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At least 1,441 records · Page 80Linked to original sources

USGS2007

Hydrogeologic characteristics of the St. Croix River basin, Minnesota and Wisconsin: Implications for the susceptibility of ground water to potential contamination

Population growth in the St. Croix River Basin in Minnesota and Wisconsin has intensified concerns of county resource managers and the National Park Service, which is charged with protecting the St. Croix National Scenic Riverway, about the potential for ground-water contamination in the basin. This report describes a previously developed method that was adapted to illustrate potential ground-water-contamination susceptibility in the St. Croix River Basin. The report also gives an estimate of ground-water-residence time and surface-water/ground-water interaction as related to natural attenuation and movement of contaminants in five tributary basins. A ground-water-contamination-susceptibility map was adapted from a state-wide map of Wisconsin to the St. Croix River Basin by use of well-driller construction records and regional maps of aquifer properties in Minnesota and Wisconsin. Measures of various subsurface properties were combined to generate a spatial index of susceptibility. The subjective index method developed for the State of Wisconsin by Schmidt (1987) 1 was not derived from analyses of water-quality data or physical processes. Nonetheless, it was adapted for this report to furnish a seamless map across state boundaries that would be familiar to many resource managers. Following this method, areas most susceptible to contamination appear to have coarse-grained sediments (sands or gravels) and shallow water tables or are underlain by carbonate-bedrock aquifers. The least susceptible areas appear to have fine-grained sediments and deep water tables. If an aquifer becomes contaminated, the ground-water-residence time can affect potential natural attenuation along the ground-water-flow path. Mean basin ground-water-residence times were computed for the Apple, Kettle, Kinnickinnic, Snake and Sunrise River Basins, which are tributary basins to the St. Croix Basin, by use of average aquifer properties of saturated thickness, porosity, and recharge rates. The Apple River Basin had the shortest mean ground-water-residence times (20–120 years), owing largely to the moderate saturated thickness and high recharge rate in the basin. The Kinnickinnic and Sunrise River Basins had the longest mean residence times (60–350 and 70–390 years, respectively) chiefly because of the relatively large saturated thickness of the basins. Owing to limitations of the residence-time calculations, actual ground-water-residence times will vary around the mean values within each basin and may range from days or weeks in karst carbonate aquifers to millennia in deep confined sandstone aquifers. Areas of relatively short residence time (less than the median residence time in each basin) were identified by use of ground-water-flow models for each of the five tributary basins. Results of simulations show that these areas, in which contaminants may have relatively less time for natural attenuation along the short flow paths, generally occur near streams and rivers where ground water discharges to the surface. Finally, the ground-water-flow models were used to simulate ground-water/surface-water interaction in the five tributary basins. Results of simulations show that some lakes and reservoirs leak surface water into the ground-water-flow system on their downgradient side, where the surface-water outflow has been restricted by a dam or a naturally constricted outlet. These locations are noteworthy because contaminated surface waters could potentially enter the ground-water-flow system at these locations.

Minnesota, Wisconsin↗

USGS2000

Unsaturated‐zone wedge beneath a large, natural lake

Lake Belle Taine (480 ha) in north central Minnesota receives on average 76,000 m 3 d −1 of water from Little Sand Creek but has no outlet. Water seeps out of the lake, flows through glacial outwash, and discharges into three nearby lakes with stages 13–14 m lower than Belle Taine. Seepage‐meter data indicate water is seeping out of Belle Taine at velocities up to 263 cm d −1 . Hydraulic‐head measurements made in the lake bed indicate the sediments are unsaturated beneath a portion of the lake edge, and a wedge of unsaturated sediments extends beneath the lake bed as much as 20 m from the shoreline. At the shoreline the water table is as much as 6.7 m below the lake surface. Modeling results of a similar hypothetical setting indicate that the horizontal extent of an unsaturated zone beneath a lake depends on (1) the permeability contrast between the outwash and the lake bed, (2) anisotropy, (3) lake bed slope, and (4) thickness of the lower‐permeability lake bed sediments. Although rarely documented, unsaturated sediments beneath a lake may not be extremely uncommon. Similar, much smaller unsaturated‐zone areas also have been observed beneath two other lakes in Minnesota.

Minnesota↗

USGS2014

Quantifying the predictive consequences of model error with linear subspace analysis

All computer models are simplified and imperfect simulators of complex natural systems. The discrepancy arising from simplification induces bias in model predictions, which may be amplified by the process of model calibration. This paper presents a new method to identify and quantify the predictive consequences of calibrating a simplified computer model. The method is based on linear theory, and it scales efficiently to the large numbers of parameters and observations characteristic of groundwater and petroleum reservoir models. The method is applied to a range of predictions made with a synthetic integrated surface-water/groundwater model with thousands of parameters. Several different observation processing strategies and parameterization/regularization approaches are examined in detail, including use of the Karhunen-Loève parameter transformation. Predictive bias arising from model error is shown to be prediction specific and often invisible to the modeler. The amount of calibration-induced bias is influenced by several factors, including how expert knowledge is applied in the design of parameterization schemes, the number of parameters adjusted during calibration, how observations and model-generated counterparts are processed, and the level of fit with observations achieved through calibration. Failure to properly implement any of these factors in a prediction-specific manner may increase the potential for predictive bias in ways that are not visible to the calibration and uncertainty analysis process.

Water Resources Research↗

USGS2020

Stress gradients interact with disturbance to reveal alternative states in salt marsh: Multivariate resilience at the landscape scale

Stress gradients influence many ecosystem processes and properties, including ecosystem recovery from and resistance to disturbance. While recent analytical approaches have advanced multivariate metrics of ecosystem resilience that allow quantification of conceptual resilience models and identification of thresholds of state change, these approaches are not often translated to landscape scales. Using natural and restored salt marshes in Louisiana, USA, we quantified plant community recovery and resistance metrics along flooding stress gradients. n ‐dimensional hypervolumes of plant community biomass and structure were simulated using field data collected from disturbance‐recovery experiments. The relationships between multivariate resilience metrics and flooding stress gradients were then mapped at community‐ and landscape‐relevant scales by scaling with airborne‐derived data across the region. Greater pre‐disturbance abiotic stress decreased live belowground, but not aboveground, biomass, and ultimately led to lower post‐disturbance total recovery, recovery rates, and resistance of plant communities. Vegetated plots flooded >52% of the time transitioned to an alternative, unvegetated state after disturbance. Mapping revealed differences in spatial patterns of resilience‐ highlighting low, interior marsh edges as especially vulnerable to the combination of chronic flooding stress and acute disturbance. At the landscape scale, approximately half of the area (48%) is vulnerable to state change after pulse disturbances. Synthesis . Ultimately, we quantify the ball‐and‐cup conceptual model for a salt marsh ecosystem and its alternative state, mudflat. We find that increasing abiotic stress due to climate change diminishes ecosystem resilience, but the interaction with common episodic disturbances is necessary to reveal transitions to alternative states and quantify state change thresholds. Quantifying and mapping resilience and where alternative states may exist in this fashion improves ecologists’ ability to investigate the mechanisms of stress gradient control on emergent ecosystem properties, while providing spatially explicit resources for managing ecosystems according to their projected resilience.

Louisiana↗

USGS2021

A structured approach to remediation site assessment: Lessons from 15 years of fish spawning habitat creation in the St. Clair‐Detroit River system

Ideally, restoration re‐establishes natural processes in degraded habitats (e.g., flow and sediment regimes). However, in altered systems where process‐based restoration is not feasible, habitat construction is another approach to mitigate degradation. Because habitat construction does not directly focus on restoring processes that build and maintain desired habitats, projects must be developed and placed within the contemporary regulatory, ecological, and hydrogeomorphic context of a system, to maximize effectiveness. Here, we develop a framework for evaluating the regulatory, ecological, and hydrogeomorphic components using 15 years of fish spawning habitat construction in the St. Clair‐Detroit River System. The process began by identifying regulatory requirements at a coarse resolution to quickly focus on locations where ecological potential and hydrogeomorphic constraints could be assessed at finer resolutions. Next, ecological potential was assessed using a lithophilic fish spawning habitat suitability index. The suitability index identified five sites for habitat construction and Lake sturgeon spawning was documented at each site following construction. However, qualitative monitoring showed fine sediments accumulated at older sites. Thus, geomorphic assessments were incorporated to identify sediment sources and model flow within targeted areas. Since geomorphic assessments required the finest resolution and had the most uncertainty, they were conducted after broad‐scale regulatory considerations and ecological assessments narrowed focus to a few candidate sites. The order of operations identified in this case study evolved from the iterative approach of the restoration team, but in retrospect, it helped develop a framework that directed project development resources to aspects with more uncertainty, where learning is most critical.

Michigan, Ontario↗

USGS2002

Three-dimensional measurements of flow in uncased wells completed in basalt, Mountain Home Air Force Base, Idaho, March 2000

Several ground-water monitoring wells on the Mountain Home Air Force Base in southwestern Idaho were constructed in February 2000 to replace existing monitoring wells that became ineffective as a result of declining water levels. Upon completion of the replacement wells, borehole geophysical logs were collected, including natural gamma radiation, electromagnetic induction, caliper, fluid temperature, and resistivity. A prototype borehole acoustic doppler velocimeter (B-ADV) was used to make experimental three-dimensional measurements of lateral and vertical flow in two of the replacement wells, MW11–2 and MW3–2, each 450 feet deep, to better understand ground-water flow in the basalt underlying this area. Measurements indicated two independent flow zones in each well: unit B, from about 380 to about 415 feet below land surface, and unit C, from about 415 to about 430 feet below land surface. In each well, direction of flow in unit B was north-northwest toward Canyon Creek and, in unit C, south-southwest toward the Snake River. Measurements also indicated downward intraborehole flow in both wells. Unit B appeared to represent a local-scale flow regime; unit C appeared to represent a regional flow regime. This information suggests the existence of a complex three-dimensional hydrogeologic setting that cannot be discriminated easily on conventional waterlevel maps. Although data from only two wells are insufficient to construct a conceptual model of the ground-water flow regime, these experimental results demonstrate the capability of the B-ADV to obtain detailed flow measurements that, combined with data from other types of geophysical logs, discrete measurements of hydraulic head, and water chemistry, would aid in future studies and management of the ground-water resources, including contaminant transport and remediation.

Idaho↗

USGS2002

A reconnaissance method for delineation of tracts for regional-scale mineral-resource assessment based on geologic-map data

The U.S. Geological Survey (USGS) is proposing to conduct a global mineral-resource assessment using geologic maps, significant deposits, and exploration history as minimal data requirements. Using a geologic map and locations of significant pluton-related deposits, the pluton-related-deposit tract maps from the USGS national mineral-resource assessment have been reproduced with GIS-based analysis and modeling techniques. Agreement, kappa, and Jaccard's C correlation statistics between the expert USGS and calculated tract maps of 87%, 40%, and 28%, respectively, have been achieved using a combination of weights-of-evidence and weighted logistic regression methods. Between the experts' and calculated maps, the ranking of states measured by total permissive area correlates at 84%. The disagreement between the experts and calculated results can be explained primarily by tracts defined by geophysical evidence not considered in the calculations, generalization of tracts by the experts, differences in map scales, and the experts' inclusion of large tracts that are arguably not permissive. This analysis shows that tracts for regional mineral-resource assessment approximating those delineated by USGS experts can be calculated using weights of evidence and weighted logistic regression, a geologic map, and the location of significant deposits. Weights of evidence and weighted logistic regression applied to a global geologic map could provide quickly a useful reconnaissance definition of tracts for mineral assessment that is tied to the data and is reproducible.

Natural Resources Research↗

USGS2010

Debris flow rheology: Experimental analysis of fine-grained slurries

The rheology of slurries consisting of ≤2-mm sediment from a natural debris flow deposit was measured using a wide-gap concentric-cylinder viscometer. The influence of sediment concentration and size and distribution of grains on the bulk rheological behavior of the slurries was evaluated at concentrations ranging from 0.44 to 0.66. The slurries exhibit diverse rheological behavior. At shear rates above 5 s −1 the behavior approaches that of a Bingham material; below 5 s −1 , sand exerts more influence and slurry behavior deviates from the Bingham idealization. Sand grain interactions dominate the mechanical behavior when sand concentration exceeds 0.2; transient fluctuations in measured torque, time-dependent decay of torque, and hysteresis effects are observed. Grain rubbing, interlocking, and collision cause changes in packing density, particle distribution, grain orientation, and formation and destruction of grain clusters, which may explain the observed behavior. Yield strength and plastic viscosity exhibit order-of-magnitude variation when sediment concentration changes as little as 2–4%. Owing to these complexities, it is unlikely that debris flows can be characterized by a single rheological model.

Water Resources Research↗

USGS1977

Ground-water supplies in the Murfreesboro area, Tennessee

Ground water occurs in the Murfreesboro area in solution openings in the otherwise dense paleozoic limestones that underlie most of central Tennessee. Test drilling based on conceptual models of ground-water occurrence in carbonate-rock aquifers indicate that multimillion-gallon-per-day supplies could be developed from strategically located production wells in the Shiloh and Overall Creek localities. The Shiloh locality which encompasses an elongated synclinal depression in the bedrock has the potential to supply 5 to 8 million gallons per day. The Overall Creek locality which straddles a joint-oriented lineament has the potential to supply 3 to 6 million gallons per day. Some local springs could be used as a supplemental source of potable water, but storage facilities would be needed to offset poorly sustained flows during dry periods. An exception is Fox Camp Spring which appears to be a natural well. The quality of ground water in the Murfreesboro area is typically hard, moderately mineralized and moderately to highly alkaline. Although the shallowest aquifers are subject to bacterial contamination from the land surface, aquifers beneath a depth of 100 feet are prone to yield potable water. (Woodard-USGS)

Tennessee↗

USGS2014

Management and monitoring of the endangered Shenandoah salamander under climate change: Workshop report 10-12 April 2012

Here we report on a structured decision making (SDM) process to identify management strategies to ensure persistence of the federally endangered Shenandoah salamander (Plethodon shenandoah), given that it may be at increased extinction risk under projected climate change. The focus of this report is the second of two SDM workshops; in the first workshop, participants developed a prototype of the decision, including problem frame, management objectives and a suite of potential management strategies, predictive models to inform the decision and link alternatives with the objectives to identify potential solutions, and identified data needs to reduce key uncertainties in the decision. Participants in this second workshop included experts in National Park Service policy at multiple administrative levels, who refined objectives, further evaluated the initial management alternatives, and discussed policy constraints on implementing active management for the species and its high-elevation habitat. The conclusion of the second workshop was similar to that of the first: the current state of information and objectives suggest that there is some value in considering active management to reduce the long-term extinction risk for the species, though there are institutional conservative policies to implementing active management at range-wide scales. The workshop participants also emphasized a conservative NPS management philosophy, including caution in implementing management actions that may ultimately harm the system, a stated assumption that ecosystem changes were “natural” unless demonstrated otherwise (therefore not warranting active management to mitigate), and a need to demonstrate that extinction risk is tied to anthropogenic influence prior to taking active management to mitigate specific anthropogenic influences. Even within a protected area having minimal human disturbance, intertwined environmental variables and interspecific relationships that drive population trends challenge our ability to demonstrate direct links with (anthropogenically influenced) climate change and the decline of a species. Thus while this policy may reduce the potential for injurious management, it may also necessitate extraordinary resources to reduce uncertainty regarding fundamental drivers of species decline prior to taking action.

Natural Resource Report↗

USGS2008

Framework for Understanding Structural Errors (FUSE): A modular framework to diagnose differences between hydrological models

The problems of identifying the most appropriate model structure for a given problem and quantifying the uncertainty in model structure remain outstanding research challenges for the discipline of hydrology. Progress on these problems requires understanding of the nature of differences between models. This paper presents a methodology to diagnose differences in hydrological model structures: the Framework for Understanding Structural Errors (FUSE). FUSE was used to construct 79 unique model structures by combining components of 4 existing hydrological models. These new models were used to simulate streamflow in two of the basins used in the Model Parameter Estimation Experiment (MOPEX): the Guadalupe River (Texas) and the French Broad River (North Carolina). Results show that the new models produced simulations of streamflow that were at least as good as the simulations produced by the models that participated in the MOPEX experiment. Our initial application of the FUSE method for the Guadalupe River exposed relationships between model structure and model performance, suggesting that the choice of model structure is just as important as the choice of model parameters. However, further work is needed to evaluate model simulations using multiple criteria to diagnose the relative importance of model structural differences in various climate regimes and to assess the amount of independent information in each of the models. This work will be crucial to both identifying the most appropriate model structure for a given problem and quantifying the uncertainty in model structure. To facilitate research on these problems, the FORTRAN‐90 source code for FUSE is available upon request from the lead author.

Water Resources Research↗

USGS2012

A science plan for a comprehensive assessment of water supply in the region underlain by fractured rock in Maryland

The fractured rock region of Maryland, which includes land areas north and west of the Interstate 95 corridor, is the source of water supply for approximately 4.4 million Marylanders, or approximately 76 percent of the State's population. Whereas hundreds of thousands of residents rely on wells (both domestic and community), millions rely on surface-water sources. In this region, land use, geology, topography, water withdrawals, impoundments, and other factors affect water-flow characteristics. The unconfined groundwater systems are closely interconnected with rivers and streams, and are affected by seasonal and climatic variations. During droughts, groundwater levels drop, thereby decreasing well yields, and in some cases, wells have gone dry. Low ground-water levels contribute to reduced streamflows, which in turn, can lead to reduced habitat for aquatic life. Increased demand, over-allocation, population growth, and climate change can affect the future sustainability of water supplies in the region of Maryland underlain by fractured rock. In response to recommendations of the 2008 Advisory Committee on the Management and Protection of the State's Water Resources report, the Maryland Department of the Environment's Water Supply Program, the Maryland Geological Survey, the Maryland Department of Natural Resources, Monitoring and Non-Tidal Assessment (MANTA) Division, and the U.S. Geological Survey have developed a science plan for a comprehensive assessment that will provide new scientific information, new data analysis, and new tools for the State to better manage water resources in the fractured rock region of Maryland. The science plan lays out five goals for the comprehensive assessment: (1) develop tools for the improved management and investigation of groundwater and surface-water resources; (2) characterize factors affecting reliable yields of individual groundwater and surface-water supplies; (3) investigate impacts on nearby water withdrawal users caused by groundwater and surface-water withdrawals; (4) assess the role of streamflow and water withdrawals on the ecological integrity of streams; and (5) improve understanding of the distribution of water-quality conditions in fractured rock aquifers. To accomplish these goals, accurate data collection, review, and analysis are needed, including the study of "Research Watersheds" that can provide detailed information about the potential effects that climate change and water withdrawals may have on groundwater, streamflow, and aquatic life. The assessment planning started in 2009 and is being conducted with close interagency coordination. A Fractured Rock Aquifer Information System is currently (2012) undergoing initial development. Other major tasks that will be performed include the development of work plans for each science goal, the estimation of daily streamflow at ungaged streams, and the design and implementation of Research Watersheds. Finally, scenarios will be modeled to evaluate current water allocation permitting methodologies, investigate effects on nearby water withdrawal users caused by groundwater and surface-water withdrawals, and assess the potential impacts of climate change on water resources. Desktop and Web-based tools will be developed in order to meet the diverse research needs of the assessment. These tools, including the Fractured Rock Aquifer Information System will be continuously improved during the assessment to store relevant groundwater and surface-water data in spatially referenced databases, estimate streamflows, locate higher-yielding wells, estimate the impacts of withdrawals on nearby users, and assess the cumulative impacts of withdrawals on the aquatic resource. Tools will be developed to serve the needs of many audiences, including water resource managers, water suppliers, planners, policymakers, and other scientific investigators.

Maryl↗

USGS2018

Grizzly bear depredation on grazing allotments in the Yellowstone ecosystem

Grizzly bear (Ursus arctos) conflicts with humans, including livestock depredation on public land grazing allotments, have increased during the last several decades within the Greater Yellowstone Ecosystem (GYE) in the western United States as the grizzly bear population has grown in number and occupied range. Minimizing conflicts and improving conservation efficacy requires information on the relationships between livestock depredations, allotment management, grizzly bear habitat conditions, and their interactions. We used generalized linear mixed models to evaluate spatio-temporal relationships between grizzly bear depredation of livestock and the characteristics of 316 United States Department of Agriculture Forest Service and National Park Service grazing allotments in the GYE during 1992–2014. We evaluated relationships at 2 spatial extents, representing daily and annual grizzly bear activity areas. During the study period, more grazing allotments became occupied by grizzly bears and most livestock depredations were associated with these areas of population expansion. Number of livestock (beta = 1.15 +/- 0.19 [SE]) and grizzly bear density index (beta = 1.13 +/- 0.10) had the greatest effects on the number of livestock depredation events relative to other allotment attributes. Estimated number of depredation events increased by approximately 20% when cow-calf pairs increased by 100 pairs and grizzly bear density index increased by 1 bear/196 km2 (the average annual home-range size of a female grizzly bear in the GYE). Additionally, grazing allotment size was positively related to the number of depredation events (beta = 0.56 +/- 0.16), whereas the presence of bull cattle or horses was associated with an approximately 50% reduction in depredations (beta = -0.71 +/- 0.37). Livestock depredation events were greater for allotments with lower road density (beta = -0.89 +/- 0.28), less rugged terrain (beta = -0.57 +/- 0.25), higher vegetative primary productivity (beta = 0.33 +/- 0.16), and more whitebark pine coverage (beta = 0.30 +/- 0.15). Relationships between depredations and grizzly bear habitat conditions varied across spatial extents. As the grizzly bear population continues to expand, natural resource managers and livestock producers could focus efforts on allotments with a higher density of grizzly bears, fewer roads, and quality grizzly bear habitat, including higher vegetative productivity, when developing cooperative management plans and preventative measures to reduce the likelihood of depredation. The perspectives gained from our analysis provide context for long-term, landscape-level planning to accommodate livestock production on public lands while meeting conservation goals for grizzly bears.

Idaho, Montana, Wyoming↗

USGS2012

National assessment of shoreline change: Historical shoreline change in the Hawaiian Islands

Sandy beaches of the United States are some of the most popular tourist and recreational destinations. Coastal property constitutes some of the most valuable real estate in the country. Beaches are an ephemeral environment between water and land with unique and fragile natural ecosystems that have evolved in equilibrium with the ever-changing winds, waves, and water levels. Beachfront lands are the site of intense residential and commercial development even though they are highly vulnerable to several natural hazards, including marine inundation, flooding and drainage problems, effects of storms, sea-level rise, and coastal erosion. Because the U.S. population continues to shift toward the coast where valuable coastal property is vulnerable to erosion, the U.S. Geological Survey (USGS) is conducting a national assessment of coastal change. One aspect of this effort, the National Assessment of Shoreline Change, uses shoreline position as a proxy for coastal change because shoreline position is one of the most commonly monitored indicators of environmental change (for example, Fletcher, 1992; Dolan and others, 1991; Douglas and others, 1998; Galgano and others, 1998). Additionally, the National Research Council (1990) recommended the use of historical shoreline analysis in the absence of a widely accepted model of shoreline change. A principal purpose of the USGS shoreline change research is to develop a common methodology so that shoreline change analyses for the continental U.S., portions of Hawaii, and Alaska can be updated periodically in a consistent and systematic manner. The primary objectives of this study were to (1) develop and implement improved methods of assessing and monitoring shoreline movement, and (2) improve current understanding of the processes controlling shoreline movement. Achieving these ongoing long-term objectives requires research that (1) examines the original sources of shoreline data (for example, maps, air photos, global positioning system (GPS), Light Detection and Ranging (lidar)); (2) evaluates the utility of different shoreline proxies (for example, geomorphic feature, water mark, tidal datum, elevation), including the errors associated with each; (3) investigates bias and potential errors associated with integrating different shoreline proxies from different sources; (4) develops standard, uniform methods of shoreline change analysis; (5) examines the effects of human activities on shoreline movement and rates of change; and (6) investigates alternative mathematical methods for calculating historical rates of change and uncertainties associated with them. This report summarizes historical shoreline changes on the three most densely populated islands of the eight main Hawaiian Islands: Kauai, Oahu, and Maui. The report emphasizes the hazard from “chronic” (decades to centuries) erosion at regional scales and strives to relate this hazard to the body of knowledge regarding coastal geology of Hawaii because of its potential impact on natural resources, the economy, and society. Results are organized by coastal regions (island side) and sub-regions (common littoral characteristics). This report of Hawaii coasts is part of a series of reports that include text summarizing methods, results, and implications of the results. In addition, geographic information system (GIS) data used in the analyses are made available for download (Romine and others, 2012). The rates of shoreline change and products presented in this report are not intended for site-specific analysis of shoreline movement, nor are they intended to replace any official source of shoreline change information identified by local or State government agencies, or other Federal entities that are used for regulatory purposes. Rates of shoreline change presented herein may differ from other published rates, and differences do not necessarily indicate that the other rates are inaccurate. Some discrepancies are to be expected, considering the many possible ways of determining shoreline positions and rates of change, and the inherent uncertainty in calculating these rates. Rates of shoreline change presented in this report represent shoreline movement under past conditions and are not intended for use in predicting future shoreline positions or future rates of shoreline change.

Hawai'i↗

USGS1980

Research on interactive genetic-geological models to evaluate favourability for undiscovered uranium resources

Current methods of evaluating favourability for undiscovered uranium resources are unduly subjective, quite possibly inconsistent and, as a consequence, of questionable reliability. This research is aimed at reducing the subjectivity and increasing the reliability by designing an improved method that depends largely on geological data and their statistical frequency of occurrence. This progress report outlines a genetic approach to modelling the geological factors that controlled uranium mineralization in order to evaluate the favourability for the occurrence of undiscovered uranium deposits of the type modeled. A genetic model is constructed from all the factors that describe the processes, in chronological sequence, that formed uranium deposits thought to have a common origin. The field and laboratory evidence for the processes constitute a geologic occurrence base that parallels the chronological sequence of events. The genetic model and the geologic-occurrence base are portrayed as two columns of an interactive matrix called the "genetic-geologic model". For each column, eight chronological stages are used to describe the overall formation of the uranium deposits. These stages consist of (1) precursor processes; (2) host-rock formation; (3) preparation of host-rock; (4) uranium-source development; (5) transport of uranium; (6) primary uranium deposition; (7) post-deposition modification; and (8) preservation. To apply the genetic-geological model to evaluate favourability, a question is posed that determines the presence or absence of each attribute listed under the geologic-occurrence base. By building a logic circuit of the attributes according to either their essential or non-essential nature, the resultant match between a well-documented control area and the test area may be determined. The degree of match is a measure of favourability for uranium occurrence as hypothesized in the genetic model. This process of geological decision analysis results in a series of favourability maps that can be combined into a final composite favourability map.

Conference Paper↗

USGS2014

Hydrology and numerical simulation of groundwater movement and heat transport in Snake Valley and surrounding areas, Juab, Miller, and Beaver Counties, Utah, and White Pine and Lincoln Counties, Nevada

Snake Valley and surrounding areas, along the Utah-Nevada state border, are part of the Great Basin carbonate and alluvial aquifer system. The groundwater system in the study area consists of water in unconsolidated deposits in basins and water in consolidated rock underlying the basins and in the adjacent mountain blocks. Most recharge occurs from precipitation on the mountain blocks and most discharge occurs from the lower altitude basin-fill deposits mainly as evapotranspiration, springflow, and well withdrawals. The Snake Valley area regional groundwater system was simulated using a three-dimensional model incorporating both groundwater flow and heat transport. The model was constructed with MODFLOW-2000, a version of the U.S. Geological Survey’s groundwater flow model, and MT3DMS, a transport model that simulates advection, dispersion, and chemical reactions of solutes or heat in groundwater systems. Observations of groundwater discharge by evapotranspiration, springflow, mountain stream base flow, and well withdrawals; groundwater-level altitudes; and groundwater temperatures were used to calibrate the model. Parameter values estimated by regression analyses were reasonable and within the range of expected values. This study represents one of the first regional modeling efforts to include calibration to groundwater temperature data. The inclusion of temperature observations reduced parameter uncertainty, in some cases quite significantly, over using just water-level altitude and discharge observations. Of the 39 parameters used to simulate horizontal hydraulic conductivity, uncertainty on 11 of these parameters was reduced to one order of magnitude or less. Other significant reductions in parameter uncertainty occurred in parameters representing the vertical anisotropy ratio, drain and river conductance, recharge rates, and well withdrawal rates. The model provides a good representation of the groundwater system. Simulated water-level altitudes range over almost 2,000 meters (m); 98 percent of the simulated values of water-level altitudes in wells are within 30 m of observed water-level altitudes, and 58 percent of them are within 12 m. Nineteen of 20 simulated discharges are within 30 percent of observed discharge. Eighty-one percent of the simulated values of groundwater temperatures in wells are within 2 degrees Celsius (°C) of the observed values, and 55 percent of them are within 0.75 °C. The numerical model represents a more robust quantification of groundwater budget components than previous studies because the model integrates all components of the groundwater budget. The model also incorporates new data including (1) a detailed hydrogeologic framework, and (2) more observations, including several new water-level altitudes throughout the study area, several new measurements of spring discharge within Snake Valley which had not previously been monitored, and groundwater temperature data. Uncertainty in the estimates of subsurface flow are less than those of previous studies because the model balanced recharge and discharge across the entire simulated area, not just in each hydrographic area, and because of the large dataset of observations (water-level altitudes, discharge, and temperatures) used to calibrate the model and the resulting transmissivity distribution. Groundwater recharge from precipitation and unconsumed irrigation in Snake Valley is 160,000 acre-feet per year (acre-ft/yr), which is within the range of previous estimates. Subsurface inflow from southern Spring Valley to southern Snake Valley is 13,000 acre-ft/yr and is within the range of previous estimates; subsurface inflow from Spring Valley to Snake Valley north of the Snake Range, however, is only 2,200 acre-ft/yr, which is much less than has been previously estimated. Groundwater discharge from groundwater evapotranspiration and springs is 100,000 acre-ft/yr, and discharge to mountain streams is 3,300 acre-ft/yr; these are within the range of previous estimates. Current well withdrawals are 28,000 acre-ft/yr. Subsurface outflow from Snake Valley moves into Pine Valley (2,000 acre-ft/yr), Wah Wah Valley (23 acre-ft/yr), Tule Valley (33,000 acre-ft/yr), Fish Springs Flat (790 acre-ft/yr), and outside of the study area towards Great Salt Lake Desert (8,400 acre-ft/yr); these outflows, totaling about 44,000 acre-ft/yr, are within the range of previous estimates. The subsurface flow amounts indicate the degree of connectivity between hydrographic areas within the study area. The simulated transmissivity and locations of natural discharge, however, provide a better estimate of the effect of groundwater withdrawals on groundwater resources than does the amount and direction of subsurface flow between hydrographic areas. The distribution of simulated transmissivity throughout the study area includes many areas of high transmissivity within and between hydrographic areas. Increased well withdrawals within these high transmissivity areas will likely affect a large part of the study area, resulting in declining groundwater levels, as well as leading to a decrease in natural discharge to springs and evapotranspiration.

Nevada, Utah↗

USGS2003

Quantile regression models of animal habitat relationships

Typically, all factors that limit an organism are not measured and included in statistical models used to investigate relationships with their environment. If important unmeasured variables interact multiplicatively with the measured variables, the statistical models often will have heterogeneous response distributions with unequal variances. Quantile regression is an approach for estimating the conditional quantiles of a response variable distribution in the linear model, providing a more complete view of possible causal relationships between variables in ecological processes. Chapter 1 introduces quantile regression and discusses the ordering characteristics, interval nature, sampling variation, weighting, and interpretation of estimates for homogeneous and heterogeneous regression models. Chapter 2 evaluates performance of quantile rankscore tests used for hypothesis testing and constructing confidence intervals for linear quantile regression estimates (0 ≤ τ ≤ 1). A permutation F test maintained better Type I errors than the Chi-square T test for models with smaller n , greater number of parameters p , and more extreme quantiles τ. Both versions of the test required weighting to maintain correct Type I errors when there was heterogeneity under the alternative model. An example application related trout densities to stream channel width:depth. Chapter 3 evaluates a drop in dispersion, F -ratio like permutation test for hypothesis testing and constructing confidence intervals for linear quantile regression estimates (0 ≤ τ ≤ 1). Chapter 4 simulates from a large ( N = 10,000) finite population representing grid areas on a landscape to demonstrate various forms of hidden bias that might occur when the effect of a measured habitat variable on some animal was confounded with the effect of another unmeasured variable (spatially and not spatially structured). Depending on whether interactions of the measured habitat and unmeasured variable were negative (interference interactions) or positive (facilitation interactions), either upper (τ > 0.5) or lower (τ < 0.5) quantile regression parameters were less biased than mean rate parameters. Sampling ( n = 20 - 300) simulations demonstrated that confidence intervals constructed by inverting rankscore tests provided valid coverage of these biased parameters. Quantile regression was used to estimate effects of physical habitat resources on a bivalve mussel ( Macomona liliana ) in a New Zealand harbor by modeling the spatial trend surface as a cubic polynomial of location coordinates.

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USGS2013

Porphyry copper assessment of Southeast Asia and Melanesia: Chapter D in Global mineral resource assessment

The U.S. Geological Survey collaborated with member countries of the Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP) on an assessment of the porphyry copper resources of Southeast Asia and Melanesia as part of a global mineral resource assessment. The region hosts world-class porphyry copper deposits and underexplored areas that are likely to contain undiscovered deposits. Examples of known porphyry copper deposits include Batu Hijau and Grasberg in Indonesia; Panguna, Frieda River, and Ok Tedi in Papua New Guinea; and Namosi in Fiji. This assessment covers the countries of Cambodia, Indonesia, Lao People’s Democratic Republic, Malaysia, Myanmar, Papua New Guinea, Singapore, Thailand, and parts of southeastern China, India, the Solomon Islands, Vanuatu, and Fiji. Twenty-two geographic areas were delineated as tracts that are permissive for porphyry copper deposits in Southeast Asia. Permissive tracts are grouped into four broadly defined geographic/geologic areas, as follows: (1) the Indochina Peninsula area, (2) Indonesian and Malaysian Islands, (3) New Guinea Island and Papuan New Guinea islands, and (4) Melanesia. Individual tracts range from less than 1,000 to more than 350,000 square kilometers in area. Permissive tracts are based on mapped and inferred subsurface (<1 kilometer depth) distributions of igneous rocks of specific age ranges that define magmatic arcs and magmatic belts that are likely to contain porphyry copper deposits. Most of these magmatic arcs are subduction-related, although some have porphyry-style deposits occurring in postcollisional and (or) poorly understood tectonic settings. Although maps at a variety of different scales were used in the compilation, the final tract boundaries are intended for use at a scale of 1:1,000,000. Global grade and tonnage models for porphyry copper deposits were evaluated. Most of the known deposits are best described as fitting the copper-gold (Cu-Au) subtype of porphyry copper deposit. For some permissive tracts, a general porphyry copper-gold-molybdenum (Cu-Au-Mo) model was used. Assessment participants estimated numbers of undiscovered deposits at different levels of confidence for most of the permissive tracts. These estimates were combined with grade and tonnage models using a Monte Carlo simulation to estimate undiscovered resources. Additional resources in extensions of deposits with identified resources were not evaluated. Assessment results, presented in tables and graphs, show mean amounts of metal and mineralized rock in undiscovered deposits at different quantile levels, as well as the arithmetic mean for each tract. This assessment estimated a mean of 89 undiscovered porphyry copper deposits for the assessed permissive tracts in Southeast Asia and Melanesia. About 288 million metric tons (Mt) of copper and 18,000 metric tons (t) of gold, as well as byproduct molybdenum and silver, could be associated with undiscovered deposits. This represents about four times the number of deposits with identified resources (23) already discovered in Southeast Asia; reliable reported identified resources for those 23 deposits total 84 Mt of copper and 6,000 t of gold. Eleven permissive tracts have no known porphyry copper deposits with reported resources. Three of those 11 tracts lacked sufficient information for a probabilistic assessment and are discussed in qualitative terms. On a regional basis, both the Indochina Peninsula area and the Indonesian-Malaysian Islands area are estimated to contain about 10 times as much in place copper in undiscovered porphyry copper deposits as has been identified to date. For the New Guinea Island areas, the ratio of undiscovered to identified copper resources is about 2. Some parts of the region have a long history of porphyry exploration cycles and mine development, interrupted at times by political and social unrest, environmental concerns, and natural disasters. Changes in mining laws within the region and the recent high price of gold on the world market have prompted renewed interest in porphyry copper deposits in Southeast Asia and Melanesia. However, predicted undiscovered deposits may not be found, and if found, may not be developed. This assessment includes an overview of the assessment results with summary tables. Detailed descriptions of each tract are included in appendixes, with estimates of numbers of undiscovered deposits, and probabilistic estimates of amounts of copper, molybdenum, gold, and silver that could be contained in undiscovered deposits for each permissive tract. A geographic information system (GIS) that accompanies the report includes tract boundaries and a database of known porphyry copper deposits and significant prospects.

Scientific Investigations Report↗