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At least 163 records · Page 9Linked to original sources
USGS1995

Analysis of steady-state flow and advective transport in the eastern Snake River Plain aquifer system, Idaho

Quantitative estimates of ground-water flow directions and traveltimes for advective flow were developed for the regional aquifer system of the eastern Snake River Plain, Idaho. The work included: (1) descriptions of compartments in the aquifer that function as intermediate and regional flow systems, (2) descriptions of pathlines for flow originating at or near the water table, and (3) quantitative estimates of traveltimes for advective transport originating at or near the water table. A particle-tracking postprocessing program was used to compute pathlines on the basis of output from an existing three-dimensional steady-state flow model. The flow model uses 1980 conditions to approximate average annual conditions for 1950-80. The advective transport model required additional information about the nature of flow across model boundaries, aquifer thickness, and porosity. Porosity of two types of basalt strata has been reported for more than 1,500 individual cores from test holes, wells, and outcrops near the south side of the Idaho National Engineering Laboratory. The central 80 percent of samples had porosities of 0.08 to 0.25, the central 50 percent of samples, O. 11 to 0.21. Calibration of the model involved choosing a value for porosity that yielded the best solution. Two radiologic contaminants, iodine-129 and tritium, both introduced to the flow system about 40 years ago, are relatively conservative tracers. Iodine- 129 was considered to be more useful because of a lower analytical detection limit, longer half-life, and longer flow path. The calibration value for porosity was 0.21. Most flow in the aquifer is contained within a regional-scale compartment and follows paths that discharge to the Snake River downstream from Milner Dam. Two intermediate-scale compartments exist along the southeast side of the aquifer and near Mud Lake.One intermediate-scale compartment along the southeast side of the aquifer discharges to the Snake River near American Fails Reservoir and covers an area of nearly 1,000 square miles. This compartment, which receives recharge from an area of intensive surface-water irrigation, is apparently fairly stable. The other intermediate-scale compartment near Mud Lake covers an area of 300 square miles. The stability and size of this compartment are uncertain, but are assumed to be in a state of change. Traveltimes for advective flow from the water table to discharge points in the regional compartment ranged from 12 to 350 years for 80 percent of the particles; in the intermediate-scale flow compartment near American Falls Reservoir, from 7 to 60 years for 80 percent of the particles; and in the intermediate-scale compartment near Mud Lake, from 25 to 100 years for 80 percent of the particles. Traveltimes are sensitive to porosity and assumptions regarding the importance of the strength of internal sinks, which represent ground-water pumpage. A decrease in porosity results in shorter traveltimes but not a uniform decrease in traveltime, because the porosity and thickness is different in each model layer. Most flow was horizontal and occurred in the top 500 feet of the aquifer. An important limitation of the model is the assumption of steady-state flow. The most recent trend in the flow system has been a decrease in recharge since 1987 because of an extended drought and changes in land use. A decrease in flow through the system will result in longer traveltimes than those predicted for a greater flow. Because the interpretation of the model was limited to flow on a larger scale, and did not consider individual wells or well fields, the interpretations were not seriously limited by the discretization of well discharge. The interpretations made from this model also were limited by the discretization of the major discharge areas. Near discharge areas, pathlines might not be representative at the resolution of the grid. Most improvement in the estimates of ground-waterflow directions and travelt

Water-Resources Investigations Report↗
USGS2007

Cross-shelf transport of pink shrimp larvae: Interactions of tidal currents, larval vertical migrations and internal tides

Transport and behavior of pink shrimp Farfantepenaeu s duorarum larvae were investigated on the southwestern Florida (SWF) shelf of the Gulf of Mexico between the Dry Tortugas spawning grounds and Florida Bay nursery grounds. Stratified plankton samples and hydrographic data were collected at 2 h intervals at 3 stations located on a cross-shelf transect. At the Marquesas station, midway between Dry Tortugas and Florida Bay, internal tides were recognized by anomalously cool water, a shallow thermocline with strong density gradients, strong current shear, and a high concentration of pink shrimp larvae at the shallow thermocline. Low Richardson numbers occurred at the pycnocline depth, indicating vertical shear instability and possible turbulent transport from the lower to the upper layer where myses and postlarvae were concentrated. Analysis of vertically stratified plankton suggested that larvae perform vertical migrations and the specific behavior changes ontogenetically; protozoeae were found deeper than myses, and myses deeper than postlarvae. Relative concentrations of protozoea in the upper, middle and bottom layers were consistent with a diel vertical migration, whereas that of postlarvae and myses were consistent with the semidiurnal tides in phase with the flood tide. Postlarvae, the shallowest dwellers that migrate with a semidiurnal periodicity, experienced the largest net onshore flux and larval concentrations were highly correlated with the cross-shelf current. These results provide the first evidence of an onshore tidal transport (a type of selective tidal stream transport, STST), in decapod larvae migrating in continental shelf waters offshore, ca. 100 km from the coast and at a depth of 20 m, while approaching the coastal nursery grounds. Longer time series would be necessary to establish whether internal tides play any role in the larval onshore transport of this species and determine if the STST is the dominant onshore transport mechanism.

Florida↗
USGS2002

Apparatus for continuous extraction of nonpolar compounds from water applied to determination of chlorinated pesticides and intermediates

A continuous, multichamber liquid-liquid extractor, with internal solvent recycle, for the extraction of nonpolar contaminants from natural waters is described. The multichamber arrangement makes it possible to judge the completeness of extraction of a given component from the aqueous stream. Recoveries as high as 100% are obtained by applying the apparatus to the extraction of the pesticides aldrin, dieldrin, and endrin and their manufacturing intermediates.

Analytical Chemistry↗
USGS2009

Remote sensing of global croplands for food security: Way forward

This book opens a new pathway for global mapping that is focused on a specific land use theme, such as irrigated or rain-fed croplands and classes within these themes. Since croplands use most of the water consumed by humans, specific knowledge of irrigated and rain-fed croplands will be critical for precise estimates of water use. At present and in the coming decades, irrigated and rain-fed cropland area mapping is crucial for food security studies. Throughout this book, various subjects pertaining to global croplands are discussed comprehensively.

Book chapter↗
USGS2016

Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport

A 6-month deployment of instrumentation from April to October 2012 in 90 m water depth near the outer edge of the mid-shelf mud belt in southern Monterey Bay, California, reveals the importance regional upwelling on water column density structure, potentially accounting for the majority of the variability in internal tidal energy flux across the shelf. Observations consisted of time-series measurements of water-column currents, temperature and salinity, and near-bed currents and suspended matter. The internal tide accounted for 15–25% of the water-column current variance and the barotropic tide accounted for up to 35%. The subtidal flow showed remarkably little shear and was dominated by the 7–14 day band, which is associated with relaxations in the dominant equatorward winds typical of coastal California in the spring and summer. Upwelling and relaxation events resulted in strong near-bed flows and accounted for almost half of the current stress on the seafloor (not accounting for wave orbital velocities), and may have driven along-shelf geostrophic flow during steady state conditions. Several elevated suspended particulate matter (SPM) events occurred within 3 m of the bed and were generally associated with higher, long-period surface waves. However, these peaks in SPM did not coincide with the predicted resuspension events from the modeled combined wave–current shear stress, indicating that the observed SPM at our site was most likely resuspended elsewhere and advected along-isobath. Sediment flux was almost equal in magnitude in the alongshore and cross-shore directions. Instances of wave–current shear stress that exceeded the threshold of resuspension for the silty-clays common at these water depths only occurred when near-bed orbital velocities due to long-period surface waves coincided with vigorous near-bed currents associated with the internal tide or upwelling/relaxation events. Thus upwelling/relaxation dynamics are primarily responsible for variability in the internal tide, as well as transport of near-bottom sediment in the mid-self mud belt during the relatively quiescent summer months.

California↗
USGS2014

Measurements of slope currents and internal tides on the Continental Shelf and slope off Newport Beach, California

An array of seven moorings housing current meters and oceanographic sensors was deployed for 6 months at 5 sites on the Continental Shelf and slope off Newport Beach, California, from July 2011 to January 2012. Full water-column profiles of currents were acquired at all five sites, and a profile of water-column temperature was also acquired at two of the five sites for the duration of the deployment. In conjunction with this deployment, the Orange County Sanitation District deployed four bottom platforms with current meters on the San Pedro Shelf, and these meters provided water-column profiles of currents. The data from this program will provide the basis for an investigation of the interaction between the deep water flow over the slope and the internal tide on the Continental Shelf.

California↗
USGS2006

Status of dugongs in waters around Palau

The dugong, Dugong dugon , is widely distributed throughout the Indo-Pacific region in shallow tropical and subtropical waters (Nishiwaki and Marsh 1985).The International Union for Conservation of Nature and Natural Resources lists the species as vulnerable (Thornback and Jenkins 1982), as it is severely depleted or extinct in many parts of its former range (Nishiwaki and Marsh 1985). Many populations at isolated archipelagos have been exterminated through direct human exploitation. Husar (1975) cited evidence of the former existence of dugongs around the Mascarene, Laccadive, Maldive, Barren, Narcondom, Cocos (Keeling), Christmas, and Lesser Sunda islands. An isolated dugong population still occurs around Palau (Republic of Belau), Western Caroline Islands, about 850 km from both Papua New Guinea to the south and the Philippines to the west. The first aerial surveys of this population, in 1977 and 1978, indicated that it was small and other evidence suggested it was subject to persistent poaching (Brownell et al. 1981). We resurveyed this population in 1983 to reassess its status and attempt to detect any changes in distribution or abundance. With the assistance of the Palau Department of Natural Resources, we also interviewed fishermen and knowledgeable residents about dugong abundance, distribution, mortality, and natural history. Surveys were conducted from 19 through 26 August, using a Cessna 206high-wing airplane flown at an altitude of 150 to 300 m and an airspeed of about 170 km/h. An observer sat in each rear seat, and a third observer, who also navigated and recorded the data directly onto maps, sat in the right front seat. Small animals close to another dugong were considered calves. The survey route, based on that of Brownell et al. (19Sl), covered much of the approximately 1,380 sq km of dugong habitat within the archipelago. The islands are surrounded by very deep water, which restricts dugong habitat to lagoon areas within about 3 km of shore. Surveys were flown about 0.5 km offshore and the same distance inside the fringing reefs, with transects about 1 km apart across the larger lagoons. The coast was divided into the same 12 segments used by Brownell et al. (1981) (Fig. 1). However, the area outside the western fringing reef was not surveyed because no dugongs were sighted there in either1977 or 1978. We surveyed the entire archipelago twice and carried out replicated surveys of the lagoon areas and Malakal Harbor, which had been used by relatively large numbers of dugongs in 1977 and 1978 (Table 1). The total survey time was 15 h.265Help Volumes Main Menu

Marine Mammal Science↗
USGS1994

Accounting for consumptive use of Lower Colorado River water in Arizona, California, Nevada, and Utah

In the Colorado River valley between the east end of Lake Mead and the international boundary with Mexico (see figure), the river is the principal source of water for agricultural, domestic, municipal, industrial, hydroelectric-power generation, and recreational purposes. Water is stored in surface reservoirs and in the river aquifer---permeable sediments and sedimentary rocks that fill the lower Colorado River valley and adjacent tributary valleys. The hydraulic connection between the river and the river aquifer, overbank flow prior to building of the dams, and infiltration as the reservoirs filled allowed the sediments and sedimentary rocks to become saturated with water from the river. Ratios of isotopes of hydrogen and oxygen in water from wells indicate that most of the water in the river aquifer beneath the flood plain and in many places beneath the adjacent alluvial slopes originated from the river. The water table in the river aquifer extends from the river, beneath the flood plain, and under the alluvial slopes until it intersects bedrock. Precipitation in the surrounding mountains and inflow from tributary valleys also contribute small quantities of water to the river aquifer. Consumptive use of river water in the valley results from evapotranspiration by vegetation (crops and phreatophytes) on the flood plain, pumpage from wells to meet domestic and municipal needs, and pumpage from the river for export to areas in California, Arizona, and Nevada outside of the river valley. Most crops are grown on the flood plain; in a few areas, land on the adjacent terraces has been cultivated. Crops were grown on about 70 percent of the total vegetated area in 1984. Phreatophytes---natural vegetation that obtains water from the river aquifer---covered the remaining vegetated areas on the uncultivated flood plain. Most of the water used for irrigation is diverted or pumped directly from the river and reservoirs. Most of the water used for domestic and municipal purposes is pumped from wells on the flood plain, on adjacent alluvial slopes, and in tributary valleys. River water also is delivered to Mexico in accordance with an international treaty.

Arizona, California, Nevada, Utah↗
USGS1998

Geology, ground-water flow, and dissolved-solids concentrations in ground water along hydrogeologic sections through Wisconsin aquifers

A cooperative project between the U.S. Geological Survey (USGS) and the Wisconsin Department of Natural Resources (DNR) was begun with the objectives of describing water quality and its relation to the hydrology of Wisconsin's principal aquifers and summarizing instances of ground-water contamination and quality problems from information available in DNR files. The first objective was met by a hydrologic investigation done by the USGS, and the second, by preparation of a report by the DNR, for their internal use, that describes the State's water resources and known ground-water quality and contamination problems and makes policy recommendations for ground-water management. The USGS investigation was divided into two phases. The first phase consisted of compiling available water-quality and hydrogeologic data and collecting new data to describe general regional water-quality and hydrogeologic relations within and between Wisconsin aquifers. The second phase began concurrently with the later part of the first phase and consisted of an areal description of water quality and flow in the State's shallow aquifer system (Kammerer, 1995). The overall purpose of this investigation was to provide a regional framework that could serve as a basis for intensive local and site specific ground-water investigations by State and local government agencies. This report presents the results of the first phase of the USGS investigation. Regional hydrogeologic and water-quality relations within and between aquifers are shown along 15 hydrogeologic sections that traverse the State. Maps are used to show surficial geology of bedrock and unconsolidated deposits and horizontal direction of ground-water flow. Interpretations on the maps and hydrogeologic sections are based on data from a variety of sources and provide the basis for the areal appraisal of water quality in the State's shallow aquifer system in the second phase of the investigation.

Wisconsin↗
USGS2025

Evaluating drought risk of the Red River of the North Basin using historical and stochastic streamflow upstream from Emerson, Manitoba

Drought and its effect on streamflow are important to understand because of the potential to adversely affect water supply, agricultural production, and ecological conditions. The Red River of the North Basin in north-central United States and central Canada is susceptible to dry conditions. During an extended drought, streamflow conditions in the Red River of the North may become inadequate to support existing water supply needs in the basin for agriculture, industry, human use, and aquatic life. To understand potential future low-streamflow conditions in the Red River of the North Basin, the U.S. Geological Survey, in cooperation with the International Joint Commission, North Dakota Department of Water Resources, Red River Joint Water Resource District, and Red River Watershed Management Board, developed a water-balance model of the Red River of the North Basin upstream from Emerson, Manitoba, Canada, and coupled the model with stochastic weather inputs to simulate possible future low-streamflow conditions. Historical changes in low-streamflow conditions were characterized across the Red River of the North Basin using multiple change-point analysis for 12 streamgages. Across these stations, significant change-point years in 1943 and 1994 marked increases in the magnitude of low-streamflow conditions. During 1920–2015, conversion of primary land (not affected by human use) to agricultural and secondary land was followed by a conversion from smalls grains to corn and soybeans as the dominant crop type. From land-use analysis, 1940–2000 was determined to have relatively stable land use and therefore was used as the calibration period for the water-balance model. A deterministic water-balance model was developed for the Red River of the North Basin upstream from Emerson, Manitoba. The water-balance model was calibrated with data from 37 U.S. Geological Survey streamgages for 1940–2000 and verified using data for 2001–15. The calibrated water-balance model simulated streamflow distributions that mirrored the seasonal patterns of the observed mean monthly streamflow and the standard deviation of the monthly streamflow data, especially during the fall and winter months when streamflow was lowest. For the verification period, during the low-streamflow months of December through January, the difference between simulated and observed data was similar to the calibration comparison and successfully reproduced seasonal trends in the distribution of streamflow, even when using weather data that were outside the calibration period. To determine the future risk of low-streamflow conditions in the Red River of the North Basin, a block-bootstrap method was used to generate multiple possible future climates. These stochastically generated weather time series were then input to a water-balance model to simulate a distribution of possible streamflows. Three sets of experiments were performed, with each experiment containing a set of scenarios. The first set of experiments from the stochastic streamflow model were designed to investigate how changes in reservoir management would affect the distribution of low streamflow. Relative to scenario 1 (present-day [2023] reservoir operation), scenario 2 (no reservoir operation) shifted the low-streamflow frequency curves downward, reducing the annual minimum monthly streamflow for the Emerson subbasin. Subbasins were defined by the contributing area upstream from a selected streamgage station. Relative to scenario 1, scenario 3 (regulated streamflow with an increased reservoir capacity of 10 percent) shifted the low-streamflow frequency curves upward for the Emerson subbasin. The magnitude of this upward shift, caused by increased reservoir capacity, was lower than the magnitude of the shift caused by the absence of the reservoirs, which indicates that the streamflow was most affected when the reservoirs were first constructed. The second set of experiments from the stochastic streamflow model included two scenarios that were performed to better understand how the Red River of the North Basin responds to long periods of low or high precipitation. The results indicate that the model consistently overestimated streamflow, but the relative change between a wet and dry climate state of simulated streamflow distribution reasonably matched the relative change of historical streamflow. Across the subbasins, the model was most accurate for low-streamflow conditions associated with nonexceedance probabilities between 20 and 40 percent. The third set of experiments from the stochastic streamflow model were done to investigate low-streamflow response across the basin to several drought events. Low-end streamflow was reduced when the basin was exposed to a drought, and the magnitude of the reduction increased with longer or more intense droughts. Compared to the low-intensity drought scenarios, the range of percent reductions (as indicated by the interquartile range) was larger for the high-intensity drought scenarios for all subbasins, and the subbasins of Grand Forks and Emerson had a smaller range of reductions compared to the other three subbasins. The larger drainage area—combined with the large contribution of the Red Lake River and several other Minnesota tributaries that generally experience wetter climate conditions—upstream from the Emerson and Grand Forks subbasins may contribute to the smaller range in reductions under the high intensity scenarios. Comparison of the percent reduction in low-end streamflow among subbasins also indicated that the effects of drought duration and intensity could be cumulative. Combining factors of time and intensity produced a larger reduction in streamflow than when each effect was isolated. The array of drought scenarios can be used to determine how a subbasin would respond to multiple possible future conditions. Based on climate predictions, the drought scenario that best matches a future anticipated drought scenario can be used to estimate a low streamflow response for a given subbasin.

Manitoba, Minnesota, North Dakota↗
USGS2024

Dissolved oxygen monitoring on the Souris River, 2019–23

The U.S. Geological Survey (USGS) in partnership with the International Joint Commission installed and operated continuous water-quality monitors at three sites on the Souris River from May 2019 to October 2023. Continuously recorded data included dissolved oxygen (DO), water temperature, and specific conductance at the Souris River near Sherwood, North Dakota (USGS station 05114000), Souris River above Minot, N. Dak. (USGS station 05117500), and Souris River near Westhope, N. Dak (USGS station 05124000). The three sites on the Souris River were chosen for additional DO monitoring because they provided the best opportunity to capture potential effects on DO in areas downstream from major flow control structures and because identifying the connection of streamflow to DO at the international border is a focus of the International Souris River Board (ISRB). The continuous water-quality monitoring at three sites on the Souris River from May 16, 2019, to October 1, 2023, indicated different patterns in DO among the three sites, and the different patterns indicate different factors affect DO concentrations among the sites. DO concentrations near Sherwood indicated the strong effect of algal dynamics at lower streamflow conditions with large diurnal fluctuations in DO concentration and indicated that streamflow does seem to affect DO concentrations when the streamflow is greater than about 100 cubic feet per second. DO concentrations were also frequently less than the water-quality objective (WQO) of 5 milligrams per liter in the summer and winter months, particularly during relatively low streamflow conditions in 2020 and 2021. DO concentrations above Minot had a different pattern with considerably fewer diurnal fluctuations than near Sherwood, high DO concentrations most winters except for the winter of 2021–22, and fewer instances when the DO was less than the WQO compared to Sherwood. The pattern of DO concentrations near Westhope seemed to be mainly influenced by the water chemistry coming out of J. Clark Salyer Pool 357 rather than streamflow and channel conditions at the site. The Westhope site also had the most days with daily minimum DO concentrations less than the WQO among the three sites, mainly in the winter when concentrations were consistently at or near 0 milligrams per liter for most of the winter months.

North Dakota↗
USGS2007

Water quality of the St. Clair River, Lake St. Clair, and their U.S. tributaries, 1946-2005

The St. Clair River/Lake St. Clair waterway forms an international boundary between the United States and Canada. The waters of the area are an important part of the cultural heritage of the area and serves as an important water-supply and power-generating resource; the waterway also supports an economy based largely on recreation, agriculture, and manufacturing. This report was undertaken as part of the Lake St. Clair Regional Monitoring Project for the purpose of providing a comprehensive assessment of the hydrological, chemical, and physical state of the surface water of Lake St. Clair and its tributaries. The data varied in focus and density over the period of compilation which in many cases this variation prevented the completion of statistical analyses because data did not meet minimum comparability or quality requirements for those tests. Comparison of water quality of the Belle, Black, Clinton, and Pine River Basins, as well as basins of minor rivers in the study area, showed that water quality in many of the tributaries, particularly the Clinton River and some of the minor rivers, was degraded compared to the water quality of the St. Clair River/Lake St. Clair waterway. Data analyses included comparison of nutrients, chloride, specific conductance, turbidity, biochemical oxygen demand (BOD), and pesticides among the basins and the St. Clair River. Median concentrations of total nitrate were well below the recommended USEPA total nitrogen ambient water-quality criterion of 0.54 mg/L as N for nutrient ecoregion VII for all study-area streams except the Clinton River. More than 93 percent of the phosphorus concentrations for the Belle, Black, Pine and minor river basins and 84 percent of the phosphorus concentrations for the Clinton River Basin are greater than the USEPA recommended ambient total phosphorus criterion of 0.033 mg/L for rivers and streams. Nine chloride concentrations exceeded the USEPA criterion maximum concentration (CMC) for chloride set at 860 mg/L for all study-area streams, with the six largest being in the Belle River Basin. Higher chloride concentrations were increasingly common from 2002 to 2005. The urban minor river basins had the highest median specific conductance, whereas the agricultural Pine River Basin had the lowest median specific conductance. The median values of BOD for the five basins in the study area ranged from 2.4 mg/L for the Pine River Basin to 3.2 mg/L for the Black and Clinton River Basins, whereas the median for the St. Clair River was 0.5 mg/L. In 1985, the highest concentrations of pesticides were found in samples from the mouth of the Clinton River; however, in 1996–98, the majority of high pesticide concentrations were found in samples from the Black River. Changing land-use patterns, specifically conversion of agricultural lands to urban/residential lands in the Clinton River Basin, may explain this difference. Trend analysis was done for four stream sites where adequate data were available. These analyses identified no significant water-quality changes at a stream site on the Black River, where land-use patterns have changed little in the past few decades. This stands in marked contrast to trend analysis for three stream sites in the Clinton River Basin, which has undergone significant land-use change. The changes at the Clinton River stream sites, ranging from 5 to 13 significant trends, were generally decreases in nutrients and increases in total dissolved solids (TDS) and chloride. The greater flow volume of the St. Clair River/Lake St. Clair waterway is able to assimilate incoming dissolved and suspended constituents from tributaries with little effect upon its overall water quality, although incomplete mixing may result in localized water-quality impairment downstream from tributary confluences. Mixing effects on Lake St. Clair water quality was also demonstrated in analysis of Escherichia coli ( E. coli ) data collected at paired nearshore/offshore sites, which reflected similarity in water quality among many paired sites.

Michigan↗
USGS2018

Hypotheses from recent assessments of climate impacts to biodiversity and ecosystems in the United States

Climate change poses multiple threats to biodiversity, and has already caused demonstrable impacts. We summarize key results from a recent national assessment of observed climate change impacts to terrestrial, marine, and freshwater ecosystems in the United States, and place results in the context of commonly articulated hypotheses about ecosystem response to climate change for global implications. Specific impacts we consider include: range shifts; phenological shifts; phenotypic changes; primary production changes; biological invasions; and novel communities. Significant effort has been made recently to incorporate adaptation measures into land and water management at both national and international scales, but the scale of impacts and associated uncertainties pose challenges to existing management institutions. Using commonly articulated hypotheses about climate change, biodiversity, and ecosystem response can provide context for informed decisions at multiple scales and can help to provide a clearer understanding of the ecological and mechanistic linkages between climate change and biodiversity.

Book chapter↗
USGS2017

Rates of soil development from four soil chronosequences in the southern Great Basin

Four soil chronosequences in the southern Great Basin were examined in order to study and quantify soil development during the Quaternary. Soils of all four areas are developed in gravelly alluvial fans in semiarid climates with 8 to 40 cm mean annual precipitation. Lithologies of alluvium are granite-gneiss at Silver Lake, granite and basalt at Cima Volcanic Field, limestone at Kyle Canyon, and siliceous volcanic rocks at Fortymile Wash. Ages of the soils are approximated from several radiometric and experimental techniques, and rates are assessed using a conservative mathematical approach. Average rates for Holocene soils at Silver Lake are about 10 times higher than for Pleistocene soils at Kyle Canyon and Fortymile Wash, based on limited age control. Holocene soils in all four areas appear to develop at similar rates, and Pleistocene soils at Kyle Canyon and Fortymile Wash may differ by only a factor of 2 to 4. Over time spans of several millennia, a preferred model for the age curves is not linear but may be exponential or parabolic, in which rates decrease with increasing age. These preliminary results imply that the geographical variation in rates within the southern Great Basin-Mojave region may be much less significant than temporal variation in rates of soil development. The reasons for temporal variation in rates and processes of soil development are complexly linked to climatic change and related changes in water and dust, erosional history, and internally driven chemical and physical processes. ?? 1991.

Quaternary Research↗
USGS2019

Population connectivity of pelagic megafauna in the Cuba-Mexico-United States triangle

The timing and extent of international crossings by billfishes, tunas, and sharks in the Cuba-Mexico-United States (U.S.) triangle was investigated using electronic tagging data from eight species that resulted in >22,000 tracking days. Transnational movements of these highly mobile marine predators were pronounced with varying levels of bi- or tri-national population connectivity displayed by each species. Billfishes and tunas moved throughout the Gulf of Mexico and all species investigated (blue marlin, white marlin, Atlantic bluefin tuna, yellowfin tuna) frequently crossed international boundaries and entered the territorial waters of Cuba and/or Mexico. Certain sharks (tiger shark, scalloped hammerhead) displayed prolonged periods of residency in U.S. waters with more limited displacements, while whale sharks and to a lesser degree shortfin mako moved through multiple jurisdictions. The spatial extent of associated movements was generally associated with their differential use of coastal and open ocean pelagic ecosystems. Species with the majority of daily positions in oceanic waters off the continental shelf showed the greatest tendency for transnational movements and typically traveled farther from initial tagging locations. Several species converged on a common seasonal movement pattern between territorial waters of the U.S. (summer) and Mexico (winter).

Scientific Reports↗
USGS1960

Chemical equilibrium diagrams for ground-water systems/les graphiques de l'équilibre chimique pour les systèmes des eaux souterrainnes

Chemical equilibrium in water in contact with calcite is expressed by means of a pH grid overlay on a log-log plot of activities of bicarbonate vs. calcium ions. Solubility of ferrous iron and the solid-phase minerals that would be stable in a solution containing activities of 10 ppm of sulfate and 100 ppm of bicarbonate or related species is expressed by means of a stability-field diagram with pH as abscissa and redox potential as ordinate.The diagrams can be used to tell whether water injected in recharge wells may form precipitates that may plug the aquifer and have other uses in studies of natural water chemistry.

International Association of Scientific Hydrology ↗
USGS1963

Preliminary results of a study of calcium carbonate saturation of ground water in central Florida

The departure of ground water from equilibrium with calcite is being studied in central Florida . Measurements of pH, temperature, and concentration of bicarbonate made in the field are used with standard laboratory analyses of water samples to calculate an ion activity product (K) for calcium carbonate . The calculated Kiap is compared with the equilibrium constant (Keq) for calcite to determine the departure from equilibrium. The calcium concentration is lowest in the area of the highest piezometric surface. Some of the highest concentrations of bicarbonate are in the area of low calcium . In about half of the area of study , the water is undersaturated with respect to calcite. This indicates that solution of limestone can occur several hundred feet below the water table.

Florida↗
USGS2006

A method to directly measure maximum volume of fish stomachs or digestive tracts

A new method for measuring maximum stomach or digestive tract volume of fish incorporates air injection at constant pressure with water displacement to measure directly the internal volume of a stomach or analogous structure. The method was tested with coho salmon, Oncorhynchus kisutch (Walbaum), which has a true stomach, and northern squawfish, Ptychocheilus oregonensis (Richardson), which has a modified foregut as a functional analogue. Both species were collected during July-October 1987 from the Columbia River, U.S.A. Relationships between fish weight (= volume) and maximum volume of the digestive organ were best fitted for coho salmon by an allometric model and for northern squawfish by an exponential model. Least squares regression analysis of individual measurements showed less variability in the volume of coho salmon stomachs ( R 2 = 0.85) than in the total digestive tracts ( R 2 = 0.55) and foreguts ( R 2 = 0.61) of northern squawfish, relative to fish size. Compared to previous methods, the new technique has the advantage of accurately measuring the internal volume of a wide range of digestive organ shapes and sizes.

Journal of Fish Biology↗