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At least 1,243 records · Page 69Linked to original sources
USGS2015

Measurement of slow-moving along-track displacement from an efficient multiple-aperture SAR interferometry (MAI) stacking

Multiple-aperture SAR interferometry (MAI) has demonstrated outstanding measurement accuracy of along-track displacement when compared to pixel-offset-tracking methods; however, measuring slow-moving (cm/year) surface displacement remains a challenge. Stacking of multi-temporal observations is a potential approach to reducing noise and increasing measurement accuracy, but it is difficult to achieve a significant improvement by applying traditional stacking methods to multi-temporal MAI interferograms. This paper proposes an efficient MAI stacking method, where multi-temporal forward- and backward-looking residual interferograms are individually stacked before the MAI interferogram is generated. We tested the performance of this method using ENVISAT data from Kīlauea Volcano, Hawai‘i, where displacement on the order of several centimeters per year is common. By comparing results from the proposed stacking methods with displacements from GPS data, we documented measurement accuracies of about 1.03 and 1.07 cm/year for the descending and ascending tracks, respectively—an improvement of about a factor of two when compared with that from the conventional stacking approach. Three-dimensional surface-displacement maps can be constructed by combining stacked InSAR and MAI observations, which will contribute to a better understanding of a variety of geological phenomena.

Hawaii↗
USGS2016

Testing the suitability of geologic frameworks for extrapolating hydraulic properties across regional scales

The suitability of geologic frameworks for extrapolating hydraulic conductivity ( K ) to length scales commensurate with hydraulic data is difficult to assess. A novel method is presented for evaluating assumed relations between K and geologic interpretations for regional-scale groundwater modeling. The approach relies on simultaneous interpretation of multiple aquifer tests using alternative geologic frameworks of variable complexity, where each framework is incorporated as prior information that assumes homogeneous K within each model unit. This approach is tested at Pahute Mesa within the Nevada National Security Site (USA), where observed drawdowns from eight aquifer tests in complex, highly faulted volcanic rocks provide the necessary hydraulic constraints. The investigated volume encompasses 40 mi 3 (167 km 3 ) where drawdowns traversed major fault structures and were detected more than 2 mi (3.2 km) from pumping wells. Complexity of the five frameworks assessed ranges from an undifferentiated mass of rock with a single unit to 14 distinct geologic units. Results show that only four geologic units can be justified as hydraulically unique for this location. The approach qualitatively evaluates the consistency of hydraulic property estimates within extents of investigation and effects of geologic frameworks on extrapolation. Distributions of transmissivity are similar within the investigated extents irrespective of the geologic framework. In contrast, the extrapolation of hydraulic properties beyond the volume investigated with interfering aquifer tests is strongly affected by the complexity of a given framework. Testing at Pahute Mesa illustrates how this method can be employed to determine the appropriate level of geologic complexity for large-scale groundwater modeling.

Nevada↗
USGS2007

Isotopic characterization of three groundwater recharge sources and inferences for selected aquifers in the upper Klamath Basin of Oregon and California, USA

Stable isotope (??D and ??18O) signatures of three principal groundwater recharge areas in the 21,000-km2 upper Klamath Basin are used to infer recharge sources for aquifers in the interior parts of the basin. Two of the principal recharge areas, the Cascade Range on the western and southern margin of the basin and uplands along the eastern margin, are defined by mean annual precipitation that exceeds approximately 60 cm. A third recharge area coincides with the extensive irrigation canal system in the south central part of the basin. The stable isotope signature for Cascade Range groundwater falls near the global meteoric water line (GMWL). The stable isotope signature for the groundwater of the eastern basin uplands also falls near the GMWL, but is depleted in heavy isotopes relative to the Cascade Range groundwater. The stable isotope signature for water from the irrigation canal system deviates from the GMWL in a manner indicative of fractionation by evaporation. Groundwater provenance was previously unknown for two aquifers of interest: that supplying deep (225-792 m), large-capacity irrigation wells along the Oregon-California border, and that of the geothermal system near Klamath Falls. Groundwater produced by the deep irrigation wells along the Oregon-California border appears to be a mixture of eastern-basin groundwater and water with an evaporative isotopic signature. The component with an evaporative isotopic signature appears in some places to consist of infiltrated irrigation water. Chloride data suggest that much of the component with the evaporative isotopic signature may be coming from an adjacent subbasin. After accounting for the 18O shift common in geothermal waters, isotope data suggest that the geothermal groundwater in the upper Klamath Basin may emanate from the eastern basin uplands. Findings demonstrate that stable isotope and chloride data can illuminate certain details of a regional groundwater flow system in a complex geologic setting where other hydrologic data are ambiguous. ?? 2007 Elsevier B.V. All rights reserved.

Journal of Hydrology↗
USGS1991

The library as a reference tool: online catalogs

Online catalogs are computerized listings of materials in a particular library or group of libraries. General characteristics of online catalogs include ability for searching interactively and for locating descriptions of books, maps, and reports on regional or topical geology. Suggestions for searching, evaluating results, modifying searches, and limitations of searching are presented. -Author

The Compass: Earth Science Journal of Sigma Gamma ↗
USGS2013

Introduction to the special issue on “Understanding and predicting change in the coastal ecosystems of the northern Gulf of Mexico”

The coastal region of the northern Gulf of Mexico owes its current landscape structure to an array of tectonic, erosional and depositional, climatic, geochemical, hydrological, ecological, and human processes that have resulted in some of the world's most complex, dynamic, productive, and threatened ecosystems. Catastrophic hurricane landfalls, ongoing subsidence and erosion exacerbated by sea-level rise, disintegration of barrier island chains, and high rates of wetland loss have called attention to the vulnerability of northern Gulf coast ecosystems, habitats, built infrastructure, and economy to natural and anthropogenic threats. The devastating hurricanes of 2005 (Katrina and Rita) motivated the U.S. Geological Survey Coastal and Marine Geology Program and partnering researchers to pursue studies aimed at understanding and predicting landscape change and the associated storm hazard vulnerability of northern Gulf coast region ecosystems and human communities. Attaining this science goal requires increased knowledge of landscape evolution on geologic, historical, and human time scales, and analysis of the implications of such changes in the natural and built components of the landscape for hurricane impact susceptibility. This Special Issue of the Journal of Coastal Research communicates northern Gulf of Mexico research results that (1) improve knowledge of prior climates and depositional environments, (2) assess broad regional ecosystem structure and change over Holocene to human time scales, (3) undertake process studies and change analyses of dynamic landscape components, and (4) integrate framework, climate, variable time and spatial scale mapping, monitoring, and discipline-specific process investigations within interdisciplinary studies.

Journal of Coastal Research↗
USGS1996

Fracture patterns and their origin in the upper Devonian Antrim Shale gas reservoir of the Michigan basin: A review

INTRODUCTION: Black shale members of the Upper Devonian Antrim Shale are both the source and reservoir for a regional gas accumulation that presently extends across parts of six counties in the northern part of the Michigan basin (fig. 1). Natural fractures are considered by most petroleum geologists and oil and gas operators who work the Michigan basin to be a necessary condition for commercial gas production in the Antrim Shale. Fractures provide the conduits for free gas and associated water to flow to the borehole through the black shale which, otherwise, has a low matrix permeability. Moreover, the fractures assist in the release of gas adsorbed on mineral and(or) organic matter in the shale (Curtis, 1992). Depths to the gas-producing intervals (Norwood and Lachine Members) generally range from 1,200 to 1,800 ft (Oil and Gas Journal, 1994). Locally, wells that produce gas from the accumulation are as deep as 2,200 (Oil and Gas Journal, 1994). Even though natural fractures are an important control on Antrim Shale gas production, most wells require stimulation by hydraulic fracturing to attain commercial production rates (Kelly, 1992). In the U.S. Geological Survey's National Assessment of United States oil and gas, Dolton (1995) estimates that, at a mean value, 4.45 trillion cubic feet (TCF) of gas are recoverable as additions to already discovered quantities from the Antrim Shale in the productive area of the northern Michigan trend. Dolton (1995) also suggests that undiscovered Antrim Shale gas accumulations exist in other parts of the Michigan basin. The character, distribution, and origin of natural fractures in the Antrim Shale gas accumulation have been studied recently by academia and industry. The intent of these investigations is to: 1) predict 'sweet spots', prior to drilling, in the existing gas-producing trend, 2) improve production practices in the existing trend, 3) predict analogous fracture-controlled gas accumulations in other parts of the Michigan basin, and 4) improve estimates of the recoverable gas in the Antrim Shale gas plays (Dolton, 1995). This review of published literature on the characteristics of Antrim Shale fractures, their origin, and their controls on gas production will help to define objectives and goals in future U.S. Geological Survey studies of Antrim Shale gas resources.

Michigan↗
USGS1988

Gold and other metals in big sagebrush (Artemisia tridentata Nutt.) as an exploration tool, Gold Run District, Humboldt County, Nevada

Big sagebrush — a cold-desert species that dominates the terrain over large parts of western United States — was sampled along several traverses that crossed thermally metamorphosed limestone, phyllitic shale, and schist of the Middle and Upper Cambrian Preble Formation that host skarn-, disseminated gold and silver-, and hot springs gold-type mineral occurrences. Patterns of detectable levels of gold (8 to 28 ppb or ng g −1 ) in ash of new growth were consistent with areas affected by known or suspected gold mineralization. Soils collected along one of the traverses where a selenium-indicator plant was common contained no gold above background levels of 2ppb, but were consistently high in As, Sb, and Zn, and several samples were unusually high in Se (maximum 11 ppm or μg g −1 ). Sagebrush along this traverse contained Li at levels above norms for this species. We also found a puzzling geochemical anomaly at a site basinward from active hot springs along a range-front fault scarp. Sagebrush at this site contained a trace of gold and an unusually high concentration of Cd (13 ppm) and the soil had anomalous concentrations of Cd and Bi (3.2 and 6 ppm, respectively). The source of this anomaly could be either metal-rich waters from an irrigation ditch or leakage along a buried fault. Despite the limited nature of the study, we conclude that gold in sagebrush could be a cost-effective guide to drilling locations in areas where the geology seems favorable for disseminated and vein precious metals.

Journal of Geochemical Exploration↗
USGS2022

Geological reservoir characterization of a gas hydrate prospect associated with the Hydrate-01 Stratigraphic Test Well, Alaska North Slope

Geological reservoir characterization is essential for accurate evaluation of gas production performance from gas hydrate reservoirs. Particularly, the understanding of reservoir architecture and heterogeneity is of great importance since these are considered as major controls on fluid hydrodynamic and thermodynamic conditions. This study deals with well log and three-dimensional (3-D) vertical seismic profile (VSP) data acquired from the Hydrate-01 Stratigraphic Test Well within the 7-11-12 prospect, Prudhoe Bay Unit, Alaska North Slope and reports on the results of geological/geophysical evaluation related to the geological structure and reservoir properties of the 7-11-12 prospect. The structural trends of the target reservoirs, based on well correlations, are mostly consistent with the predrill prediction using the surface seismic data, and infer the existence of subseismic faults cutting through the Hydrate-01 well. The 3-D VSP data confirm a down-to-the-east normal fault that offsets the reservoir units across the Hydrate-01 well, which is concordant with the well identification of the same fault, and indicate a northeast-dipping relay structure associated with the overstepping normal faults. The edge enhancement attribute associated with discontinuity generated from the 3-D VSP data shows small faults/fractures, possibly as part of a complex fault network within the imaged normal fault system. These results reveal that the 3-D VSP data provide detailed structural information that is not present from the surface seismic data. The Hydrate-01 well log data confirm the occurrence of gas hydrate at high saturation in the two targeted sand units (B1 and D1 sands), and the comparison to a nearby pre-existing well (7-11-12 well) shows the same general trend in gas hydrate saturation as a map of seismic impedance generated from surface seismic data. The well log data also suggest that the base of gas hydrate occurrence in the Hydrate-01 and 7-11-12 wells is almost aligned at the same depth in both of the targeted B1 and D1 sand reservoirs. Especially for the D1 sand in the Hydrate-01 well, the resistivity logs show a sharp transition from high gas hydrate saturation to fully water-saturated within the D1 sand, suggesting a common gas hydrate/water contact. The results of this study will be used to construct the geological models needed for reservoir simulation studies and they can provide important insights into the geological factors that control the occurrence of gas hydrate on the Alaska North Slope.

Alaska↗
USGS2012

Regional map of the 0.70 psi/ft pressure gradient and development of the regional geopressure-gradient model for the onshore and offshore Gulf of Mexico basin, USA

Characterization of the regional pressure system in the Gulf of Mexico basin is critical for assessing the occurrence of undiscovered petroleum resources, evaluating areas with potential pressure-related production, identifying potential pressure-related geohazard issues, evaluating hydrocarbon reservoir-seal integrity, and determining the feasibility of geological sequestration and long-term containment of fluids.

Gulf of Mexico↗
USGS2004

Can site response be predicted?

Large modifications of seismic waves are produced by variations of material properties near the Earth's surface and by both surface and buried topography. These modifications, usually referred to as "site response", in general lead to larger motions on soil sites than on rock-like sites. Because the soil amplifications can be as large as a factor of ten, they are important in engineering applications that require the quantitative specification of ground motions. This has been recognised for years by both seismologists and engineers, and it is hard to open an earthquake journal these days without finding an article on site response. What is often missing in these studies, however, are discussions of the uncertainty of the predicted response. A number of purely observational studies demonstrate that ground motions have large site-to-site variability for a single earthquake and large earthquake-location- dependent variability for a single site. This variability makes site-specific, earthquake-specific predictions of site response quite uncertain, even if detailed geotechnical and geological information is available near the site. Predictions of site response for average classes of sites exposed to the motions from many earthquakes can be made with much greater certainty if sufficient empirical observations are available.

Journal of Earthquake Engineering↗
USGS2009

Compositions of modern dust and surface sediments in the Desert Southwest, United States

Modern dusts across southwestern United States deserts are compositionally similar to dust-rich Av soil horizons (depths of 0-0.5 cm and 1-4 cm at 35 sites) for common crustal elements but distinctly different for some trace elements. Chemical compositions and magnetic properties of the soil samples are similar among sites relative to dust sources, geographic areas, and lithologic substrates. Exceptions are Li, U, and W, enriched in Owens Valley, California, and Mg and Sr, enriched in soils formed on calcareous fan gravel in southeast Nevada. The Av horizons are dominated by dust and reflect limited mixing with substrate sediments. Modern dust samples are also similar across the region, except that Owens Valley dusts are higher in Mg, Ba, and Li and dusts both there and at sites to the north on volcanic substrates are higher in Sb and W. Thus, dust and Av horizons consist of contributions from many different sources that are well mixed before deposition. Modern dusts contain significantly greater amounts of As, Cd, Cr, Cu, Ni, Pb, and Sb than do Av horizons, which record dust additions over hundreds to thousands of years. These results suggest that modern dust compositions are influenced by anthropogenic sources and emissions from Owens (dry) Lake after its artificial desiccation in 1926. Both modern dusts and Av horizons are enriched in As, Ba, Cu, Li, Sb, Th, U, and W relative to average crustal composition, which we interpret to indicate that the geologic sources of dust in the southwestern United States are geochemically distinctive.

Journal of Geophysical Research F: Earth Surface↗
USGS2022

Quantifying interdependencies in geyser eruptions at the Upper Geyser Basin, Yellowstone National Park

The Upper Geyser Basin at Yellowstone National Park (Wyoming, USA) harbors the greatest concentration of geysers worldwide. Research suggests that individual geysers are not isolated but rather are hydraulically connected in the subsurface with other geysers and thermal springs. To quantify such connections, we combined techniques from machine learning, causal inference, and dynamical systems to characterize the collective eruptive behavior of a set of 10 geysers over 18 months (April 2007 – September 2008) focusing on geyser-geyser interactions. Model predictions were up to 15 times more accurate when we sought to predict a geyser's eruption time series based on outflow channel temperatures from the network than based on its own time series alone, suggesting the existence of a complex interconnected subsurface groundwater system. On average, cone-type geysers had larger impacts on other geysers than did fountain-type geysers. Similarly, cone-type geysers were on average more insulated from other geysers. However, substantial unexplained variation remained after considering the cone versus fountain dichotomy. Distance between geysers also affected interactions: nearby geysers had stronger effects on focal geysers than did geysers located farther away. Collectively, results support the hypothesis of geyser interdependence at timescales of 5 min–10 days. Our analyses highlight the existence of quantifiable geyser-to-geyser interactions that can be resolved through pairwise and system-level analyses. These findings emphasize the subsurface interconnectedness of thermal features, provide information relevant to visitor experiences in Yellowstone National Park, and suggest strategies for exploring patterns of interdependence that may exist among other episodic geological phenomena.

Wyoming↗
USGS1969

History of the geomagnetic field

Direct measurements of the direction and strength of the earth's magnetic field have provided a knowledge of the field's form and behavior during the last few hundreds of years. For older times, however, it has been necessary to measure the magnetism of certain rocks to learn what the geomagnetic field was like. For example, when a lava flow solidifies (at temperatures near 1000°C) and cools through the Curie point of the magnetic minerals contained in it (around 500°C) it acquires a remanent magnetism that is (1) very weak, (2) very stablel, (3) paralle to the direction of the ambient geomagnetic field, and (4) proportional in intensity to the ambient field. Separating, by various analytical means, this magnetization from other ``unwanted'' magnetizations has allowed paleomagnetists to study the historical and prehistorical behavior of the earth's field. It has been learned, for example, that the strength of the field was almost twice its present value 2000 years ago and that it has often completely reversed its polarity. Paleo‐magnetists have also confirmed that most oceans are, geologically speaking, relatively new features, and that the continents have markedly changed their positions over the surface of the earth.

Journal of Applied Physics↗
USGS1990

Sources and summaries of water-quality information for the Rapid Creek basin, western South Dakota

This report provides a compilation of water quality information for the Rapid Creek basin in western South Dakota. Two types of information are included: First, past and current water quality monitoring data collected by the South Dakota Department of Water and Natural Resources, U.S. Forest Service, U.S. Geological Survey, and others are described. Second, a summary is included for all past water quality reports, publications, and theses that could be located during this study. A total of 62 documents were abstracted and included journal articles, abstracts, Federal agency reports and publications, university and State agency reports, local agency reports, and graduate theses. The report should be valuable to water resources managers, regulators, and others contemplating water quality research, monitoring, and regulatory programs in the Rapid Creek basin. (USGS)

Open-File Report↗
USGS2022

Geologic framework, anthropogenic impacts, and hydrodynamics contribute to variable sediment availability and shoreface morphology at the Rockaway Peninsula, NY

Recent field and modeling studies have shown that barrier island resiliency is sensitive to sediment fluxes from the shoreface, making it important to evaluate how shoreface sediment availability varies in coastal systems. To do this, we assessed shoreface geology and morphology along the Rockaway Peninsula, NY, USA. We find that spatial variability in shoreface volume is influenced by sediment accommodation above the Holocene-Pleistocene (H-P) contact, historical barrier island evolution, and natural and engineered morphologic features, suggesting that simply identifying the H-P boundary may not be adequate for defining the shoreface reservoir. Further, sediment flux from the lower shoreface to the beach may be reduced by geologically limited cross-shore sediment distribution and shoreface steepening mediated by human modifications to the shoreline. Finally, the geologic limit of the shoreface is often shallower than a wave-based estimate of shoreface extent, implying that the geologic shoreface extent at our study site can be mobilized over short time scales (years-decades) and that the wave-based shoreface extent may be inaccurate when estimating shoreline response to sea-level rise. Our results demonstrate that the combination of hydrodynamics, humans, and geology on shoreface sediment fluxes impact how barrier islands respond to future changes in sediment supply and climate.

New York↗
USGS1997

U.S. Geological Survey Studies of Energy Resources in Sub-Saharan Africa

The U.S. Government and the American public need access to information on energy resources in sub-Saharan Africa. Sub-Saharan Africa (mostly Nigeria) produces 5 percent of the world's oil, while supplying the United States with 15 percent of our imports (Energy Information Administration). In the next 10 years, sub-Saharan oil and gas will become increasingly more important to the export market. New discoveries in offshore provinces of West Africa ensure a bright future for the region. Projections indicate that increased oil production in sub-Saharan Africa will far outpace the growth of intraregional consumption, providing greater quantities of oil for export (Forman, 1996). Also, West Africa, although a marginal supplier of liquefied natural gas (LNG) today, will become an important LNG source to the international market by the year 2000 (Oil & Gas Journal, 1996). The United States needs up-to-date information about petroleum resources and the energy balance within the region to predict the future role of sub-Saharan Africa as a major oil and gas exporter. The data required to generate the needed information are often disseminated in archives of oil companies and African geologic surveys, or in obscure publications. For these reasons, the U.S. Geological Survey is collecting data on sub-Saharan energy and constructing a regional energy bibliography. The team of geoscientists will assure that this information is available quickly and from a scientifically based, objective view point.

Fact Sheet↗
USGS1985

Management of ground water and evolving hydrogeologic studies in New Jersey : a heavily urbanized and industrialized state in the northeastern United States

New Jersey is the most densely populated and one of the most industrialized states in the United States. An abundance of freshwater and proximity to major northeastern metropolitan centers has facilitated this development. Pumpage of freshwater from all aquifers in the State in 1980 was 730 million gallons per day (2.76 million cubic meters per day). Management and efficient development of the ground-water resources of the State are the responsibility of the New Jersey Department of Environmental Protection. Laws have been enacted and updated by the State legislature to manage water allocation and to control the disposal of hazardous wastes. Present resource management is guided by the New Jersey Water-Supply Master Plan of 1981. Funding for management activities is partially derived from the sale of state-approved bonds. Effective planning and regional management require accurate and up-to-date hydrologic information and analyses. The U.S. Geological Survey, in cooperation with the New Jersey Geological Survey, is conducting three intensive ground-water studies involving the collection and interpretation of hydrologic data to meet the urgent water-management needs of New Jersey. These studies are part of a long-term cooperative program and are funded through the Water-Supply Bond Act of 1981. They began in 1983 and are scheduled to be completed in 1988. The project areas are situated in the New Jersey part of the Atlantic Coastal Plain in and near Atlantic City, Camden, and South River. They range in size from 400 to 1,200 mil (1,040 to 3,120 km2). The studies are designed to define the geology, hydrology, and geochemistry of the local ground-water systems. The results of these studies will enable the State to address more effectively major problems in these areas such as declining water levels, overpumping, saltwater intrusion, and ground-water contamination resulting from the improper disposal of hazardous wastes. Specific objectives of these studies by the U.S. Geological Survey are to (1) develop an accurate and up-to-date hydrogeologic data base, (2) design and implement a data-collection program and establish a computerized information management system, (3) refine the conceptualization of the ground-water flow system, and (4) define the geochemistry of the aquifer system by conducting a water-quality appraisal. The objectives are accomplished by standard hydrogeologic methods. Information concerning hydrogeologic framework, ground-water levels, water use, hydraulic characteristics, and water quality in the study areas is compiled from all available sources. Additional data needed are collected through well inventories, surface geophysical surveys, water-quality samplings, water-level measurements, and a well-drilling program. Interpretation of the flow system is based on the use of standard analytical techniques and digital flow modeling. Calibrated flow models will provide ground-water managers with a mechanism to develop and test regional water-supply strategies. Definition of the geochemistry of the aquifer system is accomplished through a variety of methods which depend on the problems and available data in the particular study area. The approach includes statistical analysis of water-quality data, reaction-path modeling, and determination of the movement of chemical constituents using analytical and numerical modeling techniques. A combined staff of 25 to 30 professionals and technicians from the New Jersey District office of the U.S. Geological Survey is committed to the three studies. The staff has specialists in geohydrology, numerical modeling, geochemistry, geophysics, and computer science. The findings of these studies will be published in data reports, interpretive reports, instructional manuals and journal articles.

New Jersey↗
USGS1997

Digital-map grids of mean-annual precipitation for 1961-90, and generalized skew coefficients of annual maximum streamflow for Oklahoma

This digital report contains two digital-map grids of data that were used to develop peak-flow regression equations in Tortorelli, 1997, 'Techniques for estimating peak-streamflow frequency for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma,' U.S. Geological Survey Water-Resources Investigations Report 97-4202. One data set is a grid of mean annual precipitation, in inches, based on the period 1961-90, for Oklahoma. The data set was derived from the PRISM (Parameter-elevation Regressions on Independent Slopes Model) mean annual precipitation grid for the United States, developed by Daly, Neilson, and Phillips (1994, 'A statistical-topographic model for mapping climatological precipitation over mountainous terrain:' Journal of Applied Meteorology, v. 33, no. 2, p. 140-158). The second data set is a grid of generalized skew coefficients of logarithms of annual maximum streamflow for Oklahoma streams less than or equal to 2,510 square miles in drainage area. This grid of skew coefficients is taken from figure 11 of Tortorelli and Bergman, 1985, 'Techniques for estimating flood peak discharges for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma,' U.S. Geological Survey Water-Resources Investigations Report 84-4358. To save disk space, the skew coefficient values have been multiplied by 100 and rounded to integers with two significant digits. The data sets are provided in an ASCII grid format.

Oklahoma↗