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USGS2023

Chromium in minerals and selected aquifer materials

Between 1952 and 1964, hexavalent chromium, Cr(VI), was released into groundwater from a Pacific Gas and Electric Company (PG&E) compressor station in Hinkley, California, in the western Mojave Desert 80 miles northeast of Los Angeles, California. In 2015, the extent of anthropogenic Cr(VI) in groundwater in Hinkley and Water Valleys was uncertain, but some Cr(VI) in groundwater may be naturally occurring from rock and aquifer material. To evaluate potential sources of natural Cr(VI), chromium and other selected trace-element concentrations were measured by inductively coupled plasma-mass spectrometry (ICP-MS), with multi-acid digestion, on 34 samples of surficial alluvium and core material from Hinkley and Water Valleys, California, and on 2 samples of alluvium from the mafic Sheep Creek fan to the southwest. Chromium concentrations in Hinkley and Water Valleys ranged from 2 to 110 milligrams per kilogram (mg/kg), with a median concentration of 14 mg/kg; concentrations were highest in weathered mafic hornblende diorite associated with Iron Mountain. High chromium concentrations also were present within fine-textured materials and visually abundant iron- and manganese-oxide coatings on the surfaces of mineral grains. For comparison, chromium concentrations as high as 170 mg/kg were measured in mafic alluvium from the Sheep Creek fan. In contrast, chromium concentrations were lowest in Mojave-type deposits (Mojave River stream and lake margin deposits), with a median of 6 mg/kg. Chromium concentrations measured by ICP-MS compared favorably with concentrations measured by portable (handheld) X-ray fluorescence (pXRF; chapter B), on the basis of least-squares regression results and a coefficient of determination (R 2 ) of 0.97. Minerals in bulk samples and the heavy (dense) mineral fractions isolated from those samples were identified using optical techniques, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Quartz and feldspar were the most abundant minerals, especially within recent and older Mojave River deposits. Chromium concentrations were as high as 1,250 mg/kg in the heavy-mineral fraction, with specific gravity greater than 3.32. Chromium was not commonly detected in the light-mineral fraction, with specific gravity less than 2.85. Most chromium within the heavy-mineral fraction was substituted within magnetite mineral grains less than 100 micrometers (μm) in diameter, and almost no chromite was present within the heavy-mineral fraction. Although magnetite is resistive to weathering, weathering of magnetite to hematite was identified (1) in Miocene materials underlying unconsolidated deposits in the western subarea of Hinkley Valley and (2) in alluvium within Water Valley that contains weathered minerals eroded from Miocene rock. Less-dense, more easily weathered chromium-containing amphiboles, such as actinolite in older Mojave River alluvium and hornblende in locally derived alluvium from Iron Mountain, were identified optically. Magnetite was not identified in weathered hornblende diorite and was less abundant in locally derived materials and in Miocene materials than in Mojave-type deposits. A comparison of ICP-MS data and sequential extraction data shows that approximately 90 percent of chromium in aquifer material within Hinkley and Water Valleys was not extractable and was interpreted to reside within unweathered mineral grains. Most extractable chromium was within the strong acid extractable fraction. Chromium within the weakly sorbed, and specifically sorbed extractable fractions in oxide accumulations within the regulatory Cr(VI) plume is potentially mobile into groundwater with changes in ionic strength or pH. Although Hinkley and Water Valleys are regionally low in chromium, natural geologic sources of chromium may be present in aquifer materials penetrated by wells completed in (1) weathered hornblende diorite bedrock underlying the western subarea; (2) Miocene deposits underlying the western subarea and unconsolidated material in the northern subarea and Water Valley containing basalt or weathered minerals eroded from Miocene deposits; (3) unconsolidated material containing visually abundant iron- and manganese-oxide coatings on the surfaces of mineral grains that are present near the water table and near lithologic or geologic contacts; and (4) brown clay and mudflat/playa deposits in the northern subarea. Brown clay and mudflat/playa deposits in the eastern subarea near Mount General have a low-chromium, felsic mineralogy similar to Mojave River deposits and do not contain high concentrations of chromium; however, manganese(IV) oxides within these materials may facilitate oxidation of trivalent chromium, Cr(III), to Cr(VI).

California↗

USGS2013

Northern Great Plains Network water quality monitoring design for tributaries to the Missouri National Recreational River

The National Park Service (NPS) organized more than 270 parks with important natural resources into 32 ecoregional networks to conduct Inventory and Monitoring (I&M) activities for assessment of natural resources within park units. The Missouri National Recreational River (NRR) is among the 13 parks in the NPS Northern Great Plain Network (NGPN). Park managers and NGPN staff identified surface water resources as a high priority vital sign to monitor in park units. The objectives for the Missouri NRR water quality sampling design are to (1) assess the current status and long-term trends of select water quality parameters; and (2) document trends in streamflow at high-priority stream systems. Due to the large size of the Missouri River main stem, the NGPN water quality design for the Missouri NRR focuses on wadeable tributaries within the park unit. To correlate with the NGPN water quality protocols, monitoring of the Missouri NRR consists of measurement of field core parameters including dissolved oxygen, pH, specific conductance, and temperature; and streamflow. The purpose of this document is to discuss factors examined for selection of water quality monitoring on segments of the Missouri River tributaries within the Missouri NRR. Awareness of the complex history of the Missouri NRR aids in the current understanding and direction for designing a monitoring plan. Historical and current monitoring data from agencies and entities were examined to assess potential NGPN monitoring sites. In addition, the U.S. Environmental Protection Agency 303(d) list was examined for the impaired segments on tributaries to the Missouri River main stem. Because major tributaries integrate water quality effects from complex combinations of land use and environmental settings within contributing areas, a 20-mile buffer of the Missouri NRR was used to establish environmental settings that may impact the water quality of tributaries that feed the Missouri River main stem. For selection of monitoring sites, anthropogenic and natural influences to water quality were assessed for Missouri NRR tributaries. Factors that were examined include the size and contributions of tributaries within watersheds to the main stem; population density; and land use such as urban development and agricultural practices including concentrated animal feeding operations. Based on examination of these data in addition to the park’s legislation and management considerations, two sites were selected for monitoring water quality on Missouri NRR tributaries for the ice-free season (mid-May to mid-October) on a rotational basis every third year. Bow Creek at St. James was selected for water quality monitoring based on lack of long-term water quality monitoring, current recreational use, and proximity of the tributary to intense agricultural practices. In addition, land within the Bow Creek watershed is owned by the NPS. The Niobrara River at Verdel was selected for monitoring due to high use for public recreational activities, adjacent agricultural land use, and documented impairments for designated beneficial uses. Both sites will have access to real-time streamgages that will aid in a greater understanding of water quality.

Natural Resource Technical Report↗

USGS2016

Conservation planning for the Colorado River in Utah

Strategic planning is increasingly recognized as necessary for providing the greatest possible conservation benefits for restoration efforts. Rigorous, science-based resource assessment, combined with acknowledgement of broader basin trends, provides a solid foundation for determining effective projects. It is equally important that methods used to prioritize conservation investments are simple and practical enough that they can be implemented in a timely manner and by a variety of resource managers. With the help of local and regional natural resource professionals, we have developed a broad-scale, spatially-explicit assessment of 146 miles (~20,000 acres) of the Colorado River mainstem in Grand and San Juan Counties, Utah that will function as the basis for a systematic, practical approach to conservation planning and riparian restoration prioritization. For the assessment we have: 1) acquired, modified or created spatial datasets of Colorado River bottomland conditions; 2) synthesized those datasets into habitat suitability models and estimates of natural recovery potential, fire risk and relative cost; 3) investigated and described dominant ecosystem trends and human uses, and; 4) suggested site selection and prioritization approaches. Partner organizations (The Nature Conservancy, National Park Service, Bureau of Land Management and Utah Forestry Fire and State Lands) are using the assessment and datasets to identify and prioritize a suite of restoration actions to increase ecosystem resilience and improve habitat for bottomland species. Primary datasets include maps of bottomland cover types, bottomland extent, maps of areas inundated during high and low flow events, as well as locations of campgrounds, roads, fires, invasive vegetation treatment areas and other features. Assessment of conditions and trends in the project area entailed: 1) assemblage of existing data on geology, changes in stream flow, and predictions of future conditions; 2) identification of fish and wildlife species present and grouping species into Conservation Elements (CEs) based on habitat needs, and: 3) acquisition, review and creation of spatial datasets characterizing vegetation, fluvial geomorphic and human features within the bottomland. Interpretation of aerial imagery and assimilation of pre-existing spatial data were central to our efforts in characterizing resources conditions. Detailed maps of vegetation and channel habitat features in the project area were generated from true color, high resolution (0.3m) imagery flown September 16, 2010. We also mapped channel habitat features at high flow on 1.0-m resolution, publicly available, true color imagery. We obtained additional layers such as land ownership, roads, fire history, non-native vegetation treatment areas, and recreational use features from public sources and project partners. Habitat suitability models were created for groups of terrestrial species by combining spatial datasets with the habitat needs of conservation elements, guided by literature, where available, and extensive use of expert knowledge. Conservation elements for endangered fish species life stages were identified but not modeled. Terrestrial CE’s included: • Riparian Overstory -yellow-billed cuckoo, Bullock’s oriole, black-headed grosbeak, blue grosbeak, warbling vireo, Cooper's hawk, screech owl, saw-whet owl, and bald eagle, (best: tall trees, dense canopy, diverse shrub understory, no tamarisk); • Riparian Understory - southwestern willow flycatcher, common yellowthroat, yellow warbler, yellow-breasted chat, beaver, northern river otter, black-necked garter snake, (best: dense mesic shrubs near still water, no tamarisk); • Bat Feeding - Allen's big-eared bat, Townsend's big-eared bat, fringed myotis, Yuma myotis, big free-tailed bat, spotted bat (best: diverse vegetation, close to still water); • Bat Watering - big free-tailed and spotted bats (best: still water with no tall vegetation); •

Utah↗

USGS2003

Avian use of natural versus planted woodlands in eastern South Dakota, USA

We compared avian use of naturally occurring and planted woodlands in eastern South Dakota, USA, to evaluate whether planted woodlands support the same avian communities as natural woodlands. A stratified cluster sample was used to randomly select 307 public areas in which to survey planted (n = 425) and natural (n = 99) woodland patches. Eighty-five species of birds were detected in eastern South Dakota woodlands, 36 of which occurred in ??? 5 of 524 patches surveyed. The probability of occurrence for 8 of 13 woodland-obligate species was significantly greater in natural woodland habitats than in planted woodland habitats. Four of these species breed in relatively high numbers in eastern South Dakota. Only one woodland-obligate occurred less frequently in natural woodlands. Probability of occurrence for 6 edge and generalist species, including the brown-headed cowbird (Molothrus ater [Boddaert]), was significantly higher in planted woodlands. The avian community of planted woodlands was dominated by edge and generalist species. The homogeneous vegetation structure typical of planted woodlands does not appear to provide the habitat characteristics needed by woodland-obligate birds. We conclude that planted woodlands do not support significant numbers of woodland-obligate species and may negatively impact grassland-nesting birds by attracting edge and generalist bird species and predators into previously treeless habitats. Planted woodlands cannot be considered equal replacement habitats for natural woodland patches when managing for nongame woodland bird species. However, the preservation and maintenance of natural woodlands is critical for woodland-obligate species diversity in the northern Great Plains.

South Dakota↗

USGS1976

Measurement of "turbidity" and related characteristics of natural waters

The U.S. Geological Survey, Water Resources Division has adopted the following principles to be used in selecting methods for the measurement of light transmitting characteristics of natural waters: (1) standard instruments and methods are to be adopted to measure and report in optical units, avoiding ' turbidity ' as a quantitative measure; (2) reporting of ' turbidity ' in JTU 's, Hellige units, severity, or NTU 's will be phased out; (3) the basis for estimations of sediment concentrations based on light measurements must be documented adequately; and (4) use of transparency measurement by Secchi disk is not changed, although light transmittance may prove to be more precise means of obtaining the same information. A schedule has been established to implement new methods beginning October 1, 1976, and with the transition to be completed at all stations by October 1, 1977. Provisions are provided to meet requirements of cooperators who have legal requirements for ' turbidity ' data. (Woodard-USGS)

Open-File Report↗

USGS2012

Groundwater geochemical and selected volatile organic compound data, Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington, June 2011

Previous investigations indicate that concentrations of chlorinated volatile organic compounds are substantial in groundwater beneath the 9-acre former landfill at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington. Phytoremediation combined with ongoing natural attenuation processes was the preferred remedy selected by the U.S. Navy, as specified in the Record of Decision for the site. The U.S. Navy planted two hybrid poplar plantations on the landfill in spring 1999 to remove and to control the migration of chlorinated volatile organic compounds in shallow groundwater. The U.S. Geological Survey has continued to monitor groundwater geochemistry to ensure that conditions remain favorable for contaminant biodegradation as specified in the Record of Decision. This report presents groundwater geochemical and selected volatile organic compound data collected at Operable Unit 1 by the U.S. Geological Survey during June 20-22, 2011, in support of long-term monitoring for natural attenuation. In 2011, groundwater samples were collected from 13 wells and 9 piezometers. Samples from all wells and piezometers were analyzed for redox sensitive constituents and dissolved gases, and samples from 5 of 13 wells and all piezometers also were analyzed for chlorinated volatile organic compounds. Concentrations of redox sensitive constituents measured in 2011 were consistent with previous years, with dissolved oxygen concentrations all at 0.4 milligram per liter or less; little to no detectable nitrate; abundant dissolved manganese, iron, and methane; and commonly detected sulfide. The reductive declorination byproducts - methane, ethane, and ethene - were either not detected in samples collected from the upgradient wells in the landfill and the upper aquifer beneath the northern phytoremediation plantation or were detected at concentrations less than those measured in 2010. Chlorinated volatile organic compound concentrations in 2011 at most piezometers were similar to or slightly less than chlorinated volatile organic compound concentrations measured in previous years. For the upper aquifer beneath the southern phytoremediation plantation, chlorinated volatile organic compound concentrations in 2011 in groundwater from the piezometers were extremely high and continued to vary considerably over space and between years. At piezometer P1-9, the total chlorinated volatile organic compound concentrations increased from 9,500 micrograms per liter in 2010 to more than 44,000 micrograms per liter in 2011. Total chlorinated volatile organic compound concentrations decreased at piezometers P1-6, P1-7, and P1-10 compared to the concentrations measured in 2010. One or both of the reductive dechlorination byproducts ethane and ethene were detected at all piezometers and three of the four wells in the southern plantation. For the intermediate aquifer, concentrations of redox sensitive constituents and chlorinated volatile organic compounds in 2011 were consistent with concentrations measured in previous years, with the exception of notable decreases in sulfate and chloride concentrations at well MW1-28. Concentrations of the reductive dechlorination byproducts ethane and ethene decreased at wells MW1-25 and MW1-28 compared to previously measured concentrations.

Washington↗

USGS1998

Impact of alternative regeneration methods on genetic diversity in coastal Douglas-fir

Genetic implications of natural and artificial regeneration following three regeneration methods (group selection, shelterwood, and clearcut) were investigated in coastal Douglas-fir ( Pseudotsuga menziesii var. menziesii [Mirb.] Franco) using genetic markers (17 allozyme loci). In general, harvesting followed by either natural or artificial regeneration resulted in offspring populations little altered from those in the previous generation. Cutting the smallest trees to form shelterwoods, however, resulted in the removal of rare, presumably deleterious, alleles, such that slightly fewer alleles per locus were observed among residual trees (2.76) and natural regeneration (2.75) than found in uncut (control) stands (2.86). Thus, although the shelterwood regime appears quite compatible with gene conservation, it would be best to leave parent trees of a range of sizes in shelterwoods designated as gene conservation reserves, in order to maximize the number of alleles (regardless of current adaptive value) in naturally regenerated offspring. Seedling stocks used for artificial regeneration in clearcut, shelterwood, and group selection stands (7 total) had significantly greater levels of genetic diversity, on average, than found in natural regeneration. This is probably because the seeds used in artificial seedling stocks came from many wild stands and thus, sampled more diversity than found in single populations. For. Sci. 44(3): 390-396.

Forest Science↗

USGS1982

Survival, growth, and catchability of rainbow trout of four strains

Fingerling rainbow trout ( Salmo gairdneri ) of genetically different strains survived, grew, and were caught at different rates by anglers and in gill nets after release from a hatchery into a 1‐hectare pond. When two domestic strains were compared, more fish of the strain genetically selected for fast growth were caught per unit of angling effort than were fish of a strain not selected for this characteristic. When fish of a natural and domestic strain were released together, survival was higher in the natural strain, but growth was slower. Strain population estimates reflected differences in catchability and were erroneous for the strain selected for growth. These observations imply that rainbow trout of different strains vary in their suitability for different fishery management practices.

North American Journal of Fisheries Management↗

USGS1992

Methods of analysis by the U. S. Geological Survey National Water Quality Laboratory-Determination of organonitrogen herbicides in water by solid-phase extraction and capillary-column gas chromatography/mass spectrometry with selected-ion monitoring

A method for the isolation of organonitrogen herbicides from natural water samples using solid-phase extraction and analysis by capillary-column gas chromatography/mass spectrometry with selected-ion monitoring is described. Water samples are filtered to remove suspended particulate matter and then are pumped through disposable solid-phase extraction cartridges containing octadecyl-bonded porous silica to remove the herbicides. The cartridges are dried using carbon dioxide, and adsorbed herbicides are removed from the cartridges by elution with 1.8 milliliters of hexaneisopropanol (3:1). Extracts of the eluants are analyzed by capillary-column gas chromatography/mass spectrometry with selected-ion monitoring of at least three characteristic ions. The method detection limits are dependent on sample matrix and each particular herbicide. The method detection limits, based on a 100-milliliter sample size, range from 0.02 to 0.25 microgram per liter. Recoveries averaged 80 to 115 percent for the 23 herbicides and 2 metabolites in 1 reagent-water and 2 natural-water samples fortified at levels of 0.2 and 2.0 micrograms per liter.

Open-File Report↗

USGS2012

Seasonal use of shallow water habitat in the Lower Snake River reservoirs by juvenile fall Chinook salmon

The U.S. Army Corps of Engineers (COE) is preparing a long term management plan for sediments that affect the authorized project purposes of the Lower Granite, Little Goose, Lower Monumental, and Ice Harbor reservoirs (hereafter, the lower Snake River reservoirs), and the area from the mouth of the Snake River to Ice Harbor Dam. We conducted a study from spring 2010 through winter 2011 to describe the habitat use by juvenile Chinook salmon within a selected group of shallow water habitat complexes (< 6 m deep) in the lower Snake River reservoirs to help inform the long-term plan. Natural fry and parr were present within all four shallow water habitat complexes that we studied from early spring through early summer, and parr ( = 40,345 ± 18,800 [error bound]) were more abundant than fry ( = 24,615 ± 5,701). Water < 2 m deep was highly used for rearing by natural fall Chinook salmon subyearlings (fry and parr combined; hereafter natural subyearlings) based on duration of use and relative group abundances during spring and summer, whereas the 2–6 m depth interval was more highly used by migratory hatchery fall Chinook salmon subyearlings and spring, summer, and fall Chinook salmon yearlings. Overall mean spring-summer apparent density of natural subyearlings was 15.5 times higher within the < 2 m depth interval than within the 2–6 m depth interval. Density of natural subyearlings also decreased as the distance a given shallow water habitat complex was located from the riverine spawning areas increased. Reservoir-type juveniles (or fish likely destined to become reservoir-type juveniles) were present in the lower Snake River reservoirs from fall 2010 through winter 2011; however, use of shallow water habitat by reservoir-type juveniles was limited during our study. We only collected 38 reservoir-type juveniles in shallow water habitat sites in beach and lampara seines during the fall. Radiotelemetry data revealed that though many tagged fish passed shallow water habitat sites, relatively few fish entered them and the median time fish spent within a given site was less than 1.4 h. Fish located by mobile tracking away from study sites were pelagically oriented, and generally not found over shallow water or close to shore. The findings in this report: (1) support the selection of natural fall Chinook subyearlings as the indicator group for determining the potential benefits of using dredge spoils to create shallow water habitat, (2) provide evidence for shallow water habitat use by natural subyearlings, (3) provide evidence against large-scale use of shallow water habitat by reservoir-type juveniles, (4) suggest that the depth criterion for defining shallow water habitat (i.e., < 6 m deep) warrants reconsideration, and (5) provide guidance for when to dredge and create shallow water habitat. Future research on habitat preference, feeding ecology, the food web, and intra-specific competition would help to better inform the long-term management plan.

Report↗

USGS2012

Sediment loads in the Red River of the North and selected tributaries near Fargo, North Dakota, 2010--2011

Natural-resource agencies are concerned about possible geomorphic effects of a proposed diversion project to reduce the flood risk in the Fargo-Moorhead metropolitan area. The U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers collected data in the spring of 2010 and 2011, and from June to November 2011, during rainfall-runoff events and base-flow conditions to provide information on sediment transport. The data were used to examine sediment concentrations, loads, and particle-size distributions at nine selected sites in the Red River and its tributaries near the Fargo-Moorhead metropolitan area. Suspended-sediment concentration varied among sites in 2010 and 2011. The least suspended-sediment concentrations were measured at the Red River (site 1) and the Buffalo River (site 9), and the greatest concentrations were measured at the two Sheyenne River sites (sites 3 and 4). Estimated daily suspended-sediment loads were highly variable in 2010 and 2011 in the Red River and its tributaries, with the greatest loads occurring in the spring and the smallest loads occurring in the winter. For the Red River, daily suspended-sediment loads ranged from 26 to 3,500 tons per day at site 1 and from 30 to 9,010 tons per day at site 2. For the Sheyenne River, daily loads ranged from less than 10 to 10,200 tons per day at site 3 and from less than 10 to 4,530 tons per day at site 4. The mean daily load was 191 tons per day in 2010 and 377 tons per day in 2011 for the Maple River, and 610 tons per day in 2011 for the Wild Rice River (annual loads were not computed for 2010). For the three sites that were only sampled in 2011 (sites 7, 8 and 9), the mean daily suspended-sediment loads ranged from 40 tons per day at the Lower Branch Rush River (site 8) to 118 tons per day at the Buffalo River (site 9). For sites that had estimated loads in 2010 and 2011 (sites 1–5), estimated annual (March–November) suspended-sediment loads were greater in 2011 compared to 2010. In 2010, annual loads ranged from 68,650 tons per year at the Maple River (site 5) to 249,040 tons per year at the Sheyenne River (site 3). In 2011, when all nine sites were sampled, annual loads ranged from 8,716 tons per year at the Lower Branch Rush River (site 8) to 552,832 tons per year at the Sheyenne River (site 3). With the exception of the Sheyenne River (site 4), the greatest monthly loads occurred in March for 2010, with as little as 27 percent (site 1) and as much as 42 percent (site 3) of the annual load occurring in March. For 2011, the greatest monthly loads occurred in April, ranging from 33 percent (site 1) to 63 percent (site 7) of the 2011 annual load. A relatively small amount of sediment was transported past the nine sites as bedload in 2010 and 2011. For most of the samples collected at the nine sites, the bedload composed less than 1 percent of the calculated daily total sediment load.

North Dakota↗

USGS2014

Water movement through the unsaturated zone of the High Plains Aquifer in the Central Platte Natural Resources District, Nebraska, 2008-12

Uncertainty about the effects of land use and climate on water movement in the unsaturated zone and on groundwater recharge rates can lead to uncertainty in water budgets used for groundwater-flow models. To better understand these effects, a cooperative study between the U.S. Geological Survey and the Central Platte Natural Resources District was initiated in 2007 to determine field-based estimates of recharge rates in selected land-use areas of the Central Platte Natural Resources District in Nebraska. Measured total water potential and unsaturated-zone profiles of tritium, chloride, nitrate as nitrogen, and bromide, along with groundwater-age dates, were used to evaluate water movement in the unsaturated zone and groundwater recharge rates in the central Platte River study area. Eight study sites represented an east-west precipitation contrast across the study area—four beneath groundwater-irrigated cropland (sites 2, 5, and 6 were irrigated corn and site 7 was irrigated alfalfa/corn rotation), three beneath rangeland (sites 1, 4, and 8), and one beneath nonirrigated cropland, or dryland (site 3). Measurements of transient vertical gradients in total water potential indicated that periodic wetting fronts reached greater mean maximum depths beneath the irrigated sites than beneath the rangeland sites, in part, because of the presence of greater and constant antecedent moisture. Beneath the rangeland sites, greater temporal variation in antecedent moisture and total water potential existed and was, in part, likely a result of local precipitation and evapotranspiration. Moreover, greater variability was noticed in the total water potential profiles beneath the western sites than the corresponding eastern sites, which was attributed to less mean annual precipitation in the west. The depth of the peak post-bomb tritium concentration or the interface between the pre-bomb/post-bomb tritium, along with a tritium mass balance, within sampled soil profiles were used to estimate water fluxes in the unsaturated zone at three of the eight study sites: site 2 (irrigated), site 3 (dryland), and site 8 (rangeland). Estimates for recharge were about 68 millimeters per year [(mm/yr), post-bomb peak], 133 to 159 mm/yr (tritium interface), and 137 mm/yr (mass balance) at site 2 (irrigated); about 63 mm/yr (tritium interface) and 12 mm/yr (mass balance) at site 3 (dryland); and about 53 mm/yr (tritium interface) and 10 mm/yr (mass balance) at site 8 (rangeland). Recharge values from the mass balance at site 2 were more than an order of magnitude greater than recharge values at site 3, suggesting irrigation is an important control on water movement through the unsaturated zone. For the remaining five sites, the post-bomb tritium had flushed through the system and recharge was considered modern (within 10 years of sampling). The chloride mass-balance method was used to determine water fluxes below the root zone (less than 2 meters below land surface) at the rangeland sites: sites 1, 4, and 8. At these rangeland sites, water fluxes ranged from 1.8 to 96 mm/yr at site 1, 1.1 to 9.6 mm/yr at site 4, and 1.1 to 68 mm/yr at site 8, with mean rates of 21, 4.3, and 13 mm/yr, respectively. Site 1 had a greater mean water flux, which was consistent with the greater precipitation in the east than at site 8 in the west. Chloride mass balance was not calculated at the irrigated and dryland sites because of uncertainty about additional sources of chloride. Concentrations of nitrate as nitrogen in pore water in the unsaturated zone were larger beneath the irrigated and dryland (agricultural) sites compared with the rangeland sites. The larger concentrations at the agricultural sites are consistent with the application of nitrogen fertilizer at the agricultural sites and no substantial accumulation at the rangeland sites. The shape of the nitrate as nitrogen and chloride concentration profiles at site 1 (rangeland) indicate a reasonably larger and more consistent water flux in the UZ than beneath the other two rangeland sites (sites 4 or 8). Excluding site 7, the general shape of the nitrate as nitrogen profiles was similar beneath the agricultural sites and supports the estimates of water movement and recharge rates determined from the tritium and chloride methods. Movement of bromide through the unsaturated zone indicated greater water fluxes are found beneath irrigated lands than beneath rangeland. Bromide profiles in the unsaturated zone, determined from center of mass and peak displacement methods, document water fluxes ranged from 58 to 394 mm/yr beneath irrigated sites and 9 to 201 mm/yr beneath rangeland sites. Water-flux estimates from the potassium bromide tests at most sites did not represent overall recharge rates because the bromide remained primarily in the root zone. Apparent groundwater age was used to determine the groundwater residence time at the eight sites and to estimate recharge rates. Groundwater ages in the study area ranged from old water (defined here as groundwater that was recharged more than 50 years ago) to modern (defined here as groundwater that has recharged within the past 10 years). Groundwater ages indicated that the shallow monitoring wells generally had younger residence times, whereas the deeper monitoring wells generally had the older residence times. Groundwater dates from the shallowest monitoring wells were used to determine recharge rates at the water table. These rates generally were similar to recharge rates determined from tritium and chloride mass-balance methods. Groundwater recharge rates generally increased with well depth, and the deeper monitoring wells likely do not represent local recharge conditions but recharge from a regional flow system that receives recharge from distant sources. Overall, these data generally indicate that water movement within the unsaturated zone primarily is affected by spatial contrasts in mean annual precipitation and by the land use or land cover. The eight unsaturated-zone sites each generated unique, valuable datasets that likely will improve the understanding of water movement and recharge rates in the central Platte River valley.

Nebraska↗

USGS2005

Burrowing owl nesting productivity: A comparison between artificial and natural burrows on and off golf courses

Burrowing owl ( Athene cunicularia ) populations are declining in many portions of their range, and lack of suitable nesting burrows is thought to be one reason for observed declines. Burrowing owls are attracted to golf courses because the birds generally nest and forage in short-grass, open areas, yet golf courses seldom have suitable nesting burrows. We examined the efficacy of installing artificial nesting burrows on golf courses as a way to help restore local burrowing owl populations. From 2001–2004 we monitored over 175 natural burrows off golf courses, 14 natural burrows on golf courses, 86 artificial burrows off golf courses, and 130 artificial burrows on golf courses. Owls located and used 8 of the 130 artificial burrows installed on golf courses (4 were used as nests). Owls selected burrows that were closer to existing natural burrows, farther from maintained areas (areas receiving turf maintenance by golf course staff), and farther from sprinkler heads. All 4 of the artificial burrows used as nests successfully fledged young, and annual site fidelity for owls nesting on golf courses was higher than for owls nesting off golf courses. However, annual fecundity of owls nesting on golf courses was lower than that of owls nesting off golf courses. If golf courses have sufficiently large nonmaintained areas and there are nesting owls nearby, course managers potentially can help in restoring local burrowing owl populations by installing artificial nesting burrows on the periphery of the course. However, the low fecundity on golf courses reported here should be more thoroughly examined before artificial burrows are used to attract owls to golf courses.

Wildlife Society Bulletin↗

USGS2013

Identification of metrics to monitor salt marsh integrity on National Wildlife Refuges in relation to conservation and management objectives

Executive Summary Most salt marshes in the US have been degraded by human activities, and threats from physical alterations, surrounding land-use, species invasions, and global climate change persist. Salt marshes are unique and highly productive ecosystems with high intrinsic value to wildlife, and many National Wildlife Refuges (NWRs) have been established in coastal areas to protect large tracts of salt marsh and wetland-dependent species. Various management practices are employed routinely on coastal NWRs to restore and enhance marsh integrity and ensure ecosystem sustainability. Prioritizing NWR salt marshes for application of management actions and choosing among multiple management options requires scientifically-based methods for assessing marsh condition. Monitoring is integral to structured decision-making (SDM), a formal process for decomposing a decision into its essential elements. Within a natural resource context, SDM involves identifying management objectives, alternative management actions, and expected management outcomes. The core of SDM is a set of criteria for measuring system performance and evaluating management responses. Therefore, use of SDM to frame natural resource decisions leads to logical selection of monitoring attributes that are linked explicitly to management needs. We used SDM to guide selection of variables for monitoring the ecological integrity of salt marshes within the National Wildlife Refuge System (NWRS). Our objectives were to identify indicators of salt marsh integrity that are effective across large geographic regions, responsive to a wide range of threats, and feasible to implement within funding and staffing constraints of the NWRS. In April, 2008, we engaged interdisciplinary experts in a week-long rapid prototyping SDM workshop to define the essential elements of salt marsh management decisions on refuges throughout the northeastern, southwestern, and northwestern US, corresponding to respective Regions 5, 2, and 1 of the US Fish and Wildlife Service (FWS). Through this process we identified measurable attributes for monitoring salt marsh ecosystems that are integrated into conservation practice and target management objectives. The following salt marsh attributes were identified through the SDM process either for describing state condition to determine management needs or for evaluating the achievement of management objectives: historical condition and geomorphic setting; ditch density; surrounding land use; ratio of open water area to vegetation area; rate of pesticide application; environmental contaminant concentration; change in marsh surface elevation relative to sea level rise; tidal range and groundwater level; surface topography; salinity; and species composition and abundance of vegetation, invasive species, invertebrates, nekton, and breeding and wintering birds. The identified attributes were too broadly defined to serve as operational monitoring variables. Therefore, we tested specific metrics for quantifying most of these attributes in summers of 2008 and 2009. The first four attributes in the above list can be characterized by office-based analysis of existing GIS data layers. The remaining attributes require field-based methods for assessment. We were forced to exclude a small number of attributes from field tests due to inconsistent data (pesticide application rate, environmental contaminant concentrations) or requirements that exceeded the scope of this project (change in marsh surface elevation; surface topography; benthic invertebrates; wintering birds). We evaluated potential metrics for evaluating all remaining field attributes. In partnership with NWRS biologists, we tested rapid versus intensive metrics for monitoring field attributes (tidal range and groundwater level; marsh surface elevation; salinity; and species composition and abundance of vegetation, invasive species, nekton, and breeding birds) at coastal refuges throughout FWS Region 5. Seven refuges participated in metric testing in 2008: Rachel Carson (ME), Parker River (MA), Wertheim (NY), E. B. Forsythe (NJ), Bombay Hook (DE), Prime Hook (DE), and Eastern Shore of Virginia Complex (VA). These seven and two additional refuges participated in metric testing in 2009: Rhode Island Complex (RI) and Stewart B. McKinney (CT). We based all field metrics on existing protocols for salt marsh assessment. Sampling locations were determined randomly within delineated marsh study units (MSUs) at each refuge. Detailed field methods are provided in appendices to this report. Measurements for individual metrics were averaged across samples within MSUs during each year of sampling. Each year, correlation or regression analysis was conducted on average measurements across MSUs within each attribute set to identify redundant metrics. Statistical redundancy between a pair of metrics within an attribute set (i.e., correlation or regression slopes with p-values < 0.05) was considered justification for eliminating one of the pair from the regional set of monitoring metrics. Decisions regarding metric elimination versus retention were based on feasibility of monitoring, considering such factors as sampling time, resources required, and potential for regional standardization in implementation. The result of these tests is a reduced suite of monitoring metrics that targets NWRS management decisions and is practicable for implementing on a regional scale. Based on these tests, we recommend the following list of metrics for monitoring integrity of NWRS salt marshes (marsh attribute category is in parentheses): (historical condition and geomorphic setting) position of marsh in the landscape, marsh shape, degree of fill and/or fragmentation, degree of tidal flushing, amount of aquatic edge; (ditch density) ranking of ditch density from none to severe; (surrounding land use) relative proportion of agricultural land in a 150-m buffer around the marsh, relative proportion of natural land in a 150-m buffer around the marsh, relative proportion of natural land in a 1-km buffer around the marsh; (ratio of open water area to vegetation area) ratio of open water to emergent herbaceous wetlands within the marsh; (marsh surface elevation) elevation referenced to NAVD88 in a representative area of the marsh; (tidal range and groundwater level) percent of time the marsh surface is flooded during deployment of a continuous water-level monitor at a representative marsh location, mean depth of surface flooding as measured by a continuous water-level monitor at a representative location; (salinity) salinity measured in surface water; (vegetation community) vegetation species richness using the point-intercept method in 100-m diameter survey plots, percent cover of various marsh community types within 100-m diameter survey plots; (invasive species abundance) percent cover of invasive plant species measured using the point-intercept method in 100-m diameter survey plots; (nekton community) nekton density, nekton species richness, length of Fundulus heteroclitus ; (breeding bird community) abundance of Willets counted per point during standard call-broadcast surveys, summed abundance of tidal marsh obligate species (Clapper Rail, Willet, Saltmarsh Sparrow, Seaside Sparrow) counted per point during standard call-broadcast surveys. Metrics describing the historical condition, geomorphic setting, and broad landscape features can be assessed using existing GIS databases. Our results support use of rapid methods to assess the majority of field metrics; only those used to describe the nekton community must be measured using intensive methods (throw traps or ditch nets, dependant on habitat configuration). Implementation of these metrics for quantitative assessment of NWRS salt marsh integrity in FWS Region 5 requires developing sampling designs for each refuge. Additionally, it is important to determine how the monitoring information will be used within a management context. SDM should be used to complete the analysis of salt marsh management decisions. The next steps would involve 1) prioritizing and weighting the management objectives; 2) predicting responses to individual management actions in terms of objectives and metrics; 3) using multiattribute utility theory to convert all measurable attributes to a common utility scale; 4) determining the total management benefit of each action by summing utilities across objectives; and 5) maximizing the total management benefits within cost constraints for each refuge. This process would allow the optimum management decisions for NWRS salt marshes to be selected and implemented based directly on monitoring data and current understanding of marsh responses to management actions. Monitoring the outcome of management actions would then allow new monitoring data to be incorporated into subsequent decisions.

Connecticut, Delaware, Maine, Massachusetts, New J↗

USGS1983

Selective preservation and origin of petroleum-forming aquatic kerogen

Studies of a marine algal sapropel from Mangrove Lake, Bermuda, by 13C NMR and stable carbon isotopic methods show that precursors of aquatic kerogen (insoluble, macromolecular, paraffinic humic substances) are primary components of algae and possibly associated bacteria and that these substances survive microbial decomposition and are selectively preserved during early diagenesis. ?? 1983 Nature Publishing Group.

Nature↗

USGS2008

Low-Level detections of halogenated volatile organic compounds in groundwater: Use in vulnerability assessments

Concentrations of halogenated volatile organic compounds (VOCs) were determined by gas chromatography (GC) with an electron-capture detector (GC-ECD) and by gas chromatography with mass spectrometry (GC-MS) in 109 groundwater samples from five study areas in the United States. In each case, the untreated water sample was used for drinking-water purposes or was from a monitoring well in an area near a drinking-water source. The minimum detection levels (MDLs) for 25 VOCs that were identified in GC-ECD chromatograms, typically, were two to more than four orders of magnitude below the GC-MS MDLs. At least six halogenated VOCs were detected in all of the water samples analyzed by GC-ECD, although one or more VOCs were detected in only 43% of the water samples analyzed by GC-MS. In nearly all of the samples, VOC concentrations were very low and presented no known health risk. Most of the low-level VOC detections indicated post-1940s recharge, or mixtures of recharge that contained a fraction of post-1940s water. Concentrations of selected halogenated VOCs in groundwater from natural and anthropogenic atmospheric sources were estimated and used to recognize water samples that are being impacted by nonatmospheric sources. A classification is presented to perform vulnerability assessments at the scale of individual wells using the number of halogenated VOC detections and total dissolved VOC concentrations in samples of untreated drinking water. The low-level VOC detections are useful in vulnerability assessments, particularly for samples in which no VOCs are detected by GC-MS analysis.

Journal of Hydrologic Engineering↗

USGS1969

Geologic Settings of Subsidence

This paper reviews the role of geologic processes that contribute to subsidence in order to aid those starting investigations of ground-surface subsidence. Subsidence occurs, or at least is discovered, only infrequently, and little organized information has been available. In order to assess our present state of knowledge, the author gathered fragmentary bits of information from many sources widely scattered in the literature of geology and other earth sciences. The author cites examples for each geologic process that is a potential contributor to ground-surface subsidence together with geologic evidence for diagnosing their causes. The geologic processes involved are: (1) solution of gypsum and salt and redistribution of transient fill materials through solution cavities in calcareous rocks; (2) underground erosion of uncemented or lightly cemented silt and sand through temporary underground passageways; (3) lateral plastic flow of salt, gypsum and anhydrite, shale, and clay under loading; (4) compaction of sediments by loading, drainage, vibration, and hydrocompaction; (5) tectonic movements including primary and secondary effects of earthquakes, folding, and warping; and (6) volcanic activity. Because the first four processes may be accelerated by various engineering activities, examples have been selected to illustrate subsidence both under natural conditions and under conditions modified by man's activities. Although this extensive search for existing information on the role of geologic factors in subsidence indicates that much detailed work remains to be done, the future prospects for advancing our geologic knowledge are excellent. Methods of measuring ground-surface displacements are improving rapidly. Also, broadly based investigations of known areas of major subsidence throughout the world are developing new methods of diagnosis and treatment and are yielding quantitative data that will aid our evaluation of the rates and magnitude of present-day geologic processes.

Book chapter↗

USGS2006

A review of the population estimation approach of the North American landbird conservation plan

As part of their development of a continental plan for monitoring landbirds (Rich et al. 2004), Partners in Flight (PIF) applied a new method to make preliminary estimates of population size for all 448 species of landbirds present in the continental United States and Canada (Table 1). Estimation of the global population size of North American landbirds was intended to (1) identify the degree of vulnerability of each species, (2) provide estimates of the current population size for each species, and (3) provide a starting point for estimating population sizes in states, provinces, territories, and Bird Conservation Regions (Rich et al. 2004). A method proposed by Rosenberg and Blancher (2005) was used to derive population estimates from available survey data. To enhance the credibility of these estimates, PIF organized a review of the methodology used to estimate North American landbird population sizes. A planning committee selected members from the ornithological and biometrical communities (hereafter “the panel”), with the aim of selecting individuals from academia, state natural-resource agencies, and the U.S. and Canadian federal governments, including the Canadian Wildlife Service, the U.S. Geological Survey, and the U.S. Department of Agriculture Forest Service. The panel addressed three questions: (1) Were the methods of population estimation proposed by PIF reasonable? (2) What actions could be taken to improve the data or analyses on which the PIF population estimates were based? and (3) How should the PIF population estimates be interpreted?

The Auk↗