Cheryl A. Eddy-Miller

Fiber‐optic distributed temperature sensing: A new tool for assessment and monitoring of hydrologic processes

Fiber-optic distributed temperature sensing (FO DTS) is an emerging technology for characterizing and monitoring a wide range of important earth processes. FO DTS utilizes laser light to measure temperature along the entire length of standard telecommunications optical fibers. The technology can measure temperature every meter over FO cables up to 30 kilometers (km) long. Commercially available systems can measure fiber temperature as often as 4 times per minute, with thermal precision ranging from 0.1 to 0.01 °C depending on measurement integration time. In 2006, the U.S. Geological Survey initiated a project to demonstrate and evaluate DTS as a technology to support hydrologic studies. This paper demonstrates the potential of the technology to assess and monitor hydrologic processes through case-study examples of FO DTS monitoring of streamaquifer interaction on the Shenandoah River near Locke’s Mill, Virginia, and on Fish Creek, near Jackson Hole, Wyoming, and estuary-aquifer interaction on Waquoit Bay, Falmouth, Massachusetts. The ability to continuously observe temperature over large spatial scales with high spatial and temporal resolution provides a new opportunity to observe and monitor a wide range of hydrologic processes with application to other disciplines including hazards, climate-change, and ecosystem monitoring.

Groundwater and surface-water interaction within the upper Smith River Watershed, Montana 2006-2010

The 125-mile long Smith River, a tributary of the Missouri River, is highly valued as an agricultural resource and for its many recreational uses. During a drought starting in about 1999, streamflow was insufficient to meet all of the irrigation demands, much less maintain streamflow needed for boating and viable fish habitat. In 2006, the U.S. Geological Survey, in cooperation with the Meagher County Conservation District, initiated a multi-year hydrologic investigation of the Smith River watershed. This investigation was designed to increase understanding of the water resources of the upper Smith River watershed and develop a detailed description of groundwater and surface-water interactions. A combination of methods, including miscellaneous and continuous groundwater-level, stream-stage, water-temperature, and streamflow monitoring was used to assess the hydrologic system and the spatial and temporal variability of groundwater and surfacewater interactions. Collectively, data are in agreement and show: (1) the hydraulic connectedness of groundwater and surface water, (2) the presence of both losing and gaining stream reaches, (3) dynamic changes in direction and magnitude of water flow between the stream and groundwater with time, (4) the effects of local flood irrigation on groundwater levels and gradients in the watershed, and (5) evidence and timing of irrigation return flows to area streams. Groundwater flow within the alluvium and older (Tertiary) basin-fill sediments generally followed land-surface topography from the uplands to the axis of alluvial valleys of the Smith River and its tributaries. Groundwater levels were typically highest in the monitoring wells located within and adjacent to streams in late spring or early summer, likely affected by recharge from snowmelt and local precipitation, leakage from losing streams and canals, and recharge from local flood irrigation. The effects of flood irrigation resulted in increased hydraulic gradients (increased groundwater levels relative to stream stage) or even reversed gradient direction at several monitoring sites coincident with the onset of nearby flood irrigation. Groundwater-level declines in mid-summer were due to groundwater withdrawals and reduced recharge from decreased precipitation, increased evapotranspiration, and reduced leakage in some area streams during periods of low flow. Groundwater levels typically rebounded in late summer, a result of decreased evapotranspiration, decreased groundwater use for irrigation, increased flow in losing streams, and the onset of late-season flood irrigation at some sites. The effect of groundwater and surface-water interactions is most apparent along the North and South Forks of the Smith River where the magnitude of streamflow losses and gains can be greater than the magnitude of flow within the stream. Net gains consistently occurred over the lower 15 miles of the South Fork Smith River. A monitoring site near the mouth of the South Fork Smith River gained (flow from the groundwater to the stream) during all seasons, with head gradients towards the stream. Two upstream sites on the South Fork Smith River exhibited variable conditions that ranged from gaining during the spring, losing (flowing from the stream to the groundwater) during most of the summer as groundwater levels declined, and then approached or returned to gaining conditions in late summer. Parts of the South Fork Smith River became dry during periods of losing conditions, thus classifying this tributary as intermittent. The North Fork Smith River is highly managed at times through reservoir releases. The North Fork Smith River was perennial throughout the study period although irrigation diversions removed a large percentage of streamflow at times and losing conditions persisted along a lower reach. The lowermost reach of the North Fork Smith River near its mouth transitioned from a losing reach to a gaining reach throughout the study period. Groundwater and surface-water interactions occur downstream from the confluence of the North and South Fork Smith Rivers, but are less discernible compared to the overall magnitude of the main-stem streamflow. The Smith River was perennial throughout the study. Monitoring sites along the Smith River generally displayed small head gradients between the stream and the groundwater, while one site consistently showed strongly gaining conditions. Synoptic streamflow measurements during periods of limited irrigation diversion in 2007 and 2008 consistently showed gains over the upper 41.4 river miles of the main stem Smith River where net gains ranged from 13.0 to 28.9 cubic feet per second. Continuous streamflow data indicated net groundwater discharge and small-scale tributary inflow contributions of around 25 cubic feet per second along the upper 10-mile reach of the Smith River for most of the 2010 record. A period of intense irrigation withdrawal during the last two weeks in Groundwater and Surface-Water Interaction within the Upper Smith River Watershed, Montana, 2006–2010 By Rodney R. Caldwell and Cheryl A. Eddy-Miller 2 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed May was followed by a period (early June 2010 to mid-July 2010) with the largest net increase (an average of 71.1 cubic feet per second) in streamflow along this reach of the Smith River. This observation is likely due to increased groundwater discharge to the Smith River resulting from irrigation return flow. By late July, the apparent effects of return flows receded, and the net increase in streamflow returned to about 25 cubic feet per second. Two-dimensional heat and solute transport VS2DH models representing selected stream cross sections were used to constrain the hydraulic properties of the Quaternary alluvium and estimate temporal water-flux values through model boundaries. Hydraulic conductivity of the Quaternary alluvium of the modeled sections ranged from 3x10-6 to 4x10-5 feet per second. The models showed reasonable approximations of the streambed and shallow aquifer environment, and the dynamic changes in water flux between the stream and the groundwater through different model boundaries. Introduction The Smith River watershed is an important agricultural and recreational area in Meagher and Cascade Counties in west-central Montana (fig. 1). Nearly 35,000 acres of the Smith River watershed are irrigated, primarily with water directly withdrawn from the Smith River and its tributaries (Cannon and Johnson, 2004). Downstream (northward), the agricultural fields are replaced by a scenic canyon that draws thousands of recreationists each year. During a recent drought, which started in about 1999, streamflow was insufficient to meet all of the irrigation demands, much less maintain streamflow needed for boating and viable fish habitat (Montana Department of Natural Resources and Conservation, 2003). Largely in response to the lack of available surface water for irrigation, some irrigators have already switched, or are proposing to switch, from flood irrigation to sprinkler irrigation (Montana Department of Natural Resources and Conservation, 2003). Additionally, some irrigators have considered using groundwater instead of surface water as a source of irrigation water. The effects of these changes in irrigation practices on the Smith River watershed are unknown. In April 2006, the U.S. Geological Survey (USGS), in cooperation with the Meagher County Conservation District (MCCD), began a study of the hydrogeology of the Smith River Watershed. The project was supported through the combined resources of the Montana Department of Natural Resources and Conservation’s (MDNRC) Reclamation and Development Grants Program and the USGS Cooperative Water Program. The study was designed to improve understanding of the groundwater system with an emphasis on groundwater and surface-water interactions through a systematic program of data collection, research, and analysis. The findings of this study can assist water managers with the development of a comprehensive management program for the use and protection of water resources in the Smith River watershed. This report is the second in a series of reports describing the water resources of the Smith River watershed. The first report (Nilges and Caldwell, 2012) is a USGS Open-File report that summarizes the hydrologic data collected and compiled for the hydrogeologic study of Smith River watershed through water year 2010. This report describes the general hydrology and groundwater and surface-water interactions within the upper watershed based on collected data. Purpose and Scope The purpose of this report is to describe the spatial and temporal interactions of groundwater and surface water in the upper Smith River watershed. The description of groundwater and surface-water interactions includes: (1) generalized groundwater-flow direction, (2) the delineation of gaining (flow from the groundwater to the stream) and losing (flow from the stream to the groundwater) reaches of the upper Smith River and selected tributaries, (3) quantification of gains and losses under different hydrologic conditions, (4) the relation between groundwater levels and stream stage, (5) hydraulic properties of the Quaternary alluvium, and (6) estimated water fluxes between groundwater and surface water at selected stream cross sections. Description of Study Area The Smith River is a tributary to the Missouri River with a watershed encompassing approximately 2,000 square miles (mi2) or nearly 1.3 million acres in Meagher and Cascade Counties of west-central Montana. Study efforts were focused primarily on the approximately 1,200 mi2 in the upper watershed above the Tenderfoot Creek drainage (fig. 1). The Smith River watershed lies within the structurally complex Northern Rocky Mountains Physiographic Division described by Fenneman and Johnson (1946), is characterized by somewhat rugged moun

Expanded stream gauging includes groundwater data and trends

Population growth has increased water scarcity to the point that documenting current amounts of worldwide water resources is now as critical as any data collection in the Earth sciences. As a key element of this data collection, stream gauges yield continuous hydrologic information and document long-term trends, recording high-frequency hydrologic information over decadal to centennial time frames.

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). Introduction The Wyoming Landscape Conservation Initiative (WLCI) is a program created to “implement a long-term, science-based program of assessing, conserving, and enhancing fish and wildlife habitats while facilitating responsible energy and other development through local collaboration and partnerships” (Bowen and others, 2014, p. 2). The role of the U.S. Geological Survey (USGS) in the WLCI program is “to conduct science and perform technical-assistance activities that help to assess and monitor trends in overall ecosystem conditions, focal habitats, and species of concern; evaluate the effectiveness of habitat enhancement or restoration projects; and provide support to conservation planners and decisionmakers” (Bowen and others, 2014, p. 2). The WLCI study area includes much of southwestern Wyoming, including all or parts of Lincoln, Sublette, Fremont, Sweetwater, and Carbon Counties (Bowen and others, 2014, fig. 1). A study was completed as part of ongoing USGS contributions to the WLCI program with the objective to improve understanding of the primary groundwater resources used in a part of the northern Green River structural basin. Natural gas is currently (2015) extracted from tight (low permeability) gas reservoirs in a deep Late Cretaceous-age geologic formation (Lance Formation) (Law, 1984; Law and Spencer, 1989) that underlies the shallow groundwater resources that exclusively provide water to rural livestock, domestic, and industrial wells in the area (Clarey and others, 2010). Expansion of naturalgas development in the study area is expected in the future (EnCana Oil and Gas [USA], Inc., 2011; Bureau of Land Management, 2011). Drilling into the Lance Formation requires penetration of overlying aquifers that compose the regionally extensive and heterogeneous aquifer system contained within 2 Generalized Potentiometric-Surface Map of the Green River Basin Lower Tertiary Aquifer System, 2010–14 Tertiary rocks (known as the Green River Basin lower Tertiary aquifer system) that supplies water to these wells. To improve understanding of this locally and regionally important aquifer system, the USGS, in cooperation with the Bureau of Land Management (BLM), completed the following: (1) measured groundwater levels in wells completed in the aquifer system, (2) evaluated measured groundwater levels and equivalent groundwater-level altitudes in relation to well depths and lithostratigraphic/hydrostratigraphic unit designation, (3) compared newly measured groundwater levels with historical groundwater levels where possible, and (4) constructed an updated generalized potentiometric-surface map. Purpose and Scope The purpose of this report is to describe groundwater levels and the generalized potentiometric-surface of the lower Tertiary aquifer system in the northern Green River structural basin. The hydrogeology of the area also is summarized. Construction of a generalized potentiometric-surface map of the regional Green River Basin lower Tertiary aquifer system in the northern Green River structural basin Wyoming was the conclusion of an effort by the USGS to measure groundwater levels during 2010–14 (Sweat, 2013). The complex geology in the Green River structural basin greatly influences groundwater levels and movement of groundwater in the lower Tertiary aquifer system. Nomenclature of the interfingering and intertonguing Tertiary lithostratigraphic units representing many different depositional environments (lithostratigraphy) is very complex and has been repeatedly revised in the northern Green River structural basin. Similarly, the classification of these lithostratigraphic units as hydrogeologic units (hydrostratigraphy) also is very complex and also has been repeatedly revised; consequently, a summary and synthesis of past and current science related to the lithostratigraphy and hydrostratigraphy of the northern Green River structural basin is provided herein. Methods of Investigation The methods used to inventory and select existing wells for measurement of groundwater levels in the study area are described in Sweat (2013). In general, existing wells were selected that included information about the depth of the well, the open or screen/perforated interval(s) of the well, the type of surface seal, and the groundwater level at the time of well completion (Sweat, 2013). Groundwater-level measurements were made during 2010–14 using a steel tape, electrical tape, or pressure gauge using protocols and quality-control procedures described in Cunningham and Schalk (2011). Description of Study Area The study area is described in this section of the report. Brief descriptions of the geographic setting, climate, and geologic setting in the vicinity of the study area are presented. A summary and synthesis of past and current science related to lithostratigraphy and hydrostratigraphy is provided in the following “Hydrogeology” section. Geographic Setting and Climate The study area is located in parts of Sublette, Lincoln, and Sweetwater Counties in western Wyoming about 68 miles (mi) northwest of Rock Springs, Wyoming, and about 18 mi south of Pinedale, Wyo. (fig. 1). Most land is administered by the BLM (fig. 1), and one of the primary land uses is livestock grazing. The study area is located in an area of increasing energy development and includes a current gas development project (Jonah Infill Development Project) and a developing natural gas project (Normally Pressured Lance Natural Gas Development Project) on the BLM lands. Much of the study area is a rolling grass-, sagebrush-, and shrub-covered (greasewood-saltbrush) plain with intervening ridges, buttes, badlands, and ephemeral and perennial drainages. This vegetation is sparse in much of the study area and greatest near perennial streams. The study area includes critical habitat for the Greater Sage-Grouse (Centrocercus urophasianus), elk (Cervus elaphus), pronghorn (Antilocapra americana), mule deer (Odocoileus hemionus), and feral horses (Equus caballus) (Duke and others, 2011). Most of the study area is located east of the primary drainage in the Green River structural basin and drainage basin (Green River Basin), which is the perennial southward flowing Green River (fig. 1). Several prominent perennial tributaries to the Green River are present along the margins of the study area, including the southand southwest-flowing New Fork and Big Sandy Rivers. Two reservoirs (Fontenelle and Big Sandy Reservoirs) are present in the southwestern and southeastern parts of the study area, respectively (fig. 1). Climate in the study area is affected strongly by altitude and orographic effects of surrounding mountain ranges (Martner, 1986; Curtis and Grimes, 2004). In the southeastern part of the study area at Farson, Wyo. (fig. 1), the mean annual maximum temperature is about 55 degrees Fahrenheit (°F), and the mean annual minimum temperature is about 20 °F (period of record is January 1, 1915–December 31, 2005; Western Regional Climate Center, 2014a). Temperature in the northwestern part of the study area is similar, as the mean annual maximum temperature at Big Piney, Wyo., is about 53 °F, and the mean annual minimum temperature is about Description of Study Area 3

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.

Water-quality and related aquatic biological characterization of Fish Creek, Teton County, Wyoming, 2007-2011

Introduction Fish Creek, in western Wyoming near the town of Wilson (fig. 1), is a key feature in the area because it is used for irrigation, fishing, and other recreation, and adds scenic value to properties it runs through. Public concern about nuisance growths of aquatic plants in Fish Creek has been increasing since the early 2000s. To address these concerns, the U.S. Geological Survey, in cooperation with the Teton Conservation District, began studying Fish Creek in 2004 to describe the hydrology of the stream and later (2007–11) to characterize the water quality and the biological communities. In particular, the study was designed to address three specific questions: • Is algal growth in Fish Creek typical for a stream of its size and geographic area? • Are nutrients entering Fish Creek from nearby land use? • What is the quality of the water in Fish Creek and the health of its biological communities?

Characterization of water quality and biological communities, Fish Creek, Teton County, Wyoming, 2007-08

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