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At least 217 records · Page 12Linked to original sources
USGS1988

Habitat Suitability Index Models: American eider (breeding)

INTRODUCTION The common eider (Somateria mollissima) consists of five subspecies; four are found in North America (Palmer 1976). Six management populations of common eiders have recently been defined in eastern Canada and the United States (Reed and Erskine 1986). The American edier (S. mollissima dresseri), of which three populations are recognized (Reed and Erskine 1986), is the southernmost subspecies and the focus of this paper. The common eider is a member of the order Anseriformes, family Anatidae, and the tribe Mergini. A seabird of the northern latitudes of the world, the common eider is the largest duck of North America, ranging in weight from 1.2 to 2.8 kg and having a total length from 53.3 to 68.6 cm (Bellrose 1980). The American subspecies averages 2.0 kg and 61.0 cm for males, and 1.5 kg and 57.0 cm for females (Bellrose 1980). The drake is distinctly patterned,, having a white back and breast and a black belly and sides. The smaller female is brown and heavily barred with dark brown. Both sexes have a leathery extension of the bill which forms a Y-shaped frontal shield that reaches almost to the eyes. Maine, which supports part of the Atlantic population of common eiders (Reed and Erskine 1986), is the only major eider breeding population in the lower 48 States. American eiders are colonial nesters and use a variety of nesting sites, but they prefer relatively small, uninhabited islands (Mendall 1976). The coastal islands of Maine, which are essential to the eider's life cycle, are increasingly subjected to recreation and development, creating potential disturbances to eider breeding colonies. During recent years, aesthetic and sporting interest in eiders has increased. Sea ducks in Maine are experiencing increased hunting pressure. Compared to hunting seasons and bag limits for inland ducks, sea duck seasons and limits are liberal (Maine Department of Inland Fisheries and Wildlife [MDIFW] 1983).

FWS/OBS↗
USGS2000

Metal-sulfate salts from sulfide mineral oxidation

The observation of “efflorescences,” or the flowering of salts, associated with periods of dryness in soils, in closed-basin lakes, in rock outcrops, and in mines and mine wastes has been noted since early antiquity. The formation of metal-sulfate salts, in connection with the mining of metals, was a phenomenon well known to the early Greek and Roman civilizations. Alum, most commonly potash alum KAl(SO 4 ) 2 · 12H 2 O, which is from the Latin alumen , was extensively mined and used by goldsmiths, dyers, paper manufacturers, and physicians in ancient civilizations. It forms from the oxidation of pyrite in shales and slates and from oxidation of sulfurous gases in geothermal areas. The Greeks and the Romans described stalactites of atramentum (soluble metal-sulfate salts) that formed within mines and along rock faces (Agricola 1546, 1556). Furthermore, the toxic effects of these salts on animals were also noted. For example, in De Natura Fossilium , Agricola (1546) stated “….I mention the congealed acid juice which usually produces cadmia . It is white, hard, and so acrid that it can eat away walls, grills and even destroy all living matter.” Cadmia is thought to be derived from the oxidation of zinc, cobalt, and arsenic sulfides, such as cobaltite. He goes on to say that “Pyrite, unless it contains sulphates, is either a golden or silver color, rarely any other, while cadmia is black, yellow brown, or gray. The former will cure gatherings while the latter is a deadly poison and will destroy any living substance. It is used to kill grasshoppers, mice and flies.” These descriptions suggest the presence of arsenic compounds. The range of colors from white to black commonly is caused by different amounts of admixed pyrite with sulfate minerals. From the days of the Greek philosopher Theophrastus ( ca 325 BCE) and the Greek physician Dioscorides (first century CE), the efflorescent salts atramentum sutorium virida or melanterite (also called melanteria ) and atramentum sutorium caeruleum or chalcanthite were well known to form from the corrosion of pyrite and chalcopyrite by moisture (Agricola 1546, footnotes on p. 47–51). By the time of Pliny the Second (Caius Plinius Secundus, 23–79 CE), the names “green vitriol” for melanterite and “blue vitriol” for chalcanthite were in common use and continued to be used from the Middle Ages to the 20th century.

Reviews in Mineralogy and Geochemistry↗
USGS1981

The Geologic Story of Colorado National Monument

From 1946 until about 1956 I carried out fieldwork intermittently on the geology and artesian water supply of the Grand Junction area, Colorado, the results of which have been published. The area mapped geologically contains about 332 square miles in the west-central part of Mesa County and includes all of Colorado National Monument. During the field work several successive custodians or superintendents and several park naturalists urged that upon completion of my professional paper I prepare a brief account of the geology of the Monument in terms understandable by laymen, and which could be sold at the Visitor Center. This I was happy to do and there resulted 'The geologic story of Colorado National Monument', published by the Colorado and Black Canyon Natural History Association in cooperation with the National Park Service. This report contained colored sketches by John R. Stacy and a colored cover, but the photographs and many of the drawings were reproduced in black and white.

Bulletin↗
USGS1977

Role of the wolf in a deer decline in the Superior National Forest

White-tailed deer (Odocoileus virginianus) declined in the Superior National Forest of Minnesota between 1968 and 1974. In a 3,000 sq km area of the poorest habitat, deer were decimated. Contributing factors were severe winters, deteriorating habitat, and wolves. Wolves killed older deer, but insufficient fawns were available to replace them.

Research Paper↗
USGS2003

Comment on “Isotopic fractionation between Fe(III) and Fe(II) in aqueous solutions” by Clark Johnson et al., [Earth Planet. Sci. Lett. 195 (2002) 141–153]

In a recent contribution [1] , Johnson et al. reported the equilibrium isotope fractionation factor between dissolved Fe(II) and Fe(III) in aqueous solutions at pH=2.5 and 5.5. They suggest that because the iron isotope fractionation observed in their experiments spans virtually the entire range observed in sedimentary rocks, Fe(II)–Fe(III) aqueous speciation may play a major role in determining iron isotope variations in nature where Fe(II) and Fe(III) can become physically separated. They discounted earlier conclusions by us and others [2] ; [3] that significant equilibrium fractionation between specific coexisting Fe(II)- or Fe(III)-aqueous complexes (e.g., between aqueous Fe(II)(OH) x(aq) and Fe(II) (aq) ion) is capable of producing iron isotope contrasts that can be preserved in nature. This is an important contribution not only because the authors recognize the importance of abiotic equilibrium iron isotope fractionation in nature in contrast to previous assertions [4] , but also because it will help to focus discussion on the development and evaluation of experimental approaches that can reveal abiotic fractionation mechanisms. However, in this Comment we propose that the experiments presented in this paper cannot be interpreted as straightforwardly as Johnson et al. contend. In particular, we show that in one of their critical experiments attainment of either isotope mass balance or equilibrium was not demonstrated, and thus the results of that experiment cannot be used to calculate an Fe(II)–Fe(III) equilibrium fractionation factor.

Earth and Planetary Science Letters↗
USGS2016

Geologic history of the Black Hills caves, South Dakota

Cave development in the Madison aquifer of the Black Hills has taken place in several stages. Mississippian carbonates first underwent eogenetic (early diagenetic) reactions with interbedded sulfates to form breccias and solution voids. Later subaerial exposure allowed oxygenated meteoric water to replace sulfates with calcite and to form karst and small caves. All were later buried by ~2 km of Pennsylvanian–Cretaceous strata. Groundwater flow and speleogenesis in the Madison aquifer were renewed by erosional exposure during Laramide uplift. Post-Laramide speleogenesis enlarged paleokarst voids. Most interpretations of this process in the Black Hills invoke rising thermal water, but they fail to account for the cave patterns. Few passages extend downdip below the present water table or updip to outcrops. None reaches the base of the Madison Limestone, and few reach the top. Major caves underlie a thin cover of basal Pennsylvanian–Permian Minnelusa Formation (interbedded quartzarenite and carbonates). Water infiltrating through the Minnelusa Formation dissolves carbonates in a nearly closed system, producing low p CO 2 , while recharge directly into Madison outcrops has a much higher p CO 2 . Both are at or near calcite saturation when they enter caves, but their mixture is undersaturated. The caves reveal four phases of calcite deposition: eogenetic ferroan calcite (Mississippian replacement of sulfates); white scalenohedra in paleovoids deposited during deep post-Mississippian burial; palisade crusts formed during blockage of springs by Oligocene–Miocene continental sediments; and laminated crusts from late Pleistocene water-table fluctuations. The caves reveal more than 300 m.y. of geologic history and a close relationship to regional geologic events.

South Dakota, Wyoming↗
USGS1984

LANDSAT M. S. S. IMAGE MOSAIC OF TUNISIA.

The Landsat mosaic of Tunisia funded by USAID for the Remote Sensing Laboratory, Soils Division, Ministry of Agriculture, Tunisia, was completed by the USGS in September 1983. It is a mixed mosaic associating digital corrections and enhancements to manual mosaicking and corresponding to the Tunisian request for high resolution and the limited available funds. The scenes were processed by the Environmental Research Institute of Michigan, resampling the data geodesically corrected to fit the Universal Transverse Mercator projection using control points from topographic maps at 1:50,000 and 1:100,000 scales available in the U. S. The mosaicking was done in the Eastern Mapping Center under the supervision of the Graphic Arts System Section. The three black and white mosaics were made at the 1:1,000,000 scale and various products generated. They included color film positives at 1:2,000,000 and 1:4,000,000 scales reproducible in the Remote Sensing Laboratory in Tunis and corresponding color prints as well as tricolor prints at various scales from 1:500,000 to 1:2,000,000.

Conference Paper↗
USGS1997

Bobcat ( Felis rufus ) ecology and management

The bobcat ( Felis rufus ) is a medium sized predator in the family Felidae found exclusively in North America. Extensive natural history information is available and is summarized in several bibliographies and reviews (Sweeny and Poelker 1977, McCord and Cardoza 1982, Boddicker 1983, Anderson 1987, Rolley 1987). The bobcat is a spotted cat with a short white-tipped tail, small dark ear tufts and is about twice the size of the house cat ( Felis domesticus ) because of the bobcat’s longer bone structure (McCord and Cardoza 1982, Jameson and Peeters 1988). The bobcat weights between 5- 15 kg with males larger than females. TL 700- 1000, T 95-150, E (from crown) 60-75 (Jameson and Peeters 1988).

Conference Paper↗
USGS2018

The 1952 Kern County, California earthquake: A case study of issues in the analysis of historical intensity data for estimation of source parameters

Seismic intensity data based on first-hand accounts of shaking give valuable insight into historical and early instrumental earthquakes. Comparing an observed intensity distribution to intensity-prediction models based on modern calibration events allows the magnitude to be estimated for many historic earthquakes. Magnitude estimates can also potentially be refined for earthquakes for which limited instrumental data are available. However, the complicated nature of macroseismic data and the methods used to collect and interpret the data introduce significant uncertainties. In this paper, we illustrate these challenges and possible solutions using the 1952 Kern County, California, earthquake as a case study. Published estimates of its magnitude vary from M W 7.2–7.5, making it possibly the second largest in California during the 20th century. We considered over 1100 first-hand reports of shaking, supplemented with other data, and inferred the magnitude in several ways using intensity prediction equations, yielding a preferred intensity magnitude M I 7.2 ± 0.2, where the uncertainty reflects our judgement. The revised intensity distribution reveals stronger shaking on the hanging wall, south of the surface expression of the White Wolf fault, than on the footwall. Characterizing the magnitude and shaking distribution of this early instrumental earthquake can help improve estimation of the seismic hazard of the region. Such reinterpreted intensities for historic earthquakes, combined with U.S. Geological Survey (USGS) Did You Feel It? data for more recent events, can be used to produce a uniform shaking dataset with which earthquake hazard map performance can be assessed.

California↗
USGS1965

Geology and ground water in the central part of Apache County, Arizona

The central part of Apache County, Ariz., includes an area of about 3,300 square miles between the Navajo Indian Reservation to the north and U.S. Highway 60 to the south. Sedimentary rocks in the area range from Pennsylvanian to Quaternary in age and from 2,000 to more than 6,000 feet in thickness. The strata were tilted to the northeast, and part of the Upper Triassic and all the Jurassic and Lower Cretaceous rocks were eroded away before strata of Late Cretaceous age were deposited. Basaltic lava flows and cinder cones, representing four general periods of eruption in late Miocene to Quaternary time, are widespread in the southern part of the area. Pennsylvanian and Permian rocks overlie basement rocks of granite and diorite and include the Supai Formation, the Coconino Sandstone, and the Kaibab Limestone. The Supai Formation is 1,000 to 2,000 feet thick and consists of interbedded red and brown mudstone, siltstone, sandstone, limestone, and evaporites. It contains water of very poor quality outside Apache County. The Coconino Sandstone is 200 to 250 feet thick and consists of light-gray fine- to medium-grained sandstone. It contains water suitable for domestic use in the south and water unsuitable for most purposes in the north. The Coconino Sandstone underlies all Central Apache County in the subsurface. The yellowish-gray to dark-gray Kaibab Limestone is present in the southern two-thirds of the area and is 0 to 350 feet thick. It contains water where it is fractured and combines with the Coconino Sandstone to form a single hydrologic unit that yields from 6 to 74 gpm (gallons per minute) of water per foot of drawdown. An unconformity Heparates the Permian rocks from the overlying Triassic rocks, which comprise the Moenkopi and Chinle Formations and the Wingate Sandstone. The Moenkopi Formation is 35 to 250 feet thick and consists of intercalated brownish-red siltstone, sandstone, and conglomerate. It contains salty water in some areas but is dry in most. The Chinle Formation is 0 to 1,550 feet thick and unconformably overlies the Moenkopi. The Chiule consists of multicolored claystone, mudstone, siltstone, sandstone, and conglomerate. Some of the sandstone units yield small amounts of water, usually of a quality unsuitable for domestic use. The Wingate Sandstone is about 250 feet thick and is present only in the extreme northeastern corner of the area. It consists of intercalated, reddish-brown sandstone and siltstone and does not contain water. The Upper Cretaceous rocks comprise the Dakota Sandstone, from 50 to 115 feet thick; the Mancos Shale, about 150 feet thick; and the Mesaverde Group, as much as 200 feet thick. These rocks consist of yellowish-gray, light-green, and reddish-brown sandstone and carbonaceous siltstone. Some of the sandstone units contain water of suitable quality for domestic use, and wells in these units yield from 10 to 1,000 gpm. Sedimentary rocks of Eocene(?) age are about 800 feet thick and unconformably overlie Cretaceous rocks. They consist of light-brown and medium-red conglomerate, sandstone, and siltstone. These sedimentary rocks contain small amounts of water suitable for domestic use and yield from 10 to 25 gpm in the Springerville area. The Datil Formation of Miocene(?) Tertiary age consists of more than 800 feet of sedimentary rocks, which are composed largely of volcanic fragments. The Datil Formation does not contain water in the one small area where it crops out. The Bidahochi Formation of Pliocene age consists of 0 to 800 feet of white, green, and brown claystone, mudstone, and sandstone. Locally it yields from 10 to 50 gpm of water suitable for domestic use. Quaternary rocks consist of as much as 500 feet of alluvium, sand, gravel, travertine, cinders, and lava. The alluvium along the large drainages contains water that differs in quality from place to place. In most areas where it occurs, the lava

Water Supply Paper↗
USGS2020

Environmental data associated with sites infected with white-nose syndrome (WNS) before October 2011 in North America

White-nose syndrome (WNS) is an emerging infectious disease of hibernating bats caused by a fungus previously known as Geomyces destructans and reclassified as Pseudogymnoascus destructans . The disease was first documented in 2006 in New York, has since spread across much of eastern North America, and as of January 2012, had caused the death of at least 5.7 to 6.7 million bats. Previous studies have suggested that environmental conditions play a strong role in WNS mortality. However, to predict where and when the disease will spread to new sites is difficult because detailed site information and associated environmental data are notably sparse. This paper presents a chronology of where and when WNS was detected in North America before October 2011 and indicates who reported the infections. This paper also presents available data on WNS-infected site elevation, geology, sediment chemistry and biota, air temperature, and relative humidity. By the end of September 2011, at least 241 known WNS-infected sites were in North America and the number of infected sites per winter season had increased each year since 2006. The progressive increase in the number of infected sites per winter season suggests that the number of WNS infections had not peaked as of the 2010–11 winter season. WNS-infected sites include caves and mines, but the sites are not restricted by elevation, lithology, or strata age. Available data on site sediment chemistry are sparse but present a wide range of values, suggesting that caves and mines may contain a great range of microenvironments that are still poorly understood. The distribution of WNS may be restricted by air temperature and relative humidity. Published air temperature values from WNS-infected sites range from −15 to 33 degrees Celsius (but most temperature values are less than 20 degrees Celsius), and relative humidity values range from 50 to 100 percent. The spread of WNS may be restricted by a cave or mine temperature threshold of 20 degrees Celsius (which is likely to be south of most of the continental United States) and by some yet to be determined threshold of low relative humidity. These results indicate that WNS may not spread south into Mexico or to Puerto Rico.

Connecticut, Delaware, Indiana, Kentucky, Maine, M↗
USGS2020

Validation of laboratory tests for infectious diseases in wild mammals: Review and recommendations

Evaluation of the diagnostic sensitivity (DSe) and specificity (DSp) of tests for infectious diseases in wild animals is challenging, and some of the limitations may affect compliance with the OIE-recommended test validation pathway. We conducted a methodologic review of test validation studies for OIE-listed diseases in wild mammals published between 2008 and 2017 and focused on study design, statistical analysis, and reporting of results. Most published papers addressed Mycobacterium bovis infection in one or more wildlife species. Our review revealed limitations or missing information about sampled animals, identification criteria for positive and negative samples (case definition), representativeness of source and target populations, and species in the study, as well as information identifying animals sampled for calculations of DSe and DSp as naturally infected captive, free-ranging, or experimentally challenged animals. The deficiencies may have reflected omissions in reporting rather than design flaws, although lack of random sampling might have induced bias in estimates of DSe and DSp. We used case studies of validation of tests for hemorrhagic diseases in deer and white-nose syndrome in hibernating bats to demonstrate approaches for validation when new pathogen serotypes or genotypes are detected and diagnostic algorithms are changed, and how purposes of tests evolve together with the evolution of the pathogen after identification. We describe potential benefits of experimental challenge studies for obtaining DSe and DSp estimates, methods to maintain sample integrity, and Bayesian latent class models for statistical analysis. We make recommendations for improvements in future studies of detection test accuracy in wild mammals.

Journal of Veterinary Diagnostic Investigation↗
USGS1987

A color-communication scheme for digital imagery

Color pictures generated from digital images are frequently used by geologists, foresters, range managers, and others. These color products are preferred over black and white pictures because the human eye is more sensitive to color differences than to various shades of gray. Color discrimination is a function of perception, and therefore colors in these color composites are generally described subjectively, which can lead to ambiguous color communication. Numerous color-coordinate systems are available that quantitively relate digital triplets representing amounts of red, free, and blue to the parameters of hue, saturation, and intensity perceived by the eye. Most of these systems implement a complex transformation of the primary colors to a color space that is hard to visualize, thus making it difficult to relate digital triplets to perception parameters. This paper presents a color-communcation scheme that relates colors on a color triangle to corresponding values of "hue" (H), "saturation" (S), and chromaticity coordinates (x,y,z). The scheme simplifies the relation between red, green, and blue (RGB) digital triplets and the color generated by these triplets. Some examples of the use of the color-communication scheme in digital image processing are presented.

Pecora XI Symposium↗
USGS2002

Late Cenozoic deformation by evaporite tectonism in the Grand Hogback monocline, southwest of the White River uplift, Colorado

Along 50 km of the complex, southwest-dipping, Laramide Grand Hogback monocline, which wraps around the southwest flank of the White River uplift in westcentral Colorado, detailed mapping provides evidence of late Cenozoic collapse that resulted from subsurface flow, diapirism, and dissolution of Pennsylvanian Eagle Valley Evaporite. Numerous discontinuous, small-amplitude, strike-parallel folds and steeply dipping faults that overlie the evaporite are interpreted as the result of both flow-induced and dissolution-induced collapse and diapirism concentrated along cross-strike, radial valleys draining the uplift. Folding of an immature Pliocene conglomerate into a tight syncline by collapse into an underlying diapir emphasizes the young age of evaporite tectonism. Major evaporite diapirs in valleys penetrate overlying Pennsylvanian Eagle Valley and Pennsylvanian-Permian Maroon Formations. In the absence of a Miocene basaltic datum used to quantify collapse elsewhere in west-central Colorado, we quantify removal of evaporite by contrasting estimated original evaporite thicknesses with thicknesses of remaining evaporite based on surface structural control and cross section construction. We estimate that ∼40 km3 of evaporite were removed along the southwest flank, the majority of which came from cross-strike valleys and a minority from intervening drainage divides. The mechanism for initiation of flow of evaporite is interpreted to be late Cenozoic regional uplift and accompanying deep incision of valleys draining the White River uplift. Unloading of evaporite beneath these valleys channeled evaporite to flow northward up dip to diapirically extrude from overlying Maroon and Eagle Valley Formations. Laramide monoclinal structures change gradually along strike from a single monocline, which produced a complexly folded back thrust, to double monoclines stacked on one another, which are located close to bends in the flank of the uplift.

Colorado↗
USGS1976

Ecology of mangroves in the Jewfish Chain, Exuma, Bahamas

The structure and function of mangrove communities in the Jewfish Chain, Exumas, Bahamas, were investigated for 3-1/2 years. Mangrove vegetation in the Jewfish Chain is similar to that in all the Caribbean-Florida area; Rhizophora mangle L. dominates and is interspersed with Avicennia germinans (L.) Lamk. and Laguncularia racemosa (L.) Gaertn. There is no apparent zonation of these three species. The mangrove communities in the Jewfish Chain occur only where they are protected from prevailing winds, storms, and tides, although all are periodically devastated by hurricanes. We found little or no evidence of coast building within these protected locations. The importance of the mangroves appears to be in providing protection and food for other flora and fauna within this unique ecosystem. Twenty-four species of algae were found in the mangroves, 9 of which had not previously been reported from the Bahamas. Distribution of these algae appears to be correlated to incident solar radiation, desiccation, and tide level. A total of 56 species of fish were found in the mangroves, 2 of which were not previously known from the Bahamas. Many fish taken were juveniles, suggesting that mangroves are a nursery ground for numerous species. Nine species of molluscs were found. Each species had a distinct distribution pattern relative to distance from the seaward edge of the mangroves, as well as a distinct vertical distribution pattern. Seventeen species of decapod crustaceans were recorded. Though several species of birds were noted in the mangroves, three species were most abundant: the white-crowned pigeon ( Columba leucocephala ) uses the mangrove for nesting but feeds in nearby shrub-thorn communities; the gray kingbird ( Tyrannus dominicensis ) and green heron ( Butorides virescens ) nest and feed in the mangroves. Our data do not completely describe a stereotyped mangrove community in the Bahamas, but they do give an indication of community structure and suggest several aspects of function.

Conference Paper↗
USGS1995

Geochemistry and petrology of Oligocene and Miocene ash-flow tuffs of the southeastern Great Basin, Nevada

The White River Narrows area of Southeast Nevada contains 18 regionally distributed middle Tertiary dacite to rhyolite ash-flow tuffs. Geochemical data provide an excellent opportunity to study stratigraphic and petrologic relations of these tuffs. Chemical data for each of the tuffs are distinctive and provide a significant addition to other data used to identify and correlate these units. Relatively minor compositional variation within the tuffs is noteworthy.

Professional Paper↗
USGS2014

Evaluation of the expected moments algorithm and a multiple low-outlier test for flood frequency analysis at streamgaging stations in Arizona

Flooding is among the costliest natural disasters in terms of loss of life and property in Arizona, which is why the accurate estimation of flood frequency and magnitude is crucial for proper structural design and accurate floodplain mapping. Current guidelines for flood frequency analysis in the United States are described in Bulletin 17B (B17B), yet since B17B’s publication in 1982 (Interagency Advisory Committee on Water Data, 1982), several improvements have been proposed as updates for future guidelines. Two proposed updates are the Expected Moments Algorithm (EMA) to accommodate historical and censored data, and a generalized multiple Grubbs-Beck (MGB) low-outlier test. The current guidelines use a standard Grubbs-Beck (GB) method to identify low outliers, changing the determination of the moment estimators because B17B uses a conditional probability adjustment to handle low outliers while EMA censors the low outliers. B17B and EMA estimates are identical if no historical information or censored or low outliers are present in the peak-flow data. EMA with MGB (EMA-MGB) test was compared to the standard B17B (B17B-GB) method for flood frequency analysis at 328 streamgaging stations in Arizona. The methods were compared using the relative percent difference (RPD) between annual exceedance probabilities (AEPs), goodness-of-fit assessments, random resampling procedures, and Monte Carlo simulations. The AEPs were calculated and compared using both station skew and weighted skew. Streamgaging stations were classified by U.S. Geological Survey (USGS) National Water Information System (NWIS) qualification codes, used to denote historical and censored peak-flow data, to better understand the effect that nonstandard flood information has on the flood frequency analysis for each method. Streamgaging stations were also grouped according to geographic flood regions and analyzed separately to better understand regional differences caused by physiography and climate. The B17B-GB and EMA-MGB RPD-boxplot results showed that the median RPDs across all streamgaging stations for the 10-, 1-, and 0.2-percent AEPs, computed using station skew, were approximately zero. As the AEP flow estimates decreased (that is, from 10 to 0.2 percent AEP) the variability in the RPDs increased, indicating that the AEP flow estimate was greater for EMA-MGB when compared to B17B-GB. There was only one RPD greater than 100 percent for the 10- and 1-percent AEP estimates, whereas 19 RPDs exceeded 100 percent for the 0.2-percent AEP. At streamgaging stations with low-outlier data, historical peak-flow data, or both, RPDs ranged from −84 to 262 percent for the 0.2-percent AEP flow estimate. When streamgaging stations were separated by the presence of historical peak-flow data (that is, no low outliers or censored peaks) or by low outlier peak-flow data (no historical data), the results showed that RPD variability was greatest for the 0.2-AEP flow estimates, indicating that the treatment of historical and (or) low-outlier data was different between methods and that method differences were most influential when estimating the less probable AEP flows (1, 0.5, and 0.2 percent). When regional skew information was weighted with the station skew, B17B-GB estimates were generally higher than the EMA-MGB estimates for any given AEP. This was related to the different regional skews and mean square error used in the weighting procedure for each flood frequency analysis. The B17B-GB weighted skew analysis used a more positive regional skew determined in USGS Water Supply Paper 2433 (Thomas and others, 1997), while the EMA-MGB analysis used a more negative regional skew with a lower mean square error determined from a Bayesian generalized least squares analysis. Regional groupings of streamgaging stations reflected differences in physiographic and climatic characteristics. Potentially influential low flows (PILFs) were more prevalent in arid regions of the State, and generally AEP flows were larger with EMA-MGB than with B17B-GB for gaging stations with PILFs. In most cases EMA-MGB curves would fit the largest floods more accurately than B17B-GB. In areas of the State with more baseflow, such as along the Mogollon Rim and the White Mountains, streamgaging stations generally had fewer PILFs and more positive skews, causing estimated AEP flows to be larger with B17B-GB than with EMA-MGB. The effect of including regional skew was similar for all regions, and the observed pattern was increasingly greater B17B-GB flows (more negative RPDs) with each decreasing AEP quantile. A variation on a goodness-of-fit test statistic was used to describe each method’s ability to fit the largest floods. The mean absolute percent difference between the measured peak flows and the log-Pearson Type 3 (LP3)-estimated flows, for each method, was averaged over the 90th, 75th, and 50th percentiles of peak-flow data at each site. In most percentile subsets, EMA-MGB on average had smaller differences (1 to 3 percent) between the observed and fitted value, suggesting that the EMA-MGB-LP3 distribution is fitting the observed peak-flow data more precisely than B17B-GB. The smallest EMA-MGB percent differences occurred for the greatest 10 percent (90th percentile) of the peak-flow data. When stations were analyzed by USGS NWIS peak flow qualification code groups, the stations with historical peak flows and no low outliers had average percent differences as high as 11 percent greater for B17B-GB, indicating that EMA-MGB utilized the historical information to fit the largest observed floods more accurately. A resampling procedure was used in which 1,000 random subsamples were drawn, each comprising one-half of the observed data. An LP3 distribution was fit to each subsample using B17B-GB and EMA-MGB methods, and the predicted 1-percent AEP flows were compared to those generated from distributions fit to the entire dataset. With station skew, the two methods were similar in the median percent difference, but with weighted skew EMA-MGB estimates were generally better. At two gages where B17B-GB appeared to perform better, a large number of peak flows were deemed to be PILFs by the MGB test, although they did not appear to depart significantly from the trend of the data (step or dogleg appearance). At two gages where EMA-MGB performed better, the MGB identified several PILFs that were affecting the fitted distribution of the B17B-GB method. Monte Carlo simulations were run for the LP3 distribution using different skews and with different assumptions about the expected number of historical peaks. The primary benefit of running Monte Carlo simulations is that the underlying distribution statistics are known, meaning that the true 1-percent AEP is known. The results showed that EMA-MGB performed as well or better in situations where the LP3 distribution had a zero or positive skew and historical information. When the skew for the LP3 distribution was negative, EMA-MGB performed significantly better than B17B-GB and EMA-MGB estimates were less biased by more closely estimating the true 1-percent AEP for 1, 2, and 10 historical flood scenarios.

Arizona↗
USGS1977

The use of feeding habitat by a colony of herons, egrets, and ibises near Beaufort, North Carolina

Nine species of herons were followed to their feeding sites from a nesting colony near Beaufort, North Carolina, by airplane. Except for the Cattle Egret, which flew exclusively to fields and dumps, all other species flew mainly to saltmarsh habitat. In addition, habitats were selected in relation to tidal depth and it appears, at least for the Great Egret, that low tide habitats were preferred. Most Great Egrets, White Ibises, Louisiana Herons, and Snowy Egrets flew close to the colony and numbers decreased farther from the colony. The Great Egret, Black-crowned Night Heron, and White Ibis flew farther from the colony at high than at low tide. In addition, the species differed in distance flown from the colony. Great Egrets traveled farther from the colony when they used thermals. Rate of travel to feeding sites, however, was the same whether Great Egrets used thermals or not. Aggressive encounters were observed in the Great Egret, Louisiana Heron, Snowy Egret, and Black-crowned Night Heron. Cattle Egrets and White Ibises followed other individuals to feeding sites and it appeared as though they were using the colony as an information center. The Great Egret is the only species to effectively use eelgrass beds near Beaufort. The Great Egrets use of this habitat was restricted to about 1.5 hours on either side of low tide. We suspect that other shorter legged species did not use eelgrass regularly because of its depth.

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