications for future monitoring

The study area of the South-Central Texas study unit of the National Water-Quality Assessment Program comprises the Edwards aquifer in the San Antonio region and its catchment area. The first phase of the assessment includes evaluation of existing water-quality data for surface water and ground water, including volatile organic compounds, to determine the scope of planned monitoring. Most analyses of volatile organic compounds in surface water are from the National Pollutant Discharge Elimination System sites in San Antonio, Texas. Nine volatile organic compounds were detected at the six sites. The three compounds with the most detections at National Pollutant Discharge Elimination System sites are 1,2,4-trimethylbenzene, toluene, and xylene. Analysis of volatile organic compounds in ground water was limited to Edwards aquifer wells. Twenty-eight volatile organic compounds were detected in samples from 89 wells. The five most commonly detected compounds in samples from wells, in descending order, are tetrachloroethene, trichloroethene, bromoform, chloroform, and dibromochloromethane. Detections of volatile organic compounds in surface water and ground water within the South-Central Texas study area are limited to site-specific sources associated with development; therefore, planned monitoring for possible detections of volatile organic compounds as part of the National Water-Quality Assessment Program will emphasize areas of expanding population and development. Monitoring of volatile organic compounds is planned at National Pollutant Discharge Elimination System sites, at basic fixed surface-water sites, and in the ground-water study-unit surveys.

Texas↗

USGS2009

Modeling habitat of the desert tortoise (Gopherus agassizii) in the Mojave and parts of the Sonoran Deserts of California, Nevada, Utah, and Arizona

Habitat modeling is an important tool used to simulate the potential distribution of a species for a variety of basic and applied questions. The desert tortoise ( Gopherus agassizii ) is a federally listed threatened species in the Mojave Desert and parts of the Sonoran Desert of California, Nevada, Utah, and Arizona. Land managers in this region require reliable information about the potential distribution of desert tortoise habitat to plan conservation efforts, guide monitoring activities, monitor changes in the amount and quality of habitat available, minimize and mitigate disturbances, and ultimately to assess the status of the tortoise and its habitat toward recovery of the species. By applying information from the literature and our knowledge or assumptions of environmental variables that could potentially explain variability in the quality of desert tortoise habitat, we developed a quantitative habitat model for the desert tortoise using an extensive set of field-collected presence data. Sixteen environmental data layers were converted into a grid covering the study area and merged with the desert tortoise presence data that we gathered for input into the Maxent habitat-modeling algorithm. This model provides output of the statistical probability of habitat potential that can be used to map potential areas of desert tortoise habitat. This type of analysis, while robust in its predictions of habitat, does not account for anthropogenic changes that may have altered habitat with relatively high potential into areas with lower potential.

California, Nevada, Utah, Arizona↗

USGS1997

Level II scour analysis for Bridge 7 (CHARTH00010007) on Town Highway 1, crossing Mad Brook, Charleston, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure CHARTH00010007 on town highway 1 crossing Mad Brook, Charleston, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the White Mountain section of the New England physiographic province in north-central Vermont in the town of Charleston. The 6.59-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is pasture except for the upstream left bank, which is forest. The stream banks are tree covered upstream and on the downstream left bank side. In the study area, Mad Brook has an incised, sinuous channel with a slope of approximately 0.01 ft/ft, an average channel top width of 41 ft and an average channel depth of 5 ft. The predominant channel bed materials range from gravel to boulders with a median grain size (D 50 ) of 105 mm (0.344 ft). The geomorphic assessment at the time of the Level I and Level II site visit on October 28, 1994, indicated that the reach was stable. The town highway 1 crossing of Mad Brook is a 27-ft-long, two-lane bridge consisting of one 25-foot concrete T-beam span (Vermont Agency of Transportation, written communication, August 4, 1994). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 10 degrees to the opening. The opening-skew-to-roadway computed from surveyed data is 5 degrees, but historical bridge records indicate this angle is closer to 10 degrees. There was scour evident during the Level I assessment due to the presence of two subfootings at the base of each abutment wall. Although the subfootings may have been constructed at the same time as the abutment walls, the subfootings may have been constructed at a later time in response to streambed degradation under the bridge. The right abutment was noted as undermined during the Level I assessment. Scour protection measures at the site were type-1 stone fill (less than 12 inches diameter) on the upstream right and downstream road embankments and type-2 stone fill on each wingwall and the downstream left bank. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour for all modelled flows ranged from 0.0 to 0.3 ft. The worst-case contraction scour occurred at the incipient overtopping discharge, which was less than the 100-year discharge. Abutment scour ranged from 6.2 to 9.4 ft. The worst-case abutment scour for the right abutment was 9.4 feet at the 100-year discharge. The worst-case abutment scour for the left abutment was 8.6 feet at the incipient overtopping discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS1995

Hydrologic data and description of a hydrologic monitoring plan for the Borax Lake area, Oregon

Borax Lake is located in southeastern Oregon, within the Alvord Valley Known Geothermal Resource Area. Borax Lake is a large hot spring; there are more than 50 smaller hot springs within about one-half mile to the north of the lake. Several geothermal exploration wells have been drilled near Borax Lake, and there is concern that development of the geothermal resources could affect the lake and nearby hot springs. A factor to consider in developing the resource is that the Borax Lake chub is an endangered species of fish that is found exclusively in Borax Lake. This study was designed to collect basic hydrologic data to develop a long-term monitoring plan. Baseline data, collected before geothermal production wells are used extensively, will provide an understanding of natural trends and will help identify change caused by development. Basic data collected during reconnaissance field visits to the area included spring temperatures, specific conductances, and discharge; field measurements in wells included water-level measurements and temperature, specific conductance, and discharge measurements in flowing wells. The study of the Borax Lake area included depth and temperature measurements in the vent area of the lake, point velocity measurements, underwater video photography, and an evaluation of methods to measure discharge from the lake. Water-quality samples were collected at Borax Lake, one hot spring, and one flowing well. Information from field visits was used to develop a monitoring plan. The plan would include monitoring Borax Lake by measuring discharge, stage, evaporation, temperature, and specific conductance; water-quality sampling and analysis; and monitoring shallow ground-water levels near Borax Lake using shallow piezometers. Minimally, one hot spring in North Borax Lake Spring Group 1 would be monitored for temperature and specific conductance and sampled for water-quality analysis. In addition, two flowing wells would be monitored for water levels, temperature, specific conductance, and discharge and sampled for water-quality analysis. The construction characteristics of these wells must be verified before long-term data collection begins. In the future, it may be helpful to monitor shallow and (or) deep observation wells drilled into the thermal aquifer to understand the possible effects of geothermal development on Borax Lake and nearby springs.

Oregon↗