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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 91 records · Page 5Linked to original sources
USGS2001

Annual movements of a steppe eagle (Aquila nipalensis) summering in Mongolia and wintering in Tibet

An adult female steppe eagle (Aquila nipalensis Hodgson) was captured and fitted with a satellite transmitter in June 1995 in southeastern Mongolia. In fall, it traveled southwest towards India as expected, but stopped in southeastern Tibet and wintered in a restricted zone within the breeding range of the steppe eagle. In spring, the bird returned to the same area of Mongolia where it was captured. These observations, though derived from the movements of a single bird, suggest three things that are contrary to what is generally believed about steppe eagle biology. First, not all steppe eagles move to warmer climes in winter. Second, not all steppe eagles are nomadic in winter. Finally, because our bird wintered at the periphery of the steppe eagle breeding range in Tibet, perhaps birds that breed in this same area also winter there. If so, not all steppe eagles are migratory.

Journal of the Bombay Natural History Society↗
USGS2007

Mangrove forest distributions and dynamics (1975–2005) of the tsunami-affected region of Asia

Aim We aimed to estimate the present extent of tsunami-affected mangrove forests and determine the rates and causes of deforestation from 1975 to 2005. Location Our study region covers the tsunami-affected coastal areas of Indonesia, Malaysia, Thailand, Burma (Myanmar), Bangladesh, India and Sri Lanka in Asia. Methods We interpreted time-series Landsat data using a hybrid supervised and unsupervised classification approach. Landsat data were geometrically corrected to an accuracy of plus-or-minus half a pixel, an accuracy necessary for change analysis. Each image was normalized for solar irradiance by converting digital number values to the top-of-the atmosphere reflectance. Ground truth data and existing maps and data bases were used to select training samples and also for iterative labelling. We used a post-classification change detection approach. Results were validated with the help of local experts and/or high-resolution commercial satellite data. Results The region lost 12% of its mangrove forests from 1975 to 2005, to a present extent of c . 1,670,000 ha. Rates and causes of deforestation varied both spatially and temporally. Annual deforestation was highest in Burma ( c . 1%) and lowest in Sri Lanka (0.1%). In contrast, mangrove forests in India and Bangladesh remained unchanged or gained a small percentage. Net deforestation peaked at 137,000 ha during 1990–2000, increasing from 97,000 ha during 1975–90, and declining to 14,000 ha during 2000–05. The major causes of deforestation were agricultural expansion (81%), aquaculture (12%) and urban development (2%). Main conclusions We assessed and monitored mangrove forests in the tsunami-affected region of Asia using the historical archive of Landsat data. We also measured the rates of change and determined possible causes. The results of our study can be used to better understand the role of mangrove forests in saving lives and property from natural disasters such as the Indian Ocean tsunami, and to identify possible areas for conservation, restoration and rehabilitation.

Journal of Biogeography↗
USGS1983

Migration and winter distributions of canvasbacks staging on the Upper Mississippi River

Fall and winter distribution patterns of canvasbacks (Aythya valisineria) staging on the upper Mississippi River near LaCrosse, Wisconsin (navigational Pools 7 and 8) and Keokuk, Iowa (Pool 19) were studied during 1973-77. Sightings and recoveries obtained from 1,488 color-marked males during 1973-75 and 3,789 banded males and females during 1973-77 suggested 2 principal migration corridors: 1 extending eastward from Pools 7 and 8 to the eastern Great Lakes and southeast to the Mid-Atlantic Region and another southward from Pools 7 and 8 to the lower Mississippi Valley, Gulf Coast, and east Texas regions. These discrete populations stage concurrently on Pools 7 and 8 during the fall, but winter in different areas of the Atlantic, Mississippi, and Central flyways. Populations staging on Pool 19 were not discrete from those staging on Pools 7 and 8. A continual turnover of birds passing through these staging areas was indicated. Canvasbacks wintering in the Mississippi and Central flyways were widely dispersed among a variety of habitats, whereas canvasbacks wintering in the Atlantic Flyway were concentrated in a few traditional habitats. Canvasbacks exhibited strong fidelity to wintering areas. Distribution patterns and population attributes of canvasbacks during fall and winter may be explained by the predictability of natural foods and their ability to exploit these foods.

Journal of Wildlife Management↗
USGS2005

Multi-stage sampling for large scale natural resources surveys: A case study of rice and waterfowl

Large-scale sample surveys to estimate abundance and distribution of organisms and their habitats are increasingly important in ecological studies. Multi-stage sampling (MSS) is especially suited to large-scale surveys because of the natural clustering of resources. To illustrate an application, we: (1) designed a stratified MSS to estimate late autumn abundance (kg/ha) of rice seeds in harvested fields as food for waterfowl wintering in the Mississippi Alluvial Valley (MAV); (2) investigated options for improving the MSS design; and (3) compared statistical and cost efficiency of MSS to simulated simple random sampling (SRS). During 2000–2002, we sampled 25–35 landowners per year, 1 or 2 fields per landowner per year, and measured seed mass in 10 soil cores collected within each field. Analysis of variance components and costs for each stage of the survey design indicated that collecting 10 soil cores per field was near the optimum of 11–15, whereas sampling >1 field per landowner provided few benefits because data from fields within landowners were highly correlated. Coefficients of variation (CV) of annual estimates of rice abundance ranged from 0.23 to 0.31 and were limited by variation among landowners and the number of landowners sampled. Design effects representing the statistical efficiency of MSS relative to SRS ranged from 3.2 to 9.0, and simulations indicated SRS would cost, on average, 1.4 times more than MSS because clustering of sample units in MSS decreased travel costs. We recommend MSS as a potential sampling strategy for large-scale natural resource surveys and specifically for future surveys of the availability of rice as food for waterfowl in the MAV and similar areas.

Arkansas, Kentucky, Louisiana, Mississippi, Missou↗
USGS2021

Quantitative modeling of secondary migration: Understanding the origin of natural gas charge of the Haynesville Formation in the Sabine Uplift area of Louisiana and Texas

The Upper Jurassic (Kimmeridgian) mudstones of the Haynesville Formation in the Sabine Uplift, Louisiana and Texas, are widely considered to be a self-sourced natural gas reservoir; however, additional sources of gas may have charged the mudstones in the Louisiana portion of the uplift. Secondary migration of hydrocarbons into the Sabine Uplift from downdip, gas-generating Jurassic source rocks in the North Louisiana Salt Basin was quantitively modeled in this study. Jurassic source rocks include the Smackover, Haynesville, and Bossier Formations. Thermodynamic equations of state were used to determine thermophysical properties of supercritical methane and water under reservoir conditions. A time-dependent derivation of Darcy’s Law for pressure-driven laminar fluid flow through porous media was used to model secondary migration at reservoir conditions. This study indicates secondary migration requires approximately 100,000 yr for pore fluids to migrate through 1.0 km of carrier beds having representative petrophysical, fluid, and reservoir properties of the Haynesville Formation. As an example migration pathway, the distance from the middle of the North Louisiana Salt Basin to the center of the Sabine Uplift is approximately 96 mi (155 km). Given migration velocities over this distance, 15.5 m.y. is required for hydrocarbons to migrate from the North Louisiana Salt Basin and charge the Haynesville Formation in the Sabine Uplift. This study also indicates supercritical water is 6 times more thermally conductive than methane under reservoir conditions; however, the relatively small volumes of migrated water likely did not transfer sufficient heat for the metagenesis of methane. Based on this study, a component of natural gas charging the Haynesville Formation of the Sabine Uplift area can reasonably be explained by lateral migration and hydrodynamic flow from thermally mature Jurassic source rocks located in adjacent basins.

Louisiana, Texas↗
USGS1976

A simplified slope-area method for estimating flood discharges in natural channels

Discharge of a stream may be computed from the slope of the water surface, the cross-sectional area, and an estimate of channel roughness. This, the slope-area method, is widely used to compute flood peak discharges from high-water marks. Reliability of a computed discharge depends largely on the roughness coefficient, which must be estimated. This paper shows that results of comparable accuracy can be obtained from area and slope alone in natural channels; a roughness coefficient is not needed because roughness and slope are related. The estimating equation and suggestions for application of the simplified method are included.

Journal of Research of the U.S. Geological Survey↗
USGS1989

Relation of salinity and selenium in shallow groundwater to hydrologic and geochemical processes, Western San Joaquin Valley, California

Salinity and selenium concentrations in shallow groundwater of the western San Joaquin Valley, California, are related to the geomorphology and hydrology of the alluvial fans. The highest salinity and selenium concentrations in shallow groundwater occur in alluvium deposited by ephemeral streams and at the margins of the major alluvial fans, where there were naturally saline, fine-grained soils. Low-to-moderate salinity and selenium concentrations in shallow groundwater are associated with upper and middle areas of the major alluvial fans deposited by intermittent streams. Areas with the most naturally saline soils have been irrigated in the last 40 years. These are now the areas of highest salinity and selenium concentrations in the shallow groundwater. Present-day (1986) groundwater salinity is spatially correlated with natural soil salinity in these areas. Isotopic data indicate that the highest salinity and selenium concentrations in groundwater present at low altitudes resulted from evaporative concentration when the water table was shallow.

California↗
USGS2009

Distribution and conservation status of coastal sage scrub in southwestern California

A landscape-based characterization of vegetation has been developed for southwestern California using satellite imagery, air photos, existing vegetation maps, and field data. Distribution maps of nine dominant coastal scrub species and 13 species assemblages that were identified by divisive information analysis have been analyzed to quantify spatial patterns of species co-occurrence. Three general distribution patterns are identified that suggest the Diegan, Ventaran and Riversidian Associations identified by other workers. Vegetation data have also been related to land ownership and management to assess the conservation status of upland plant communities. A large proportion of the mapped distribution of species and vegetation types is on private land, and several taxa show less than 4 % of mapped distribution in nature reserves. The analysis highlights the need to extend current conservation planning efforts into the northern part of the region to encompass areas where Salvia leucophylla is a frequent community dominant.

Journal of Vegetation Science↗
USGS2009

Instrumental record of debris flow initiation during natural rainfall: Implications for modeling slope stability

The middle of a hillslope hollow in the Oregon Coast Range failed and mobilized as a debris flow during heavy rainfall in November 1996. Automated pressure transducers recorded high spatial variability of pore water pressure within the area that mobilized as a debris flow, which initiated where local upward flow from bedrock developed into overlying colluvium. Postfailure observations of the bedrock surface exposed in the debris flow scar reveal a strong spatial correspondence between elevated piezometric response and water discharging from bedrock fractures. Measurements of apparent root cohesion on the basal ( C b ) and lateral ( C l ) scarp demonstrate substantial local variability, with areally weighted values of C b = 0.1 and C l = 4.6 kPa. Using measured soil properties and basal root strength, the widely used infinite slope model, employed assuming slope parallel groundwater flow, provides a poor prediction of hydrologic conditions at failure. In contrast, a model including lateral root strength (but neglecting lateral frictional strength) gave a predicted critical value of relative soil saturation that fell within the range defined by the arithmetic and geometric mean values at the time of failure. The 3‐D slope stability model CLARA‐W, used with locally observed pore water pressure, predicted small areas with lower factors of safety within the overall slide mass at sites consistent with field observations of where the failure initiated. This highly variable and localized nature of small areas of high pore pressure that can trigger slope failure means, however, that substantial uncertainty appears inevitable for estimating hydrologic conditions within incipient debris flows under natural conditions.

Oregon↗
USGS2012

Disparate stakeholder management: the case of elk and bison feeding in southern Greater Yellowstone

For resource decisions to make the most possible progress toward achieving agency mandates, managers must work with stakeholders and may need to at least partially accommodate some of their key underlying interests. To accommodate stakeholder interests, while also substantively working toward fulfilling legal mandates, managers must understand the sociopolitical factors that influence the decision-making process. We coin the phrase disparate stakeholder management (DSM) to describe situations with disparate stakeholders and disparate management solutions. A DSM approach (DSMA) requires decision makers to combine concepts from many sciences, thus releasing them from disciplinary bonds that often constrain innovation and effectiveness. We combined three distinct approaches to develop a DSMA that assisted in developing a comprehensive range of elk and bison management alternatives in the Southern Greater Yellowstone Area. The DSMA illustrated the extent of compromise between meeting legal agency mandates and accommodating the preferences of certain stakeholder groups.

Wyoming↗
USGS2015

Direct measurement of asperity contact growth in quartz at hydrothermal conditions

Earthquake recurrence requires interseismic fault restrengthening which results from solid state deformation in room-temperature friction and indentation experiments. In contrast exhumed fault zones show solution-transport processes such as pressure solution and contact overgrowths influence fault zone properties . In the absence of fluid flow, overgrowths are driven by gradients in surface curvature where material is dissolved, diffuses, and precipitates at the contact without convergence normal to the contact. To determine the rate of overgrowth for quartz, we conducted single contact experiments in an externally heated pressure vessel. Convergence was continuously monitored using reflected-light interferometry through a long-working-distance microscope. Contact normal force was constant with an initial effective normal stress of 1.7 MPa, temperature was between 350 and 530{degree sign}C, and water pressure was constant at 150 MPa. Two control experiments were conducted: one dry at 425{degree sign}C and one bi-material (sapphire) at 425{degree sign}C and 150 MPa water pressure. No contact growth or convergence was observed in the controls. For wet single-phase contacts, growth was initially rapid and then decreased with time. No convergence was observed. Fluid inclusions indicate that the contact is not uniformly wetted. The contact is bounded by small regions of high aperture, reflecting local free-face dissolution as the source for the overgrowth. The apparent activation energy is ~125 kJ/mol. Extrapolation predicts rates of contact area increase orders of magnitude faster than in dry, room-temperature and hydrothermal friction experiments, suggesting that natural strength recovery near the base of the seismogenic zone could be dominated by contact overgrowth.

Journal of Geophysical Research B: Solid Earth↗
USGS1996

Sediment distribution on a storm-dominated insular shelf, Luquillo, Puerto Rico, U.S.A.

A sea-floor mapping investigation designed to assess the sediment distribution, the movement of the nearshore sand supply, and the fate of sediment eroded from the shoreline was conducted using high-resolution sidescan-sonar, seismic reflection, and sediment sampling techniques on the northern insular shelf of Puerto Rico, off the town of Luquillo. Sea-floor structures and the distribution of sediment texture and composition suggest that regional oceanographic processes result in a net offshore direction for cross-shelf sediment transport on the middle and outer shelf during storms. If these same processes are active on the inner shelf, mapping results indicate that this sediment is not transported seaward of a series of east-west trending Pleistocene-age eolianite ridges that outcrop on the middle shelf. The eolianite ridges may act as natural dams, preventing the removal of sediment from the nearshore area. Sand deposits behind the "dams" are up to 20 m thick on the shoreward flank of the ridges.

Puerto Rico↗
USGS2008

Selecting remediation goals by assessing the natural attenuation capacity of groundwater systems

Remediation goals for the source areas of a chlorinated ethene‐contaminated groundwater plume were identified by assessing the natural attenuation capacity of the aquifer system. The redox chemistry of the site indicates that sulfate‐reducing (H 2 ∼ 2 nanomoles [nM]) per liter conditions near the contaminant source grade to Fe(III)‐reducing conditions (H 2 ∼ 0.5 nM) downgradient of the source. Sulfate‐reducing conditions facilitate the initial reduction of perchloroethene (PCE) to trichloroethene (TCE), cis ‐dichloroethene ( cis ‐DCE), and vinyl chloride (VC). Subsequently, the Fe(III)‐reducing conditions drive the oxidation of cis ‐DCE and VC to carbon dioxide and chloride. This sequence gives the aquifer a substantial capacity for biodegrading chlorinated ethenes. Natural attenuation capacity (the slope of the steady‐state contaminant concentration profile along a groundwater flowpath) is a function of biodegradation rates, aquifer dispersive characteristics, and groundwater flow velocity. The natural attenuation capacity at the Kings Bay, Georgia site was assessed by estimating groundwater flowrates (∼0.23 ± 0.12 m/d) and aquifer dispersivity (∼1 m) from hydrologic and scale considerations. Apparent biodegradation rate constants (PCE and TCE ∼ 0.01 d −1 ; cis ‐DCE and VC ∼ 0.025 d −1 ) were estimated from observed contaminant concentration changes along aquifer flowpaths. A boundary‐value problem approach was used to estimate levels to which contaminant concentrations in the source areas must be lowered (by engineered removal), or groundwater flow velocities lowered (by pumping) for the natural attenuation capacity to achieve maximum concentration limits (MCLs) prior to reaching a predetermined regulatory point of compliance.

Bioremediation Journal↗
USGS2023

The Chesapeake Bay Land Change Model (CBLCM): Simulating future land use scenarios and potential impacts on water quality

The Chesapeake Bay Land Change Model (CBLCM) is an open-source pseudo-cellular automata land change model tailored for loose coupling with watershed models. The CBLCM simulates infill development, residential and commercial development, natural land and agricultural land conversion, and growth served by sewer or septic wastewater treatment. The CBLCM is unique among land change models by simulating multiple types of development and explicitly accounting for infill development and the spatial patterns of development densities. The CBLCM was used to simulate five future land use scenarios, holding population constant, for all counties within and adjacent to the Chesapeake Bay watershed from 2013 to 2055. Results are presented here for the state of Maryland over the period 2013–2025 to illustrate model functionality and validation. The growth management (GM) scenario achieved the least development and potential impacts to natural and agricultural lands while accommodating the same amount of population growth as the other four scenarios. Scenarios focusing exclusively on natural or agricultural land protection shifted development to unprotected areas resulting in unforeseen water quality consequences. Simultaneously achieving more compact development while protecting the most valued natural and agricultural lands requires a combination of GM and land conservation policies and actions.

Maryland↗
USGS2007

Geochemical characterization of shallow ground water in the Eutaw aquifer, Montgomery, Alabama

Ground water samples were collected from 30 wells located in, or directly down gradient from, recharge areas of the Eutaw aquifer in Montgomery, Alabama. The major ion content of the water evolves from calcium-sodium-chloride- dominated type in the recharge area to calcium-bicarbonate-dominated type in the confined portion of the aquifer. Ground water in the recharge area was undersaturated with respect to aluminosilicate and carbonate minerals. Ground water in the confined portion of the aquifer was at equilibrium levels for calcite and potassium feldspar. Dissolved oxygen and nitrite-plus-nitrate concentrations decreased as ground water age increased; pH, iron, and sulfate concentrations increased as ground water age increased. Aluminum, copper, and zinc concentrations decreased as ground water age and pH increased. These relations indicate that nitrate, aluminum, copper, and zinc are removed from solution as water moves from recharge areas to the confined areas of the Eutaw aquifer. The natural evolution of ground water quality, which typically increases the pH and decreases the dissolved oxygen content, may be an important limiting factor to the migration of nitrogen based compounds and metals.

Alabama↗
USGS2004

Assessing land cover performance in Senegal, West Africa using 1-km integrated NDVI and local variance analysis

The researchers calculated seasonal integrated normalized difference vegetation index (NDVI) for each of 7 years using a time-series of 1-km data from the Advanced Very High Resolution Radiometer (AVHRR) (1992-93, 1995) and SPOT Vegetation (1998-2001) sensors. We used a local variance technique to identify each pixel as normal or either positively or negatively anomalous when compared to its surroundings. We then summarized the number of years that a given pixel was identified as an anomaly. The resulting anomaly maps were analysed using Landsat TM imagery and extensive ground knowledge to assess the results. This technique identified anomalies that can be linked to numerous anthropogenic impacts including agricultural and urban expansion, maintenance of protected areas and increased fallow. Local variance analysis is a reliable method for assessing vegetation degradation resulting from human pressures or increased land productivity from natural resource management practices. ?? 2004 Published by Elsevier Ltd.

Journal of Arid Environments↗
USGS2017

Nocturnal arboreality in snakes in the swamplands of the Atchafalaya Basin of south-central Louisiana and Big Thicket National Preserve of Southeast Texas

The southeastern United States is home to a diverse assemblage of snakes, but only one species, the Rough Greensnake ( Opheodrys aestivus ), is considered specialized for a predominantly arboreal lifestyle. Other species, such as Ratsnakes (genus Pantherophis ) and Ribbonsnakes/Gartersnakes (genus Thamnophis ), are widely known to climb into vegetation and trees. Some explanations given for snake climbing behavior are foraging, thermoregulation, predator avoidance, and response to flood. Reports of arboreality in snake species typically not associated with life in the trees (such as terrestrial, aquatic, and even fossorial species) usually come from single observations, with no knowledge of prevalence of the behavior. Here, we report on arboreality of snake species detected during 8 years of night surveys in the Atchafalaya Basin of south-central Louisiana and 5+ years of night surveys in Big Thicket National Preserve in southeast Texas. We recorded a total of 1,088 detections of 19 snake species between the two study areas, with 348 detections above ground level (32%). The Rough Greensnake and Western Ribbonsnake ( Thamnophis proximus ) accounted for nearly 75% of total arboreal detections among the two study areas. However, with one exception, all snake species detected more than once between both study areas had at least one arboreal detection. These observations demonstrate that snakes with widely varying natural histories may be found in the trees at night, and for some species, this behavior may be more common than previously believed.

Louisiana, Texas↗
USGS2021

Drivers of methane flux differ between lakes and reservoirs, complicating global upscaling efforts

Methane is an important greenhouse gas with growing atmospheric concentrations. Freshwater lakes and reservoirs contribute substantially to atmospheric methane concentrations, but the magnitude of this contribution is poorly constrained. Uncertainty stems partially from whether the sites currently sampled represent the global population as well as incomplete knowledge of which environmental variables predict methane flux. Thus, determining the main drivers of methane flux across diverse waterbody types will inform more accurate upscaling approaches. Here we use a new database of total, diffusive, and ebullitive areal methane emissions from 313 lakes and reservoirs (ranging in surface area from 6 m 2 to 5,400 km 2 ) to identify the best predictors of methane emission. We found that the best predictors of methane emission differed by waterbody type (lakes vs. reservoirs), and that ecosystem morphometric variables (e.g., surface area and maximum depth) were more important predictors in lakes whereas metrics of autochthonous production (e.g., chlorophyll a ) were more important in reservoirs. We also found that productivity strongly predicted methane ebullition, whereas ecosystem morphometry and waterbody type were more important predictors of diffusive methane flux. Finally, we identify several knowledge gaps that limit upscaling efforts. First, we need more methane emission measurements in small reservoirs, large lakes, and both natural and artificial ponds. Additionally, more accurate upscaling efforts require improved global information about waterbody surface area, waterbody type (lake vs. reservoir), ice phenology, and the distribution of productivity‐related predictor variables such as total phosphorus, DOC, and chlorophyll a .

Journal of Geophysical Research-Biogeosciences↗