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USGS2018

Northern Great Plains

In the Northern Great Plains, the timing and quantity of both precipitation and runoff have important consequences for water supplies, agricultural activities, and energy production. Overall, climate projections suggest that the number of heavy precipitation events (events with greater than 1 inch per day of rainfall) is projected to increase. Moving forward, the magnitude of year-to-year variability overshadows the small projected average decrease in streamflow. Changes in extreme events are likely to overwhelm average changes in both the eastern and western regions of the Northern Great Plains. Major flooding across the basin in 2011 was followed by severe drought in 2012, representing new and unprecedented variability that is likely to become more common in a warmer world. The Northern Great Plains region plays a critical role in national food security. Among other anticipated changes, projected warmer and generally wetter conditions with elevated atmospheric carbon dioxide concentrations are expected to increase the abundance and competitive ability of weeds and invasive species, increase livestock production and efficiency of production, and result in longer growing seasons at mid- and high latitudes. Net primary productivity, including crop yields and forage production, is also likely to increase, although an increasing number of extreme temperature events during critical pollination and grain fill periods is likely to reduce crop yields. Ecosystems across the Northern Great Plains provide recreational opportunities and other valuable goods and services that are ingrained in the region’s cultures. Higher temperatures, reduced snow cover, and more variable precipitation will make it increasingly challenging to manage the region’s valuable wetlands, rivers, and snow-dependent ecosystems. In the mountains of western Wyoming and western Montana, the fraction of total water in precipitation that falls as snow is expected to decline by 25% to 40% by 2100 under a higher scenario (RCP8.5), which would negatively affect the region’s winter recreation industry. At lower-elevation areas of the Northern Great Plains, climate-induced land-use changes in agriculture can have cascading effects on closely entwined natural ecosystems, such as wetlands, and the diverse species and recreational opportunities they support. Energy resources in the Northern Great Plains include abundant crude oil, natural gas, coal, wind, and stored water, and to a lesser extent, corn-based ethanol, solar energy, and uranium. The infrastructure associated with the extraction, distribution, and energy produced from these resources is vulnerable to the impacts of climate change. Railroads and pipelines are vulnerable to damage or disruption from increasing heavy precipitation events and associated flooding and erosion. Declining water availability in the summer would likely increase costs for oil production operations, which require freshwater resources. These cost increases will either lead to lower production or be passed on to consumers. Finally, higher maximum temperatures, longer and more severe heat waves, and higher overnight lows are expected to increase electricity demand for cooling in the summer, further stressing the power grid. Indigenous peoples in the region are observing changes to climate, many of which are impacting livelihoods as well as traditional subsistence and wild foods, wildlife, plants and water for ceremonies, medicines, and health and well-being. Because some tribes and Indigenous peoples are among those in the region with the highest rates of poverty and unemployment, and because many are still directly reliant on natural resources, they are among the most at risk to climate change (e.g., Gamble et al. 2016, Cozzetto et al. 2013, Espey et al. 2014, Wong et al. 2014, Kornfeld 2016, Paul and Caplins 2016, Maynard 2014, USGCRP 2017)

Report↗

USGS2007

Integrated geoscience studies in the Greater Yellowstone Area - Volcanic, tectonic, and hydrothermal processes in the Yellowstone geoecosystem

Yellowstone National Park, rimmed by a crescent of older mountainous terrain, has at its core the Quaternary Yellowstone Plateau, an undulating landscape shaped by forces of volcanism, tectonism, and later glaciation. Its spectacular hydrothermal systems cap this landscape. From 1997 through 2003, the United States Geological Survey Mineral Resources Program conducted a multidisciplinary project of Yellowstone National Park entitled Integrated Geoscience Studies of the Greater Yellowstone Area, building on a 130-year foundation of extensive field studies (including the Hayden survey of 1871, the Hague surveys of the 1880s through 1896, the studies of Iddings, Allen, and Day during the 1920s, and NASA-supported studies starting in the 1970s—now summarized in USGS Professional Paper 729 A through G) in this geologically dynamic terrain. The project applied a broad range of scientific disciplines and state-of-the-art technologies targeted to improve stewardship of the unique natural resources of Yellowstone and enable the National Park Service to effectively manage resources, protect park visitors from geologic hazards, and better educate the public on geologic processes and resources. This project combined a variety of data sets in characterizing the surficial and subsurface chemistry, mineralogy, geology, geophysics, and hydrothermal systems in various parts of the park. The sixteen chapters presented herein in USGS Professional Paper 1717, Integrated Geoscience Studies in the Greater Yellowstone Area—Volcanic, Tectonic, and Hydrothermal Processes in the Yellowstone Geoecosystem , can be divided into four major topical areas: (1) geologic studies, (2) Yellowstone Lake studies, (3) geochemical studies, and (4) geophysical studies. The geologic studies include a paper by Ken Pierce and others on the influence of the Yellowstone hotspot on landscape formation, the ecological effects of the hotspot, and the human experience and human geography of the greater Yellowstone ecosystem as influenced by the Yellowstone hotspot. Another paper by Paul Carrara describes the recent movement of a large landslide block dated by tree-ring analyses in the Tower Falls area. The section under Yellowstone Lake studies begins with a classic paper by J. David Love and others on ancestral Lake Yellowstone. Other papers in this section include results and interpretation of the high-resolution bathymetric, seismic reflection, and submersible studies by Lisa Morgan and others. Ken Pierce and others describe results from their studies of shorelines along Yellowstone Lake and their interpretation of inflation-deflation cycles, tilting, and faulting in the Yellowstone caldera. The influence of sublacustrine hydrothermal vent fluids on the geochemistry of Yellowstone Lake is described by Laurie Balistrieri and others. In Pat Shanks and others’ chapter, hydrothermal reactions, stable-isotope systematics, sinter deposition, and spire formation are related to the geochemistry of sublacustrine hydrothermal deposits in Yellowstone Lake. The geochemical studies section considers park-wide geochemical systems in Yellowstone National Park. In Bob Rye and Alfred Truesdell’s paper, the question of recharge to the deep thermal reservoir underlying the geysers and hot springs of Yellowstone National Park is discussed. Irving Friedman and Dan Norton report on the chloride flux emissions from Yellowstone in their paper questioning whether Yellowstone is losing its steam. Wildlife issues as addressed by examining trace-element and stable-isotope geochemistry are discussed in a chapter by Maurice Chaffee and others. In another chapter by Chaffee and others, natural and anthropogenic anomalies and their potential impact on the environment using geochemistry is reported. Pam Gemery-Hill and others present geochemical data for selected rivers, lake waters, hydrothermal vents, and subaerial geysers for the time interval of 1996–2004. The life cycle of gold deposits near the northeast corner of the park is discussed by Brad Van Gosen. Under the geophysical studies segment, Ray Kokaly and others use AVIRIS (Airborne Visible and Infrared Spectroscopy) data to map vegetation cover and microbial communities in Yellowstone National Park. Eric Livo and others report their results using AVIRIS data on hydrothermally altered rock and hot-spring deposits. In his final paper following a half century of scientific research, Irving Friedman presents data on monitoring changes in geothermal activity at Norris Geyser Basin using satellite telemetry. These papers summarize a near-decade-long effort by the USGS from the late 1990s to mid-2000s. In 2001, the USGS in cooperation with the National Park Service (Yellowstone National Park) and the University of Utah established the Yellowstone Volcano Observatory, the 5th volcano observatory in the United States.

Professional Paper↗

USGS2007

Application of FTLOADDS to Simulate Flow, Salinity, and Surface-Water Stage in the Southern Everglades, Florida

The Comprehensive Everglades Restoration Plan requires numerical modeling to achieve a sufficient understanding of coastal freshwater flows, nutrient sources, and the evaluation of management alternatives to restore the ecosystem of southern Florida. Numerical models include a regional water-management model to represent restoration changes to the hydrology of southern Florida and a hydrodynamic model to represent the southern and western offshore waters. The coastal interface between these two systems, however, has complex surface-water/ground-water and freshwater/saltwater interactions and requires a specialized modeling effort. The Flow and Transport in a Linked Overland/Aquifer Density Dependent System (FTLOADDS) code was developed to represent connected surface- and ground-water systems with variable-density flow. The first use of FTLOADDS is the Southern Inland and Coastal Systems (SICS) application to the southeastern part of the Everglades/Florida Bay coastal region. The need to (1) expand the domain of the numerical modeling into most of Everglades National Park and the western coastal area, and (2) better represent the effect of water-delivery control structures, led to the application of the FTLOADDS code to the Tides and Inflows in the Mangroves of the Everglades (TIME) domain. This application allows the model to address a broader range of hydrologic issues and incorporate new code modifications. The surface-water hydrology is of primary interest to water managers, and is the main focus of this study. The coupling to ground water, however, was necessary to accurately represent leakage exchange between the surface water and ground water, which transfers substantial volumes of water and salt. Initial calibration and analysis of the TIME application produced simulated results that compare well statistically with field-measured values. A comparison of TIME simulation results to previous SICS results shows improved capabilities, particularly in the representation of coastal flows. This improvement most likely is due to a more stable numerical representation of the coastal creek outlets. Sensitivity analyses were performed by varying frictional resistance, leakage, barriers to flow, and topography. Changing frictional resistance values in inland areas was shown to improve water-level representation locally, but to have a negligible effect on area-wide values. These changes have only local effects and are not physically based (as are the unchanged values), and thus have limited validity. Sensitivity tests indicate that the overall accuracy of the simulation is diminished if leakage between surface water and ground water is not simulated. The inclusion of a major road as a complete barrier to surface-water flow influenced the local distribution and timing of flow; however, the changes in total flow and individual creekflows were negligible. The model land-surface altitude was lowered by 0.1 meter to determine the sensitivity to topographic variation. This topographic sensitivity test produced mixed results in matching field data. Overall, the representation of stage did not improve definitively. A final calibration utilized the results of the sensitivity analysis to refine the TIME application. To accomplish this calibration, the friction coefficient was reduced at the northern boundary inflow and increased in the southwestern corner of the model, the evapotranspiration function was varied, additional data were used for the ground-water head boundary along the southeast, and the frictional resistance of the primary coastal creek outlet was increased. The calibration improved the match between measured and simulated total flows to Florida Bay and coastal salinities. Agreement also was improved at most of the water-level sites throughout the model domain.

Scientific Investigations Report↗

USGS2009

Status and trends of prey fish populations in Lake Michigan, 2008

The Great Lakes Science Center (GLSC) has conducted lake-wide surveys of the fish community in Lake Michigan each fall since 1973 using standard 12-m bottom trawls towed along contour at depths of 9 to 110 m at each of seven index transects. The resulting data on relative abundance, size structure, and condition of individual fishes are used to estimate various population parameters that are in turn used by state and tribal agencies in managing Lake Michigan fish stocks. All seven established index transects of the survey were completed in 2008. The survey provides relative abundance and biomass estimates between the 5-m and 114-m depth contours of the lake (herein, lake-wide) for prey fish populations, as well as burbot, yellow perch, and the introduced dreissenid mussels. Lake-wide biomass of alewives in 2008 was estimated at 8.27 kilotonnes (kt) (1 kt = 1000 metric tons), which was the smallest biomass estimate in the entire time series and 29% lower than the 2007 estimate. Lake-wide biomass of bloater in 2008 was estimated at 3.33 kt, which was the lowest estimate since 1977 and 38% lower than the 2007 estimate. Rainbow smelt lake-wide biomass equaled 0.89 kt, which was only 0.01 kt higher than 2007, which is the lowest estimate in the time series. Deepwater sculpin lake-wide biomass equaled 5.23 kt, which is the fourth straight year of declining biomass. The 2008 estimate is the second smallest in the time series, and 39% lower than the 2007 estimate. Slimy sculpin lake-wide biomass remained relatively high in 2008 (2.75 kt), increasing 25% over 2007. Ninespine stickleback lake-wide biomass equaled only 0.50 kt in 2008, which was 79% lower than the 2007 estimate. The final prey fish, exotic round goby, increased two orders of magnitude between 2007 and 2008, from 0.02 to 4.65 kt. Round gobies now represent 18% of the prey fish biomass. Burbot lake-wide biomass (0.91 kt in 2008) has remained fairly constant since 2002. Numeric density of age-0 yellow perch (i.e., < 100 mm) equaled 0.7 fish per ha, which is indicative of a relatively poor year-class. Lake-wide biomass of dreissenid mussels dropped precipitously in 2008, down to 9.47 kt, and a 96% decline from the 2007 biomass estimate. Overall, the total lake-wide prey fish biomass estimate (sum of alewife, bloater, rainbow smelt, deepwater sculpin, slimy sculpin, round goby, and ninespine stickleback) in 2008 was 25.62 kt, which was the lowest observed since the survey began in 1973.

Lake Michigan↗

USGS2009

Estimating Locations of Perennial Streams in Idaho Using a Generalized Least-Squares Regression Model of 7-Day, 2-Year Low Flows

Many State and Federal agencies use information regarding the locations of streams having intermittent or perennial flow when making management and regulatory decisions. For example, the application of some Idaho water quality standards depends on whether streams are intermittent. Idaho Administrative Code defines an intermittent stream as one having a 7-day, 2-year low flow (7Q2) less than 0.1 ft3/s. However, there is a general recognition that the cartographic representation of perennial/intermittent status of streams on U.S. Geological Survey (USGS) topographic maps is not as accurate or consistent as desirable from one map to another, which makes broad management and regulatory assessments difficult and inconsistent. To help resolve this problem, the USGS has developed a methodology for predicting the locations of perennial streams based on regional generalized least-squares (GLS) regression equations for Idaho streams for the 7Q2 low-flow statistic. Using these regression equations, the 7Q2 streamflow may be estimated for naturally flowing streams in most areas in Idaho. The use of these equations in conjunction with a geographic information system (GIS) technique known as weighted flow accumulation allows for an automated and continuous estimation of 7Q2 streamflow at all points along stream reaches. The USGS has developed a GIS-based map of the locations of streams in Idaho with perennial flow based on a 7Q2 of 0.1 ft3/s and a transition zone of plus or minus 1 standard error. Idaho State cooperators plan to use this information to make regulatory and water-quality management decisions. Originally, 7Q2 equations were developed for eight regions of similar hydrologic characteristics in the study area, using long-term data from 234 streamflow-gaging stations. Equations in five of the regions were revised based on spatial patterns observed in the initial perennial streams map and unrealistic behavior of the equations in extrapolation. The standard errors of prediction for the final equations ranged from a minimum of +75.0 to -42.9 percent in the central part of the study area to a maximum of +277 to -73.5 percent in the southern part of the study area. The equations are applicable only to unregulated, naturally-flowing streams and may produce unreliable results outside the range of explanatory variables used for equation development. Extrapolation outside the range of available data was necessary, however, to predict perennial flow initiation points and transition zones along stream reaches. The map of perennial streams was evaluated by comparing predicted stream classifications with four independent datasets, including field observations by other government agencies. Overall, 81 percent of the comparison data points agreed with the USGS perennial streams model. Regions with the highest number of disagreements had a high percentage of mountainous and forested area with potential mountain front recharge zones, and regions with the highest agreements had a high percentage of low gradient, low elevation area. As a whole, the USGS model predicted a higher number of perennial streams than predictions made with the independent datasets. Some disagreements were due to poor site location coordinates, timing of the comparison site visits during unusually wet or dry years, discrepancies in classification criteria, and variable ground water contributions to flow in some areas. The Idaho Department of Environmental Quality Beneficial Use Reconnaissance Program (BURP) dataset is considered the most representative dataset for comparison because it covered a range of climate conditions and the number of sites visited were consistent from year to year during the study period. Eighty-five percent of BURP comparison data points agreed with the USGS perennial streams model. Although site-specific flow data may be needed to correctly classify streams in some areas, this information rarely is available and is not always practical to o

Scientific Investigations Report↗

USGS2018

Development of an aerial population survey method for elk (Cervus elaphus) in Rocky Mountain National Park, Colorado

Executive Summary Since the early 1990s, substantial effort and funding have been expended to conduct research to guide development of a 20-year Elk and Vegetation Management Plan for Rocky Mountain National Park (RMNP) in Colorado. One goal of the plan is to maintain the elk ( Cervus elaphus ) population size at the lower end of the natural range of variation. To implement management actions called for in the plan, accurate and reliable population estimates are needed, as well as a better understanding of the spatial and temporal distribution of elk. The previous aerial survey protocol and population estimation model used by the park had not been updated since the model’s initial calibration more than 15 years ago and the model was developed with an insufficient number (n=44) of observations. Thus we initiated research to reevaluate, update, and improve elk population estimation protocols for RMNP. We considered several alternative survey and analysis methods, and concluded that a hybrid population-estimation model using a simultaneous double-observer technique with sighting covariates was the most appropriate and effective aerial survey methodology for this population and the environmental conditions in RMNP. Instructional protocols for conducting these surveys in the future, along with datasheets, are provided in this report’s appendixes. To develop an improved method for aerial elk surveys, we used elk radio-collar location data from our study and other studies, and applied geographic information system analyses to define the survey area and develop effective, repeatable survey transect lines. We used telemetry data from radio-collared elk to inform our understanding of the temporal and spatial scale of elk movements across the park boundary, elk use of tree cover during potential survey hours, and elk use of different elevations within their range. Determining where elk were during surveys helped to fine-tune a survey design that improved spatial cover-age and decreased costs where possible, while standardizing the method to make it repeatable from year to year. We conducted aerial helicopter surveys to test our methodology in an adaptive, iterative process during three winters: 2007–2008, 2008–2009, and 2009–2010. We gained new information on each survey and used results to refine subsequent surveys. Our results confirm that elk movements were highly dynamic with respect to park boundary crossings; an average of six round trips from the park to Estes Park, Colorado, and back per month were taken by global positioning system-collared bull elk. We observed a strong diurnal temporal pattern of bull elk use of trees; elk were found in dense tree cover from 15:00−22:00 but not as often during morning and early afternoon hours when surveys were conducted. We used information on elk use of different altitudes to refine and establish a more efficient survey area. During the time of our study, a concurrent study in the park deployed 120 very high frequency radio collars on elk cows. We used those collar locations during our flights to increase sample size and to evaluate the level of precision we would gain by using “known fates analysis” (in which elk were known to be in the survey area, out of the survey area, or deceased based on radio-collar locations collected simultaneously during aerial surveys). Using radio-collar locations reduced bias by 1.1–8.8 percent and increased precision (that is, reduced the width of confidence intervals). This report provides final population estimates analyzed with and without radio-collar data to demonstrate what is gained by using marked individuals.

Colorado↗

USGS2001

Statewide water-quality network for Massachusetts

A water-quality monitoring program is proposed that would provide data to meet multiple information needs of Massachusetts agencies and other users concerned with the condition of the State's water resources. The program was designed by the U.S. Geological Survey and the Massachusetts Department of Environmental Protection, Division of Watershed Management, with input from many organizations involved in water-quality monitoring in the State, and focuses on inland surface waters (streams and lakes). The proposed monitoring program consists of several components, or tiers, which are defined in terms of specific monitoring objectives, and is intended to complement the Massachusetts Watershed Initiative (MWI) basin assessments. Several components were developed using the Neponset River Basin in eastern Massachusetts as a pilot area, or otherwise make use of data from and sampling approaches used in that basin as part of a MWI pilot assessment in 1994. To guide development of the monitoring program, reviews were conducted of general principles of network design, including monitoring objectives and approaches, and of ongoing monitoring activities of Massachusetts State agencies.Network tiers described in this report are primarily (1) a statewide, basin-based assessment of existing surface-water-quality conditions, and (2) a fixed-station network for determining contaminant loads carried by major rivers. Other components, including (3) targeted programs for hot-spot monitoring and other objectives, and (4) compliance monitoring, also are discussed. Monitoring programs for the development of Total Maximum Daily Loads for specific water bodies, which would constitute another tier of the network, are being developed separately and are not described in this report. The basin-based assessment of existing conditions is designed to provide information on the status of surface waters with respect to State water-quality standards and designated uses in accordance with the reporting requirements [Section 305(b)] of the Clean Water Act (CWA). Geographic Information System (GIS)-based procedures were developed to inventory streams and lakes in a basin for these purposes. Several monitoring approaches for this tier and their associated resource requirements were investigated. Analysis of the Neponset Basin for this purpose demonstrated that the large number of sites needed in order for all the small streams in a basin to be sampled (about half of stream miles in the basin were headwater or first-order streams) pose substantial resource-based problems for a comprehensive assessment of existing conditions. The many lakes pose similar problems. Thus, a design is presented in which probabilistic monitoring of small streams is combined with deterministic or targeted monitoring of large streams and lakes to meet CWA requirements and to provide data for other information needs of Massachusetts regulatory agencies and MWI teams.The fixed-station network is designed to permit the determination of contaminant loads carried by the State's major rivers to sensitive inland and coastal receiving waters and across State boundaries. Sampling at 19 proposed sites in 17 of the 27 major basins in Massachusetts would provide information on contaminant loads from 67 percent of the total land area of the State; unsampled areas are primarily coastal areas drained by many small streams that would be impossible to sample within realistic resource limitations. Strategies for hot-spot monitoring, a targeted monitoring program focused on identifying contaminant sources, are described with reference to an analysis of the bacteria sampling program of the 1994 Neponset Basin assessment. Finally, major discharge sites permitted under the National Pollutant Discharge Elimination System (NPDES) were evaluated as a basis for ambient water-quality monitoring. The discharge sites are well distributed geographically among basins, but are primarily on large rivers (two-thirds or more

Water-Resources Investigations Report↗

USGS2012

Design and maintenance of a network for collecting high-resolution suspended-sediment data at remote locations on rivers, with examples from the Colorado River

Management of sand and finer sediment in fluvial settings has become increasingly important for reasons ranging from endangered-species habitat to transport of sediment-associated contaminants. In all rivers, some fraction of the suspended load is transported as washload, and some as suspended bed material. Typically, the washload is composed of silt-and-clay-size sediment, and the suspended bed material is composed of sand-size sediment. In most rivers, as a result of changes in the upstream supply of silt and clay, large, systematic changes in the concentration of the washload occur over time, independent of changes in water discharge. Recent work has shown that large, systematic, discharge-independent changes in the concentration of the suspended bed material are also present in many rivers. In bedrock canyon rivers, such as the Colorado River in Grand Canyon National Park, changes in the upstream tributary supply of sand may cause large changes in the grain-size distribution of the bed sand, resulting in changes in both the concentration and grain-size distribution of the sand in suspension. Large discharge-independent changes in suspended-sand concentration coupled to discharge-independent changes in the grain-size distribution of the suspended sand are not unique to bedrock canyon rivers, but also occur in large alluvial rivers, such as the Mississippi River. These systematic changes in either suspended-silt-and-clay concentration or suspended-sand concentration may not be detectable by using conventional equal-discharge- or equal-width-increment measurements, which may be too infrequently collected relative to the time scale over which these changes in the sediment load are occurring. Furthermore, because large discharge-independent changes in both suspended-silt-and-clay and suspended-sand concentration are possible in many rivers, methods using water discharge as a proxy for suspended-sediment concentration (such as sediment rating curves) may not produce sufficiently accurate estimates of sediment loads. Finally, conventional suspended-sediment measurements are both labor and cost intensive and may not be possible at the resolution required to resolve discharge-independent changes in suspended-sediment concentration, especially in more remote locations. For these reasons, the U.S. Geological Survey has pursued the use of surrogate technologies (such as acoustic and laser diffraction) for providing higher-resolution measurements of suspended-sediment concentration and grain size than are possible by using conventional suspended-sediment measurements alone. These factors prompted the U.S. Geological Survey's Grand Canyon Monitoring and Research Center to design and construct a network to automatically measure suspended-sediment transport at 15-minute intervals by using acoustic and laser-diffraction surrogate technologies at remote locations along the Colorado River within Marble and Grand Canyons in Grand Canyon National Park. Because of the remoteness of the Colorado River in this reach, this network also included the design of a broadband satellite-telemetry system to communicate with the instruments deployed at each station in this network. Although the sediment-transport monitoring network described in this report was developed for the Colorado River in Grand Canyon National Park, the design of this network can easily be adapted for use on other rivers, no matter how remote. In the Colorado River case-study example described in this report, suspended-sediment concentration and grain size are measured at five remote stations. At each of these stations, surrogate measurements of suspended-sediment concentration and grain size are made at 15-minute intervals using an array of different single-frequency acoustic-Doppler side-looking profilers. Laser-diffraction instruments are also used at two of these stations to measure both suspended-sediment concentrations and grain-size distributions. Cross-section calibrations of these instruments have been constructed and verified by using either equal-discharge-increment (EDI) or equal-width-increment (EWI) measurements of the velocity-weighted suspended-sediment concentration and grain-size distribution. The suspended-silt-and-clay concentration parts of these calibration relations have also included information from EDI- or EWI-calibrated samples collected by automatic pump samplers. Three of the monitoring stations are equipped with two-way satellite broadband telemetry systems that operate once a day to remotely monitor and program the instruments and download data. Data from these stations are typically downloaded twice per month; data from stations without satellite-telemetry systems are downloaded during site visits, which occur every 2 months or semiannually, depending on the remoteness of the site. Upon downloading and processing, suspended-silt-and-clay concentration, suspended-sand concentration, and suspended-sand median grain size are posted on the World Wide Web. Satellite telemetry in combination with the high-resolution sediment surrogate measurements can generate near-real-time suspended-sediment-concentration and grain-size data (limited only by the time required to download the instruments and process the data). The approach for measuring suspended-sediment concentration and grain size using this monitoring network is more practical, and can be done at a much lower cost and with higher temporal resolution, than any other method.

Arizona;Nevada;Utah↗

USGS2009

Regression equations for estimation of annual peak-streamflow frequency for undeveloped watersheds in Texas using an L-moment-based, PRESS-minimized, residual-adjusted approach

Annual peak-streamflow frequency estimates are needed for flood-plain management; for objective assessment of flood risk; for cost-effective design of dams, levees, and other flood-control structures; and for design of roads, bridges, and culverts. Annual peak-streamflow frequency represents the peak streamflow for nine recurrence intervals of 2, 5, 10, 25, 50, 100, 200, 250, and 500 years. Common methods for estimation of peak-streamflow frequency for ungaged or unmonitored watersheds are regression equations for each recurrence interval developed for one or more regions; such regional equations are the subject of this report. The method is based on analysis of annual peak-streamflow data from U.S. Geological Survey streamflow-gaging stations (stations). Beginning in 2007, the U.S. Geological Survey, in cooperation with the Texas Department of Transportation and in partnership with Texas Tech University, began a 3-year investigation concerning the development of regional equations to estimate annual peak-streamflow frequency for undeveloped watersheds in Texas. The investigation focuses primarily on 638 stations with 8 or more years of data from undeveloped watersheds and other criteria. The general approach is explicitly limited to the use of L-moment statistics, which are used in conjunction with a technique of multi-linear regression referred to as PRESS minimization. The approach used to develop the regional equations, which was refined during the investigation, is referred to as the 'L-moment-based, PRESS-minimized, residual-adjusted approach'. For the approach, seven unique distributions are fit to the sample L-moments of the data for each of 638 stations and trimmed means of the seven results of the distributions for each recurrence interval are used to define the station specific, peak-streamflow frequency. As a first iteration of regression, nine weighted-least-squares, PRESS-minimized, multi-linear regression equations are computed using the watershed characteristics of drainage area, dimensionless main-channel slope, and mean annual precipitation. The residuals of the nine equations are spatially mapped, and residuals for the 10-year recurrence interval are selected for generalization to 1-degree latitude and longitude quadrangles. The generalized residual is referred to as the OmegaEM parameter and represents a generalized terrain and climate index that expresses peak-streamflow potential not otherwise represented in the three watershed characteristics. The OmegaEM parameter was assigned to each station, and using OmegaEM, nine additional regression equations are computed. Because of favorable diagnostics, the OmegaEM equations are expected to be generally reliable estimators of peak-streamflow frequency for undeveloped and ungaged stream locations in Texas. The mean residual standard error, adjusted R-squared, and percentage reduction of PRESS by use of OmegaEM are 0.30log 10 , 0.86, and -21 percent, respectively. Inclusion of the OmegaEM parameter provides a substantial reduction in the PRESS statistic of the regression equations and removes considerable spatial dependency in regression residuals. Although the OmegaEM parameter requires interpretation on the part of analysts and the potential exists that different analysts could estimate different values for a given watershed, the authors suggest that typical uncertainty in the OmegaEM estimate might be about +or-0.10 10 . Finally, given the two ensembles of equations reported herein and those in previous reports, hydrologic design engineers and other analysts have several different methods, which represent different analytical tracks, to make comparisons of peak-streamflow frequency estimates for ungaged watersheds in the study area.

Texas↗

USGS2016

A spatially explicit suspended-sediment load model for western Oregon

We calibrated the watershed model SPARROW (Spatially Referenced Regressions on Watershed attributes) to give estimates of suspended-sediment loads for western Oregon and parts of northwestern California. Estimates of suspended-sediment loads were derived from a nonlinear least squares regression that related explanatory variables representing landscape and transport conditions to measured suspended-sediment loads at 68 measurement stations. The model gives estimates of model coefficients and their uncertainty within a spatial framework defined by the National Hydrography Dataset Plus hydrologic network. The resulting model explained 64 percent of the variability in suspended-sediment yield and had a root mean squared error value of 0.737. The predictor variables selected for the final model were (1) generalized lithologic province, (2) mean annual precipitation, and (3) burned area (by recent wildfire). Other landscape characteristics also were considered, but they were not significant predictors of sediment transport, were strongly correlated with another predictor variable, or were not as significant as the predictors selected for the final model. The northern Oregon coastal drainages had the highest predicted suspended sediment yields (median yield 475 kilograms per hectare per year) and the Klamath River Basin had the lowest (median yield 53 kilograms per hectare per year). Quaternary deposits were, on average, the largest contributor to incremental suspended-sediment yield even though this lithologic province only makes up 17 percent of the modeling domain. Coast Range sedimentary rocks and Coast Range volcanic rocks had high suspended-sediment yields whereas, in addition to the Klamath terrane, the Western Cascade and High Cascade lithologic provinces had low suspended-sediment yields. Precipitation and the area affected by recent wildfire both positively correlated with suspended-sediment load. Suspended-sediment transport rates predicted by this SPARROW model are less than historical (1956–73) and long‑term (thousands of years) geological rates. This difference likely results, in part, from biases in the data underlying the SPARROW model, probably resulting in predicted suspended-sediment estimates that underestimate actual transport rates. However, the differences also likely owe to natural and human-caused variation in suspended-sediment yields as they respond to changes in climate, vegetation, fire frequency, and land use. In particular, decreases in mean annual suspended-sediment yields within the Umpqua River Basin since 1956–73 may owe to less intense forest harvest, passage of the Oregon Forest Practices Act of 1971, and increased emphasis in habitat protection in recent decades. Such sensitivity may have implications for the spatial and temporal distributions of aquatic and riparian habitats. Knowledge of the regionally important patterns and factors in suspended-sediment sources and transport could support broad-scale, water-quality management objectives and priorities. Because of biases and limitations of this model, however, these results are most applicable for general comparisons and for broad areas such as large watersheds. For example, despite having similar area, precipitation, and land-use, the Umpqua River Basin generates 68 percent more suspended sediment than the Rogue River Basin, chiefly because of the large area of Coast Range sedimentary province in the Umpqua River Basin. By contrast, the Rogue River Basin contains a much larger area of Klamath terrane rocks, which produce significantly less suspended load, although recent fire disturbance (in 2002) has apparently elevated suspended sediment yields in the tributary Illinois River watershed. Fine-scaled analysis, however, will require more intensive, locally focused measurements.

Scientific Investigations Report↗

USGS2020

Methods for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations on streams in Alabama

Streamflow data and statistics are vitally important for proper protection and management of the water quality and water quantity of Alabama streams. Such data and statistics are generally available at U.S. Geological Survey streamflow-gaging stations, also referred to as streamgages or stations, but are often needed at ungaged stream locations. To address this need, the U.S. Geological Survey, in cooperation with numerous Alabama State agencies and organizations, developed regional regression equations for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations on streams in Alabama that are not substantially affected by tides, regulation, diversions, or other anthropogenic influences. A small percentage of the streamgages included in this study experience zero flows during certain periods; thus, the final low-flow frequency regression equations were developed by using weighted left-censored regression analyses to analyze the flow data in an unbiased manner, with weights based on number of years of record. The equations developed include the annual minimum 1- and 7-day average streamflows with a 10-year recurrence interval (referred to as the 1Q10 and 7Q10 flows), the annual minimum 7-day average streamflow with a 2-year recurrence interval (referred to as the 7Q2 flow), and the mean annual flow using data from 174 streamgages from Alabama and surrounding States. For the 1Q10, 7Q2, and 7Q10 low-flow frequency statistics, the regional regression equations are functions of drainage area, streamflow-variability index, mean annual precipitation, and percentage of the drainage basin located in the Piedmont and Southeastern Plains ecoregions. The mean annual flow regression equation is a function of drainage area, mean annual precipitation, and percentage of the drainage basin located in the Southeastern Plains ecoregion. For the mean annual flow regression equation, the average standard error of estimate was 11.2 percent. For the selected low-flow frequency equations, the average standard errors of estimate ranged from 18.1 to 38.8 percent. The regional regression equations developed from this investigation have been incorporated into the U.S. Geological Survey StreamStats application for Alabama. StreamStats ( https://streamstats.usgs.gov/ss/ ) is a web-based geographic information system application that delineates drainage basins at selected stream locations and then generates the needed basin characteristics for available regional regression equations. Along with the low-flow frequency equations developed in this investigation, the StreamStats application also has regional regression equations for estimating flood-frequency statistics at locations on rural and urban streams in Alabama.

Alabama↗

USGS2010

Contamination movement around a permeable reactive barrier at Solid Waste Management Unit 12, Naval Weapons Station Charleston, North Charleston, South Carolina, 2009

The U.S. Geological Survey and the Naval Facilities Engineering Command Southeast investigated natural and engineered remediation of chlorinated volatile organic compound groundwater contamination at Solid Waste Management Unit 12 at the Naval Weapons Station Charleston, North Charleston, South Carolina, beginning in 2000. In early 2004, groundwater contaminants began moving around the southern end of a permeable reactive barrier (PRB) installed by a consultant in December 2002. The PRB is a 130-foot-long and 3-foot-wide barrier consisting of varying amounts of zero-valent iron with or without sand mixture. Contamination moving around the PRB probably has been transported at least 75 feet downgradient from the PRB at a rate of about 15 to 29 feet per year. The diversion of contamination around the southern end of the PRB may be due to construction difficulties associated with the PRB installation or to reduced permeability in the PRB. An event that took place during installation of the PRB, which may have caused permeability loss, was the collapse and subsequent abandonment of a 110-foot-long trench originally designed to be the PRB on November 11, 2002, approximately 25 feet upgradient (west) from the final PRB. Guar gum with antimicrobial preservative in a polymer slurry had been used to stabilize the abandoned trench prior to collapse and was only partially recovered. Residual guar gum can cause permeability reduction in a PRB. It also is possible that permeability reduction took place within the PRB by slow degradation of the guar gum slurry or mineral precipitation. Despite the likely permeability reduction in and near the PRB immediately following installation, there is evidence that contaminants moved through the PRB and were degraded, consistent with the planned purpose of the PRB. Volatile organic compound contamination in groundwater downgradient from the PRB is subject to attenuation by phytovolatilization, sorption, and biodegradation. Pulses of contamination increases have been observed in some monitoring wells downgradient from the PRB. The pulses may reflect downgradient transport of contaminant pulses; however, lateral shifting of the plume is a more likely explanation for the concentration changes at well 12MW-12S. The ability to monitor the fate and behavior of the plume in the forest is severely limited because the present axis of maximum contamination in that area bypasses all but one of the existing monitoring wells (12MW-12S). Moreover, the 2009 data indicate that there are no optimally placed sentinel wells in the probable path of contaminant transport. Thus the monitoring network is no longer adequate to monitor the groundwater contamination downgradient from the PRB.

South Carolina↗

USGS2008

Regression Analysis of Stage Variability for West-Central Florida Lakes

The variability in a lake's stage depends upon many factors, including surface-water flows, meteorological conditions, and hydrogeologic characteristics near the lake. An understanding of the factors controlling lake-stage variability for a population of lakes may be helpful to water managers who set regulatory levels for lakes. The goal of this study is to determine whether lake-stage variability can be predicted using multiple linear regression and readily available lake and basin characteristics defined for each lake. Regressions were evaluated for a recent 10-year period (1996-2005) and for a historical 10-year period (1954-63). Ground-water pumping is considered to have affected stage at many of the 98 lakes included in the recent period analysis, and not to have affected stage at the 20 lakes included in the historical period analysis. For the recent period, regression models had coefficients of determination (R2) values ranging from 0.60 to 0.74, and up to five explanatory variables. Standard errors ranged from 21 to 37 percent of the average stage variability. Net leakage was the most important explanatory variable in regressions describing the full range and low range in stage variability for the recent period. The most important explanatory variable in the model predicting the high range in stage variability was the height over median lake stage at which surface-water outflow would occur. Other explanatory variables in final regression models for the recent period included the range in annual rainfall for the period and several variables related to local and regional hydrogeology: (1) ground-water pumping within 1 mile of each lake, (2) the amount of ground-water inflow (by category), (3) the head gradient between the lake and the Upper Floridan aquifer, and (4) the thickness of the intermediate confining unit. Many of the variables in final regression models are related to hydrogeologic characteristics, underscoring the importance of ground-water exchange in controlling the stage of karst lakes in Florida. Regression equations were used to predict lake-stage variability for the recent period for 12 additional lakes, and the median difference between predicted and observed values ranged from 11 to 23 percent. Coefficients of determination for the historical period were considerably lower (maximum R2 of 0.28) than for the recent period. Reasons for these low R2 values are probably related to the small number of lakes (20) with stage data for an equivalent time period that were unaffected by ground-water pumping, the similarity of many of the lake types (large surface-water drainage lakes), and the greater uncertainty in defining historical basin characteristics. The lack of lake-stage data unaffected by ground-water pumping and the poor regression results obtained for that group of lakes limit the ability to predict natural lake-stage variability using this method in west-central Florida.

Scientific Investigations Report↗

USGS2000

Simple Techniques For Assessing Impacts Of Oil And Gas Operations On Federal Lands - A Field Evaluation At Big South Fork National River And Recreation Area, Scott County, Tennessee

Simple, cost-effective techniques are needed for land managers to assess the environmental impacts of oil and gas production activities on public lands so that sites may be prioritized for further, more formal assessment or remediation. These techniques should allow the field investigator to extend the assessment beyond the surface disturbances documented by simple observation and mapping using field-portable instruments and expendable materials that provide real-time data. The principal contaminants of current concern are hydrocarbons, produced water, and naturally occurring radioactive materials (NORM). Field investigators can examine sites for the impacts of hydrocarbon releases using a photoionization detector (PID) and a soil auger. Volatile organic carbon (VOC) in soil gases in an open auger hole or in the head space of a bagged and gently warmed auger soil sample can be measured by the PID. This allows detection of hydrocarbon movement in the shallow subsurface away from areas of obvious oil-stained soils or oil in pits at a production site. Similarly, a field conductivity meter and chloride titration strips can be used to measure salts in water and soil samples at distances well beyond areas of surface salt scarring. Use of a soil auger allows detection of saline subsoils in areas where salts may be flushed from the surface soil layers. Finally, a microRmeter detects the presence of naturally occurring radioactive materials (NORM) in equipment and soils. NORM often goes undetected at many sites although regulations limiting NORM in equipment and soils are being promulgated in several States and are being considered by the USEPA. With each technique, background sampling should be done for comparison with impacted areas. The authors examined sites in the Big South Fork National River and Recreation Area in November of 1999. A pit at one site at the edge of the flood plain of a small stream had received crude oil releases from a nearby tank. Auger holes down gradient from the pit showed the presence of anomalous concentrations of VOCs at depths of 3 feet for a distance of about 50 feet. PID readings at other sites showed 1) one reclaimed site where hydrocarbon biodegradation was incomplete; 2) one reclaimed site where biodegradation had left no traces of VOCS; and 3) two sites where traces of substantial offsite migration of hydrocarbons occurred. Produced water salts at one site have migrated many 100s of feet downvalley from the area of salt scarring and tree death adjacent to the pits. Naturally occurring radioactivity (NORM) at most sites was at background. One site showed anomalous radioactivity related to NORM in a small brine pit. Some of this NORM has moved downslope from the outlet pipe to the pit.

Open-File Report↗

USGS2025

Development of regression equations to estimate flow durations, low-flow frequencies, and mean flows at ungaged stream sites in Connecticut using data through water year 2022

To aid Federal and State regulatory agencies in the effective management of water resources, the U.S. Geological Survey, in cooperation with the Connecticut Department of Energy and Environmental Protection and the Connecticut Department of Transportation, updated flow statistics for 118 streamgages and developed 47 regression equations to estimate selected flow duration, low flow, and mean flow statistics for the entire State of Connecticut, for the following: 1-, 5-, 10-, 25-, 50-, 75-, 90-, 99-percent flow durations; 7-day, 10-year low-flow frequency and 30-day, 2-year low-flow frequency; and mean flow, spring mean flow, and harmonic mean flow. In addition, regression equations were developed for monthly and seasonal flow durations, ranging from 25 to 99 percent for aquatic biological processes of salmonid spawning (November), overwinter (December–February), clupeid spawning (May), resident spawning (June), and rearing and growth (July–October) periods, and for flow durations ranging from 1 to 99 percent for the habitat forming (March–April) period. Statistics were derived from daily mean streamflow data collected from streamgages with at least 10 years of data through water year 2022 in southern New England and eastern New York. Forty streamgages in Connecticut and adjacent areas of neighboring States were used in the regression analysis. Regression methods of weighted least squares and generalized least squares were used to derive the final coefficients and measures of uncertainty for the regression equations. The equations used to estimate selected streamflow statistics were developed by relating the flow statistics to different basin characteristics (physical, land cover, and climatic) at the 40 streamgages. Nine basin characteristics served as the explanatory variables in the statewide regression equations: drainage area, percentage of area with coarse-grained stratified deposits, stream density, mean basin slope, mean basin elevation, percentage of area with hydrologic soil group A, mean monthly precipitation for November, mean seasonal precipitation in the winter (December, January, and February), and mean annual temperature. The root mean square error of the 47 equations ranged from 7.9 to 121.9 percent, with an average of 27.9 percent. The equations estimate flows most accurately near the mean (50-percent flow duration), become less accurate for low flows, and are the least accurate for extreme low flows. The root mean square error for the 50-percent flow duration is 15.1 percent, with an average of 17.6 percent across the six periods. The extreme low flow statistics of 7-day, 10-year low-flow frequency, 99-percent flow duration, and 99-percent rearing and growth period flow durations have root mean square errors of 121.9, 105.1, and 121.9 percent, respectively. The adjusted coefficient of determination of the 47 equations ranged from 73.4 to 99.5 percent, with an average of 95.1 percent.

Connecticut↗

USGS2018

Spatial and temporal trends in selenium in the upper Blackfoot River watershed, southeastern Idaho, 2001–16

Phosphate mining in southeastern Idaho has been an important economic driver for the region and State for over 100 years, but weathering of mining waste rock has also released selenium into the Blackfoot River. This report analyzes and presents data from three separate but complementary studies monitoring selenium in streams in the region. The U.S. Geological Survey (USGS), in cooperation with the Bureau of Land Management, has been collecting streamflow and water-quality samples year-round on the Blackfoot River above reservoir near Henry, Idaho, (USGS streamgage 13063000) since 2001. Over the same period, the Idaho Department of Environmental Quality (IDEQ) has collected streamflow and water-quality samples from the Blackfoot River and tributaries during spring runoff. Data collected from 2001 to 2012 during these two studies were analyzed previously. This report extends the analysis using new data collected through 2016. This report also presents the results of a joint USGS and IDEQ seepage study conducted in June 2016 in the Blackfoot River near Dry Valley. Although limited in scope, this study explored the hypothesis that unaccounted selenium loading (loading in excess of tributary inputs) in this reach could be caused by groundwater inflow. USGS dissolved selenium concentration data from streamgage 13063000 on the Blackfoot River and IDEQ data from the mainstem and mining-affected tributaries are highest shortly after peak runoff and correlate with streamflow magnitude. Although earlier analyses indicated increasing selenium concentrations from 2001 to 2012, this study shows that runoff and baseflow dissolved selenium concentrations increased and then decreased during 2001–16. High median runoff concentrations from 2005 through 2011 are associated with high snowpack and streamflow. This result suggests that more snowmelt moving through selenium-bearing waste rock leads to increased instream concentrations. The time lag between peak runoff and then peak selenium concentrations suggests that selenium mobilization may occur as snowmelt percolates through waste rock rather than by faster surface runoff. However, variability in local snow accumulation and snowmelt conditions likely affects interannual variability in selenium concentrations in the mainstem Blackfoot River and tributaries. In contrast to runoff selenium concentrations, median baseflow (August to October) dissolved selenium concentrations were highest from 2009 to 2013. Aquatic plant senescence and release of selenium is an unlikely explanation for this trend because plants are still growing during this time of year. In addition, this trend is observed during and shortly after the observed period of high snowpack. Thus, increased baseflow selenium concentrations suggest that increased selenium loading to alluvial groundwater may occur during periods of high snowmelt and manifest in later years as higher instream concentrations during baseflows when the majority of streamflow is attributable to groundwater gains. Runoff-period streamflow and selenium loads were calculated for the tributaries and mainstem Blackfoot River. Selenium loads vary from year to year with mainstem loads greater than the total tributary contributions in some years and less than tributary contributions in other years. In general, East Mill Creek usually accounted for the largest proportion of the total Blackfoot River load, and unaccounted loads (loads in excess of tributary inputs) often occurred in the vicinity of Spring Creek and Dry Valley. The latter observation led the USGS and IDEQ to conduct a seepage study to further investigate groundwater and selenium loading to the Blackfoot River near Dry Valley. The seepage study results show consistent albeit small unaccounted increases in streamflow and dissolved selenium load in the Blackfoot River near Dry Valley. Field observation of a spring to the north of the river and independent groundwater monitoring data from Dry Valley to the south of the river suggest that alluvial groundwater may discharge to the river from both sides. However, the small unaccounted selenium load measured in the June 2016 study relative to loads measured during runoff suggest that groundwater loading in this reach may occur primarily during runoff. An improved understanding of alluvial groundwater extent, gradient, hydraulic conductivity, and quality would aid in interpreting unaccounted gains and losses in selenium loads in the Blackfoot River. Finally, State of Idaho selenium water-quality criteria have recently shifted to a hierarchical fish tissue and water concentration scheme. This report summarizes existing fish tissue and water-quality data in the mainstem and offers considerations for future selenium monitoring in the Blackfoot River.

Idaho↗

USGS2018

Delineation of the hydrogeologic framework of the Big Sioux aquifer near Sioux Falls, South Dakota, using airborne electromagnetic data

The U.S. Geological Survey, in cooperation with the City of Sioux Falls, South Dakota, began developing a groundwater-flow model of the Big Sioux aquifer in 2014 that will enable the City to make more informed water management decisions, such as delineation of areas of the greatest specific yield, which is crucial for locating municipal wells. Innovative tools are being evaluated as part of this study that can improve the delineation of the hydrogeologic framework of the aquifer for use in development of a groundwater-flow model, and the approach could have transfer value for similar hydrogeologic settings. The first step in developing a groundwater-flow model is determining the hydrogeologic framework (vertical and horizontal extents of the aquifer), which typically is determined by interpreting geologic information from drillers’ logs and surficial geology maps. However, well and borehole data only provide hydrogeologic information for a single location; conversely, nearly continuous geophysical data are collected along flight lines using airborne electromagnetic (AEM) surveys. These electromagnetic data are collected every 3 meters along a flight line (on average) and subsequently can be related to hydrogeologic properties. AEM data, coupled with and constrained by well and borehole data, can substantially improve the accuracy of aquifer hydrogeologic framework delineations and result in better groundwater-flow models. AEM data were acquired using the Resolve frequency-domain AEM system to map the Big Sioux aquifer in the region of the city of Sioux Falls. The survey acquired more than 870 line-kilometers of AEM data over a total area of about 145 square kilometers, primarily over the flood plain of the Big Sioux River between the cities of Dell Rapids and Sioux Falls. The U.S. Geological Survey inverted the survey data to generate resistivity-depth sections that were used in two-dimensional maps and in three-dimensional volumetric visualizations of the Earth resistivity distribution. Contact lines were drawn using a geographic information system to delineate interpreted geologic stratigraphy. The contact lines were converted to points and then interpolated into a raster surface. The methods used to develop elevation and depth maps of the hydrogeologic framework of the Big Sioux aquifer are described herein. The final AEM interpreted aquifer thickness ranged from 0 to 31 meters with an average thickness of 12.8 meters. The estimated total volume of the aquifer was 1,060,000,000 cubic meters based on the assumption that the top of the aquifer is the land-surface elevation. A simple calculation of the volume (length times width times height) of a previous delineation of the aquifer estimated the aquifer volume at 378,000,000 cubic meters; thus, the estimation based on AEM data is more than twice the previous estimate. The depth to top of Sioux Quartzite, which ranged in depth from 0 to 90 meters, also was delineated from the AEM data.

South Dakota↗

USGS2013

Selenium in ecosystems within the mountaintop coal mining and valley-fill region of southern West Virginia-assessment and ecosystem-scale modeling

Coal and associated waste rock are among environmental selenium (Se) sources that have the potential to affect reproduction in fish and aquatic birds. Ecosystems of southern West Virginia that are affected by drainage from mountaintop coal mines and valleys filled with waste rock in the Coal, Gauley, and Lower Guyandotte watersheds were assessed during 2010 and 2011. Sampling data from earlier studies in these watersheds (for example, Upper Mud River Reservoir) and other mining-affected watersheds also are included to assess additional hydrologic settings and food webs for comparison. Basin schematics give a comprehensive view of sampled species and Se concentration data specific to location and date. Food-web diagrams document the progression of Se trophic transfer across suspended particulate material, invertebrates, and fish for each site to serve as the basis for developing an ecosystem-scale model to predict Se exposure within the hydrologic conditions and food webs of southern West Virginia. This approach integrates a site-specific predator’s dietary exposure pathway into modeling to ensure an adequate link to Se toxicity and, thus, to species vulnerability. Site-specific fish abundance and richness data in streams documented various species of chub, shiner, dace, darters, bass, minnow, sunfish, sucker, catfish, and central stoneroller (Campostoma anomalum), mottled sculpin (Cottus bairdii), and least brook lamprey (Lampetra aepyptera). However, Se assessment species for streams, and hence, model species for streams, were limited to creek chub (Semotilus atromaculatus) and central stoneroller. Both of these species of fish are generally considered to have a high tolerance for environmental stress based on traditional comparative fish community assessment, with creek chub being present at all sites. Aquatic insects (mayfly, caddisfly, stonefly, dobsonfly, chironomid) were the main invertebrates sampled in streams. Collection of suspended particulate material acted as an integrator of organic-rich, fine-grained biomass present in streams. The base-case food web modeled for streams was suspended particulate material to aquatic insect to creek chub, with comparative modeling of a direct particulate-to-stoneroller food web. Model species for a reservoir setting were based on an earlier study of bluegill sunfish (Lepomis macrochirus), green sunfish (Lepomis cyanellus), and largemouth bass (Micropterus salmoides). Several reservoir food webs were considered based on a variety of invertebrates (insect, snail, clam). For stream and reservoir settings, predicted Se concentrations in exposure scenarios showed a high degree of correlation (r 2 = 0.91 for invertebrates and 0.75 for fish) with field observations of Se concentrations when modeling was initiated from suspended-particulate-material Se concentrations and model transfer parameters defined previously in the literature were used. These strong correlations validate the derived site-specific model and establish sufficient confidence that the predictions from the developed model can be quantitatively applied to the ecosystems in southern West Virginia. An application of modeling used a metric describing the partitioning of Se between particulate material and dissolved phases (K d ) to allow determination of a dissolved Se concentration that would be necessary to attain a site-specific Se fish body burden. The operationally defined K d quantifies the complex process of transformation at the base of a food web on a site-specific basis. The magnitude of this metric is known to vary with such factors as Se speciation, particulate-material type, and hydrology. This application (1) ties dissolved Se concentrations to fish tissue concentrations; (2) allows consideration of different choices for intervening site-specific exposure steps that set Se bioaccumulation, partitioning, and bioavailability; and (3) generates implications for management decisions that define protection through different regulatory pathways and guidelines. The range of model outcomes accounts for critical sources of variability and establishes whether site and food-web characterization were adequate to represent the dynamics of the system with certainty. This is especially true in terms of particulate-material phases at the base of the food web and utilization of K d in different hydrologic settings. For streams, a range of field-derived K d ds were applied to food-web exposure scenarios within a framework of locational and hydrologic variables (area of stream basin; stream gradient and discharge) that may affect the magnitude of K d . Overlaying even a coarse temporal scale that acknowledges variability in stream dissolved Se and Se speciation, such as through seasonal derivation of K d , can substantially narrow model uncertainty. Modeling that constrains the place and time of greatest ecosystem Se sensitivity within a specified food web gives insight into Se risk and identifies controlling management alternatives within a watershed or stream basin. If there is a range of hydrologic settings, specificity is needed to establish a hierarchy of in-stream and off-stream habitats for a watershed approach that takes into account Se-enriched water moving through different K d and food web environments. If there is a range of predator vulnerabilities (measured as a combination of food-web Se biodynamics and response in Se toxicity tests) within the site-specific community of fish species to be protected, then choice of fish species is critical to protection because it determines the food web and, hence, the magnitude of biotransfer through which Se is modeled. Whether creek chub is representative of the vulnerability to Se of all fish species encountered within the study-site ecosystems will require additional species-specific data and analysis. A range of site-specific scenarios illustrated here set model outcomes, but the final quantitative evaluation of alternatives and their implications will be those generated through choices and guidance formulated by state and other agencies in their decisionmaking processes. Proposed additions and refinements to the ecosystem-scale site-specific approach developed here include consideration of: measurement of temporally matched pairs of dissolved and suspended-particulate-material Se concentrations across a broader range of stream sites to expand the stream K d database and to test the representativeness of a suspended-particulate-material sample within a stream; characterization of different phases of particulate material across seasons to better define the base of the food web and connect to invertebrate feeding; refinement of model assumptions concerning dietary preferences and composition for fish to develop additional trophic transfer factors (TTFs) (for example, calculation of TTFinvertebrate composite for mixed diets); expansion of modeling of fish species and their food webs to include Se-vulnerable species; temporal characterization of a predator’s life cycle and habitat use as additional model layers to integrate with Se biodynamics in streams; investigation of the effect of stream gradient on K d based on a finer scale than presented here in terms of such variables as residence time, watershed dilution, and physical habitat attributes (for example, amount of ponding versus run or riffle within a stream); and linkage to discharge through use of stream gaging to record variability and enable model organization within water-year types and discharge seasons. Investigating the presence and variability of prey and predator species in demographically open systems such as streams also is key to model outcomes given the overall environmental stressors (for example, general landscape change, food-web disruption, recolonization potential) imposed on the composition of biological communities in coal mining and valley-fill affected watersheds

West Virginia↗