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At least 289 records · Page 16Linked to original sources
USGS2004

Ecoregions and ecoregionalization: geographical and ecological perspectives

Ecoregions, i.e., areas exhibiting relative homogeneity of ecosystems, are units of analysis that are increasingly important in environmental assessment and management. Ecoregions provide a holistic framework for flexible, comparative analysis of complex environmental problems. Ecoregions mapping has intellectual foundations in both geography and ecology. However, a hallmark of ecoregions mapping is that it is a truly interdisciplinary endeavor that demands the integration of knowledge from a multitude of sciences. Geographers emphasize the role of place, scale, and both natural and social elements when delineating and characterizing regions. Ecologists tend to focus on environmental processes with special attention given to energy flows and nutrient cycling. Integration of disparate knowledge from the many key sciences has been one of the great challenges of ecoregions mapping, and may lie at the heart of the lack of consensus on the “optimal” approach and methods to use in such work. Through a review of the principal existing US ecoregion maps, issues that should be addressed in order to advance the state of the art are identified. Research related to needs, methods, data sources, data delivery, and validation is needed. It is also important that the academic system foster education so that there is an infusion of new expertise in ecoregion mapping and use.

Environmental Management↗
USGS2009

Evaluation of trap capture in a geographically closed population of brown treesnakes on Guam

1. Open population mark-recapture analysis of unbounded populations accommodates some types of closure violations (e.g. emigration, immigration). In contrast, closed population analysis of such populations readily allows estimation of capture heterogeneity and behavioural response, but requires crucial assumptions about closure (e.g. no permanent emigration) that are suspect and rarely tested empirically. 2. In 2003, we erected a double-sided barrier to prevent movement of snakes in or out of a 5-ha semi-forested study site in northern Guam. This geographically closed population of >100 snakes was monitored using a series of transects for visual searches and a 13 ?? 13 trapping array, with the aim of marking all snakes within the site. Forty-five marked snakes were also supplemented into the resident population to quantify the efficacy of our sampling methods. We used the program mark to analyse trap captures (101 occasions), referenced to census data from visual surveys, and quantified heterogeneity, behavioural response, and size bias in trappability. Analytical inclusion of untrapped individuals greatly improved precision in the estimation of some covariate effects. 3. A novel discovery was that trap captures for individual snakes consisted of asynchronous bouts of high capture probability lasting about 7 days (ephemeral behavioural effect). There was modest behavioural response (trap happiness) and significant latent (unexplained) heterogeneity, with small influences on capture success of date, gender, residency status (translocated or not), and body condition. 4. Trapping was shown to be an effective tool for eradicating large brown treesnakes Boiga irregularis (>900 mm snout-vent length, SVL). 5. Synthesis and applications. Mark-recapture modelling is commonly used by ecological managers to estimate populations. However, existing models involve making assumptions about either closure violations or response to capture. Physical closure of our population on a landscape scale allowed us to determine the relative importance of covariates influencing capture probability (body size, trappability periods, and latent heterogeneity). This information was used to develop models in which different segments of the population could be assigned different probabilities of capture, and suggests that modelling of open populations should incorporate easily measured, but potentially overlooked, parameters such as body size or condition. ?? 2008 The Authors.

Journal of Applied Ecology↗
USGS2023

Range-wide population trend analysis for greater sage-grouse (Centrocercus urophasianus)—Updated 1960–2022

Greater sage-grouse ( Centrocercus urophasianus ) are at the center of state and national land-use policies largely because of their unique life-history traits as an ecological indicator for health of sagebrush ecosystems. This updated population trend analysis provides state and federal land and wildlife managers with best-available science to help guide current management and conservation plans aimed at benefitting sage-grouse populations. This analysis relied on previously published population trend modeling methodology from Coates and others (2021, 2022a) and incorporated population lek count data through 2022. Bayesian state-space models estimated 2.9 percent average annual decline in sage-grouse populations across their geographical range, which varied among subpopulations at the largest scale of analysis, termed climate clusters (2.2–4.7). Cumulative declines were 40.9, 65.0, and 79.6 percent range-wide across short (19 years), medium (35 years), and long (55 years) temporal periods, respectively. These results indicate that the most recent nadir for range-wide populations occurred during 2021. However, growth during 2022 was modest, making 2021 a tentative final nadir at this point.

Data Report↗
USGS2003

Land use and land cover change in the Greater Yellowstone Ecosystem: 1975-1995

Shifts in the demographic and economic character of the Greater Yellowstone Ecosystem (GYE) are driving patterns of land cover and land use change in the region. Such changes may have important consequences for ecosystem functioning. The objective of this paper is to quantify the trajectories and rates of change in land cover and use across the GYE for the period 1975-1995 using satellite imagery. Spectral and geographic variables were used as inputs to classification tree regression analysis (CART) to find "rules" which defined land use and land cover classes on the landscape. The resulting CART functions were used to map land cover and land use across seven Landsat TM scenes for 1995. We then used a thresholding technique to identify locations that differed in spectral properties between the 1995 and 1985 time periods. These "changed" locations were classified using CART functions derived from spectral and geographic data from 1985. This was similarly done for the year 1975 based on Landsat MSS data. Differences between the 1975, 1985, and 1995 maps were considered change in land cover and use. We calibrated and tested the accuracy of our models using data acquired through manual interpretation of aerial photos. Elevation and vegetative indices derived from the remotely sensed satellite imagery explained the most variance in the land use and land cover classes (-i.e., defined the "rules" most often). Overall accuracies from our study were good, ranging from 94% at the coarsest level of detail to 74% at the finest. The largest changes over the study period were the increases in burned, urban, and mixed conifer-herbaceous classes and decreases in woody deciduous, mixed woody deciduous-herbaceous, and conifer habitats. These changes have important implications for ecological function and biodiversity. The expansion of mixed conifer classes may increase fuel loads and enhance risk to the growing number of rural homes. The reduction of woody deciduous cover types is likely reducing population sizes for the numerous plant and animal species that specialize on this habitat type. Some of these species are also negatively influenced by the increase of rural homes in and near woody deciduous habitats.

Idaho, Montana, Wyoming↗
USGS2015

Not to put too fine a point on it - does increasing precision of geographic referencing improve species distribution models for a wide-ranging migratory bat?

Bat specimens held in natural history museum collections can provide insights into the distribution of species. However, there are several important sources of spatial error associated with natural history specimens that may influence the analysis and mapping of bat species distributions. We analyzed the importance of geographic referencing and error correction in species distribution modeling (SDM) using occurrence records of hoary bats ( Lasiurus cinereus ). This species is known to migrate long distances and is a species of increasing concern due to fatalities documented at wind energy facilities in North America. We used 3,215 museum occurrence records collected from 1950–2000 for hoary bats in North America. We compared SDM performance using five approaches: generalized linear models, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy models. We evaluated results using three SDM performance metrics (AUC, sensitivity, and specificity) and two data sets: one comprised of the original occurrence data, and a second data set consisting of these same records after the locations were adjusted to correct for identifiable spatial errors. The increase in precision improved the mean estimated spatial error associated with hoary bat records from 5.11 km to 1.58 km, and this reduction in error resulted in a slight increase in all three SDM performance metrics. These results provide insights into the importance of geographic referencing and the value of correcting spatial errors in modeling the distribution of a wide-ranging bat species. We conclude that the considerable time and effort invested in carefully increasing the precision of the occurrence locations in this data set was not worth the marginal gains in improved SDM performance, and it seems likely that gains would be similar for other bat species that range across large areas of the continent, migrate, and are habitat generalists.

Acta Chiropterologica↗
USGS1963

Deuterium in Iceland waters

From the deuterium analysis of 159 samples of water collected in Iceland from hot-water boreholes, cold and hot springs, rivers and rain, the geographical distribution of deuterium in surface waters is plotted. On the basis of the deuterium analysis, the water from boreholes near Reykjavik does not originate from local precipitation. The variation of deuterium content of these water wells with time suggests that these data can be used to determine the time of travel of recharge water to the various boreholes, as well as the surface recharge area.

Geochimica et Cosmochimica Acta↗
USGS2014

A landscape-based reconnaissance survey of estrogenic activity in streams of the upper Potomac, upper James,and Shenandoah Rivers, USA

Endocrine-disrupting compounds (EDCs) are becoming of increasing concern in waterways of the USA and worldwide. What remains poorly understood, however, is how prevalent these emerging contaminants are in the environment and what methods are best able to determine landscape sources of EDCs. We describe the development of a spatially structured sampling design and a reconnaissance survey of estrogenic activity along gradients of land use within sub-watersheds. We present this example as a useful approach for state and federal agencies with an interest in identifying locations potentially impacted by EDCs that warrant more intensive, focused research. Our study confirms the importance of agricultural activities on levels of a measured estrogenic equivalent (E2Eq) and also highlights the importance of other potential sources of E2Eq in areas where intensive agriculture is not the dominant land use. Through application of readily available geographic information system (GIS) data, coupled with spatial statistical analysis, we demonstrate the correlation of specific land use types to levels of estrogenic activity across a large area in a consistent and unbiased manner.

Environmental Monitoring and Assessment↗
USGS2016

Bitumen prices and structural changes in North American crude oil markets

In an earlier report, changes in bitumen prices at Hardesty, Alberta, Canada, were modeled as the responses to changes in monthly prices of Hardesty light/medium crude oil for the period 2000–2006 with a simple error correction econometric model. This note re-examines that price relationship for the period 2009–2014. Over the period 2006–2014, there was also rapid growth in North American light oil production from low-permeability carbonate, sandstone, and shale reservoirs. During that period, Canadian raw bitumen production grew by more than 12% per year and there was significant geographical diversification in its markets. Results of the statistical analysis showed that the change in the dynamic relationships between bitumen prices and Hardesty light oil prices probably reflected, in part, the maturation of bitumen markets and closer integration with North American light oil markets. The analysis also examines the dynamic relationships between bitumen prices and West Texas Intermediate and Brent international benchmark crude oil prices. Ideally, if bitumen prices are found to be closely related to a widely traded benchmark crude oil, the benchmark crude oil price forecasts could be used as a basis for predicting bitumen prices. However, neither of international benchmark crude oils tested had high explanatory power.

Natural Resources Research↗
USGS2014

Reach-scale comparison of habitat and mollusk assemblages for select sites in the Clinch River with regional context

Several hypotheses, including habitat degradation and variation in fluvial geomorphology, have been posed to explain extreme spatial and temporal variation in Clinch River mollusk assemblages. We examined associations between mollusk assemblage metrics (richness, abundance, recruitment) and physical habitat (geomorphology, streambed composition, fish habitat, and riparian condition) at 10 sites selected to represent the range of current assemblage condition in the Clinch River. We compared similar geomorphological units among reaches, employing semi-quantitative and quantitative protocols to characterize mollusk assemblages and a mix of visual assessments and empirical measurements to characterize physical habitat. We found little to no evidence that current assemblage condition was associated with 54 analyzed habitat metrics. When compared to other sites in the Upper Tennessee River Basin (UTRB) that once supported or currently support mollusk assemblages, Clinch River sites were more similar to each other, representing a narrower range of conditions than observed across the larger geographic extent of the UTRB. A post-hoc analysis suggested stream size and average boundary shear stress at bankfull stage may have historically limited species richness in the UTRB (p < 0.001). Associations between mollusk assemblages and physical habitat in the UTRB and Clinch River currently appear obscured by other factors limiting richness, abundance, and recruitment.

Tennessee, Virginia↗
USGS2011

Going coastal: Shared evolutionary history between coastal British Columbia and Southeast Alaska wolves (canis lupus)

Many coastal species occupying the temperate rainforests of the Pacific Northwest in North America comprise endemic populations genetically and ecologically distinct from interior continental conspecifics. Morphological variation previously identified among wolf populations resulted in recognition of multiple subspecies of wolves in the Pacific Northwest. Recently, separate genetic studies have identified diverged populations of wolves in coastal British Columbia and coastal Southeast Alaska, providing support for hypotheses of distinct coastal subspecies. These two regions are geographically and ecologically contiguous, however, there is no comprehensive analysis across all wolf populations in this coastal rainforest. By combining mitochondrial DNA datasets from throughout the Pacific Northwest, we examined the genetic relationship between coastal British Columbia and Southeast Alaska wolf populations and compared them with adjacent continental populations. Phylogenetic analysis indicates complete overlap in the genetic diversity of coastal British Columbia and Southeast Alaska wolves, but these populations are distinct from interior continental wolves. Analyses of molecular variation support the separation of all coastal wolves in a group divergent from continental populations, as predicted based on hypothesized subspecies designations. Two novel haplotypes also were uncovered in a newly assayed continental population of interior Alaska wolves. We found evidence that coastal wolves endemic to these temperate rainforests are diverged from neighbouring, interior continental wolves; a finding that necessitates new international strategies associated with the management of this species.

Alaska↗
USGS1988

Selected papers in the applied computer sciences, 1988

This compilation of short papers is intended to describe technical advances in the applied computer sciences. The aim of the series is to provide a forum for discussions on innovative uses of computing techniques in the earth sciences. Papers are presented on ( 1) an expert system to facilitate land analysis, (2) data-generalization processes for use with geographic information systems, (3) digital image processing for map production, (4) connecting local- and wide-area networks, and (5) generic file structures for hydrologic data.

Bulletin↗
USGS1993

National geophysical data grids; gamma-ray, gravity, magnetic, and topographic data for the conterminous United States

Overview and installation Note: the information on this site was copied from an optical medium publication. Although all data and software published on this CD-ROM have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials. This CD-ROM has been produced in accordance with the ISO 9660 CD- ROM Standard and is therefore capable of being read on any computing platform that has appropriate CD-ROM driver software installed. However, the access software used on the disc currently executes only under DOS on IBM or compatible personal computers. OVERVIEW This CD-ROM contains gridded geophysical data, images generated from the data, software for displaying and analyzing the images, software for processing potential-field (gravity and magnetic) geophysical data, and documentation files that describe the data and software. The gridded data include gamma-ray data (uranium, thorium, and potassium channels), Bouguer gravity data, isostatic residual gravity data, aeromagnetic anomalies, topography, and topography with bathymetry. These data are available in ASCII format under the ASCII directory. This publication contains only data from the conterminous United States. The images on this CD-ROM include graytone and color images of each gridded data set, color shaded-relief images of the potential-field and topographic data, color composite images of the gamma-ray data, and color composite images of potential-field data painted on shaded and edge-enhanced topography. These images are 8-bit data and can be imported for viewing by many different software packages, but the color display tables are only designed for DOS computers and displays. The display and analysis software includes the ability to register images with geographic and geologic overlays, generate three-color composite images for display on a super VGA video system, generate perspective view images, and analyze images in five dimensions. The potential-field software on this CD-ROM can be used to extract subsets of the geophysical data, process them, and display them as images or contour maps. The software can also be used to generate gridded data from point data, generate profiles from grids, and generate geological models from gridded or profile data. This software is written in FORTRAN and, with minor modifications, can be adapted to a variety of computer systems. The documentation files reside under the directory DOSMENU\DOCFILES and are named with a suffix of DOC. This directory also contains a WordPerfect 5.1 file (CDROM.WPS) that contains all of the documentation. This CD-ROM is released in the Digital Data Series of CD-ROM's produced by the U.S. Geological Survey. This new publication series is intended to improve distribution of important earth science information to the public. The disc contains the results of work performed by the U.S. Geological Survey. INSTALLATION If you have not already done so, run the INSTALL program by making the CD-ROM drive the active drive and typing INSTALL followed by pressing the key. Follow the instructions printed on the screen. When the INSTALL program is finished, it will invoke the national geophysics (NATGP) menu program, and you will see a menu of your options. If you have previously run the INSTALL program and you have added C:\ to the PATH statement in your AUTOEXEC.BAT file, run the menu program directly by typing NATGP followed by pressing the key. If C:\ is not in your search path, you will have to type C:\NATGP followed by pressing the key. A menu of your options will appear on the screen.

Data Series↗
USGS2024

The 3D Elevation Program—Supporting Florida's economy

Introduction Florida has the longest coastline of any State in the contiguous United States, and its coastal resources are one of the main drivers of its economic growth. High-quality elevation data are beneficial for use in emergency management, especially for hurricane response, recovery, and mitigation, as well as for coastal zone management, flood risk management, infrastructure planning, agriculture, forestry, and natural resources management. Having regional or statewide elevation data coverage that was collected at about the same time allows for improved results from in-depth modeling and more meaningful analysis to support the State’s Chief Science Officer, Geographic Information Officer, State agencies, water management districts, and local governments that will use these data for decision making. Critical applications that meet the State’s management needs depend on light detection and ranging (lidar) data that provide a highly detailed three-dimensional (3D) model of the Earth’s surface and aboveground features.

Florida↗
USGS2001

Map Showing Susceptibility to Earthquake-Induced Landsliding, San Juan Metropolitan Area, Puerto Rico

Analysis of slope angle and rock type using a geographic information system indicates that about 68 percent of the San Juan metropolitan area has low to no susceptibility to earthquake-induced landslides. This is at least partly due to the fact that 45 percent of the San Juan metropolitan area is constructed on slopes of 3 degrees or less, which are too gentle for landslides to occur. The areas with the highest susceptibility to earthquake-induced landslides account for 6 percent of the surface area. Almost one-quarter (24 percent) of the San Juan metropolitan area is moderately susceptible to earthquake-induced landslides. These areas are mainly in the southern portions of the San Juan metropolitan area, where housing development pressures are currently high because of land availability and the esthetics of greenery and hillside views. The combination of new development and moderate earthquake-induced landslide susceptibility indicate that the southern portions of the San Juan metropolitan area are be at greatest risk.

Open-File Report↗
USGS1978

Tin and related elements in sediments and beach sands from Afghanistan, Iran, and Turkey

Sixty samples of sediments from stream beds, outwash plains, and beaches were collected in Afghanistan, Iran, and Turkey by Fred L. Klinger, U.S. Bureau of Mines, as part of the field work undertaken by the National Geographic-Smithsonian Pyrotechnological Expedition of 1968. Facilities for the analysis of the samples for tin and other metals were not immediately available, but in 1973 arrangements were made for analyses to be made on a time-permitting basis in the U.S. Geological Survey. The original purpose in collecting the samples was to determine whether tin was present in amounts indicative of sources for tin ores used in antiquity for the manufacture of bronze. The results of the analyses not only permitted an evaluation of the potential for tin in the localities sampled, but also afforded chemical and mineralogical data that were interpretable in the context of regional potential for other elements of current industrial use. These include gold, base metals, ferro-alloy metals, beryllium, rare earths, and barium. The original 60 samples of sand were sieved to make three size fraction (>0.707 mm, <O.707->O.177 mm, and <0.177 mm) for spectrographic and chemical analysis. Splits of these fractions were used for replicate analyses to permit evaluation of the precision of the analytical procedures. Further splitting of the <0.707->0.177 mm sand gave fractions from each sample that were separated in bromoform. Concentrates from the heavy-liquid separations were divided magnetically into six parts from most magnetic to least magnetic. These concentrates were analyzed spectrographically. The precision of the spectrographic analyses is well within the limits of precision expected from semiquantitative procedures. Such precision allows semiquantitative spectrographic procedures to be used with confidence as a valuable tool for reconnaissance investigations in which multi-element analyses are necessary. The analyses of the various fractions of sediments and sediment concentrates indicate the sample media in which an element was most likely to occur. Tin exhibited no preferential concentration into any particular medium. However, many elements with which tin is associated, and other elements of industrial use, do concentrate into one or more of the sample media. This indication of a preferred medium permits interpretation of the analyses as to the best sample medium for a particular element in the environment of western Asia. Cassiterite and/or tin were detected in many samples from Afghanistan, Iran, and Turkey, but in most of the samples the tin was present in normal crustal abundance. Sixteen samples, including seven from Afghanistan, eight from Iran, and one from Turkey contain unusually large amounts of tin. The most notable areas of anomalous tin are near Mirzaka, Qala-i-Asad, and Shah Agha in Afghanistan; near Meshed, Shir Kuh, Natanz, Nodus, and Talmesi in Iran; and on the shore of the Balck Sea just west of Trabzon in Turkey. Even in these localities the tin appears to be a minor element associated with other ores. The most common association of tin is with copper at known mineralized areas. This relation may have historical significance in the context of the development of bronze. The results of the analyses provided geochemical data on the distribution of other elements of industrial use and clearly identified nine of the ten known mineral deposits represented by the samples. The known metallization at the reported deposits may be only a part of more complex groups of metals. In Afghanistan an array of anomalous elements at the known gold placers around Mirzaka and along the Anguri River signals the presence of complex ore deposits. These elements are silver, arsenic, gold, bismuth, cadmium, copper, mercury, indium, molybdenum, lead, antimony, tin, thallium, tungsten, and zinc. They may indicate a Carlin-type gold deposit in which the wall-rocks are enriched in micron-sized particles of gold. Other localities in Afghanistan signalled by the results of the analyses to be anomalous and to merit further geochemical exploration are: (1) a reach of the Panjshir River for beryllium, lead, zinc, chromium and nickel; (2) the area near Bamian for beryllium; (3) the Siakhak village area for gold and copper; (4) around Qala-i-Asad and Shah Agha for lead, zinc, gold, and tungsten. Some attention to the distribution of monazite around Siakhak, Shahjui, Qala-i-Asad, and Shah Agha is justified to determine if this ore mineral for the rare earths and thorium is enriched over its normally expectable trace as an accessory mineral in granitic rocks, pelitic schists, and gneisses. In Iran, the pluton of granodiorite porphyry near Sar Cheshmeh, an area where a huge porphyry copper deposit was being investigated by the Geological Survey of Iran when the present samples were collected in 1968, shows as a strong geochemical anomaly for copper and molybdenum. The granitic area near Meshed is geochemically enriched persistently in beryllium, tin, and barium, and locally in gold, lanthanum, niobium, yttrium, and other elements. This area deserves a thorough regional geochemical survey for beryl and nonberyl sources of beryllium, for fluorite, and for the ores of niobium, tin, barium, the rare earths, and thorium. Other localities in Iran that merit geochemical exploration on the basis of these data are: ;1) the areas between Tabas and Deyhuk, east of Naiband, and south of Naiband for barium and zinc; (2) a locality about midway between Kerman and Sirdjan for barium, lanthanum, strontium, and zinc; (4) the Meskani copper mine area for mercury, lead, and nickel as well as copper; (5) the Talmesi copper mine area for such other elements as barium, cobalt, mercury, strontium, and zinc; (6) a small pluton of granodiorite north of Natanz for tungsten and base metals; (7) the vicinity of Zendjan for auriferous polymetallic sufide deposits; (8) gold in the gorge 15 km east of Miyaneh; and (9) the area near Nodus for gold, base metals, molybdenum, and niobium, and possibly uranium. The Harsit River basin in Turkey appears to be a suitable target for geochemical exploration for gold and low-temperature hydrothermal deposits of base metals, barium, and mercury.

Open-File Report↗
USGS1996

Digital representation of the Washington state geologic map: a contribution to the Interior Columbia River Basin Ecosystem Management Project

This report describes the digital representation of the Washington state geologic map (Hunting and others, 1961). This report contains an explantion of why the data were prepared, a description of the digital data, and information on obtaining the digital files. This report is one in a series of digital maps, data files, and reports generated by the U.S. Geological Survey to provide geologic process and mineral resource information to the Interior Columbia Basin Ecosystem Management Project (ICBEMP). The various digital maps and data files are being used in a geographic information system (GIS)-based ecosystem assessment including an analysis of diverse questions relating to past, present, and future conditions within the general area of the Columbia River Basin east of the Cascade Mountains.

Open-File Report↗
USGS2009

Magnitude and frequency of rural floods in the southeastern United States, 2006: Volume 1, Georgia

A multistate approach was used to update methods for estimating the magnitude and frequency of floods in rural, ungaged basins in Georgia, South Carolina, and North Carolina that are not substantially affected by regulation, tidal fluctuations, or urban development. Annual peak-flow data through September 2006 were analyzed for 943 streamgaging stations having 10 or more years of data on rural streams in Georgia, South Carolina, North Carolina, and adjacent parts of Alabama, Florida, Tennessee, and Virginia. Flood-frequency estimates were computed for the 943 stations by fitting the logarithms of annual peak flows for each station to a Pearson Type III distribution. As part of the computation of flood-frequency estimates for these streamgaging stations, a new value for the generalized-skew coefficient was developed by using a Bayesian generalized least-squares regression model. Additionally, basin characteristics for the streamgaging stations were computed by using a geographical information system and automated computer algorithms. Regional regression analysis, using generalized least-squares regression, was used to develop a set of predictive equations for estimating the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent chance exceedance flows for rural ungaged basins in Georgia, South Carolina, and North Carolina. Flood-frequency estimates and basin characteristics for 828 stream-gaging stations were combined to form the final database used in the regional regression analysis. Five hydrologic regions were developed for Georgia, South Carolina, and North Carolina. The final predictive equations are all functions of drainage area and percentage of the drainage basin within each hydrologic region. Average standard errors of prediction for these regression equations range from 34.5 to 47.7 percent.

Georgia↗
USGS2013

Analytical properties of some commercially available nitrate reductase enzymes evaluated as replacements for cadmium in automated, semiautomated, and manual colorimetric methods for determination of nitrate plus nitrite in water

A multiyear research effort at the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) evaluated several commercially available nitrate reductase (NaR) enzymes as replacements for toxic cadmium in longstanding automated colorimetric air-segmented continuous-flow analyzer (CFA) methods for determining nitrate plus nitrite (NO x ) in water. This research culminated in USGS approved standard- and low-level enzymatic reduction, colorimetric automated discrete analyzer NO x methods that have been in routine operation at the NWQL since October 2011. The enzyme used in these methods (AtNaR2) is a product of recombinant expression of NaR from Arabidopsis thaliana (L.) Heynh. (mouseear cress) in the yeast Pichia pastoris. Because the scope of the validation report for these new automated discrete analyzer methods, published as U.S. Geological Survey Techniques and Methods 5–B8, was limited to performance benchmarks and operational details, extensive foundational research with different enzymes—primarily YNaR1, a product of recombinant expression of NaR from Pichia angusta in the yeast Pichia pastoris—remained unpublished until now. This report documents research and development at the NWQL that was foundational to development and validation of the discrete analyzer methods. It includes: (1) details of instrumentation used to acquire kinetics data for several NaR enzymes in the presence and absence of known or suspected inhibitors in relation to reaction temperature and reaction pH; and (2) validation results—method detection limits, precision and bias estimates, spike recoveries, and interference studies—for standard- and low-level automated colorimetric CFA-YNaR1 reduction NO x methods in relation to corresponding USGS approved CFA cadmium-reduction (CdR) NO x methods. The cornerstone of this validation is paired sample statistical and graphical analysis of NOx concentrations from more than 3,800 geographically and seasonally diverse surface-water and groundwater samples that were analyzed in parallel by CFA-CdR and CFA enzyme-reduction methods. Finally, (3) demonstration of a semiautomated batch procedure in which 2-milliliter analyzer cups or disposable spectrophotometer cuvettes serve as reaction vessels for enzymatic reduction of nitrate to nitrite prior to analytical determinations. After the reduction step, analyzer cups are loaded onto CFA, flow injection, or discrete analyzers for simple, rapid, automatic nitrite determinations. In the case of manual determinations, analysts dispense colorimetric reagents into cuvettes containing post-reduction samples, allow time for color to develop, insert cuvettes individually into a spectrophotometer, and record percent transmittance or absorbance in relation to a reagent blank. Data presented here demonstrate equivalent analytical performance of enzymatic reduction NO x methods in these various formats to that of benchmark CFA-CdR NO x methods.

Scientific Investigations Report↗