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At least 217 records · Page 12Linked to original sources

Development of a solenoid pumped in situ zinc analyzer for environmental monitoring

A battery powered submersible chemical analyzer, the Zn-DigiScan (Zn Digital Submersible Chemical Analyzer), has been developed for near real-time, in situ monitoring of zinc in aquatic systems. Microprocessor controlled solenoid pumps propel sample and carrier through an anion exchange column to separate zinc from interferences, add colorimetric reagents, and propel the reaction complex through a simple photometric detector. The Zn-DigiScan is capable of self-calibration with periodic injections of standards and blanks. The detection limit with this approach was 30 μg L −1 . Precision was 5–10% relative standard deviation (R.S.D.) below 100 μg L −1 , improving to 1% R.S.D. at 1000 μg L −1 . The linear range extended from 30 to 3000 μg L −1 . In situ field results were in agreement with samples analyzed by inductively coupled plasma mass spectrometry (ICPMS). This pump technology is quite versatile and colorimetric methods with complex online manipulations such as column reduction, preconcentration, and dilution can be performed with the DigiScan. However, long-term field deployments in shallow high altitude streams were hampered by air bubble formation in the photometric detector.

Analytica Chimica Acta

Assessing the influence of multiple stressors on stream diatom metrics in the upper Midwest, USA

Water resource managers face increasing challenges in identifying what physical and chemical stressors are responsible for the alteration of biological conditions in streams. The objective of this study was to assess the comparative influence of multiple stressors on benthic diatoms at 98 sites that spanned a range of stressors in an agriculturally dominated region in the upper Midwest, USA. The primary stressors of interest included: nutrients, herbicides and fungicides, sediment, and streamflow; although the influence of physical habitat was incorporated in the assessment. Boosted Regression Tree was used to examine both the sensitivity of various diatom metrics and the relative importance of the primary stressors. Percent Sensitive Taxa, percent Highly Motile Taxa, and percent High Phosphorus Taxa had the strongest response to stressors. Habitat and total phosphorous were the most common discriminators of diatom metrics, with herbicides as secondary factors. A Classification and Regression Tree (CART) model was used to examine conditional relations among stressors and indicated that fine-grain streams had a lower percentage of Sensitive Taxa than coarse-grain streams, with Sensitive Taxa decreasing further with increased water temperature (>30 °C) and triazine concentrations (>1500 ng/L). In contrast, streams dominated by coarse-grain substrate contained a higher percentage of Sensitive Taxa, with relative abundance increasing with lower water temperatures (<29 °C) and shallower water depth (<0.3 m). Quantile regression indicated that maximum water temperature appears to be a major limiting factor in Midwest streams; whereas both total phosphorus and percent fines showed a slight subsidy-stress response. While using benthic algae for assessing stream quality can be challenging, field-based studies can elucidate stressor effects and interactions when the response variables are appropriate, sufficient stressor resolution is achieved, and the number and type of sites represent a gradient of stressor conditions and at least a quasi-factorial design.

Ecological Indicators

Effects of groundwater-flow paths on nitrate concentrations across two riparian forest corridors

Groundwater levels, apparent age, and chemistry from field sites and groundwater-flow modeling of hypothetical aquifers collectively indicate that groundwater-flow paths contribute to differences in nitrate concentrations across riparian corridors. At sites in Virginia (one coastal and one Piedmont), lowland forested wetlands separate upland fields from nearby surface waters (an estuary and a stream). At the coastal site, nitrate concentrations near the water table decreased from more than 10 mg/L beneath fields to 2 mg/L beneath a riparian forest buffer because recharge through the buffer forced water with concentrations greater than 5 mg/L to flow deeper beneath the buffer. Diurnal changes in groundwater levels up to 0.25 meters at the coastal site reflect flow from the water table into unsaturated soil where roots remove water and nitrate dissolved in it. Decreases in aquifer thickness caused by declines in the water table and decreases in horizontal hydraulic gradients from the uplands to the wetlands indicate that more than 95% of the groundwater discharged to the wetlands. Such discharge through organic soil can reduce nitrate concentrations by denitrification. Model simulations are consistent with field results, showing downward flow approaching toe slopes and surface waters to which groundwater discharges. These effects show the importance of buffer placement over use of fixed-width, streamside buffers to control nitrate concentrations.

Virginia

VS2DI: Model use, calibration, and validation

VS2DI is a software package for simulating water, solute, and heat transport through soils or other porous media under conditions of variable saturation. The package contains a graphical preprocessor for constructing simulations, a postprocessor for displaying simulation results, and numerical models that solve for flow and solute transport (VS2DT) and flow and heat transport (VS2DH). Flow is described by the Richards equation, and solute and heat transport are described by advection-dispersion equations; the finite-difference method is used to solve these equations. Problems can be simulated in one, two, or three (assuming radial symmetry) dimensions. This article provides an overview of calibration techniques that have been used with VS2DI; included is a detailed description of calibration procedures used in simulating the interaction between groundwater and a stream fed by drainage from agricultural fields in central Indiana. Brief descriptions of VS2DI and the various types of problems that have been addressed with the software package are also presented.

Transactions of the ASABE

Local variability mediates vulnerability of trout populations to land use and climate change

Land use and climate change occur simultaneously around the globe. Fully understanding their separate and combined effects requires a mechanistic understanding at the local scale where their effects are ultimately realized. Here we applied an individual-based model of fish population dynamics to evaluate the role of local stream variability in modifying responses of Coastal Cutthroat Trout ( Oncorhynchus clarkii clarkii ) to scenarios simulating identical changes in temperature and stream flows linked to forest harvest, climate change, and their combined effects over six decades. We parameterized the model for four neighboring streams located in a forested headwater catchment in northwestern Oregon, USA with multi-year, daily measurements of stream temperature, flow, and turbidity (2007&ndash;2011), and field measurements of both instream habitat structure and three years of annual trout population estimates. Model simulations revealed that variability in habitat conditions among streams (depth, available habitat) mediated the effects of forest harvest and climate change. Net effects for most simulated trout responses were different from or less than the sum of their separate scenarios. In some cases, forest harvest countered the effects of climate change through increased summer flow. Climate change most strongly influenced trout (earlier fry emergence, reductions in biomass of older trout, increased biomass of young-of-year), but these changes did not consistently translate into reductions in biomass over time. Forest harvest, in contrast, produced fewer and less consistent responses in trout. Earlier fry emergence driven by climate change was the most consistent simulated response, whereas survival, growth, and biomass were inconsistent. Overall our findings indicate a host of local processes can strongly influence how populations respond to broad scale effects of land use and climate change.

Oregon

Processing of Landsat imagery to map surface mineral alteration on the Alaska Peninsula: A section in USGS research on mineral resources, 1985 program and abstracts

Landsat images were digitally processed to facilitate assessment of the mineral resources of the Port Moller, Stepovak Bay, and Simeonof Island 1:250,000 quadrangles. Field mapping and assessment of these quadrangles were begun in 1983 as part of the Alaska Mineral Resource Assessment Program (AMRAP). It was quickly realized that time and budget constraints would limit mapping coverage. Therefore, at the suggestion of Roger Ashley, we used existing Landsat multispectral scanner imagery to aid in locating surface alteration, which could be field checked or related to stream-sediment or hand-sample geochemical data.

Circular

Arkansas and Landsat

Scenic Arkansas certainly lives up to its nickname, “The Natural State.” The Ozark Plateau and Ouachita Mountains boast stunning views, vast resources, and recreation. Hardwood and pine forests cover one-half of the State. The major rivers—Arkansas, Ouachita, Red, and White—offer recreation and navigation as they drain toward the Mississippi River, which forms the State’s eastern border. Smaller streams and rivers, reservoirs, and rice fields serve as homes for wildlife as well, including birds migrating along the Mississippi Flyway. Agriculture has always been a key industry in Arkansas, which is the top rice producer in the United States. Poultry, soybeans, cotton, cattle, and timber are among other agricultural products that contribute to the State’s economy. The aquaculture industry has diversified from just goldfish to more than 20 species of fish and crustaceans. Geological features include waterfalls, limestone caves, and the country’s only active diamond mine, Crater of Diamonds State Park, where visitors can keep any rock or mineral they find in the volcanic crater. Hot Springs National Park—within the city of Hot Springs—features thermal springs of water heated deep belowground that follow a fault line of the Ouachita Mountains up to the surface. Here are a few ways Landsat has benefited Arkansas.

Arkansas

Hydrologic data for selected streams in the coal area of southeastern Oklahoma, July 1978 to September 1982

Hydrologic data on quantity and quality of surface waters were collected in the coal resource area of southeastern Oklahoma during an investigation of the effects of coal surface mining on the hydrology of the area. The objective of the study was to determine the characteristics of the regional hydrologic system and to detect and document changes in the system that may occur as the result of coal surface mining. This report presents data which were collected at 13 sites in 4 counties between July 1978 and September 1982. The data include: (1) mean daily stream discharge; (2) physical properties, selected field constituents, and concentration of suspended sediment of water samples; (3) concentration of selected common constituents, nutrients, and trace elements of water samples; (4) mean daily specific conductance, pH, water temperature, and dissolved oxygen; and (5) analyses of biological samples.

Open-File Report

A technique for preliminary appraisal of potential and observed scour as applied to state-maintained highway bridges in Maryland

This report describes a technique that can be used to assess potential and observed scour at highway bridges over waterways. Channel-stability assessments were conducted at 876 State highway, U.S. highway, and Interstate highway bridges over waterways in the State of Maryland. Conventional data-collection techniques were used in the field to collect bridge and stream-channel data for each bridge. A potential-scour index and an observed- scour index were developed by assigning numerical-index values to specific diagnostic characteristics of the bridge and stream channel. Potential-scour ratings and observed-scour ratings for assessed bridges were obtained by summing numerical-index values that were assigned to each diagnotic characteristic in the potential-scour index and the observed-scour index.

Open-File Report

Creating a monthly time series of the potentiometric surface in the Upper Floridan aquifer, Northern Tampa Bay area, Florida, January 2000-December 2009

In Florida’s karst terrain, where groundwater and surface waters interact, a mapping time series of the potentiometric surface in the Upper Floridan aquifer offers a versatile metric for assessing the hydrologic condition of both the aquifer and overlying streams and wetlands. Long-term groundwater monitoring data were used to generate a monthly time series of potentiometric surfaces in the Upper Floridan aquifer over a 573-square-mile area of west-central Florida between January 2000 and December 2009. Recorded groundwater elevations were collated for 260 groundwater monitoring wells in the Northern Tampa Bay area, and a continuous time series of daily observations was created for 197 of the wells by estimating missing daily values through regression relations with other monitoring wells. Kriging was used to interpolate the monthly average potentiometric-surface elevation in the Upper Floridan aquifer over a decade. The mapping time series gives spatial and temporal coherence to groundwater monitoring data collected continuously over the decade by three different organizations, but at various frequencies. Further, the mapping time series describes the potentiometric surface beneath parts of six regionally important stream watersheds and 11 municipal well fields that collectively withdraw about 90 million gallons per day from the Upper Floridan aquifer. Monthly semivariogram models were developed using monthly average groundwater levels at wells. Kriging was used to interpolate the monthly average potentiometric-surface elevations and to quantify the uncertainty in the interpolated elevations. Drawdown of the potentiometric surface within well fields was likely the cause of a characteristic decrease and then increase in the observed semivariance with increasing lag distance. This characteristic made use of the hole effect model appropriate for describing the monthly semivariograms and the interpolated surfaces. Spatial variance reflected in the monthly semivariograms decreased markedly between 2002 and 2003, timing that coincided with decreases in well-field pumping. Cross-validation results suggest that the kriging interpolation may smooth over the drawdown of the potentiometric surface near production wells. The groundwater monitoring network of 197 wells yielded an average kriging error in the potentiometric-surface elevations of 2 feet or less over approximately 70 percent of the map area. Additional data collection within the existing monitoring network of 260 wells and near selected well fields could reduce the error in individual months. Reducing the kriging error in other areas would require adding new monitoring wells. Potentiometric-surface elevations fluctuated by as much as 30 feet over the study period, and the spatially averaged elevation for the entire surface rose by about 2 feet over the decade. Monthly potentiometric-surface elevations describe the lateral groundwater flow patterns in the aquifer and are usable at a variety of spatial scales to describe vertical groundwater recharge and discharge conditions for overlying surface-water features.

Florida

Physical characteristics and fish assemblage composition at site and mesohabitat scales over a range of streamflows in the Middle Rio Grande, New Mexico, winter 2011-12, summer 2012

In winter 2011&ndash;12 and summer 2012, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, Albuquerque District and the U.S. Fish and Wildlife Service New Mexico Fish and Wildlife Conservation Office in Albuquerque, New Mexico, evaluated the physical characteristics and fish assemblage composition of available mesohabitats over a range of streamflows at 15 sites on the Middle Rio Grande in New Mexico. The fish assemblage of the Middle Rio Grande includes several minnow species adapted to hydrologically variable but seasonably predictable rivers, including the Hybognathus amarus (Rio Grande silvery minnow), a federally listed endangered species. Gaining a better understanding of habitat usage by the Rio Grande silvery minnow was the impetus for studying physical characteristics and fish assemblages in the Middle Rio Grande during different streamflow conditions. Data were collected at all 15 sites during winter 2011&ndash;12 (moderate streamflow), and a subset was collected at the 13 most downstream sites in summer 2012 (low streamflow). Sites were grouped into four river reaches separated by diversion dams listed in downstream order (names of the diversion dams are followed by short names of the sites nearest each dam in parentheses, listed in downstream order): (1) Cochiti (Pe&ntilde;a Blanca), (2) Angostura (Bernalillo, La Orilla, Barelas, Los Padillas), (3) Isleta (Los Lunas I, Los Lunas II, Abeytas, La Joya, Rio Salado), and (4) San Acacia (Lemitar, Arroyo del Tajo, San Pedro, Bosque del Apache I, and Bosque del Apache II). Stream habitat was mapped in the field by using a geographic information system in conjunction with a Global Positioning System. Fish assemblage composition was determined during both streamflow regimes, and fish were collected by seining in each mesohabitat where physical characteristic data (depth, velocity, dominant substrate type and size, and percent embeddedness) and water-quality properties (temperature, dissolved oxygen, specific conductance, and pH; during summer 2012 only) were measured. Nineteen species of fish were collected among the 15 sites and four reaches over both sampling periods; 10 of these 19 species are introduced. Fish-species richness (total number of fish species collected at each site during each sampling event) among sites that were sampled during both sampling periods ranged from 6 at Rio Salado to 12 at La Orilla. Fish were most abundant at the Lemitar site (1,786 individuals) and least abundant at the San Pedro site (275 individuals). The native Cyprinella lutrensis (red shiner) was the most abundant species collected among all of the sites, accounting for about 42 percent of fish collected. Fish-species richness and catch per unit effort (CPUE) were higher (or equivalent) at all sites during summer 2012 compared to winter 2011&ndash;12. The relations between fish assemblage composition (that is, total abundance, which refers to the number of individuals of each species that were collected) and selected environmental variables (physical characteristic data collected at the mesohabitat scale [depth, velocity, and substrate particle size], and mesohabitat types) were explored by using canonical correspondence analysis. Environmental variables explained 8 percent (p=0.48) of the variability in the Middle Rio Grande fish assemblage during winter 2011&ndash;12, and Rio Grande silvery minnow were weakly associated with sand substrates, relatively moderate velocities (qualitative descriptors are derived from synthetic gradients extracted from CCAs), and relatively shallow depths. Environmental variables explained 14 percent (p < 0.01) of the variability in the Middle Rio Grande fish assemblage during summer 2012, when Rio Grande silvery minnow were associated with run mesohabitats, relatively high velocities, sand substrates, and relatively moderate depths. The mean fish-species richness was greater in summer 2012 than in winter 2011&ndash;12 for each mesohabitat type, and the overall fish-species richness across all mesohabitat types was 0.62 during winter 2011&ndash;12, compared to 1.49 during summer 2012. The highest mean CPUE during winter 2011&ndash;12 was in isolated pools (54.3 fish per 100 square meters [m 2 ]), whereas the lowest was in flats (18.9 fish per 100 m 2 ). Ranges in CPUE were higher in summer 2012 relative to winter 2011&ndash;12 in each mesohabitat type sampled. As in winter 2011&ndash;12, the highest mean CPUE during summer 2012 was in isolated pools (233 fish per 100 m 2 ), whereas the lowest was in flats (29.6 fish per 100 m 2 ). Overall mean CPUE per mesohabitat across all mesohabitat types was 29.1 fish per 100 m 2 during winter 2011&ndash;12 compared to 85.3 fish per 100 m 2 during summer 2012. Four species of minnows (red shiner, Rio Grande silvery minnow, Pimephales promelas [fathead minnow], and Platygobio gracilis [flathead chub]) were selected to compare preferred mesohabitat characteristics because all are small-bodied minnows and because more than 200 individuals of each of these species were collected. Red shiner were collected across the largest range of depths in both winter 2011&ndash;12 (0.02&ndash;4.31 feet [ft]) and summer 2012 (0.05&ndash;3.4 ft), as well as the largest range of velocities (0.0&ndash;4.31 feet per second [ft/s]) during winter 2011&ndash;12 among the four minnow species of interest. Rio Grande silvery minnow occurred in the narrowest range of depths (0.30&ndash;2.1 ft) during summer 2012, as well as the narrowest range of velocities in both winter 2011&ndash;12 (0.0&ndash;3.18 ft/s) and summer 2012 (0.02&ndash;1.51 ft/s). Water-quality properties were only collected during summer 2012, when low-streamflow conditions existed and water-quality properties were thought to be potentially most limiting to aquatic life. Area-weighted mean water temperatures tended to be higher at the sites that were sampled in August 2012 (25.57 degrees Celsius [&deg;C]) compared to June 2012 (24.61 &deg;C). The highest area-weighted mean water temperature at a given site (29.03 &deg;C) was measured at the Lemitar site on August 7, 2012, coincident with the lowest measured discharge (4.13 cubic feet per second [ft 3 /s]). Area-weighted mean dissolved oxygen concentrations tended to be lower in August (7.46 milligrams per liter [mg/L]) compared to June (8.33 mg/L). The highest area-weighted mean dissolved oxygen concentration (9.13 mg/L) was measured at the Lemitar site on August 7, 2012, and the lowest area-weighted mean dissolved oxygen concentration (6.23 mg/L) was measured at the Los Padillas site on August 10, 2012. Area-weighted specific conductance in the sites upstream from La Joya did not exceed 400 microsiemens per centimeter (&mu;S/cm) at 25 &deg;C, whereas the area-weighted mean specific conductance at La Joya (837 &mu;s/cm at 25 &deg;C), Rio Salado (857 &mu;s/cm at 25 &deg;C), and Lemitar (1,300 &mu;s/cm at 25 &deg;C) were all well above the average of the area-weighted means for the 10 remaining sites (433 &mu;s/cm at 25 &deg;C). Lower area-weighted mean pH values were measured at the 3 sites in and near Albuquerque (La Orilla, Barelas, and Los Padillas&mdash;7.98, 8.08, and 7.81, respectively) compared to any of the 10 remaining sites, which had an overall mean pH of 8.44.

New Mexico

Numerical simulation of ground-water flow in La Crosse County, Wisconsin, and into nearby pools of the Mississippi River

This report describes a two-dimensional regional screening model and two associated three-dimensional ground-water flow models that were developed to simulate the ground-water flow systems in La Crosse County, Wisconsin, and Pool 8 of the Mississippi River. Although the geographic extents of the three-dimensional models were slightly different, both were derived from the same geologic interpretation and regional screening model, and their calibrations were performed concurrently. The objectives of the La Crosse County (LCC) model were to assess the effects of recent (1990s) and potential future ground-water withdrawals and to provide a tool suitable to evaluate the effects of proposed water-management programs. The Pool 8 model objectives were to quantify the magnitude and distribution of ground-water flow into the Pool. The Wisconsin Geological and Natural History Survey and the U.S. Geological Survey developed the models cooperatively. The report describes: 1) the conceptual hydrogeologic model; 2) the methods used in simulating flow; 3) model calibration and sensitivity analysis; and 4) model results, such as simulation of predevelopment conditions and location and magnitude of ground-water discharge into Pool 8 of the Mississippi. Three aquifer units underlie the model area: 1) a shallow unconsolidated sand and gravel aquifer; 2) an upper bedrock aquifer, composed of Cambrian and Ordovician sandstone and dolomite; and 3) a lower bedrock aquifer composed of Cambrian sandstone of the Eau Claire Formation and the Mount Simon Formation. A shale layer that is part of the Eau Claire Formation forms a confining unit separating the upper and lower bedrock aquifers. This confining unit is absent in the Black River and parts of the La Crosse and Mississippi River valleys. Precambrian crystalline basement rock forms the lower base of the ground-water flow system. The U.S. Geological Survey ground-water flow model code, MODFLOW, was used to develop the La Crosse County (LCC) and Pool 8 ground-water flow models. Boundary conditions for the MODFLOW model were extracted from an analytic element screening model of the regional flow system surrounding La Crosse County. Model input was obtained from previously published and unpublished geologic and hydrologic data. Pumpages from municipal and high-capacity wells were also simulated. Model calibration included a comparison of modeled and field-measured water levels and field-measured base flows to simulated stream flows. At calibration, most measured water levels compared favorably to model-calculated water levels. Simulated streamflows at two targets were within 3 percent of estimated measured base flows. Mass balance results from the LCC and Pool 8 models indicated that 63 to 74 percent of ground water was from recharge and 19 to 26 percent was from surface-water sources. Ground-water flow out of the model was to rivers and streams (85 to 87 percent) and pumping wells (11 and 13 percent). The model demonstrates the effects of development on ground water in the study area. The maximum simulated water-level decline in the city of La Crosse metropolitan area is 9.3 feet. Simulated stream losses are similar to the amount of ground water pumped by wells. This indicates that ground water withdrawn by La Crosse County wells is water that under predevelopment conditions discharged to streams and lakes. The models provide estimates of the locations and amount of ground-water flow into Pool 8 and the southern portion of Pool 7 of the Mississippi River. Ground-water discharges into all areas of the pools, except along the eastern shore in the vicinity of the city of La Crosse and immediately downgradient from lock and dam 7 and 8. Ground-water flow into the pools is generally greatest around the perimeter with decreasing amounts away from the perimeter. An area of relatively high ground-water discharge extends out towards the center of Pool 7 from the upper reaches of the pool and may

Wisconsin

Surface-water and streambed-sediment quality of streams draining surface-mined land reclaimed with sewage sludge, Fulton County, Illinois, 1972-89

Sewage sludge has been used to reclaim surface- mined land in Fulton County, Ill. The sludge contains substantial concentrations of nutrients and significant concentrations of toxic organic compounds. Because of the concern of the fate of these toxins, the U.S. Geological Survey in cooperation with the Metropolitan Water Reclamation District of Greater Chicago began an analysis of historical data in 1989 to compare the quality of water and streambed sediments to determine whether the application of sludge is adversely affecting the quality of surface water. Trend analyses on surface-water-quality data suggest that sludge application is affecting the quality of water in Evelyn Branch in the form of increased concentrations of nitrite plus nitrate and kjeldahl nitrogen. However, the concentrations of these constituents in Evelyn Branch, the stream draining the sludge-application field, are small compared to the concentrations upstream from the project area. Analysis of the streambed-quality data indicates that, for the constituents measured, the application of sludge is not affecting the streambed quality in Evelyn Branch. Trend analyses of streambed constituents did not indicate any adverse effects that could be related to the application of sludge. However, the avail- able data are not adequate to determine if the quality of the streambed has been adversely affected by the sludge application. A refinement of the sampling scheme would be necessary to rule out the possibility of present and future adverse effects of sludge application on streambed quality.

Water-Resources Investigations Report

Gradient self-potential logging in the Rio Grande to identify gaining and losing reaches across the Mesilla Valley

The Rio Grande/Río Bravo del Norte (hereinafter referred to as the “Rio Grande”) is the primary source of recharge to the Mesilla Basin/Conejos-Médanos aquifer system in the Mesilla Valley of New Mexico and Texas. The Mesilla Basin aquifer system is the U.S. part of the Mesilla Basin/Conejos-Médanos aquifer system and is the primary source of water supply to several communities along the United States–Mexico border in and near the Mesilla Valley. Identifying the gaining and losing reaches of the Rio Grande in the Mesilla Valley is therefore critical for managing the quality and quantity of surface and groundwater resources available to stakeholders in the Mesilla Valley and downstream. A gradient self-potential (SP) logging survey was completed in the Rio Grande across the Mesilla Valley between 26 June and 2 July 2020, to identify reaches where surface-water gains and losses were occurring by interpreting an estimate of the streaming-potential component of the electrostatic field in the river, measured during bankfull flow. The survey, completed as part of the Transboundary Aquifer Assessment Program, began at Leasburg Dam in New Mexico near the northern terminus of the Mesilla Valley and ended ~72 kilometers (km) downstream at Canutillo, Texas. Electric potential data indicated a net losing condition for ~32 km between the Leasburg Dam and Mesilla Diversion Dam in New Mexico, with one ~200-m long reach showing an isolated saline-groundwater gaining condition. Downstream from the Mesilla Diversion Dam, electric-potential data indicated a neutral-to-mild gaining condition for 12 km that transitioned to a mild-to-moderate gaining condition between 12 and ~22 km downstream from the dam, before transitioning back to a losing condition along the remaining 18 km of the survey reach. The interpreted gaining and losing reaches are substantiated by potentiometric surface mapping completed in hydrostratigraphic units of the Mesilla Basin aquifer system between 2010 and 2011, and corroborated by surface-water temperature and conductivity logging and relative median streamflow gains and losses, quantified from streamflow measurements made annually at 16 seepage-measurement stations along the survey reach between 1988 and 1998 and between 2004 and 2013. The gaining and losing reaches of the Rio Grande in the Mesilla Valley, interpreted from electric potential data, compare well with relative median streamflow gains and losses along the 72-km long survey reach.

New Mexico, Texas

Waterborne gradient Self-Potential (WaSP) logging in the Rio Grande to map localized and regional surface and groundwater exchanges across the Mesilla Valley

The Rio Grande is the primary source of recharge to the Mesilla Basin/Conejos-Médanos aquifer system (“Mesilla Basin aquifer system”) in the Mesilla Valley of New Mexico and Texas. The Mesilla Basin aquifer system is the primary source of water supply to several large cities along the United States–Mexico border. Identifying gaining and losing reaches of the Rio Grande in the Mesilla Valley is therefore critical for managing the quality and quantity of surface and groundwater-resources available to stakeholders in the Mesilla Valley and downstream. A Waterborne gradient Self-Potential (WaSP) logging survey was completed in the Rio Grande across the Mesilla Valley between June 26 and July 2, 2020 to identify reaches where surface-water gains and losses were occurring by interpreting an estimate of the streaming-potential component of the electrostatic field in the river, measured during bank-full flow. The WaSP survey, completed as part of the Transboundary Aquifer Assessment Program, began at Leasburg Dam State Park, New Mexico near the northern terminus of the Mesilla Valley and ended ~72 kilometers (km) downstream in Canutillo, Texas. Electric potential data indicated a net losing condition for ~32 km between Leasburg Dam and Mesilla Diversion Dam in New Mexico, with one 200-m long reach showing a localized gaining condition. Downstream from Mesilla Diversion Dam, electric-potential data indicated a neutral-to-mild gaining condition for 12-km that transitioned to a mild-to-moderate gaining condition between 12 and ~22 km from the dam before transitioning back to a losing condition along the remaining 18 km of the survey reach. The interpreted gaining and losing reaches are substantiated by potentiometric surface mapping in hydrostratigraphic units of the Mesilla Basin aquifer system between 2010 and 2011 and streamflow gains and losses quantified from annual streamflow gaging at 16 stations along the survey reach between 1988 and 1998 and between 2004 and 2013. The gaining and losing reaches of the Rio Grande in the Mesilla Valley, interpreted from electric potential data, compare notably well with streamflow gains and losses quantified at 16 locations along the 72-km long survey reach.

New Mexico, Texas

Remote measurement of river discharge using thermal particle image velocimetry (PIV) and various sources of bathymetric information

Although river discharge is a fundamental hydrologic quantity, conventional methods of streamgaging are impractical, expensive, and potentially dangerous in remote locations. This study evaluated the potential for measuring discharge via various forms of remote sensing, primarily thermal imaging of flow velocities but also spectrally-based depth retrieval from passive optical image data. We acquired thermal image time series from bridges spanning five streams in Alaska and observed strong agreement between velocities measured in situ and those inferred by Particle Image Velocimetry (PIV), which quantified advection of thermal features by the flow. The resulting surface velocities were converted to depth-averaged velocities by applying site-specific, calibrated velocity indices. Field spectra from three clear-flowing streams provided strong relationships between depth and reflectance, suggesting that, under favorable conditions, spectrally-based bathymetric mapping could complement thermal PIV in a hybrid approach to remote sensing of river discharge; this strategy would not be applicable to larger, more turbid rivers, however. A more flexible and efficient alternative might involve inferring depth from thermal data based on relationships between depth and integral length scales of turbulent fluctuations in temperature, captured as variations in image brightness. We observed moderately strong correlations for a site-aggregated data set that reduced station-to-station variability but encompassed a broad range of depths. Discharges calculated using thermal PIV-derived velocities were within 15% of in situ measurements when combined with depths measured directly in the field or estimated from field spectra and within 40% when the depth information also was derived from thermal images. The results of this initial, proof-of-concept investigation suggest that remote sensing techniques could facilitate measurement of river discharge.

Journal of Hydrology

Remotely mapping gullying and incision in Maryland Piedmont headwater streams using repeat airborne lidar

Headwater streams can contribute significant amounts of fine sediment to downstream waterways, especially when severely eroded and incised. Potential upstream sediment source identification is crucial for effective management of water quality, aquatic habitat, and sediment loads in a watershed. This study explored topographic openness (TO) derived from 1-m lidar for its ability to predict incision in headwater streams and to remotely detect changes in incision over time. Field surveys were conducted in one forested and two recently urbanized headwater watersheds in the Maryland Piedmont physiographic province, USA to characterize the level of stream channel incision (none, moderate, or severe) in the main stem of each watershed. Predictions of the severity of stream channel incision derived from TO were compared against the field surveys. Channel incision was detected with an overall accuracy of 67 %, with best performance in reaches with either severe or no incision (79–86 % accuracy). The method was also applied to repeat lidar collected over the same area to model the extent of channel incision in 2002 before urban development began and in 2008 and 2013 during active construction in the urban watersheds. Results showed increasing incision over time in all three watersheds, with similar patterns in the forested and urban watersheds. This new method of remotely measuring channel incision can be used to identify potential sediment sources across a watershed, enhance water and habitat quality predictions, and detect changes over time where multiple years of overlapping lidar are available.

Maryland

Let's Sing 'Auld Lang Syne' for the Upper Brandywine: Or, to continue with Burns, how the best laid environmental schemes of men "gang aft a-gley"

Perhaps the most lamentable mistake that one can make is to be right too soon. This was the story of the Brandywine Plan, an attempt to organize local people for the permanent protection of the environmental amenities of their own land. The Upper East Branch of Brandywine Creek drains a rolling basin of farms, fields, woodlands, and a sprinkling of residential areas. Because it lies at the far edge of the commuting range to the population centers of Philadelphia and Wilmington, the basin's natural beauty has barely been touched by the blight of suburban sprawl. The waters of its streams are clear; its ample woodlands and fields are filled with wildlife. Driving slowly through the basin's winding roads and across its narrow bridges evokes the feeling of a pastoral painting, of the ideal landscape of rural eastern America. For two years, I had the privilege of working closely with a group preparing a land plan for the Brandywine area. The plan was designed to offer the inhabitants of the basin a feasible way to preserve forever the natural qualities of their region from the inevitable wave of urbanization. A report in Science magazine called it the perfect plan that failed.

Natural History