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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 1,513 records · Page 84Linked to original sources
USGS1980

Geohydrology and model analysis for water-supply management in a small area of west-central Kansas

The Ogallala Formation in the intensive-study area, an area of 12 square miles in northeastern Wichita County, west-central Kansas, has had a substantial decrease in saturated thickness since the development of irrigation. The annual water-level decline during 1950-78 ranged from 1.08 to 2.22 feet per year. The hydrologic system was investigated to study methods of conserving the remaining ground water in the intensive-study area. During 1977-78, the average annual ground-water withdrawal was 7,400 acre-feet, and the water-level decline ranged from 0.91 to 5.05 feet. The saturated thickness in 1977 ranged from about 40 to 80 feet, and aquifer storage was about 61,000 acre-feet. Natural recharge is estimated to be 0.28 inch per year. Projections from a digital ground-water flow model were used to indicate the additional water-level decline that might occur from 1978 to 1988 if pumpages in the 480-square-mile model area were one-half, equal to, or double the 1977 pumpage rate. The additional water-level declines in the intensive-study area would range from 5 to 15 feet if pumpages were one-half, 15 to 30 feet if pumpages were equal to, and 25 to 40 feet if pumpages were double the 1977 rate. Projections also were used to indicate the water-level declines if pumpages in the model area were equal to the 1977 rate and if pumpages in the intensive-study area were one-half or double the 1977 rate. Additional water-level declines in the intensive-study area would range from 10 to 20 feet if pumpages were one-half and from 20 to 25 feet if pumpages were doubled. Decreased pumpage in the area could reduce the water-level declines, but continued pumpage in adjacent areas would cause declines to be greater near the edge than near the center. The digital model was more sensitive to changes in pumpage than to changes in hydraulic conductivity, specific yield, and recharge.

Kansas↗
USGS2017

Climate change refugia and habitat connectivity promote species persistence

Background Climate change refugia, areas buffered from climate change relative to their surroundings, are of increasing interest as natural resource managers seek to prioritize climate adaptation actions. However, evidence that refugia buffer the effects of anthropogenic climate change is largely missing. Methods Focusing on the climate-sensitive Belding’s ground squirrel ( Urocitellus beldingi ), we predicted that highly connected Sierra Nevada meadows that had warmed less or shown less precipitation change over the last century would have greater population persistence, as measured by short-term occupancy, fewer extirpations over the twentieth century, and long-term persistence measured through genetic diversity. Results Across California, U. beldingi were more likely to persist over the last century in meadows with high connectivity that were defined as refugial based on a suite of temperature and precipitation factors. In Yosemite National Park, highly connected refugial meadows were more likely to be occupied by U. beldingi . More broadly, populations inhabiting Sierra Nevada meadows with colder mean winter temperatures had higher values of allelic richness at microsatellite loci, consistent with higher population persistence in temperature-buffered sites. Furthermore, both allelic richness and gene flow were higher in meadows that had higher landscape connectivity, indicating the importance of metapopulation processes. Conversely, anthropogenic refugia, sites where populations appeared to persist due to food or water supplementation, had lower connectivity, genetic diversity, and gene flow, and thus might act as ecological traps. This study provides evidence that validates the climate change refugia concept in a contemporary context and illustrates how to integrate field observations and genetic analyses to test the effectiveness of climate change refugia and connectivity. Conclusions Climate change refugia will be important for conserving populations as well as genetic diversity and evolutionary potential. Our study shows that in-depth modeling paired with rigorous fieldwork can identify functioning climate change refugia for conservation.

California↗
USGS2000

Simulation of the shallow hydrologic system in the vicinity of Middle Genesee Lake, Wisconsin, using analytic elements and parameter estimation

Middle Genesee Lake is a ground-water flow-through lake located in a developing area in southeastern Wisconsin. Because the lake is in good connection with the shallow ground-water system, hydrologic stresses to the shallow ground-water system could adversely affect the lake system. In order to assess the effects of potential stresses on the lake, a study was completed by the U.S. Geological Survey, in cooperation with the Middle Genesee Lake Management District. The objective of the study was to identify areas that contribute ground water to the lake and estimate the hydrologic budget of the lake and hydraulic parameters affecting ground-water flow. A two-dimensional, steady-state analytic element model of the lake and surrounding area was developed using the computer code GFLOW. A parameter estimation model, UCODE, was used to optimize the calibration to measured water levels and streamflow. The calibrated model was used to evaluate the effect of three hypothetical stress scenarios on the stage of Middle Genesee Lake; the simulations were linked to UCODE, which formally incorporated parameter uncertainty into 95-percent confidence intervals around the simulated value. The scenarios included: (1) pumping from upgradient irrigation wells, (2) pumping from Lower Genesee Lake to lower lake levels, and (3) reduction in recharge resulting from development. The results of the simulations demonstrated that lake levels could be affected by hydrologic stresses in the shallow hydrologic system, with effects ranging from a 2.7 feet decline in lake stage resulting from pumping in Lower Genesee Lake to a 0.1 feet decline in lake stage from development in part of the upgradient recharge area. The range of lake stage decline increased when parameter uncertainty was included, from a decline of 3.1 feet for pumping from Lower Genesee Lake to no reduction in lake stage for the development in the recharge area. Whereas these simulated effects are within the natural variation in lake stage, they represent a systematic reduction of ground-water flow to the lake. Therefore, these hypothetical stresses are expected to establish a new, lower, baseline lake stage over which the natural variation due to climatic effects are added and subtracted.

Wisconsin↗
USGS2010

The mobilization of aluminum in a natural soil system: Effects of hydrologic pathways

A two-component soil water flow model was used in conjunction with an equilibrium speciation model WATEQF to study aluminum mobility in soils of a forested watershed, White Oak Run, in the Shenandoah National Park, Virginia. Soil solution samples, taken from the O, E, B, C 1 , and C 2 horizons, were collected from zero-tension lysimeters designed to collect faster gravitational macropore flow and tension lysimeters designed to collect slower capillary micropore flow. Dissolved aluminum was fractionated into acid-soluble, inorganic monomeric, and organic monomeric aluminum. Soil water aluminum concentrations decreased with depth indicating that the deep soil is a sink for aluminum. All waters contained significant concentrations of acid-soluble aluminum and exhibited a negative correlation between p H and the inorganic monomeric aluminum concentrations. Water in the shallow soil showed distinctly different chemical compositions for the two flow types, while C horizon micropore and macropore waters were more similar. Because of its shorter residence time, water flowing in deep soil macropores underwent less extensive neutralization and immobilization of aqueous aluminum than micropore water. The O horizon macropore waters were undersaturated for all hydroxide, silicate, and sulfate mineral phases considered. The C horizon samples from both flow types were near equilibrium with respect to kaolinite and synthetic gibbsite, indicating that mineral solubility controls water chemistry in the deep soil, while organic substances are the key control in the shallow macropore waters.

Water Resources Research↗
USGS2022

Assessment of cropland inundation due to the operation of the Reelfoot Lake spillway in West Tennessee

Running Reelfoot Bayou (RRB) is the outlet canal of Reelfoot Lake, the largest natural lake in Tennessee. RRB is not able to contain discharge from Reelfoot Lake greater than the bankfull discharge of 28 m 3 /s (1000 ft 3 /s), which typically occurs at the beginning of the growing season (April–June). Historically, the planting of crops has been delayed until flooding subsides and cropland has drained. The objective of this study is a preliminary quantification of cropland inundation to determine its spatial distribution in the RRB floodplain. Inundated croplands in the RRB floodplain were delineated over a range of spillway discharges from 2 to 57 m 3 /s (70–2000 ft 3 /s), using one-dimensional–two-dimensional hydrodynamic modeling and multispectral satellite images (Landsat 8 and Sentinel-2). The composite maps made by combining the simulated and image-derived flood maps were overlaid on the United States Department of Agriculture CropScape layer to determine the inundation of individual summer crops during the growing season. About 25% of the inundated croplands are flooded at discharges of RRB less than 28 m 3 /s, implying wetland hydrology. The results of this analysis can be used to inform operational management of the Reelfoot Lake spillway.

Tennessee↗
USGS1994

User's guide to revised method-of-characteristics solute-transport model (MOC--version 31)

The U.S. Geological Survey computer model to simulate two-dimensional solute transport and dispersion in ground water (Konikow and Bredehoeft, 1978; Goode and Konikow, 1989) has been modified to improve management of input and output data and to provide progressive run-time information. All opening and closing of files are now done automatically by the program. Names of input data files are entered either interactively or using a batch-mode script file. Names of output files, created automatically by the program, are based on the name of the input file. In the interactive mode, messages are written to the screen during execution to allow the user to monitor the status and progress of the simulation and to anticipate total running time. Information reported and updated during a simulation include the current pumping period and time step, number of particle moves, and percentage completion of the current time step. The batch mode enables a user to run a series of simulations consecutively, without additional control. A report of the model's activity in the batch mode is written to a separate output file, allowing later review. The user has several options for creating separate output files for different types of data. The formats are compatible with many commercially available applications, which facilitates graphical postprocessing of model results. Geohydrology and Evaluation of Stream-Aquifer Relations in the Apalachicola-Chattahoochee-Flint River Basin, Southeastern Alabama, Northwestern Florida, and Southwestern Georgia By Lynn J. Torak, Gary S. Davis, George A. Strain, and Jennifer G. Herndon Abstract The lower Apalachieola-Chattahoochec-Flint River Basin is underlain by Coastal Plain sediments of pre-Cretaceous to Quaternary age consisting of alternating units of sand, clay, sandstone, dolomite, and limestone that gradually thicken and dip gently to the southeast. The stream-aquifer system consism of carbonate (limestone and dolomite) and elastic sediments, which define the Upper Floridan aquifer and Intermediate system, in hydraulic connection with the principal rivers of the basin and other surface-water features, natural and man made. Separate digital models of the Upper Flori-dan aquifer and Intermediate system were constructed by using the U.S. Geological Survey's MODular Finite-Element model of two dimensional ground-water flow, based on concep- tualizations of the stream-aquifer system, and calibrated to drought conditions of October 1986. Sensitivity analyses performed on the models indicated that aquifer hydraulic conductivity, lateral and vertical boundary flows, and pumpage have a strong influence on groundwater levels. Simulated pumpage increases in the Upper Floridan aquifer, primarily in the Dougherty Plain physiographic district of Georgia,. caused significant reductions in aquifer discharge to streams that eventually flow to Lake Seminole and the Apalachicola River and Bay. Simulated pumpage increases greater than 3 times the October 1986 rates caused drying ofsome stream reaches and parts of the Upper Floridan aquifer in Georgia. Water budgets prepared from simulation results indicate that ground- water discharge to streams and recharge by horizontal and vertical flow are the principal mechanisms for moving water through the flow system. The potential for changes in ground-water quality is high in areas where chemical constituents can be mobilized by these mechanisms. Less than 2 percent of ground-water discharge to streams comes from the Intermediate system; thus, it plays a minor role in the hydrodynamics of the stream- aquifer system.

Water-Resources Investigations Report↗
USGS2021

Optimal allocation of law enforcement patrol effort to mitigate poaching activities

Poaching is a global problem causing the decline of species worldwide. Optimizing the efficiency of ranger patrols to deter poaching activity at the lowest possible cost is crucial for protecting species with limited resources. We applied decision analysis and spatial optimization algorithms to allocate efforts of ranger patrols throughout a national park. Our objective was to mitigate poaching activity at or below management risk targets for the lowest monetary cost. We examined this trade‐off by constructing a Pareto efficiency frontier using integer linear programming. We used data from a ranger‐based monitoring program in Nyungwe National Park, Rwanda. Our measure of poaching risk is based on dynamic occupancy models that account for imperfect detection of poaching activities. We found that in order to achieve a 5% reduction in poaching risk, 622 ranger patrol events (each corresponding to patrolling 1‐km 2 sites) were needed within a year at a cost of US$49,760. In order to attain a 60% reduction in poaching risk, 15,560 patrol events were needed at a cost of US \$ 1,244,800. We evaluated the trade‐off between patrol cost and poaching risk based on our model by constructing a Pareto efficiency frontier and park managers found the solution for a 50% risk reduction to be a practical trade‐off based on funding constraints (comparable to recent years) and the diminishing returns between risk mitigation and cost. This expected reduction in risk required 8,558 patrol events per year at a cost of US \$ 684,640. Our results suggest that optimal solutions could increase efficiency compared to the actual effort allocations from 2006 to 2016 in Nyungwe National Park (e.g., risk reductions of ~30% under recent budgets compared to ~50% reduction in risk under the optimal strategy). The modeling framework in this study took into account imperfect detection of poaching risk as well as the directional and conditional nature of ranger patrol events given the spatial adjacency relationships of neighboring sites and access points. Our analyses can help to improve the efficiency of ranger patrols, and the modeling framework can be broadly applied to other spatial conservation planning problems with conditional, multilevel, site selection.

Nyungwe National Park↗
USGS2007

Summary of the Ground-Water-Level Hydrologic Conditions in New Jersey 2006

Ground water is one of the Nation's most important natural resources. It provides about 40 percent of our Nation's public water supply. Currently, nearly one-half of New Jersey's drinking-water is supplied by over 300,000 wells that serve more than 4.3 million people (John P. Nawyn, U.S. Geological Survey, written commun., 2007). New Jersey's population is projected to grow by more than a million people by 2030 (U.S. Census Bureau, accessed March 2, 2006, at http://www.census.gov). As demand for water increases, managing the development and use of the ground-water resource so that the supply can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences is of paramount importance. This report describes the U.S. Geological Survey (USGS) New Jersey Water Science Center Observation Well Networks. Record low ground-water levels during water year 2006 (October 1, 2005 to September 30, 2006) are listed, and water levels in six selected water-table observation wells and three selected confined wells are shown in hydrographs. The report describes the trends in water levels in various confined aquifers in southern New Jersey and in water-table and fracture rock aquifers throughout the State. Web site addresses to access the data also are included. The USGS has operated a network of observation wells in New Jersey since 1923 for the purpose of monitoring ground-water-level changes throughout the State. Long-term systematic measurement of water levels in observation wells provides the data needed to evaluate changes in the ground-water resource over time. Records of ground-water levels are used to evaluate the effects of climate changes and water-supply development, to develop ground-water models, and to forecast trends.

Fact Sheet↗
USGS2010

Mixing effects on apparent reaction rates and isotope fractionation during denitrification in a heterogeneous aquifer

Gradients in contaminant concentrations and isotopic compositions commonly are used to derive reaction parameters for natural attenuation in aquifers. Differences between field‐scale (apparent) estimated reaction rates and isotopic fractionations and local‐scale (intrinsic) effects are poorly understood for complex natural systems. For a heterogeneous alluvial fan aquifer, numerical models and field observations were used to study the effects of physical heterogeneity on reaction parameter estimates. Field measurements included major ions, age tracers, stable isotopes, and dissolved gases. Parameters were estimated for the O 2 reduction rate, denitrification rate, O 2 threshold for denitrification, and stable N isotope fractionation during denitrification. For multiple geostatistical realizations of the aquifer, inverse modeling was used to establish reactive transport simulations that were consistent with field observations and served as a basis for numerical experiments to compare sample‐based estimates of “apparent” parameters with “true“ (intrinsic) values. For this aquifer, non‐Gaussian dispersion reduced the magnitudes of apparent reaction rates and isotope fractionations to a greater extent than Gaussian mixing alone. Apparent and true rate constants and fractionation parameters can differ by an order of magnitude or more, especially for samples subject to slow transport, long travel times, or rapid reactions. The effect of mixing on apparent N isotope fractionation potentially explains differences between previous laboratory and field estimates. Similarly, predicted effects on apparent O 2 threshold values for denitrification are consistent with previous reports of higher values in aquifers than in the laboratory. These results show that hydrogeological complexity substantially influences the interpretation and prediction of reactive transport.

Water Resources Research↗
USGS1996

Synthesis of monthly natural flows for selected sites in the Musselshell River basin, Montana, base period 1929-89

Synthesized monthly natural streamflows were required at 13 sites for use in a streamflow- accounting model to evaluate the effects of various water-allocation schemes on water availability in the Musselshell River Basin in central Montana. Records of monthly streamflow at 14 streamflow-gaging stations were used to synthesize monthly natural flows at tributaries and the 13 synthesis sites. A streamflow-record extension program was used to extend flow records at the 14 gaged sites to a common base period, 1929-89. To synthesize monthly natural flows at 10 sites on the Musselshell River mainstem, synthesized monthly natural flows at all signi- ficant tributary streams were required. Results from a previous study were used to synthesize tributary natural flows. Monthly natural flows at each mainstem site downstream from the first site were synthesized by successively adding monthly natural flows from intervening tributaries to the next upstream mainstem site. Special methods using extended-record flows from gaged tributaries were used to synthesize monthly natural flows at three tributary sites. Synthesized mean annual natural flows were found to be greater than mean annual extended-record flows at three selected comparison sites on the Musselshell River. The differences between mean natural and extended-record flows (depletions) at Harlowton and Musselshell were considered to be reasonable given the amount of irrigated acreage upstream from the two sites. The differences at Mosby, the site farthest downstream, was less than at Musselshell, the next upstream site, indicating that the methods of synthesis had error. The synthesis error generally was attributed to the larger natural variability of tributary flows in the lower portion of the Musselshell River Basin.

Water-Resources Investigations Report↗
USGS2020

Deposition potential and flow-response dynamics of emergent sandbars in a braided river

Sandbars are ubiquitous in sandy‐braided rivers throughout the world. In the Great Plains of the United States, recovery and expansion of emergent sandbar habitat (ESH) has been a priority in lowland rivers where the natural extent of sandbars has been degraded. Recovery efforts are aimed at protection of populations of the interior least tern ( Sterna antillarum ) and piping plover ( Charadrius melodus ). But quantitative observations of deposition and erosion dynamics of populations of sandbars across long segments of rivers are rare. We present a three‐part case study which used Bayesian regression models to examine relations between hydrology, channel morphology, and ESH responses in the Platte River, eastern Nebraska. Logistic regression indicates presence of ESH is positively related to the Parker, (1976) stability criterion and a gradient in sediment transport mode, and negatively related to presence of vegetation. Hierarchical linear regression modeling shows direct coupling between sandbar top‐surface height and formative flood magnitude, but the gap between formative flood stage and sandbar top‐surface increases with increasing discharge. Finally, linear regression modeling of sandbar erosion demonstrates rates of ESH erosion are on the order of 10 −1 ha/day during high‐flow periods and 10 −2 during low‐flow periods, but sandbar persistence is largely a function of sandbar starting size. The collective observations highlight the importance of large floods (>3‐year recurrence) in creating very large sandbars that persist as high‐quality ESH over periods of years whereas lower‐magnitude, more‐frequent flood events create lower‐quality ESH that typically does not persist into the following nesting season.

Nebraska↗
USGS2020

Scenarios for valuing sample information in natural resources

Uncertainty is ubiquitous in natural resource systems, science and management. Sample data are obtained in order to reduce uncertainty, thereby increasing knowledge and improving resource management, but sampling always comes at a cost of some sort. Is that cost worthwhile? Analysis of the value of sample information ( VSI ) addresses this question. In this paper we develop the valuation of sample information in terms of five elements: (a) a system whose attributes are the focus of analysis; (b) a range of management actions that affect the system's status; (c) uncertainty about system status or structure, as characterized by initial (prior) probabilities of possible system states or structures; (d) an experiment or other information source that produces new data points and updated (posterior) probabilities; and (e) a value measure that is a function of the management action taken, conditional on either the system state or structure. We describe five scenarios for analysing the VSI under uncertainty about system structure and state. Scenarios 1–3 comprise analyses of conditional, expected and optimal expected values of sample information. They focus primarily on choice of management adaptations with new information. Scenarios 4 and 5 involve pre-selected management actions, and are useful for comparing designs of data collection rather than for choosing a management action. These last scenarios expand the framework for VSI to include actions that have been selected independently of the updating of uncertainty. We discuss other extensions of VSI analysis, which include spatial applications, hybrid scenarios, applications involving dynamic systems, and a focus on costs rather than net benefits. Value of sample information analysis holds promise in emerging areas of ecology such as ecological forecasting and the use of remote sensing in conservation, where potential new data from models and satellites can be evaluated in advance, thereby allowing more efficient prioritization of scientific efforts. More generally, VSI can contribute to better ecological understanding and more effective management in a wide range of ecological situations.

Methods in Ecology and Evolution↗
USGS2016

Bitumen prices and structural changes in North American crude oil markets

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

Natural Resources Research↗
USGS1998

Molybdate transport in a chemically complex aquifer: Field measurements compared with solute-transport model predictions

A natural-gradient tracer test was conducted in an unconfined sand and gravel aquifer on Cape Cod, Massachusetts. Molybdate was included in the injectate to study the effects of variable groundwater chemistry on its aqueous distribution and to evaluate the reliability of laboratory experiments for identifying and quantifying reactions that control the transport of reactive solutes in groundwater. Transport of molybdate in this aquifer was controlled by adsorption. The amount adsorbed varied with aqueous chemistry that changed with depth as freshwater recharge mixed with a plume of sewage-contaminated groundwater. Molybdate adsorption was strongest near the water table where p H (5.7) and the concentration of the competing solutes phosphate (2.3 micromolar) and sulfate (86 micromolar) were low. Adsorption of molybdate decreased with depth as p H increased to 6.5, phosphate increased to 40 micromolar, and sulfate increased to 340 micromolar. A one-site diffuse-layer surface-complexation model and a two-site diffuse-layer surface-complexation model were used to simulate adsorption. Reactions and equilibrium constants for both models were determined in laboratory experiments and used in the reactive-transport model PHAST to simulate the two-dimensional transport of molybdate during the tracer test. No geochemical parameters were adjusted in the simulation to improve the fit between model and field data. Both models simulated the travel distance of the molybdate cloud to within 10% during the 2-year tracer test; however, the two-site diffuse-layer model more accurately simulated the molybdate concentration distribution within the cloud.

Massachusetts↗
USGS2002

SUTRA: A model for 2D or 3D saturated-unsaturated, variable-density ground-water flow with solute or energy transport

SUTRA (Saturated-Unsaturated Transport) is a computer program that simulates fluid movement and the transport of either energy or dissolved substances in a subsurface environment. This upgraded version of SUTRA adds the capability for three-dimensional simulation to the former code (Voss, 1984), which allowed only two-dimensional simulation. The code employs a two- or three-dimensional finite-element and finite-difference method to approximate the governing equations that describe the two interdependent processes that are simulated: 1) fluid density-dependent saturated or unsaturated ground-water flow; and 2) either (a) transport of a solute in the ground water, in which the solute may be subject to: equilibrium adsorption on the porous matrix, and both first-order and zero-order production or decay; or (b) transport of thermal energy in the ground water and solid matrix of the aquifer. SUTRA may also be used to simulate simpler subsets of the above processes. A flow-direction-dependent dispersion process for anisotropic media is also provided by the code and is introduced in this report. As the primary calculated result, SUTRA provides fluid pressures and either solute concentrations or temperatures, as they vary with time, everywhere in the simulated subsurface system. SUTRA flow simulation may be employed for two-dimensional (2D) areal, cross sectional and three-dimensional (3D) modeling of saturated ground-water flow systems, and for cross sectional and 3D modeling of unsaturated zone flow. Solute-transport simulation using SUTRA may be employed to model natural or man-induced chemical-species transport including processes of solute sorption, production, and decay. For example, it may be applied to analyze ground-water contaminant transport problems and aquifer restoration designs. In addition, solute-transport simulation with SUTRA may be used for modeling of variable-density leachate movement, and for cross sectional modeling of saltwater intrusion in aquifers at near-well or regional scales, with either dispersed or relatively sharp transition zones between freshwater and saltwater. SUTRA energy-transport simulation may be employed to model thermal regimes in aquifers, subsurface heat conduction, aquifer thermal-energy storage systems, geothermal reservoirs, thermal pollution of aquifers, and natural hydrogeologic convection systems. Mesh construction, which is quite flexible for arbitrary geometries, employs quadrilateral finite elements in 2D Cartesian or radial-cylindrical coordinate systems, and hexahedral finite elements in 3D systems. 3D meshes are currently restricted to be logically rectangular; in other words, they are similar to deformable finite-difference-style grids. Permeabilities may be anisotropic and may vary in both direction and magnitude throughout the system, as may most other aquifer and fluid properties. Boundary conditions, sources and sinks may be time dependent. A number of input data checks are made to verify the input data set. An option is available for storing intermediate results and restarting a simulation at the intermediate time. Output options include fluid velocities, fluid mass and solute mass or energy budgets, and time-varying observations at points in the system. Both the mathematical basis for SUTRA and the program structure are highly general, and are modularized to allow for straightforward addition of new methods or processes to the simulation. The FORTRAN-90 coding stresses clarity and modularity rather than efficiency, providing easy access for later modifications.

Water-Resources Investigations Report↗
USGS2006

Linking landscape characteristics to mineral site use by band-tailed pigeons in Western Oregon: Coarse-filter conservation with fine-filter tuning

Mineral sites are scarce resources of high ion concentration used heavily by the Pacific Coast subpopulation of band-tailed pigeons. Over 20% of all known mineral sites used by band-tailed pigeons in western Oregon, including all hot springs, have been abandoned. Prior investigations have not analyzed stand or landscape level habitat composition in relation to band-tailed pigeon use of mineral sites. We used logistic regression models to evaluate the influence of habitat types, identified from Gap Analysis Program (GAP) products at two spatial scales, on the odds of mineral site use in Oregon (n = 69 currently used and 20 historically used). Our results indicated that the odds of current use were negatively associated with non-forested terrestrial and private land area around mineral sites. Similarly, the odds of current mineral site use were positively associated with forested and special status (GAP stewardship codes 1 and 2) land area. The most important variable associated with the odds of mineral site use was the amount of non-forested land cover at either spatial scale. Our results demonstrate the utility of meso-scale geographic information designed for regional, coarse-filter approaches to conservation in fine-filter investigation of wildlife-habitat relationships. Adjacent landcover and ownership status explain the pattern of use for known mineral sites in western Oregon. In order for conservation and management activities for band-tailed pigeons to be successful, mineral sites need to be addressed as important and vulnerable resources. Management of band-tailed pigeons should incorporate the potential for forest management activities and land ownership patterns to influence the risk of mineral site abandonment.

Natural Areas Journal↗
USGS2000

Delineation and Analysis of Uncertainty of Contributing Areas to Wells at the Southbury Training School, Southbury, Connecticut

Contributing areas to public-supply wells at the Southbury Training School in Southbury, Connecticut, were mapped by simulating ground-water flow in stratified glacial deposits in the lower Transylvania Brook watershed. The simulation used nonlinear regression methods and informational statistics to estimate parameters of a ground-water flow model using drawdown data from an aquifer test. The goodness of fit of the model and the uncertainty associated with model predictions were statistically measured. A watershed-scale model, depicting large-scale ground-water flow in the Transylvania Brook watershed, was used to estimate the distribution of groundwater recharge. Estimates of recharge from 10 small basins in the watershed differed on the basis of the drainage characteristics of each basin. Small basins having well-defined stream channels contributed less ground-water recharge than basins having no defined channels because potential ground-water recharge was carried away in the stream channel. Estimates of ground-water recharge were used in an aquifer-scale parameter-estimation model. Seven variations of the ground-water-flow system were posed, each representing the ground-water-flow system in slightly different but realistic ways. The model that most closely reproduced measured hydraulic heads and flows with realistic parameter values was selected as the most representative of the ground-water-flow system and was used to delineate boundaries of the contributing areas. The model fit revealed no systematic model error, which indicates that the model is likely to represent the major characteristics of the actual system. Parameter values estimated during the simulation are as follows: horizontal hydraulic conductivity of coarse-grained deposits, 154 feet per day; vertical hydraulic conductivity of coarse-grained deposits, 0.83 feet per day; horizontal hydraulic conductivity of fine-grained deposits, 29 feet per day; specific yield, 0.007; specific storage, 1.6E-05. Average annual recharge was estimated using the watershed-scale model with no parameter estimation and was determined to be 24 inches per year in the valley areas and 9 inches per year in the upland areas. The parameter estimates produced in the model are similar to expected values, with two exceptions. The estimated specific yield of the stratified glacial deposits is lower than expected, which could be caused by the layered nature of the deposits. The recharge estimate produced by the model was also lower?about 32 percent of the average annual rate. This could be caused by the timing of the aquifer test with respect to the annual cycle of ground-water recharge, and by some of the expected recharge going to parts of the flow system that were not simulated. The data used in the calibration were collected during an aquifer test from October 30 to November 4, 1996. The model fit was very good, as indicated by the correlation coefficient (0.999) between the weighted simulated values and weighted observed values. The model also reproduced the general rise in ground-water levels caused by ground-water recharge and the cyclic fluctuations caused by pumping prior to the aquifer test. Contributing areas were delineated using a particle-tracking procedure. Hypothetical particles of water were introduced at each model cell in the top layer and were tracked to determine whether or not they reached the pumped well. A deterministic contributing area was calculated using the calibrated model, and a probabilistic contributing area was calculated using a Monte Carlo approach along with the calibrated model. The Monte Carlo simulation was done, using the parameter variance/covariance matrix generated by the regression model, to estimate probabilities associated with the contributing area to the wells. The probabilities arise from uncertainty in the estimated parameter values, which in turn arise from the adequacy of the data available to comprehensively describe the groundwater-flow sy

Water-Resources Investigations Report↗
USGS2018

Contaminants in tropical island streams and their biota

Environmental contamination is problematic for tropical islands due to their typically dense human populations and competing land and water uses. The Caribbean island of Puerto Rico (USA) has a long history of anthropogenic chemical use, and its human population density is among the highest globally, providing a model environment to study contaminant impacts on tropical island stream ecosystems. Polycyclic Aromatic Hydrocarbons, historic-use chlorinated pesticides, current-use pesticides, Polychlorinated Biphenyls (PCBs), and metals (mercury, cadmium, copper, lead, nickel, zinc, and selenium) were quantified in the habitat and biota of Puerto Rico streams and assessed in relation to land-use patterns and toxicological thresholds. Water, sediment, and native fish and shrimp species were sampled in 13 rivers spanning broad watershed land-use characteristics during 2009–2010. Contrary to expectations, freshwater stream ecosystems in Puerto Rico were not severely polluted, likely due to frequent flushing flows and reduced deposition associated with recurring flood events. Notable exceptions of contamination were nickel in sediment within three agricultural watersheds (range 123–336 ppm dry weight) and organic contaminants (PCBs, organochlorine pesticides) and mercury in urban landscapes. At an urban site, PCBs i n several fish species (Mountain Mullet Agonostomus monticola [range 0.019–0.030 ppm wet weight] and American Eel Anguilla rostrata [0.019–0.031 ppm wet weight]) may pose human health hazards, with concentrations exceeding the U.S. Environmental Protection Agency (EPA) consumption limit for 1 meal/month. American Eel at the urban site also contained dieldrin (range < detection-0.024 ppm wet weight) that exceeded the EPA maximum allowable consumption limit. The Bigmouth Sleeper Gobiomorous dormitor , an important piscivorus sport fish, accumulated low levels of organic contaminants in edible muscle tissue (due to its low lipid c ontent) and may be most suitable for human consumption island-wide; only mercury at one site (an urban location) exceeded EPA's consumption limit of 3 meals/month for this species. These results comprise the first comprehensive island-wide contaminant assessment of Puerto Rico streams and biota and provide natural resource and public health agencies here and in similar tropical islands elsewhere with information needed to guide ecosystem and fisheries conservation and management and human health risk assessment.

Environmental Research↗