Geology topics

Timothy T. Bartos

Publications and source records attributed to Timothy T. Bartos.

At least 19 recordsLinked to original sources

USGS2025

Land application of drill waste: A scope analysis

Drilling fluid waste land application, a process where drilling wastes are spread and tilled into the land surface, has become common in some petroleum-producing states, however, the potential benefits and risks of this practice are not well studied. Drilling fluids can be water- or oil-based and can have high concentrations of total soluble salts and total petroleum hydrocarbons. Comprehensive chemical characterization of these fluids is not well documented in the literature, and the extent of land application is largely unknown. We hypothesized that the land application of drill waste would fluctuate over time due to economic factors. To begin to understand the extent of historical and potential future land application, we analyzed data from over 5,800 drilling fluid land application permits collected by the Oklahoma Corporation Commission for years 2000, 2005, 2010, and 2015–2020. During the years studied, drilling fluid wastes were applied to more than 250,000 acres in Oklahoma, with over 54,000 thousand barrels (Mbbl) of liquids and nearly 21,000 Mbbl of solids applied. Land application is widespread (occurring in 59/77 counties), however recent drilling activity, land availability, and the economics of transportation have created conditions favorable for land application specifically in the Anadarko Basin. Land application can co-occur with sensitive areas, such as important groundwater and surface-water drinking sources and agricultural fields used for subsistence or feed crop production. Our approach for quantifying the extent of land application, along with further chemical characterization studies, can aid operators and land managers who are considering this practice in assessing the associated benefits and risks.

Oklahoma↗

USGS2025

Hydrogeology and groundwater quality in the Snake River alluvial aquifer at Jackson Hole Airport, Wyoming, 2011–20

The Snake River alluvial aquifer underlying the Jackson Hole Airport (JHA) in northwest Wyoming is an important source of water used for domestic, commercial, and irrigation purposes by the airport and nearby residents. The U.S. Geological Survey, in response to previously identified water-quality concerns in the area, monitored and evaluated changes in hydrogeologic characteristics and groundwater-quality conditions of the alluvial aquifer during 2011–20. During that period, the Jackson Hole Airport made several changes that potentially improved water quality at and downgradient from the airport. Well, water level, and hydrogeologic data were collected from the alluvial aquifer to identify hydrogeologic characteristic and groundwater quality changes. Additionally, results of statistical tests were applied to water-quality results to evaluate trends in selected physical properties and constituent concentrations with time. The trends of those data show that water quality did improve overall during the study period compared to previously collected data. Presumably, these trends are in response to the changes in the aircraft deicing/anti-icing fluid (ADAF) formulation used by the JHA, the many JHA infrastructure improvements made during 2011–20, the degradation of existing ADAFs in subsurface soils and groundwater, or some combination of these possibilities.

Wyoming↗

USGS2023

U.S. Geological Survey and Blackfeet Water Department Hydrologic Assessment of the Blackfeet Indian Reservation, Montana

The Blackfeet Nation seeks an increased scientific understanding of the water resources within the Blackfeet Indian Reservation of northwestern Montana. Hydrologic information is needed to better inform water-management decisions as the Blackfeet Nation implements the Blackfeet Water Rights Compact, initiates new water-use projects, and improves the Blackfeet Irrigation Project. The U.S. Geological Survey and the Blackfeet Water Department began cooperating in 2019 to design and implement a hydrologic data-collection program. The program is being implemented in phases that include discrete and continuous discharge measurements of streams and canals, installation, operation of streamgages, groundwater-level monitoring, and database management. Data collected will be used to characterize current hydrologic conditions on the reservation and will act as a baseline for comparison as Blackfeet Nation water projects are implemented.

Montana↗

USGS2022

Potential effects of energy development on environmental resources of the Williston Basin in Montana, North Dakota, and South Dakota—Water resources

The Williston Basin has been a leading oil and gas producing area for more than 50 years. While oil production initially peaked within the Williston Basin in the mid-1980s, production rapidly increased in the mid-2000s, largely because of improved horizontal (directional) drilling and hydraulic fracturing methods. In 2012, energy development associated with the Bakken Formation was identified as a priority requiring collaboration toward improved timeliness of issuing permits for new wells combined with reasonable measures to maintain environmental quality. Shortly thereafter, the Bakken Federal Executive Group was created to address common challenges associated with energy development. The Bakken Federal Executive Group partner agencies identified a gap in current understanding of the cumulative environmental challenges attributed to energy development throughout the area, resulting in an effort to aggregate scientific data and identify additional research and information needs related to natural resources within areas of energy development in the Williston Basin. As part of this effort, water resources in the area (including groundwater; streams and rivers; and lakes, reservoirs, and wetlands) were characterized and described in terms of physical occurrence, flow characteristics, recharge, water quality, and water use. Similarly, waters produced during energy-development activities also were characterized even though these waters are not considered usable resources within the area. Groundwater resources were characterized by the major hydrogeologic units, or aquifers, identifying the units that supply most groundwater used for domestic, stock, agricultural, and industrial purposes. The groundwater characterization included other deeper hydrogeologic units in the Williston Basin that may be a useable source of water with treatment, have utility as a reservoir for reinjection of produced waters, or be a source of minerals and energy resources. A generalized groundwater budget and flow system identifying the sources of recharge (stream infiltration, precipitation, and movement [leakage] from other aquifers) and the general groundwater flow direction is included for each of the major hydrogeologic units. Rivers and streams within the Williston Basin with 10 or more years of continuous streamflow data were identified. For a subset of these sites, streamflow characteristics, including the monthly and annual mean flow, were generated to identify seasonal and interannual changes in streamflow and thus provide information on the drivers and reliability of streamflow at the seasonal or multiyear scale. Daily streamflow and annual extreme flows (peak and low flow) also were estimated for the subset of sites. The daily streamflow and annual extreme flow values provide information on short-term or extreme events that are relevant to infrastructure design and evaluating spills, leaks, or accidental discharges of water or petroleum products. Surface-water features (lakes, ponds, and wetlands) were classified using the Cowardin system and identified on the National Wetlands Inventory maps generated by the U.S. Fish and Wildlife Service. The spatial distribution of the surface-water features was analyzed by State, county, and specifically in comparison to the Prairie Pothole Region. The proximity of the surface-water features to energy development infrastructure (specifically oil or gas well pads) was evaluated. It was determined that, although oil or gas wells are often near a surface-water feature, most surface-water features do not have wells nearby, with the exception of wells in the Prairie Pothole Region. Water-quality data were aggregated from two data sources: (1) the Water-Quality Portal, sponsored by the U.S. Geological Survey (USGS), U.S. Environmental Protection Agency (EPA), and National Water Quality Monitoring Council; and (2) a data compilation completed as part of the USGS National Water-Quality Assessment project. The Water-Quality Portal integrates publicly available water-quality data from databases maintained by the USGS, EPA, and U.S. Department of Agriculture, including water-quality data from Tribal, State, and local databases. Water-quality data for 15 commonly measured water-quality constituents were aggregated for groundwater, rivers and streams, and lakes and reservoirs. For each aggregated dataset (groundwater, rivers and streams, and lakes and reservoirs), analyses of the water-quality data included summary statistics, maps of spatial distribution of constituent values, boxplots of constituent values by timeframe or hydrogeologic unit, spatial comparisons of site locations and constituent values to petroleum well density, and comparisons of the constituent values measured to EPA drinking-water standards/guidelines. Produced water includes all fluids brought to the surface along with the targeted hydrocarbons as part of the oil and gas exploration and extraction processes. These fluids may include formation water (waters that co-exist with rock/oil/gas), hydraulic fracturing fluids, and other combinations of water and chemicals used during oil and gas well drilling, development, treatments, recompletions, and workovers. Produced water datasets were aggregated from two sources: the USGS National Produced Waters Geochemical database (ver. 2.1) and a series of projects focused specifically on sampling produced water in the Williston Basin from 2010 to 2014. The National Produced Waters Geochemical database was useful for a general understanding of produced-water chemistry. Produced waters are characterized by extreme salinity and contain elevated concentrations of other constituents (including arsenic, barium, cadmium, lead, zinc, radium-226/radium-228, and ammonium) that could negatively affect water and aquatic resources if released. Produced waters also have a generally unique chemical (isotopic) signature that may be useful in tracking water from different geologic units; for example, the oxygen/deuterium and strontium ratio values measured in brine waters from the Bakken Formation are distinct from brines collected from other geologic units in the Williston Basin. Water-use information related to energy production in the area also was aggregated and summarized. The summary of water use is not limited to oil and gas production but includes water used to produce all types of energy resources in the Williston Basin, including coal/lignite, thermoelectric power, oil and gas, hydropower, biomass and biofuels, wind, geothermal, and solar. Each State has its own methods for regulating and reporting water usage within its jurisdiction. These methods can introduce problems when examining water use from sources, such as the Missouri River or Fox Hills aquifer, that are shared across political boundaries. Without the one-to-one match for usage types and amounts used from a water source, it is difficult to develop a comprehensive water budget for the water source being evaluated. A large amount of freshwater is required to prepare a well for oil and gas well production; in some cases, 3 to 7 million gallons of water are needed per well. The EPA estimates that hydraulic fracturing in the Williston Basin uses between 70 to 140 billion gallons per year. Water also is used for myriad other purposes related to ancillary oil and gas extraction. In addition to water used for immediate energy development, the expanded human workforce migrating into the area and other support staff who have moved into the area during the development also use water. Research and information needs were identified that could be relevant in the evaluation of the effects of energy development on water resources. Information needs related to the evaluation of groundwater resources include the following: improved potentiometric-surface maps for glacial units; availability of a uniform stream network digital geographic coverage that spans the international boundary with Canada; enhanced surface-water use information with regards to the gain and loss of streamflow to shallow groundwater, which would increase understanding groundwater and surface-water interactions; and expanded geophysical assessments. Gaps in the availability of streamflow data include the lack of information on ice-jam flooding despite potential for effects to infrastructure (pipelines, roads, and facilities) and an understanding of the cumulative effects of largely undocumented stock and diversion dams. Although this study resulted in the aggregation of a large quantity of water-quality data, the availability of consistently collected, systematically processed and reported data over large parts of the Williston Basin is sparse. Few samples have been analyzed for constituents that may indicate the effect of energy development on water resources. Constituents that could be considered include boron, chloride, bromide, iodine, fluoride, manganese, lithium, radium, strontium isotopes, volatile organic compounds, and isotopes of inorganic ions (such as hydrogen and carbon). Collaboration between Tribal, Federal, State, and local entities to identify a common study design, common monitoring constituents, and consistent sampling locations would generate datasets with broad utility and would likely result in overall cost savings for monitoring over time. Similarly, there is a need for standardized sample collection, processing, laboratory analytical methods, and the collection of ancillary data for produced waters sampling. Additional characterization of the range of chemical, microbial, and isotopic compositions and quantities of “end-member” produced waters, and the collection of time-series datasets to document the changes in produced waters during and after well development also were needs identified during this study. Water-use estimates would be improved through the implementation of comprehensive studies of water use from groundwater and surface-water sources using consistent methodologies across the Williston Basin. The submission of chemical and water data related to hydraulic fracturing collected by the oil and gas industry would add to the quantity of available data. Consistent implementation of regulations and monitoring controls across political boundaries (State, county, and international) would further improve the consistency of data available for the estimates of water use.

Montana, North Dakota, South Dakota↗

USGS2021

Geologic and hydrogeologic characteristics of the White River Formation, Lance Formation, and Fox Hills Sandstone, northern greater Denver Basin, southeastern Laramie County, Wyoming

In cooperation with the Wyoming State Engineer’s Office, the U.S. Geological Survey studied the geologic and hydrogeologic characteristics of Cenozoic and Upper Cretaceous strata at a location in southeastern Laramie County within the Wyoming part of the Cheyenne Basin, the northern subbasin of the greater Denver Basin. The study aimed to improve understanding of the aquifers/aquifer systems in these strata, motivated in part by declining groundwater levels and interest in exploring future groundwater supplies. Based on detailed geologic characterization using information obtained by drilling and coring a 960-foot-(ft) deep exploratory borehole, and comparisons with previously published descriptions, identified Cenozoic lithostratigraphic units included 40 ft of Quaternary older alluvial fan deposits consisting of an unconsolidated mixture of sand and gravel with lesser quantities of silt and clay in varying proportions and the underlying 407.3-ft-thick White River Formation of late Eocene-Oligocene age consisting largely of mudrocks with sparse thin beds of sandstone, muddy gravel, and conglomeratic mudrocks. Identified Upper Cretaceous lithostratigraphic units included the 351.6-ft-thick Lance Formation, consisting of terrestrial sedimentary rocks including mudrocks (muddy shale and silty and sandy shale, siltstone, claystone, and mudstone) interbedded with much smaller quantities of very fine- to medium-grained muddy and silty sandstone and coal; the 79.6-ft-thick Fox Hills Sandstone, consisting of a transitional marine sequence of muddy or silty sandstone present in five individual beds; and 86.7 ft of the upper transition member of the Pierre Shale, consisting largely of marine sedimentary rocks such as muddy shale. Beds of the upper and lower Fox Hills Sandstone were separated by tongues of the Lance Formation and upper transition member of the Pierre Shale, respectively. The White River hydrogeologic unit, consisting of the entire White River Formation or Group at the study site, did not contain any substantial secondary permeability features in the mudrocks that composed almost all the unit. A monitoring well (BR–1) was completed in the White River aquifer with the well screen open to the only coarse-grained unit (muddy sandstone) that had sufficient thickness and permeability to be considered as an aquifer. Sampling of the well for a broad suite of constituents indicated groundwater generally was of excellent quality except dissolved arsenic was detected at a concentration greater than the U.S. Environmental Protection Agency (EPA) Maximum Contaminant Level, and dissolved sodium was measured at a concentration greater than several EPA Drinking Water Advisory Levels (DWAs) for the constituent. Well development, well purging for groundwater sampling, and calculated aquifer properties indicated the sandstone aquifer screened by monitoring well BR–1 was not very productive. Analysis of the well water-level responses in BR–1 to atmospheric loading and Earth tides indicated the responses were consistent with a confined-aquifer response with wellbore-storage effects. Hydraulic properties estimated based on these responses yielded values of hydraulic conductivity ( K , 0.057 foot per day [ft/d]), specific storage ( Ss , 1.6×10 −6 per foot [ft −1 ]) and porosity ( n , 0.43). Water levels filtered to remove the effects of atmospheric loading and Earth tides indicated an upward trend (+1.13 foot per year [ft/yr]) during the period analyzed, September 5, 2014, to September 30, 2017. Lithologic characteristics of the Lance hydrogeologic unit, consisting of the entire Lance Formation at the study site, indicated a potential aquifer in a “sandy” interval in the upper part of the unit. Most of the Lance hydrogeologic unit below the “sandy” interval consisted of various low-permeability lithologies unlikely to yield substantial quantities of water. This lower part of the hydrogeologic unit likely functions as a confining unit separating the underlying Lance-Fox Hills aquifer. A geologic cross section constructed for this study indicated fine-grained sediments composed most of the Lance Formation/hydrogeologic unit not only at the study location, but also throughout southern Laramie County along the line of section and throughout the Wyoming and Colorado parts of the Cheyenne Basin. A monitoring well (LN–1) completed in a sandstone bed in the “sandy” interval of the Lance hydrogeologic unit produced a mean of about 23 gallons per minute (gal/min) during well development, indicating sandstone beds can form moderately productive confined subaquifers in this part of the hydrogeologic unit. Analysis of the well water-level responses in well LN–1 to atmospheric loading and Earth tides indicated the responses were consistent with a confined-aquifer response. Hydraulic properties estimated based on these responses yielded values for a lower bounding K of 0.60 ft/d, Ss of 1.6×10 −6 ft −1 , and n of 0.38. Water levels filtered to remove the effects of atmospheric loading and Earth tides indicated a downward trend (−0.86 ft/yr) during the period analyzed (November 8, 2014, to September 30, 2017). Analyses for a broad suite of constituents in samples from well LN–1 indicated groundwater quality generally was excellent, although dissolved sodium was measured at a concentration greater than two EPA DWA levels for the constituent. Because of the absence of any overlying or intertonguing sandstone beds belonging to the lower/basal part of the Lance Formation, the Lance-Fox Hills aquifer at the study site consisted only of the five sandstone beds of the Fox Hills Sandstone. The cross section constructed for this study illustrated how the Fox Hills Sandstone, and thus, most of the Lance-Fox Hills aquifer, consists of a series of sandstone bodies that overlap (shingle) upward to the east across southern Laramie County. These bodies collectively form a fairly continuous body of sandstone, thus potentially forming an areally extensive aquifer across southern Laramie County, and by extension, throughout most of the formation’s extent in the Wyoming part of the Cheyenne Basin, as is the case in the Colorado part of the basin. A monitoring well (FH–1) completed in part of the thickest sandstone bed of the Lance-Fox Hills aquifer was moderately to highly productive and easily produced 25 to 30 gal/min after development. Substantially larger water production rates likely could be obtained by penetrating the full thickness of this bed and by completing a well open to the other overlying and underlying sandstone beds of the aquifer. Analysis of the water-level responses in well FH–1 to atmospheric loading and Earth tides indicated the responses were consistent with a confined-aquifer response. Hydraulic properties computed based on these responses yielded values for a lower bounding estimate for K of 0.26 ft/d, for Ss of 1.0×10 −6 ft −1 , and for n of 0.41. Water levels filtered to remove the effects of atmospheric loading and Earth tides indicated a downward trend (−1.74 ft/yr) during the period analyzed, December 19, 2014, to September 30, 2017. Sampling of monitoring well FH–1 and two production wells completed in the Fox Hills Sandstone in other parts of Laramie County indicated groundwater quality generally is excellent, although pH exceeded a recommended EPA aesthetic drinking-water standard (Secondary Maximum Contaminant Level) in two of three sampled wells, total dissolved solids concentrations exceeded the Secondary Maximum Contaminant Level in one of the two sampled production wells, and dissolved sodium was measured in all three sampled wells at a concentration greater than two EPA DWA levels for the constituent. The Wyoming Class II agricultural (irrigation) sodium adsorption ratio standard of 8 was exceeded in all three sampled wells, indicating these waters are not suitable for irrigation use. Computed vertical hydraulic gradients indicated a strong potential for downward flow throughout the groundwater system at the study site, including from the low-yielding aquifer in the upper White River Formation/hydrogeologic unit (monitoring well BR–1) to the sandstone subaquifer in the Lance Formation/hydrogeologic unit (monitoring well LN–1), and from the Lance subaquifer (monitoring well LN–1) to the sandstone bed/aquifer that composes much of the Lance-Fox Hills aquifer thickness at the study site (monitoring well FH–1). However, large hydraulic-head differences between wells indicated high resistance to vertical flow attributable to the low vertical hydraulic conductivity of intervening strata, which consisted almost entirely of low-permeability mudrocks. The confined nature of the sandstone aquifers monitored by the various wells coupled with dissimilarities between groundwater-level fluctuations and trends in groundwater levels indicated downward flow through the intervening strata (primarily mudrocks in the various lithostratigraphic/hydrogeologic units) between the examined sets of wells likely was small.

Wyoming↗

USGS2018

Groundwater availability of the Williston Basin, United States and Canada

Executive Summary The Williston Basin of the Northern Great Plains is a sedimentary basin—a geologic bowl-like structure filled with layered sedimentary rocks dating as far back as the Paleozoic age. The basin, which is nationally important for the production of energy resources, spans Montana, North Dakota, and South Dakota in the United States, and Manitoba and Saskatchewan in Canada. The three uppermost principal aquifer systems are the glacial, lower Tertiary, and Upper Cretaceous aquifer systems. As deep as 3,000 feet (ft) at the center of the basin, these are the most accessible aquifer systems in the basin and are the primary sources of potable groundwater in much of this area. The glacial aquifer system consists of Quaternary-age unconsolidated till, silt, clay, outwash sand and gravel, and occasional cobbles and boulders. The lower Tertiary and Upper Cretaceous aquifer systems consist primarily of sandstone, siltstone, mudstone, shale, and coal. As energy demands have increased in the basin, horizontal drilling and hydraulic-fracturing have been used (especially since 2005) to develop previously inaccessible formations—namely, the Bakken and Three Forks Formations. The basin has yielded a large supply of domestic oil and natural gas since the 1950s, but the technologies required to extract those materials use large amounts of freshwater. The increasing freshwater demands of energy production in the Williston Basin, in addition to population growth, have led to a need for new tools to assess groundwater resources.

Williston Basin↗

USGS2016

U.S. Geological Survey science for the Wyoming Landscape Conservation Initiative—2015 annual report

This is the eighth annual report highlighting U.S. Geological Survey (USGS) science and decision-support activities conducted for the Wyoming Landscape Conservation Initiative (WLCI). The activities address specific management needs identified by WLCI partner agencies. In 2015, USGS scientists continued 24 WLCI projects in 5 categories: (1) acquiring and analyzing resource-condition data to form a foundation for understanding and monitoring landscape conditions and projecting changes; (2) using new technologies to improve the scope and accuracy of landscape-scale monitoring and assessments, and applying them to monitor indicators of ecosystem conditions and the effectiveness of on-the-ground habitat projects; (3) conducting research to elucidate the mechanisms that drive wildlife and habitat responses to changing land uses; (4) managing and making accessible the large number of databases, maps, and other products being developed; and (5) coordinating efforts among WLCI partners, helping them to use USGS-developed decision-support tools, and integrating WLCI outcomes with future habitat enhancement and research projects. Of the 24 projects, 21 were ongoing, including those that entered new phases or more in-depth lines of inquiry, 2 were new, and 1 was completed. A highlight of 2015 was the WLCI science conference sponsored by the USGS, Bureau of Land Management, and National Park Service in coordination with the Wyoming chapter of The Wildlife Society. Of 260 participants, 41 were USGS professionals representing 13 USGS science centers, field offices, and Cooperative Wildlife Research Units. Major themes of USGS presentations included using new technologies for developing more efficient research protocols for modeling and monitoring natural resources, researching effects of energy development and other land uses on wildlife species and habitats of concern, and modeling species distributions, population trends, habitat use, and effects of land-use changes. There was also a special session on the effectiveness of Wyoming’s Sage-Grouse Executive Order. Combined, USGS presentations provided WLCI partners with a wealth of information and conservation tools. The project completed in 2015 yielded an index of important agricultural lands in the WLCI region. The index improves upon existing measures of agricultural productivity and provides planners and managers with additional values to consider when making decisions about land use and conservation actions. The two new projects include an analysis of satellite imagery to quantify sagebrush productivity and mortality, and an evaluation of how groundwater and small streams interact in the upper Green River Basin. Initiated in response to concern among WLCI partners that large areas of sagebrush appear to have died recently, the sagebrush study objectives are to assess effects of these mortality events on overall sagebrush ecosystem productivity, evaluate the feasibility of using satellite imagery to detect patterns in sagebrush mortality over time, and identify factors driving these mortality events. The groundwater-streamflow interaction study is being conducted by hydrologists and fish ecologists to better understand how groundwater-streamflow interactions are affected by energy-resource development and how native fish communities are affected by these factors. Expected outcomes of both new projects will provide WLCI partners with additional information and decision-support tools. Highlights of ongoing science foundation activities included simulations of nine alternative build-out scenarios for oil and gas development and an associated online fact sheet that explains how the simulations were conducted, with an applied example for the Atlantic Rim. Also completed in 2015 was an update of the USGS online inventory of mineral resources data, and publication of a USGS uranium resource survey for the WLCI region. Combined, the outcomes of this work provide decisionmakers and managers with important baseline information for existing and (or) future planning and monitoring efforts. Terrestrial monitoring activities in 2015 emphasized the use of satellite data in combination with other technologies and field data to monitor, assess, and (or) forecast distribution patterns and (or) trends in sagebrush ecosystems, seasonal and migration stopover habitats used by mule deer and elk, and semi-arid aspen woodlands. Several professional papers detailing new monitoring models and results have been published. Combined, this and related work will help managers understand distribution patterns and trends among priority habitats, identify areas in need of restoration or conservation, and monitor the effectiveness of habitat-management actions. Aquatic monitoring activities entailed not only the new groundwater-streamflow interaction study already mentioned, but also continued monitoring with streamgages paired with nearby wells in the Green River Basin to assess groundwater effects on streamflow and surface water temperatures. A map that portrays groundwater levels and general direction of flow in the Green River Basin was published as well . Overall, outcomes of USGS hydrological research and monitoring will inform WLCI partners about water resources in the WLCI region and help to explain fish-community responses to energy-resource development. In 2015, USGS terrestrial wildlife ecologists continued to make crucial strides towards better understanding wildlife species responses to energy-resource development and other land-use changes. This body of research includes six taxa that require or heavily depend on sagebrush habitats: sage-grouse, pygmy rabbits, 3 songbird species, and mule deer. Native fish communities are also being evaluated. Approaches include modeling and mapping wildlife species distributions, abundances, and trends; using satellite and other technologies to track wildlife seasonal movements; conducting successive phases of research that build on the knowledge gained through prior phases to reveal the specific factors or thresholds that drive population- or individual-level responses to changes; and conducting population viability analyses. Additionally, wildlife habitat association models for pygmy rabbit and sage-grouse were combined with the oil and gas build-out scenarios to project species responses to alternative energy development scenarios. Outcomes of the wildlife response research are helping decisionmakers and managers identify specific factors that contribute to species population trends, the potential for spatial overlap between important wildlife habitats and proposed energy-resource development, locations of priority habitats for restoration and conservation, and more. Data and WLCI Web site management highlights of 2015 included not only ongoing software upgrades, but also an update of the datasets displayed in two of the online products developed for the WLCI effort: (1) a map of 15,532 oil and natural gas well pad scars and other features associated with oil and gas extraction, and (2) a map of oil and gas, oil shale, uranium, and solar energy production, both for southwestern Wyoming. In addition, a map viewer was developed for a previously published map of coal and wind production in relation to sage-grouse distribution and core management areas in southwestern Wyoming. Combined, these maps place valuable decision-support tools in the hands of WLCI partners. The USGS coordination efforts on behalf of the WLCI in 2015 included significant work on planning and executing the WLCI science conference. They also included ongoing efforts to support Local Project Development Teams and the WLCI Coordination Team (CT) with developing conservation priorities and strategies, identifying priority areas for future conservation actions, supporting the evaluation and ranking of conservation projects, and evaluating the ways in which proposed habitat projects relate to WLCI priorities. In 2015, the USGS also assisted the WLCI CT with updating the WLCI Conservation Action Plan.

Wyoming↗

USGS2015

Hydrogeology, groundwater levels, and generalized potentiometric-surface map of the Green River Basin lower Tertiary aquifer system, 2010–14, in the northern Green River structural basin

In cooperation with the Bureau of Land Management, groundwater levels in wells located in the northern Green River Basin in Wyoming, an area of ongoing energy development, were measured by the U.S. Geological Survey from 2010 to 2014. The wells were completed in the uppermost aquifers of the Green River Basin lower Tertiary aquifer system, which is a complex regional aquifer system that provides water to most wells in the area. Except for near perennial streams, groundwater-level altitudes in most aquifers generally decreased with increasing depth, indicating a general downward potential for groundwater movement in the study area. Drilled depth of the wells was observed as a useful indicator of depth to groundwater such that deeper wells typically had a greater depth to groundwater. Comparison of a subset of wells included in this study that had historical groundwater levels that were measured during the 1960s and 1970s and again between 2012 and 2014 indicated that, overall, most of the wells showed a net decline in groundwater levels. The groundwater-level measurements were used to construct a generalized potentiometric-surface map of the Green River Basin lower Tertiary aquifer system. Groundwater-level altitudes measured in nonflowing and flowing wells used to construct the potentiometric-surface map ranged from 6,451 to 7,307 feet (excluding four unmeasured flowing wells used for contour construction purposes). The potentiometric-surface map indicates that groundwater in the study area generally moves from north to south, but this pattern of flow is altered locally by groundwater divides, groundwater discharge to the Green River, and possibly to a tributary river (Big Sandy River) and two reservoirs (Fontenelle and Big Sandy Reservoirs).

Wyoming↗

USGS2015

U.S. Geological Survey science for the Wyoming Landscape Conservation Initiative—2014 annual report

This is the seventh report produced by the U.S. Geological Survey (USGS) for the Wyoming Landscape Conservation Initiative (WLCI) to detail annual activities conducted by the USGS for addressing specific management needs identified by WLCI partners. In FY2014, there were 26 projects, including a new one that was completed, two others that were also completed, and several that entered new phases or directions. The 26 projects fall into several categories: (1) synthesizing and analyzing existing data to identify current conditions on the landscape and using the data to develop models for projecting past and future landscape conditions; (2) monitoring indicators of ecosystem conditions and the effectiveness of on-the-ground habitat projects; (3) conducting research to elucidate the mechanisms underlying wildlife and habitat responses to changing land uses; (4) managing and making accessible the large number of databases, maps, and other products being developed; and (5) coordinating efforts among WLCI partners, helping them use USGS-developed decision-support tools, and integrating WLCI outcomes with future habitat enhancement and research projects. The new (completed) project was the development and publication of a public outreach piece for visitors of Fossil Butte National Monument. The final product was a USGS Fact Sheet that capitalized on previously collected elk-monitoring data to interpret the ecology of the Monument’s elk population and the importance of the Monument’s habitats to this highly visible wildlife species. One of the completed projects entailed developing and evaluating a synthetic approach to high-resolution satellite imagery for use in effectiveness monitoring, which culminated in a journal article. The other completed project was a coalescing of two similar tasks under data and information management that pertain to Web application development and the development of outreach and graphic products into a single integrated project that focuses on developing and maintaining/upgrading Web applications and other tools for visualizing, mapping, and using geospatial data. Major accomplishments for FY2014 included several publications, including Part B of an energy resources map that (with Part A) depicts coal, wind, oil, gas, oil shale, uranium, and solar energy production in the WLCI region. Two published works associated with sage-grouse included a Wildlife Monograph on prioritizing species’ habitats across large landscapes, multiple seasons, and novel areas (using sage-grouse in Wyoming as an example), and a USGS Data Series report that includes both the data used in the habitat-prioritization models and the habitat prioritization models developed for sage-grouse. Our Science Team also published a framework for conducting large, collaborative projects that rely on geospatial data, and a paper that describes the efficacy of fusing satellite data collected at various resolutions for measuring and monitoring vegetation changes. These products are all invaluable tools for maximizing the efficiency and effectiveness of managing species of concern, conducting future landscape-scale assessments, and monitoring status and trends of landscape conditions. Other highlights of FY2014 included a renewed effort to gather and analyze wildlife and habitat status and trend data for the WLCI Interagency Monitoring Database (IAMD) to assess long-term trends and cumulative effects associated with land-use and climate changes. Water-monitoring efforts included drilling four new groundwater-monitoring wells in the Green and New Fork River basins near the proposed Normally Pressured Lance Formation energy development, and continued data collection at established water-monitoring sites. Three additional wells were sampled as part of the Wyoming Groundwater Monitoring Network, bringing the total to 19 Network wells sampled in the WLCI region since 2010. Combined, these water-monitoring efforts can help to identify potential changes in water quality or levels that may result from land-use changes. Major terrestrial monitoring accomplishments included processing satellite imagery from 1985−2010 to develop a historical perspective of long-term vegetation changes, which can serve as a basis for monitoring current and future trends in sagebrush steppe. Such data are crucial tools for agencies tasked with sage-grouse management and conservation. The USGS WLCI Science Team also continued monitoring and testing methods for evaluating WLCI habitat treatments designed to promote aspen regeneration and enhance sage-grouse habitat, and to assess how those treatments influence invasive species distributions and ungulate herbivory. Highlights included analyzing field data collected to elucidate the relationships between sage-grouse habitat use and the proximity of energy infrastructure, and using new instruments to measure productivity responses of aspen woodlands to various factors. Numerous FY2014 accomplishments specifically addressed agency needs to manage and conserve Wyoming’s wildlife species of concern. A pygmy rabbit habitat model and Wyoming distribution map were completed to identify factors associated with rabbit habitat occupancy. Previous work on sage-grouse population dynamics was expanded to better understand the factors that drive long-term viability of sage-grouse populations and to develop a tool that helps to identify key factors limiting sage-grouse persistence in Wyoming. Field work and data analyses continued for elucidating the relationships between sagebrush songbird abundance and productivity, the intensity of energy development, and community dynamics of nest predators. For the mule deer study, mixed mountain shrublands important to migrating and wintering mule deer were mapped and delivered to WLCI partners. Additionally, the relationships between energy development and crucial winter habitat for mule deer were evaluated, and a new phase of work was implemented to better understand relationships between plant phenology and mule deer migration movements. Finally, initial analyses of data collected to evaluate fish-community composition in relation to habitat quality indicate that water quality, as measured by concentrations of hydrocarbons, water temperature, and others parameters, has been diminished in subwatersheds with higher levels of energy development. Overall, the outcomes and products of these wildlife studies contribute significantly to the information and tools needed for addressing effects of land-use changes on Wyoming’s species of concern. Finally, capabilities of the WLCI Web site and the USGS ScienceBase infrastructure were maintained and upgraded to help ensure access to and efficient use of all the WLCI data, products, assessment tools, and outreach materials that have been developed. Of particular note is the completion of three Web applications developed for mapping (1) the 1900−2008 progression of oil and gas development;(2) the predicted distributions of Wyoming’s Species of Greatest Conservation Need; and (3) the locations of coal and wind energy production, sage-grouse distribution and core management areas, and alternative routes for transmission lines within the WLCI region. Collectively, these applications tools provide WLCI planners and managers with powerful tools for better understanding the distributions of wildlife species and potential alternatives for energy development.

Wyoming↗

USGS2014

Geologic and hydrogeologic characteristics of the Ogallala Formation and White River Group, Belvoir Ranch near Cheyenne, Laramie County, Wyoming

The geologic and hydrogeologic characteristics of Tertiary lithostratigraphic units (Ogallala Formation and White River Group) that typically compose or underlie the High Plains aquifer system in southeastern Wyoming were described physically and chemically, and evaluated at a location on the Belvoir Ranch in Laramie County, Wyoming. On the basis of this characterization and evaluation, three Tertiary lithostratigraphic units were identified using physical and chemical characteristics determined during this study and previous studies, and these three units were determined to be correlative with three identified hydrogeologic units composing the groundwater system at the study site—a high-yielding aquifer composed of the entire saturated thickness of the heterogeneous and coarse-grained fluvial sediments assigned to the Ogallala Formation (Ogallala aquifer); an underlying confining unit composed primarily of very fine-grained volcaniclastic sediments and mudrocks assigned to the Brule Formation of the White River Group and some additional underlying sediments that belong to either the Brule or Chadron Formation, or both (Brule confining unit); and an underlying low-yielding aquifer composed primarily of poorly sorted fluvial sediments assigned to the Chadron Formation of the White River Group (Chadron aquifer). Despite widely varying sediment heterogeneity and consolidation, some limited hydraulic connection throughout the full vertical extent of the Ogallala aquifer was indicated but not conclusively proven by interpretation of similar chemical and isotopic characteristics, modern apparent groundwater ages, and similar hydraulic-head responses measured continuously in two Ogallala aquifer monitoring wells installed for this study at two different widely separated (83 feet) depth intervals. Additional work beyond the scope of this study, such as aquifer tests, would be required to conclusively determine hydraulic connection within the Ogallala aquifer. Groundwater levels (hydraulic heads) measured continuously using water-level recorders in both monitoring wells completed in the Ogallala aquifer showed a consistent strong upward vertical gradient in the Ogallala aquifer, indicating the potential for water to move from deeper to shallower parts of the aquifer, regardless of the time of year and the presumed effects of pumping of public-supply and industrial wells in the area. Continuous measurement of groundwater levels in the shallowest monitoring well, installed near the water table, and examination of subsequently constructed water-level hydrographs indicated substantial groundwater recharge is likely during the spring of 2009 and 2010 from the ephemeral stream (Lone Tree Creek) located adjacent to the study site that flows primarily in response to spring snowmelt from the adjacent Laramie Mountains and surface runoff from precipitation events. Using the water-table fluctuation method, groundwater recharge was estimated to be about 13 inches for the period beginning in early October 2009 and ending in late June 2010, and about 4 inches for the period beginning in March 2011 and ending in early July 2011. Comparison of previously measured groundwater levels (hydraulic heads) and groundwater-quality characteristics in nearby monitoring wells completed in the Chadron aquifer with those measured in the two monitoring wells installed for this study in the Ogallala aquifer, combined with detailed lithologic characterization, strongly indicated the Brule confining unit hydraulically confines and isolates the Chadron aquifer from the overlying Ogallala aquifer, thus likely limiting hydraulic connection between the two units. Consequently, because of the impermeable nature of the Brule confining unit and resulting hydraulic separation of the Ogallala and Chadron aquifers, and compared with local and regional hydrostratigraphic definitions of the High Plains aquifer system, the groundwater system in Tertiary lithostratigraphic units overlying the Upper Cretaceous Lance Formation at the location studied on the Belvoir Ranch was defined as being composed of, from shallowest to deepest, the High Plains aquifer system (high-yielding Ogallala aquifer only, composed of the saturated Ogallala Formation); the Brule confining unit composed of the Brule Formation of the White River Group and an underlying fine-grained depth interval with sediments that belong to either the Brule or Chadron Formation, or both; and the low-yielding Chadron aquifer (composed of poorly sorted coarse-grained sediments with substantial fine-grained matrix material assigned to the Chadron Formation of the White River Group).

Wyoming↗

USGS2013

Pesticides in Wyoming Groundwater, 2008-10

Groundwater samples were collected from 296 wells during 1995-2006 as part of a baseline study of pesticides in Wyoming groundwater. In 2009, a previous report summarized the results of the baseline sampling and the statistical evaluation of the occurrence of pesticides in relation to selected natural and anthropogenic (human-related) characteristics. During 2008-10, the U.S. Geological Survey, in cooperation with the Wyoming Department of Agriculture, resampled a subset (52) of the 296 wells sampled during 1995-2006 baseline study in order to compare detected compounds and respective concentrations between the two sampling periods and to evaluate the detections of new compounds. The 52 wells were distributed similarly to sites used in the 1995-2006 baseline study with respect to geographic area and land use within the geographic area of interest. Because of the use of different types of reporting levels and variability in reporting-level values during both the 1995-2006 baseline study and the 2008-10 resampling study, analytical results received from the laboratory were recensored. Two levels of recensoring were used to compare pesticides—a compound-specific assessment level (CSAL) that differed by compound and a common assessment level (CAL) of 0.07 microgram per liter. The recensoring techniques and values used for both studies, with the exception of the pesticide 2,4-D methyl ester, were the same. Twenty-eight different pesticides were detected in samples from the 52 wells during the 2008-10 resampling study. Pesticide concentrations were compared with several U.S. Environmental Protection Agency drinking-water standards or health advisories for finished (treated) water established under the Safe Drinking Water Act. All detected pesticides were measured at concentrations smaller than U.S. Environmental Protection Agency drinking-water standards or health advisories where applicable (many pesticides did not have standards or advisories). One or more pesticides were detected at concentrations greater than the CAL in water from 16 of 52 wells sampled (about 31 percent) during the resampling study. Detected pesticides were classified into one of six types: herbicides, herbicide degradates, insecticides, insecticide degradates, fungicides, or fungicide degradates. At least 95 percent of detected pesticides were classified as herbicides or herbicide degradates. The number of different pesticides detected in samples from the 52 wells was similar between the 1995-2006 baseline study (30 different pesticides) and 2008-2010 resampling study (28 different pesticides). Thirteen pesticides were detected during both studies. The change in the number of pesticides detected (without regard to which pesticide was detected) in groundwater samples from each of the 52 wells was evaluated and the number of pesticides detected in groundwater did not change for most of the wells (32). Of those that did have a difference between the two studies, 17 wells had more pesticide detections in groundwater during the 1995-2006 baseline study, whereas only 3 wells had more detections during the 2008-2010 resampling study. The difference in pesticide concentrations in groundwater samples from each of the 52 wells was determined. Few changes in concentration between the 1995-2006 baseline study and the 2008-2010 resampling study were seen for most detected pesticides. Seven pesticides had a greater concentration detected in the groundwater from the same well during the baseline sampling compared to the resampling study. Concentrations of prometon, which was detected in 17 wells, were greater in the baseline study sample compared to the resampling study sample from the same well 100 percent of the time. The change in the number of pesticides detected (without regard to which pesticide was detected) in groundwater samples from each of the 52 wells with respect to land use and geographic area was calculated. All wells with land use classified as agricultural had the same or a smaller number of pesticides detected in the resampling study compared to the baseline study. All wells in the Bighorn Basin geographic area also had the same or a smaller number of pesticides detected in the resampling study compared to the baseline study.

Wyoming↗

USGS2012

Hydrologic and geochemical data collected near Skewed Reservoir, an impoundment for coal-bed natural gas produced water, Powder River Basin, Wyoming

The Powder River Structural Basin is one of the largest producers of coal-bed natural gas (CBNG) in the United States. An important environmental concern in the Basin is the fate of groundwater that is extracted during CBNG production. Most of this produced water is disposed of in unlined surface impoundments. A 6-year study of groundwater flow and subsurface water and soil chemistry was conducted at one such impoundment, Skewed Reservoir. Hydrologic and geochemical data collected as part of that study are contained herein. Data include chemistry of groundwater obtained from a network of 21 monitoring wells and three suction lysimeters and chemical and physical properties of soil cores including chemistry of water/soil extracts, particle-size analyses, mineralogy, cation-exchange capacity, soil-water content, and total carbon and nitrogen content of soils.

Wyoming↗

USGS2011

Generalized potentiometric surface, estimated depth to water, and estimated saturated thickness of the High Plains aquifer system, March–June 2009, Laramie County, Wyoming

The High Plains aquifer system, commonly called the High Plains aquifer in many publications, is a nationally important water resource that underlies a 111-million-acre area (173,000 square miles) in parts of eight States including Wyoming. Through irrigation of crops with groundwater from the High Plains aquifer system, the area that overlies the aquifer system has become one of the major agricultural regions in the world. In addition, the aquifer system also serves as the primary source of drinking water for most residents of the region. The High Plains aquifer system is one of the largest aquifers or aquifer systems in the world. The High Plains aquifer system underlies an area of 8,190 square miles in southeastern Wyoming. Including Laramie County, the High Plains aquifer system is present in parts of five counties in southeastern Wyoming. The High Plains aquifer system underlies 8 percent of Wyoming, and 5 percent of the aquifer system is located within the State. Based on withdrawals for irrigation, public supply, and industrial use in 2000, the High Plains aquifer system is the most utilized source of groundwater in Wyoming. With the exception of the Laramie Mountains in western Laramie County, the High Plains aquifer system is present throughout Laramie County. In Laramie County, the High Plains aquifer system is the predominant groundwater resource for agricultural (irrigation), municipal, industrial, and domestic uses. Withdrawal of groundwater for irrigation (primarily in the eastern part of the county) is the largest use of water from the High Plains aquifer system in Laramie County and southeastern Wyoming. Continued interest in groundwater levels in the High Plains aquifer system in Laramie County prompted a study by the U.S. Geological Survey in cooperation with the Wyoming State Engineer's Office to update the potentiometric-surface map of the aquifer system in Laramie County. Groundwater levels were measured in wells completed in the High Plains aquifer system from March to June 2009. The groundwater levels were used to construct a map of the potentiometric surface of the High Plains aquifer system. In addition, depth to water and estimated saturated-thickness maps of the aquifer system were constructed using the potentiometric-surface map.

Wyoming↗

USGS2009

Pesticides in Ground Water of Wyoming, 1995-2006

In 1991, members of local, State, and Federal governments, as well as industry and interest groups, formed the Ground-water and Pesticides Strategy Committee (GPSC) to prepare the State of Wyoming Generic Management Plan for Pesticides in Ground Water. Little existing information was available describing pesticide occurrence in ground water; therefore, statewide baseline ground-water sampling was considered a high priority by the GPSC. The GPSC identified 20 pesticides and degradates for baseline ground-water sampling (referred to herein as focal pesticides). Sampling focused on the State's most vulnerable ground water (Wyoming Ground-water and Pesticides Strategy Committee, 1999) as determined by Hamerlinck and Arneson (1998; fig. 1). Ground-water vulnerability is based on inherent sensitivity of the hydrogeology (such as a shallow water table or highly permeable aquifer materials) and overlying land use.

Fact Sheet↗

USGS2009

Occurrence of Pesticides in Ground Water of Wyoming, 1995-2006

Little existing information was available describing pesticide occurrence in ground water of Wyoming, so the U.S. Geological Survey, in cooperation with the Wyoming Department of Agriculture and the Wyoming Department of Environmental Quality on behalf of the Wyoming Ground-water and Pesticides Strategy Committee, collected ground-water samples twice (during late summer/early fall and spring) from 296 wells during 1995-2006 to characterize pesticide occurrence. Sampling focused on the State's ground water that was mapped as the most vulnerable to pesticide contamination because of either inherent hydrogeologic sensitivity (for example, shallow water table or highly permeable aquifer materials) or a combination of sensitivity and associated land use. Because of variations in reporting limits among different compounds and for the same compound during this study, pesticide detections were recensored to two different assessment levels to facilitate qualitative and quantitative examination of pesticide detection frequencies - a common assessment level (CAL) of 0.07 microgram per liter and an assessment level that differed by compound, referred to herein as a compound-specific assessment level (CSAL). Because of severe data censoring (fewer than 50 percent of the data are greater than laboratory reporting limits), categorical statistical methods were used exclusively for quantitative comparisons of pesticide detection frequencies between seasons and among various natural and anthropogenic (human-related) characteristics. One or more pesticides were detected at concentrations greater than the CAL in water from about 23 percent of wells sampled in the fall and from about 22 percent of wells sampled in the spring. Mixtures of two or more pesticides occurred at concentrations greater than the CAL in about 9 percent of wells sampled in the fall and in about 10 percent of wells sampled in the spring. At least 74 percent of pesticides detected were classified as herbicides. Considering only detections using the CAL, triazine pesticides were detected much more frequently than all other pesticide classes, and the number of different pesticides classified as triazines was the largest of all classes. More pesticides were detected at concentrations greater than the CSALs in water from wells sampled in the fall (28 different pesticides) than in the spring (21 different pesticides). Many pesticides were detected infrequently as nearly one-half of pesticides detected in the fall and spring at concentrations greater than the CSALs were detected only in one well. Using the CSALs for pesticides analyzed for in 11 or more wells, only five pesticides (atrazine, prometon, tebuthiuron, picloram, and 3,4-dichloroaniline, listed in order of decreasing detection frequency) were each detected in water from more than 5 percent of sampled wells. Atrazine was the pesticide detected most frequently at concentrations greater than the CSAL. Concentrations of detected pesticides generally were small (less than 1 microgram per liter), although many infrequent detections at larger concentrations were noted. All detected pesticide concentrations were smaller than U.S. Environmental Protection Agency (USEPA) drinking-water standards or applicable health advisories. Most concentrations were at least an order of magnitude smaller; however, many pesticides did not have standards or advisories. The largest percentage of pesticide detections and the largest number of different pesticides detected were in samples from wells located in the Bighorn Basin and High Plains/ Casper Arch geographic areas of north-central and southeastern Wyoming. Prometon was the only pesticide detected in all eight geographic areas of the State. Pesticides were detected much more frequently in samples from wells located in predominantly urban areas than in samples from wells located in predominantly agricultural or mixed areas. Pesticides were detected distinctly less often in sa

Scientific Investigations Report↗

USGS2008

Infiltration from an impoundment for coal‐bed natural gas, Powder River Basin, Wyoming: Evolution of water and sediment chemistry

Development of coal‐bed natural gas (CBNG) in the Powder River Basin, Wyoming, has increased substantially in recent years. Among environmental concerns associated with this development is the fate of groundwater removed with the gas. A preferred water‐management option is storage in surface impoundments. As of January 2007, permits for more than 4000 impoundments had been issued within Wyoming. A study was conducted on changes in water and sediment chemistry as water from an impoundment infiltrated the subsurface. Sediment cores were collected prior to operation of the impoundment and after its closure and reclamation. Suction lysimeters were used to collect water samples from beneath the impoundment. Large amounts of chloride (12,300 kg) and nitrate (13,500 kg as N), most of which accumulated naturally in the sediments over thousands of years, were released into groundwater by infiltrating water. Nitrate was more readily flushed from the sediments than chloride. If sediments at other impoundment locations contain similar amounts of chloride and nitrate, impoundments already permitted could release over 48 × 10 6 kg of chloride and 52 × 10 6 kg of nitrate into groundwater in the basin. A solute plume with total dissolved solid (TDS) concentrations at times exceeding 100,000 mg/L was created in the subsurface. TDS concentrations in the plume were substantially greater than those in the CBNG water (about 2300 mg/L) and in the ambient shallow groundwater (about 8000 mg/L). Sulfate, sodium, and magnesium are the dominant ions in the plume. The elevated concentrations are attributed to cation‐exchange‐enhanced gypsum dissolution. As gypsum dissolves, calcium goes into solution and is exchanged for sodium and magnesium on clays. Removal of calcium from solution allows further gypsum dissolution.

Water Resources Research↗

USGS2008

Quality of Shallow Ground Water in Three Areas of Unsewered Low-Density Development in Wyoming and Montana, 2001

The quality of shallow ground water underlying unsewered low-density development outside of Sheridan and Lander, Wyo., and Red Lodge, Mont., was evaluated. In 2001, 29 wells (10 each in Sheridan and Lander and 9 in Red Lodge) were installed at or near the water table and sampled for a wide variety of constituents to identify potential effects of human activities on shallow ground-water quality resulting from development on the land surface. All wells were completed in unconfined aquifers in unconsolidated deposits of Quaternary age with shallow water tables (less than 50 feet below land surface). Land use and land cover was mapped in detail within a 500-meter radius surrounding each well, and potential contaminant sources were inventoried within the radii to identify human activities that may affect shallow ground-water quality. This U.S. Geological Survey National Water-Quality Assessment ground-water study was conducted to examine the effects of unsewered low-density development that often surrounds cities and towns of many different sizes in the western United States?a type of development that often is informally referred to as ?exurban? or ?rural ranchette? development. This type of development has both urban and rural characteristics. Residents in these developments typically rely on a private ground-water well for domestic water supply and a private septic system for sanitary waste disposal. Although the quality of shallow ground water generally was suitable for domestic or other uses without treatment, some inorganic constituents were detected infrequently in ground water in the three study areas at concentrations larger than U.S. Environmental Protection Agency drinking-water standards or proposed standards. Natural factors such as geology, aquifer properties, and ground-water recharge rates likely influence most concentrations of these constituents. These inorganic constituents generally occur naturally in the study areas and were more likely to limit suitability of water for drinking or other intended uses rather than any constituents suspected of being introduced as a result of human activities. Effects of human activities associated with low-density development, such as septic systems; fertilizer and pesticide use on pastures, lawns and gardens; manure from horses, cattle, and pets; and increases in road construction and vehicular traffic, were minimal at the time of sampling (2001) but were apparent in the presence of a few types of constituents in shallow ground water. Concentrations of nitrate generally were less than a national background level (1.1 milligrams per liter) assumed to indicate effects from human activities. Total coliform bacteria were detected infrequently (in samples from three wells), and Escherichia coli were not detected in samples from a subset of wells. Trace concentrations of methylene blue active substances (ingredients in laundry detergents) were detected at concentrations slightly greater than laboratory reporting levels in samples from 11 wells, but it is unclear if the detections are indicative of natural sources or possible aquifer contamination from septic-tank effluent. Pesticides were detected in both the Sheridan and Lander, Wyo., study areas. Volatile organic compounds were detected very infrequently in all three study areas. Most pesticides and volatile organic compounds were found in water from a few wells in each study area, and commonly as mixtures. The primary exception to this generalization was the relatively widespread detection of the pesticide prometon at trace levels in the Sheridan and Lander study areas. Concentrations of pesticides and volatile organic compounds generally were small and always were smaller than applicable drinking-water standards. Detections of all constituents indicating possible human effects on shallow ground-water quality were consistent with overlying land use mapped during the study, and potential sources of contamination inventoried du

Scientific Investigations Report↗

USGS2006

Estimated water use in Wyoming during 2000

The U.S. Geological Survey (USGS) has compiled and published estimates of water withdrawals every 5 years since 1950. This series of water-use reports serves as one of the few sources of information about regional or national trends in water withdrawals (Hutson and others, 2004). In Wyoming, six categories—irrigation, mining, thermoelectric power, public supply, self-supplied domestic, and industrial—were included in the most recent (2000) USGS compilation of estimated water use. For each category, withdrawal volumes were compiled by water source (surface water or ground water), and by county. Irrigation, public supply, and industrial ground-water withdrawals also were compiled by aquifer. With the exception of saline ground-water mining withdrawals totaling 222 million gallons per day (Mgal/d), all withdrawals in Wyoming were freshwater. Estimated withdrawals are listed from largest to smallest throughout this fact sheet.

Wyoming↗