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At least 559 records · Page 31Linked to original sources
USGS2003

Probabilistic assessment methodology for continuous-type petroleum accumulations

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

International Journal of Coal Geology↗
USGS2024

Improved computational methods for probabilistic liquefaction hazard analysis

Current procedures for analysis of and design against liquefaction hazards focus primarily on the use of probabilistic ground motions at a single ground-shaking hazard level, with the cyclic loading represented by a peak ground acceleration ( PGA ) corresponding to a target return period and a single representative moment magnitude M w . These parameters are typically used in conjunction with deterministic simplified procedures for estimating liquefaction triggering and consequences that largely neglect the considerable uncertainties inherent to liquefaction problems. Motivated by these limitations and the resulting inconsistencies in liquefaction design levels, early methods for probabilistic liquefaction hazard analysis (PLHA) were proposed that incorporate the full ground motion hazard space, integrated with probabilistic liquefaction triggering models. Such methods provide liquefaction factor of safety ( FS L ) hazard curves for standard penetration test (SPT) data. Recognizing the increased use of higher-resolution cone penetrometer test (CPT) data in engineering analysis and design and the potential computational challenges it presents, an expanded suite of probabilistic triggering models, and wider availability of more detailed seismic hazard data, an improved PLHA computational methodology is presented in this study. The methods described utilize the U.S. Geological Survey National Seismic Hazard Model directly through web services to obtain PGA hazard and disaggregation calculations for any site and average shear wave velocity in the upper 30 m of the site ( V s 30 ) in the conterminous United States, to reconstruct the PGA hazard space for use in PLHA calculations, and to employ array calculations for efficient liquefaction hazard curve estimates for the thousands of CPT measurements in a given profile. The framework presented here is modular in nature, and discussion on the use of alternative models and extension to probabilistic liquefaction consequence evaluation is presented. The importance of appropriate representation of probabilistic liquefaction model uncertainties is also highlighted, along with the impacts of different levels of uncertainty on the PLHA calculation. Finally, a potential roadmap for incorporation of the PLHA framework in seismic provisions is presented, with an illustration of how it can address current limitations and impacts in liquefaction hazard analysis and design.

Soil Dynamics and Earthquake Engineering↗
USGS1979

Digital image processing system For Landsat 3

The Department of Interior (DOI) and the National Aeronautics and Space Administration (NASA) have entered into a joint program to provide a digital image processing system in support of the Landsat 3 mission. NASA will provide the data reception and pre-processing facilities, while the DOI provides the production image processing system that generates film products and computer compatible tapes for users. The system procured by the DOI's U.S. Geological Survey was installed at the Earth Resources Observation System Data Center (EDC) in Sioux Falls, South Dakota. The EDC Digital Image Processing System (EDIPS) is capable of operating in standard or special formats. During 13 hours of operation, the system can process up to 200 five-band Multispectral Scanner (MSS) scenes and 160 Return Beam Vidicon (RBV) subscenes in the standard mode plus up to 60 scenes/subscenes in the special-order mode. The input media for the system are High Density Tapes (HDT's) generated by NASA's Goddard Space Flight Center (GSFC). These tapes contain two types of data: those that have been radiometrically and geometrically corrected with resampling of the data to fit a known map projection, and those that have been radiometrically corrected but have not been geometrically corrected or resampled. The system can provide 185 mm (MSS) and 198 mm (RBV) black and white film products for each MSS band or RBV subscene via a high resolution laser beam recorder. The CCT's generated by the system are compatible with the HDT format, and are available either in Band Sequential (BSQ) or Band Interleaved by Line (BIL) data. This paper will present both an overview of the total NASA/DOI system and a detailed discussion of the EDC Digital Image Processing System that is installed at the USGS facility in Sioux Falls, South Dakota.

South Dakota↗
USGS2008

Streamflow characteristics of streams in the Helmand Basin, Afghanistan

A majority of the Afghan population lacks adequate and safe supplies of water because of contamination, lack of water-resources management regulation, and lack of basic infrastructure, compounded by periods of drought and seasonal flooding. Characteristics of historical streamflows are needed to assist with efforts to quantify the water resources of the Helmand Basin. The Helmand Basin is the largest river basin in Afghanistan. It comprises the southern half of the country, draining waters from the Sia Koh Mountains in Herat Province to the eastern mountains in Gardez Province (currently known as the Paktia Province) and the Parwan Mountains northwest of Kabul, and finally draining into the unique Sistan depression between Iran and Afghanistan (Favre and Kamal, 2004). The Helmand Basin is a desert environment with rivers fed by melting snow from the high mountains and infrequent storms. Great fluctuations in streamflow, from flood to drought, can occur annually. Knowledge of the magnitude and time distribution of streamflow is needed to quantify water resources and for water management and environmental planning. Agencies responsible for the development and management of Afghanistan's surface-water resources can use this knowledge for making safe, economical, and environmentally sound water-resource planning decisions. To provide the Afghan managers with necessary streamflow information, the U.S. Geological Survey (USGS), in cooperation with the U.S. Agency for International Development (USAID), computed streamflow statistics for data collected at historical gaging stations within the Helmand Basin. The historical gaging stations used are shown in figure 1 and listed in table 1.

Helmand Basin↗
USGS2010

Real Time Flood Alert System (RTFAS) for Puerto Rico

The Real Time Flood Alert System is a web-based computer program, developed as a data integration tool, and designed to increase the ability of emergency managers to rapidly and accurately predict flooding conditions of streams in Puerto Rico. The system includes software and a relational database to determine the spatial and temporal distribution of rainfall, water levels in streams and reservoirs, and associated storms to determine hazardous and potential flood conditions. The computer program was developed as part of a cooperative agreement between the U.S. Geological Survey Caribbean Water Science Center and the Puerto Rico Emergency Management Agency, and integrates information collected and processed by these two agencies and the National Weather Service.

Fact Sheet↗
USGS2002

Geologic and isostatic gravity map of the Nenana basin area, central Alaska

The Nenana Basin area is a prospective petroleum province in central Alaska, and this geologic and isostatic gravity map is part of a petroleum resource assessment of the area. The geology was compiled from published sources as shown on the index map (map sheet). Map units are organized and presented according to the scheme of lithotectonic terranes proposed by Jones and others (1987) and Silberling and Jones (1984); we recognize, however, that this terrane scheme is controversial and likely to be revised in the future. In some cases, we combined certain terranes because we were unable to match the terrane boundaries given by Jones and others (1987) and Silberling and Jones (1984) with specific faults shown on existing geologic maps. Postaccretion cover deposits represent overlap assemblages that depositionally overlie accreted terranes. Plutonic igneous rocks shown on this map include several plutons that are clearly postaccretionary, based on isotopic ages and (or) field relations. It is possible that some of the plutons predate accretion, but this has not been demonstrated. According to Jones and others (1982), the terranes in the area of our map were assembled during late Mesozoic or earliest Cenozoic time. The gravity contours are derived from data used in earlier compilations that are supplemented by some National Oceanic and Atmospheric Administration data along the Alaska Pipeline level line. The earlier compilations were used for simple Bouguer maps, prepared primarily by non-digital methods, and are superseded by this map. The present map is the result of digital processing that includes the 1967 Geodetic Reference System, the IGSN-71 datum, digital terrain corrections, and conversion to isostatic gravity so that geologic structures on the margin of the Alaska Range are more clearly portrayed. Computation procedures are described in part by Barnes (1972, 1984), Jachens and Roberts (1981), and Barnes and others (1994). The calculations used a crustal density of 2.67 g/cm 3 , a density contrast at the base of the isostatic root of 0.4 g/cm 3 , and a root thickness at sea level of 25 km. The distribution of data within the map area is uneven and locally controls the shape of the computer-generated contours. Altimetry was used for most of the elevation control and its inconsistency is responsible for many of the small contour irregularities. Ninety percent of the measurements are estimated to have an accuracy of about 1.5 mgal or about a quarter of the 5 mgal contour interval. Data collection and analysis were assisted by R.V. Allen, R.C. Jachens, M.A. Fisher, T.R. Bruns, J.G. Blank, J.W. Bader, Z.C. Valin, J.W. Cady, R.L. Morin, and P.V. Woodward. The most promising area for petroleum exploration is a prominent 25 mgal isostatic gravity low north of Nenana (T. 2 S., R. 8 W.). This gravity low probably corresponds to the deepest part of a sedimentary basin filled by Cenozoic strata that includes nonmarine fluvial and lacustrine deposits of the Eocene to Miocene Usibelli Group. Smaller gravity lows are associated with outcrops of these sedimentary rocks north of Suntrana (T. 12 S., R. 6-9 W.) and Sable Pass (T. 16 S., R. 11 W.). A broad low on the north flank of the Alaska Range east of the Wood River (T. 10 S., R. 1 E.) indicates another basin under the Tanana lowland that extends eastward off the map area towards Delta Junction, where its presence was confirmed by both gravity and seismic data. Gravity modelling suggests that the base of the Usibelli Group in the area north of Nenana (T. 2 S., R. 8 W.) is about 3,000 to 3,350 m beneath the ground surface. Organic geochemical studies indicate that mudstones and coals in the Usibelli Group are potential sources of petroleum; calculations based on borehole temperatures suggest that, in the area of the gravity low, these rocks may have been buried deeply enough to generate oil and gas. Two exploratory wells, the Union Nenana No. 1 and the ARCO Totek Hills No. 11, were drilled some distance away from the gravity low in areas where the Usibelli Group is thin. Mudlogs show that both wells were dry holes that bottomed in schist and had gas shows associated with coal beds in the Usibelli Group, but no reported signs of oil.

Alaska↗
USGS2010

Simulation of Streamflow, Evapotranspiration, and Groundwater Recharge in the Lower San Antonio River Watershed, South-Central Texas, 2000-2007

The U.S. Geological Survey (USGS), in cooperation with the San Antonio River Authority, the Evergreen Underground Water Conservation District, and the Goliad County Groundwater Conservation District, configured, calibrated, and tested a watershed model for a study area consisting of about 2,150 square miles of the lower San Antonio River watershed in Bexar, Guadalupe, Wilson, Karnes, DeWitt, Goliad, Victoria, and Refugio Counties in south-central Texas. The model simulates streamflow, evapotranspiration (ET), and groundwater recharge using rainfall, potential ET, and upstream discharge data obtained from National Weather Service meteorological stations and USGS streamflow-gaging stations. Additional time-series inputs to the model include wastewater treatment-plant discharges, withdrawals for cropland irrigation, and estimated inflows from springs. Model simulations of streamflow, ET, and groundwater recharge were done for 2000-2007. Because of the complexity of the study area, the lower San Antonio River watershed was divided into four subwatersheds; separate HSPF models were developed for each subwatershed. Simulation of the overall study area involved running simulations of the three upstream models, then running the downstream model. The surficial geology was simplified as nine contiguous water-budget zones to meet model computational limitations and also to define zones for which ET, recharge, and other water-budget information would be output by the model. The model was calibrated and tested using streamflow data from 10 streamflow-gaging stations; additionally, simulated ET was compared with measured ET from a meteorological station west of the study area. The model calibration is considered very good; streamflow volumes were calibrated to within 10 percent of measured streamflow volumes. During 2000-2007, the estimated annual mean rainfall for the water-budget zones ranged from 33.7 to 38.5 inches per year; the estimated annual mean rainfall for the entire watershed was 34.3 inches. Using the HSPF model it was estimated that for 2000-2007, less than 10 percent of the annual mean rainfall on the study watershed exited the watershed as streamflow, whereas about 82 percent, or an average of 28.2 inches per year, exited the watershed as ET. Estimated annual mean groundwater recharge for the entire study area was 3.0 inches, or about 9 percent of annual mean rainfall. Estimated annual mean recharge was largest in water-budget zone 3, the zone where the Carrizo Sand outcrops. In water-budget zone 3, the estimated annual mean recharge was 5.1 inches or about 15 percent of annual mean rainfall. Estimated annual mean recharge was smallest in water-budget zone 6, about 1.1 inches or about 3 percent of annual mean rainfall. The Cibolo Creek subwatershed and the subwatershed of the San Antonio River upstream from Cibolo Creek had the largest and smallest basin yields, about 4.8 inches and 1.2 inches, respectively. Estimated annual ET and annual recharge generally increased with increasing annual rainfall. Also, ET was larger in zones 8 and 9, the most downstream zones in the watershed. Model limitations include possible errors related to model conceptualization and parameter variability, lack of data to quantify certain model inputs, and measurement errors. Uncertainty regarding the degree to which available rainfall data represent actual rainfall is potentially the most serious source of measurement error.

Open-File Report↗
USGS2012

Automated delineation and characterization of watersheds for more than 3,000 surface-water-quality monitoring stations active in 2010 in Texas

The U.S. Geological Survey (USGS), in cooperation with the Texas Commission on Environmental Quality, developed computer scripts and applications to automate the delineation of watershed boundaries and compute watershed characteristics for more than 3,000 surface-water-quality monitoring stations in Texas that were active during 2010. Microsoft Visual Basic applications were developed using ArcGIS ArcObjects to format the source input data required to delineate watershed boundaries. Several automated scripts and tools were developed or used to calculate watershed characteristics using Python, Microsoft Visual Basic, and the RivEX tool. Automated methods were augmented by the use of manual methods, including those done using ArcMap software. Watershed boundaries delineated for the monitoring stations are limited to the extent of the Subbasin boundaries in the USGS Watershed Boundary Dataset, which may not include the total watershed boundary from the monitoring station to the headwaters.

Texas↗
USGS1989

Review of edgematchimg procedures for digital cartographic data used in Geographic Information Systems (GIS)

In the process of developing a continuous hydrographic data layer for water resources applications in the Pacific Northwest, map-edge discontinuities in the U.S. Geological Survey 1:100 ,000-scale digital data that required application of computer-assisted edgematching procedures were identified. The spatial data sets required by the project must have line features that match closely enough across map boundaries to ensure full line topology when adjacent files are joined by the computer. Automated edgematching techniques are evaluated as to their effects on positional accuracy. Interactive methods such as selective node-matching and on-screen editing are also reviewed. Interactive procedures complement automated methods by allowing supervision of edgematching in a cartographic and hydrologic context. Common edge conditions encountered in the preparation of the Northwest Rivers data base are described, as are recommended processing solutions. Suggested edgematching procedures for 1:100,000-scale hydrography data are included in an appendix to encourage consistent processing of this theme on a national scale. (USGS)

Open-File Report↗
USGS2010

Simulation of streamflow, evapotranspiration, and groundwater recharge in the lower San Antonio River Watershed, South-Central Texas, 2000-2007

The U.S. Geological Survey (USGS), in cooperation with the San Antonio River Authority, the Evergreen Underground Water Conservation District, and the Goliad County Groundwater Conservation District, configured, calibrated, and tested a watershed model for a study area consisting of about 2,150 square miles of the lower San Antonio River watershed in Bexar, Guadalupe, Wilson, Karnes, DeWitt, Goliad, Victoria, and Refugio Counties in south-central Texas. The model simulates streamflow, evapotranspiration (ET), and groundwater recharge using rainfall, potential ET, and upstream discharge data obtained from National Weather Service meteorological stations and USGS streamflow-gaging stations. Additional time-series inputs to the model include wastewater treatment-plant discharges, withdrawals for cropland irrigation, and estimated inflows from springs. Model simulations of streamflow, ET, and groundwater recharge were done for 2000-2007. Because of the complexity of the study area, the lower San Antonio River watershed was divided into four subwatersheds; separate HSPF models were developed for each subwatershed. Simulation of the overall study area involved running simulations of the three upstream models, then running the downstream model. The surficial geology was simplified as nine contiguous water-budget zones to meet model computational limitations and also to define zones for which ET, recharge, and other water-budget information would be output by the model. The model was calibrated and tested using streamflow data from 10 streamflow-gaging stations; additionally, simulated ET was compared with measured ET from a meteorological station west of the study area. The model calibration is considered very good; streamflow volumes were calibrated to within 10 percent of measured streamflow volumes. During 2000-2007, the estimated annual mean rainfall for the water-budget zones ranged from 33.7 to 38.5 inches per year; the estimated annual mean rainfall for the entire watershed was 34.3 inches. Using the HSPF model it was estimated that for 2000-2007, less than 10 percent of the annual mean rainfall on the study watershed exited the watershed as streamflow, whereas about 82 percent, or an average of 28.2 inches per year, exited the watershed as ET. Estimated annual mean groundwater recharge for the entire study area was 3.0 inches, or about 9 percent of annual mean rainfall. Estimated annual mean recharge was largest in water-budget zone 3, the zone where the Carrizo Sand outcrops. In water-budget zone 3, the estimated annual mean recharge was 5.1 inches or about 15 percent of annual mean rainfall. Estimated annual mean recharge was smallest in water-budget zone 6, about 1.1 inches or about 3 percent of annual mean rainfall. The Cibolo Creek subwatershed and the subwatershed of the San Antonio River upstream from Cibolo Creek had the largest and smallest basin yields, about 4.8 inches and 1.2 inches, respectively. Estimated annual ET and annual recharge generally increased with increasing annual rainfall. Also, ET was larger in zones 8 and 9, the most downstream zones in the watershed. Model limitations include possible errors related to model conceptualization and parameter variability, lack of data to quantify certain model inputs, and measurement errors. Uncertainty regarding the degree to which available rainfall data represent actual rainfall is potentially the most serious source of measurement error.

Texas↗
USGS2018

Geomorphic characteristics of Tenmile Creek, Montgomery County, Maryland, 2014–16

Data collected from April 2014 through September 2016 were used to assess geomorphic characteristics and geomorphic changes over time in a selected reach of Tenmile Creek, a small rural watershed near Clarksburg, Maryland. Longitudinal profiles of the channel bed, water surface, and bank features were developed from field surveys. Changes in cross-section geometry between field surveys were documented. Grain-size distributions for the channel bed were developed from pebble counts. Continuous-record streamflow and precipitation data were also collected in the Tenmile Creek watershed and used to supplement the geomorphic analyses. The Rosgen system of stream classification was used to classify the stream channel according to morphological measurements of slope, entrenchment ratio, width-to-depth ratio, sinuosity, and median particle diameter of the channel materials. Boundary shear stress near the U.S. Geological Survey (USGS) streamflow-gaging station was assessed by using hydraulic variables computed from the cross-section surveys and slope measurements derived from crest-stage gages and temporary data loggers installed along the study reach. Analysis of the longitudinal profiles indicated relatively small changes in the percentage and distribution of riffles, pools, and runs in the study reach between April 2014 and March 2015. More noticeable changes were observed during surveys conducted in March 2016 and September 2016. The channel-bed slope showed a net reduction over time from 0.0072 to 0.0040 feet per foot (ft/ft). The low-flow water-surface slope also showed a net reduction over time from 0.0065 to 0.0045 ft/ft. Net aggradation in the lower section of the study reach combined with net degradation in the upper section of the study reach contributed to the net reduction in channel-bed and water-surface slope. The large storm and resulting flood on July 30, 2016 was a major factor in observed changes in the longitudinal profiles between the March 2016 and September 2016 surveys. Comparison of data from the cross-sectional surveys indicated vertical changes in all cross sections, with more extreme changes observed between surveys in the lower section of the study reach due in part to alternating periods of net storage and transport of sand. Lateral erosion was not a major factor in the study reach, with the exception of cross section Dd, where considerable lateral erosion was documented during the study period. The flood that resulted from the large storm on July 30, 2016 was a major factor in some of the vertical changes observed in the channel bed of the study reach cross sections. Particle-size analyses of the channel bed from pebble counts indicated median particle diameters ranging from 15.5 millimeters (mm) to 23.1 mm, which is characterized as medium to coarse gravel. Sand percentages ranging from 3.4 percent to 16.4 percent of the total counts were observed over time. Net increases in storage of fine sediment in the reach were observed between April 2014 and March 2016, and a considerable reduction in storage was observed between March 2016 and September 2016. The Tenmile Creek stream channel was classified as a C4 channel, based on morphological descriptions from the Rosgen system of stream classification. The C4 classification describes a single-thread channel with a slight entrenchment ratio; a moderate to high width-to-depth ratio; moderate to high sinuosity; a water-surface slope of less than 2 percent; and a median particle diameter in the gravel range of 2 to 64 mm. The analysis of boundary shear stress indicated a range of 0.35 to 1.18 pounds per square foot for instantaneous streamflow ranging from 79 to 2,860 cubic feet per second during the study period. The relation between discharge and boundary shear stress for Tenmile Creek was compared to similar relations that were previously developed for Minebank Run, a small, urban watershed in the eastern section of the Piedmont Physiographic Province in Baltimore County, Md. that was physically restored during 2004–05. The comparison indicated a much flatter slope in the relation for Minebank Run in both its unrestored and restored conditions. This difference in the relations indicates that the erosive power in the urban watershed of Minebank Run is much more sensitive to increases in discharge magnitude than in the non-urban watershed of Tenmile Creek.

Maryland↗
USGS1987

Investigation of techniques to estimate rainfall-loss parameters for Illinois

An attempt was made by the U.S. Geological Survey to develop parameter-estimation techniques for two rainfall-loss computation methods used in the U.S. Army Corps of Engineers ' flood-hydrograph model (HEC-1). Six rainfall-loss parameters were investigated - four for the Exponential Loss-Rate method and two for the Initial and Uniform Loss-Rate method. Multiple-regression analyses using data from 616 storms at 98 gaged basins were used to attempt to develop parameter-estimation techniques for ungaged basins in Illinois. Techniques were evaluated using 102 storms at 36 uncalibrated gage basins. Estimated unit-hydrograph and rainfall-loss parameters were used to compute discharge hydrograph characteristics, which were compared with characteristics of observed discharge hydrographs. Seventy and 50% of the simulations using the Exponential Loss-Rate and the Initial and Uniform Loss-Rate methods, respectively, produced valid hydrographs. Model-sensitivity analyses to one standard error of estimate indicate that the storm-dependent rainfall-loss parameters are most significant in reproducing the sum of incremental flows and peak discharge. Time of concentrations and storage coefficient are significant in reproducing time to peak discharge and peak discharge, respectively. The small percentage of variation explained by the estimation techniques and the evaluation results using 102 storms indicates that a large degree of uncertainty exists in the computed hydrographs. (USGS)

Water-Resources Investigations Report↗
USGS1997

Bibliography of selected references on the hydrogeologic and chemical properties of the Galena-Platteville bedrock unit in Illinois and Wisconsin, 1877-1997

This report presents selected references concerning the Galena-Platteville deposits in Illinois and Wisconsin published from 1877 to 1997. Sources of the bibliographic information are the Universities of Illinois and Wisconsin Library Computer Systems; Illinet Online; the Illinois and Wisconsin District Libraries of the U.S. Geological Survey; U.S. Geological Survey Selected Water Resources Abstracts; U.S. Environmental Protection Agency reports; and Federal, State, and local agencies, corporations, and consultants. The bibliography is arranged alphabetically, by county, in Illinois and Wisconsin. The references available for each county are arranged alphabetically by author. In addition, one or more selected hydrogeologic key words describing the content of the reference follow each listing. These key words are geophysical properties, hydraulic properties, inorganic geochemistry, lithology, organic geochemistry, physical properties, and water use. Included in the bibliography are 186 references obtained for 15 counties in Illinois and 21 counties in Wisconsin.

Water-Resources Investigations Report↗
USGS1999

Site-specific estimation of peak-streamflow frequency using generalized least-squares regression for natural basins in Texas

The U.S. Geological Survey, in cooperation with the Texas Department of Transportation, has developed a computer program to estimate peak-streamflow frequency for ungaged sites in natural basins in Texas. Peak-streamflow frequency refers to the peak streamflows for recurrence intervals of 2, 5, 10, 25, 50, and 100 years. Peak-streamflow frequency estimates are needed by planners, managers, and design engineers for flood-plain management; for objective assessment of flood risk; for cost-effective design of roads and bridges; and also for the desin of culverts, dams, levees, and other flood-control structures. The program estimates peak-streamflow frequency using a site-specific approach and a multivariate generalized least-squares linear regression. A site-specific approach differs from a traditional regional regression approach by developing unique equations to estimate peak-streamflow frequency specifically for the ungaged site. The stations included in the regression are selected using an informal cluster analysis that compares the basin characteristics of the ungaged site to the basin characteristics of all the stations in the data base. The program provides several choices for selecting the stations. Selecting the stations using cluster analysis ensures that the stations included in the regression will have the most pertinent information about flooding characteristics of the ungaged site and therefore provide the basis for potentially improved peak-streamflow frequency estimation. An evaluation of the site-specific approach in estimating peak-streamflow frequency for gaged sites indicates that the site-specific approach is at least as accurate as a traditional regional regression approach.

Texas↗
USGS2017

Emulation of long-term changes in global climate: application to the late Pliocene and future

Multi-millennial transient simulations of climate changes have a range of important applications, such as for investigating key geologic events and transitions for which high-resolution palaeoenvironmental proxy data are available, or for projecting the long-term impacts of future climate evolution on the performance of geological repositories for the disposal of radioactive wastes. However, due to the high computational requirements of current fully coupled general circulation models (GCMs), long-term simulations can generally only be performed with less complex models and/or at lower spatial resolution. In this study, we present novel longterm “continuous” projections of climate evolution based on the output from GCMs, via the use of a statistical emulator. The emulator is calibrated using ensembles of GCM simulations, which have varying orbital configurations and atmospheric CO2 concentrations and enables a variety of investigations of long-term climate change to be conducted, which would not be possible with other modelling techniques on the same temporal and spatial scales. To illustrate the potential applications, we apply the emulator to the late Pliocene (by modelling surface air temperature – SAT), comparing its results with palaeo-proxy data for a number of global sites, and to the next 200 kyr (thousand years) (by modelling SAT and precipitation). A range of CO2 scenarios are prescribed for each period. During the late Pliocene, we find that emulated SAT varies on an approximately precessional timescale, with evidence of increased obliquity response at times. A comparison of atmospheric CO2 concentration for this period, estimated using the proxy sea surface temperature (SST) data from different sites and emulator results, finds that relatively similar CO2 concentrations are estimated based on sites at lower latitudes, whereas higher-latitude sites show larger discrepancies. In our second illustrative application, spanning the next 200 kyr into the future, we find that SAT oscillations appear to be primarily influenced by obliquity for the first ∼ 120 kyr, whilst eccentricity is relatively low, after which precession plays a more dominant role. Conversely, variations in precipitation over the entire period demonstrate a strong precessional signal. Overall, we find that the emulator provides a useful and powerful tool for rapidly simulating the long-term evolution of climate, both past and future, due to its relatively high spatial resolution and relatively low computational cost. However, there are uncertainties associated with the approach used, including the inability of the emulator to capture deviations from a quasi-stationary response to the forcing, such as transient adjustments of the deep-ocean temperature and circulation, in addition to its limited range of fixed ice sheet configurations and its requirement for prescribed atmospheric CO2 concentrations.

Climate of the Past↗
USGS1962

Gravity survey of the Nevada Test Site and vicinity, Nye, Lincoln, and Clark Counties, Nevada--interim report

The gravity survey of the Nevada Test Site and contiguous areas of southern Nevada and southeastern California (fig. 1) has been made by the U.S. Geological Survey on behalf of the U.S. Atomic Energy Commission. The objective of this study is to delineate and interpret gravity anomalies and regional trends so that the configuration and depth of the buried erosional surface of the Paleozoic rocks may be determined. This buried surface is of utmost importance in understanding the geologic history of the Nevada Test Site region, the thickness and distribution of the overlying volcanic rocks and alluvium, and the movement of ground water. The Paleozoic rocks cause positive gravity anomalies where they outcrop or occur near the surface and negative anomalies where they are buried in valleys or capped by low-density Tertiary volcanic rocks. Gravity trends which extend over the entire area provide a basis for computing the regional gravity gradient. The regional gravity gradient must be removed from the data for geologic interpretation of the paleotopographic surface in any limited area. Knowledge of the thickness of low-density material overlying the paleotopographic surface is useful in several ways. Proposed underground test sites, such as drill holes and tunnels, may be evaluated in terms of rock unit thickness and alluvial cover requirements. Recent work by the Water Resources Division of the U.S. Geological Survey has demonstrated ground-water movement through the Paleozoic rocks in the vicinity of the Nevada Test Site. Therefore, knowledge of the position of buried Paleozoic rocks is important in evaluating (a) the rate and direction of flow of the ground water, (b) ground-water supplies for domestic and industrial uses, and (c) the possibility of radioactive contamination of ground water. Finally, regional gravity trends and paleotopography are useful in working out the structural history of the area in connection with geologic studies now in progress. The purpose of this interim report is to present the major part of the gravity data obtained as of December 31, 1961. The data are presented as a complete Bouguer gravity anomaly map. Although the gravity contours are somewhat generalized because the map has a scale of 1:250,000 and a contour interval of 5 milligals, the largest anomalies are adequately delineated. Preliminary results of this gravity survey have been reported by Wilmarth and others, 1960, and by Diment and others, 1959 and 1960.

Nevada↗
USGS2018

Computing under-ice discharge: A proof-of-concept using hydroacoustics and the Probability Concept

Under-ice discharge is estimated using open-water reference hydrographs; however, the ratings for ice-affected sites are generally qualified as poor. The U.S. Geological Survey (USGS), in collaboration with the Colorado Water Conservation Board, conducted a proof-of-concept to develop an alternative method for computing under-ice discharge using hydroacoustics and the Probability Concept. The study site was located south of Minturn, Colorado (CO), USA, and was selected because of (1) its proximity to the existing USGS streamgage 09064600 Eagle River near Minturn, CO, and (2) its ease-of-access to verify discharge using a variety of conventional methods. From late September 2014 to early March 2015, hydraulic conditions varied from open water to under ice. These temporal changes led to variations in water depth and velocity. Hydroacoustics (tethered and uplooking acoustic Doppler current profilers and acoustic Doppler velocimeters) were deployed to measure the vertical-velocity profile at a singularly important vertical of the channel-cross section. Because the velocity profile was non-standard and cannot be characterized using a Power Law or Log Law, velocity data were analyzed using the Probability Concept, which is a probabilistic formulation of the velocity distribution. The Probability Concept-derived discharge was compared to conventional methods including stage-discharge and index-velocity ratings and concurrent field measurements; each is complicated by the dynamics of ice formation, pressure influences on stage measurements, and variations in cross-sectional area due to ice formation. No particular discharge method was assigned as truth. Rather one statistical metric (Kolmogorov-Smirnov; KS), agreement plots, and concurrent measurements provided a measure of comparability between various methods. Regardless of the method employed, comparisons between each method revealed encouraging results depending on the flow conditions and the absence or presence of ice cover. For example, during lower discharges dominated by under-ice and transition (intermittent open-water and under-ice) conditions, the KS metric suggests there is not sufficient information to reject the null hypothesis and implies that the Probability Concept and index-velocity rating represent similar distributions. During high-flow, open-water conditions, the comparisons are less definitive; therefore, it is important that the appropriate analytical method and instrumentation be selected. Six conventional discharge measurements were collected concurrently with Probability Concept-derived discharges with percent differences (%) of −9.0%, −21%, −8.6%, 17.8%, 3.6%, and −2.3%. This proof-of-concept demonstrates that riverine discharges can be computed using the Probability Concept for a range of hydraulic extremes (variations in discharge, open-water and under-ice conditions) immediately after the siting phase is complete, which typically requires one day. Computing real-time discharges is particularly important at sites, where (1) new streamgages are planned, (2) river hydraulics are complex, and (3) shifts in the stage-discharge rating are needed to correct the streamflow record. Use of the Probability Concept does not preclude the need to maintain a stage-area relation. Both the Probability Concept and index-velocity rating offer water-resource managers and decision makers alternatives for computing real-time discharge for open-water and under-ice conditions.

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