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At least 937 records · Page 52Linked to original sources

A comparison of macroinvertebrate and habitat methods of data collection in the Little Colorado River Watershed, Arizona 2007

The Arizona Department of Environmental Quality (ADEQ) and the U.S. Environmental Protection Agency (USEPA) Ecological Monitoring and Assessment Program (EMAP), use different field methods for collecting macroinvertebrate samples and habitat data for bioassessment purposes. Arizona’s Biocriteria index was developed using a riffle habitat sampling methodology, whereas the EMAP method employs a multi-habitat sampling protocol. There was a need to demonstrate comparability of these different bioassessment methodologies to allow use of the EMAP multi-habitat protocol for both statewide probabilistic assessments for integration of the EMAP data into the national (305b) assessment and for targeted in-state bioassessments for 303d determinations of standards violations and impaired aquatic life conditions. The purpose of this study was to evaluate whether the two methods yield similar bioassessment results, such that the data could be used interchangeably in water quality assessments. In this Regional EMAP grant funded project, a probabilistic survey of 30 sites in the Little Colorado River basin was conducted in the spring of 2007. Macroinvertebrate and habitat data were collected using both ADEQ and EMAP sampling methods, from adjacent reaches within these stream channels. All analyses indicated that the two macroinvertebrate sampling methods were significantly correlated. ADEQ and EMAP samples were classified into the same scoring categories (meeting, inconclusive, violating the biocriteria standard) 82% of the time. When the ADEQ-IBI was applied to both the ADEQ and EMAP taxa lists, the resulting IBI scores were significantly correlated (r=0.91), even though only 4 of the 7 metrics in the IBI were significantly correlated. The IBI scores from both methods were significantly correlated to the percent of riffle habitat, even though the average percent riffle habitat was only 30% of the stream reach. Multivariate analyses found that the percent riffle was an important attribute for both datasets in classifying IBI scores into assessment categories. Habitat measurements generated from EMAP and ADEQ methods were also significantly correlated; 13 of 16 habitat measures were significantly correlated (p<0.01). The visual-based percentage estimates of percent riffle and pool habitats, vegetative cover and percent canopy cover, and substrate measurements of percent fine substrate and embeddedness were all remarkably similar, given the different field methods used. A multivariate analysis identified substrate and flow conditions, as well as canopy cover as important combinations of habitat attributes affecting both IBI scores. These results indicate that similar habitat measures can be obtained using two different field sampling protocols. In addition, similar combinations of these habitat parameters were important to macroinvertebrate community condition in multivariate analyses of both ADEQ and EMAP datasets. These results indicate the two sampling methods for macroinvertebrates and habitat data were very similar in terms of bioassessment results and stressors. While the bioassessment category was not identical for all sites, overall the assessments were significantly correlated, providing similar bioassessment results for the cold water streams used in this study. The findings of this study indicate that ADEQ can utilize either a riffle-based sampling methodology or a multi-habitat sampling approach in cold water streams as both yield similar results relative to the macroinvertebrate assemblage. These results will allow for use of either macroinvertebrate dataset to determine water quality standards compliance with the ADEQ Indexes of Biological Integrity, for which threshold values were just recently placed into the Arizona Surface Water Quality Standards. While this survey did not include warm water desert streams of Arizona, we would predict that EMAP and ADEQ sampling methodologies would provide similar bioassessment results and would not be significantly different, as we have found that the percent riffle habitat in cold and warm water perennial, wadeable streams is not significantly different. However, a comparison study of sampling methodologies in warm water streams should be conducted to confirm the predicted similarity of bioassessment results. ADEQ will continue to implement a monitoring strategy that includes probabilistic monitoring for a statewide ecological assessment of stream conditions. Conclusions from this study will guide decisions regarding the most appropriate sampling methods for future probabilistic monitoring sample plans.

Arizona↗

Variability in expression of anadromy by female Oncorhynchus mykiss within a river network

We described and predicted spatial variation in marine migration (anadromy) of female Oncorhynchus mykiss in the John Day River watershed, Oregon. We collected 149 juvenile O. mykiss across 72 sites and identified locations used by anadromous females by assigning maternal origin (anadromous versus non-anadromous) to each juvenile. These assignments used comparisons of strontium to calcium ratios in otolith primordia and freshwater growth regions to indicate maternal origin. We used logistic regression to predict probability of anadromy in relation to mean annual stream runoff using data from a subset of individuals. This model correctly predicted anadromy in a second sample of individuals with a moderate level of accuracy (e.g., 68% correctly predicted with a 0.5 classification threshold). Residuals from the models were not spatially autocorrelated, suggesting that remaining variability in the expression of anadromy was due to localized influences, as opposed to broad-scale gradients unrelated to mean annual stream runoff. These results are important for the management of O. mykiss because anadromous individuals (steelhead) within the John Day River watershed are listed as a threatened species, and it is difficult to discern juvenile steelhead from non-anadromous individuals (rainbow trout) in the field. Our results provide a broad-scale description and prediction of locations supporting anadromy, and new insight for habitat restoration, monitoring, and research to better manage and understand the expression of anadromy in O. mykiss .

Oregon↗

Uranium and coexisting element behaviour in surface waters and associated sediments with varied sampling techniques used for uranium exploration

Optimum sampling methods in surface water and associated sediments for use in uranium exploration are being studied at thirty sites in Colorado, New Mexico, Arizona and Utah. For water samples, filtering is recommended to increase sample homogeneity and reproducibility because for most elements studied water samples which were allowed to remain unfiltered until time of analysis contained higher concentrations than field-filtered samples of the same waters. Acidification of unfiltered samples resulted in still higher concentrations. This is predominantly because of leaching of the elements from the suspended fraction. U in water correlates directly with Ca, Mg, Na, K, Ba, B, Li and As. In stream sediments, U and other trace elements are concentrated in the finer size fractions. Accordingly, in prospecting, grain size fractions less than 90 μm (170 mesh) should be analyzed for U. A greater number of elements (21) show a significant positive correlation with U in stream sediments than in water. Results have revealed that anomalous concentrations of U found in water may not be detected in associated sediments and vice versa. Hence, sampling of both surface water and coexisting sediment is strongly recommended.

Journal of Geochemical Exploration↗

GSTARS computer models and their applications, Part II: Applications

In part 1 of this two-paper series, a brief summary of the basic concepts and theories used in developing the Generalized Stream Tube model for Alluvial River Simulation (GSTARS) computer models was presented. Part 2 provides examples that illustrate some of the capabilities of the GSTARS models and how they can be applied to solve a wide range of river and reservoir sedimentation problems. Laboratory and field case studies are used and the examples show representative applications of the earlier and of the more recent versions of GSTARS. Some of the more recent capabilities implemented in GSTARS3, one of the latest versions of the series, are also discussed here with more detail. ?? 2008 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.

International Journal of Sediment Research↗

Biogeochemistry of beetle-killed forests: Explaining a weak nitrate response

A current pine beetle infestation has caused extensive mortality of lodgepole pine ( Pinus contorta ) in forests of Colorado and Wyoming; it is part of an unprecedented multispecies beetle outbreak extending from Mexico to Canada. In United States and European watersheds, where atmospheric deposition of inorganic N is moderate to low (<10 kg⋅ha⋅y), disturbance of forests by timber harvest or violent storms causes an increase in stream nitrate concentration that typically is close to 400% of predisturbance concentrations. In contrast, no significant increase in streamwater nitrate concentrations has occurred following extensive tree mortality caused by the mountain pine beetle in Colorado. A model of nitrate release from Colorado watersheds calibrated with field data indicates that stimulation of nitrate uptake by vegetation components unaffected by beetles accounts for significant nitrate retention in beetle-infested watersheds. The combination of low atmospheric N deposition (<10 kg⋅ha⋅y), tree mortality spread over multiple years, and high compensatory capacity associated with undisturbed residual vegetation and soils explains the ability of these beetle-infested watersheds to retain nitrate despite catastrophic mortality of the dominant canopy tree species.

Colorado↗

Environmental impact analysis; the example of the proposed Trans-Alaska Pipeline

The environmental impact analysis made as required by the National Environmental Policy Act of 1969 for the proposed trans-Alaska pipeline included consideration of the (1) technologically complex and geographically extensive proposed project, (2) extremely different physical environments across Alaska along the proposed route and elsewhere in Alaska and in Canada along alternative routes, (3) socioeconomic environment of the State of Alaska, and (4) a wide variety of alternatives. The analysis was designed specifically to fit the project and environment that would be affected. The environment was divided into two general parts--natural physical systems and superposed socioeconomic systems--and those parts were further divided into discipline-oriented systems or components that were studied and analyzed by scientists of the appropriate discipline. Particular attention was given to potential feedback loops in the impact network and to linkages between the project's impacting effects and the environment. The results of the analysis as reported in the final environmental impact statement were that both unavoidable and threatened environmental impacts would result from construction, operation, and maintenance of the proposed pipeline system and the developments related to it. The principal unavoidable effects would be (1) disturbances of terrain, fish and wildlife habitat, and human environs, (2) the results of the discharge of effluent from the tanker-ballast-treatment facility into Port Valdez and of some indeterminate amount of oil released into the ocean from tank-cleaning operations at sea, and (3) the results associated with increased human pressures of all kinds on the environment. Other unavoidable effects would be those related to increase of State and Native Corporation revenues, accelerated cultural change of the Native population, and extraction of the oil and gas resource. The main threatened environmental effects would all be related to unintentional oil loss from the pipeline, from tankers, or in the oil field. Oil losses from the pipeline could be caused by direct or indirect effects of earthquakes, destructive sea waves, slope failure caused by natural or artificial processes, thaw-plug instability (in permafrost), differential settlement of permafrost terrain, and bed scour and bank erosion at stream crossings. Oil loss from tankers could be caused by accidents during transfer operations at Valdez and at destination ports and by casualties involving tankers and other ships. Comparison of alternative routes and transportation systems and of their environmental impacts provided information which indicates to the author that one corridor containing both oil and gas pipelines would have less environmental impact than would separate corridors. Considering also the threat to the marine environment that any tanker system would impose and the threat that zones of high earthquake frequency and magnitude would impose on pipelines, it is apparent to the author that environmental impact and cost would be least for a single-corridor on-land route that avoided earthquake zones. The alternative trans-Alaska-Canada routes would meet these criteria. The decisions of the U.S. Department of the Interior, the U.S. Congress, and the President of the United States in favor of the proposed trans-Alaska pipeline system indicate the relative weight given by the decision makers in balancing the importance of potential environmental consequences against the advantages to be derived from rapid resource development.

Circular↗

Science for the stewardship of the groundwater resources of Cape Cod, Massachusetts

Groundwater is the sole source of drinking water and a major source of freshwater for domestic, industrial, and agricultural uses on Cape Cod, Massachusetts. Groundwater discharged from aquifers also supports freshwater pond and stream ecosystems and coastal wetlands. Six hydraulically distinct groundwater-flow systems (lenses) have been delineated on Cape Cod. Of the approximately 450 million gallons per day of water that enters these lenses as recharge from precipitation, about 69 percent discharges directly to the coast, about 24 percent discharges to streams, and almost 7 percent is withdrawn by public-supply wells. In most areas, groundwater in the sand and gravel aquifers is shallow and susceptible to contamination from anthropogenic sources and saltwater intrusion. Continued land development and population growth on Cape Cod have created concerns that potable water will become less available and that the quantity and quality of water flowing to natural discharge areas such as ponds, streams, and coastal waters will continue to decline. The U.S. Geological Survey (USGS) has been investigating groundwater and surface-water resources on Cape Cod for more than 50 years. Recent studies highlighted in this fact sheet have focused on the sources of water to public-supply wells, ponds, streams, and coastal areas; the transport and discharge of nitrogen derived from domestic and municipal disposal of wastewater; and the effects of climate change on groundwater and surface-water resources. Other USGS activities include long-term monitoring of groundwater and pond levels and field research on groundwater contamination at the USGS Cape Cod Toxic Substances Hydrology Research Site ( http://ma.water.usgs.gov/MMRCape/ ) near the Joint Base Cape Cod (JBCC), formerly the Massachusetts Military Reservation.

Massachusetts↗

Cost-effectiveness of the stream-gaging program in Missouri

This report documents the results of an evaluation of the cost effectiveness of the 1986 stream-gaging program in Missouri. Alternative methods of developing streamflow information and cost-effective resource allocation were used to evaluate the Missouri program. Alternative methods were considered statewide, but the cost effective resource allocation study was restricted to the area covered by the Rolla field headquarters. The average standard error of estimate for records of instantaneous discharge was 17 percent; assuming the 1986 budget and operating schedule, it was shown that this overall degree of accuracy could be improved to 16 percent by altering the 1986 schedule of station visitations. A minimum budget of $203,870, with a corresponding average standard error of estimate 17 percent, is required to operate the 1986 program for the Rolla field headquarters; a budget of less than this would not permit proper service and maintenance of the stations or adequate definition of stage-discharge relations. The maximum budget analyzed was $418,870, which resulted in an average standard error of estimate of 14 percent. Improved instrumentation can have a positive effect on streamflow uncertainties by decreasing lost records. An earlier study of data uses found that data uses were sufficient to justify continued operation of all stations. One of the stations investigated, Current River at Doniphan (07068000) was suitable for the application of alternative methods for simulating discharge records. However, the station was continued because of data use requirements. (Author 's abstract)

Water-Resources Investigations Report↗

Common marsh plants of the United States and Canada

This is the fourth of a series of publications on field identification of North American marsh and water plants. It describes the emergent and semiemergent plants most likely to be found in inland and coastal marshes. It omits hundreds of uncommon marsh plants and plants less characteristic of marshes than of marsh edges, lake and stream shores, or wet meadows. The first of the series, "Pondweeds and Pondweedlike Plants of Eastern North America," Circular 187, was broadened in scope as Resource Publication 44, "Underwater and Floating-leaved Plants of the United States and Canada," and is superseded by it. The present publication, widens the scope of "Bulrushes and Bulrushlike Plants of Eastern North America," Circular 221, and contains most of the species listed therein. This guide is designed for identification of marsh plants without recourse to technical botanical keys. To use it, read pages 1 to 4 and then look at the drawings. To identify a plant, find the group in which it fits, then find a drawing and description that match it.

Resource Publication↗

Geology and hydrogeology of the Caribbean Islands aquifer system of the Commonwealth of Puerto Rico and the U.S. Virgin Islands

Poorly lithified to unconsolidated carbonate and clastic sedimentary rocks of Tertiary (Oligocene to Pliocene) and Quaternary (Pleistocene to Holocene) age compose the South Coast aquifer and the North Coast limestone aquifer system of Puerto Rico; poorly lithified to unlithified carbonate rocks of late Tertiary (early Miocene to Pliocene) age make up the Kingshill aquifer of St. Croix, U.S. Virgin Islands. The South Coast aquifer, North Coast limestone aquifer system, and Kingshill aquifer are the most areally extensive and function as the major sources of ground water in the U.S. Caribbean Islands Regional Aquifer-System Analysis (CI-RASA) study area. In Puerto Rico's South Coast ground-water province, more than 1,000 meters of clastic and carbonate rocks of Oligocene to Pliocene age infill the South Coast Tertiary Basin. The pattern of lithofacies within this basin appears to have been controlled by changes in base level that were, at times, dominated by tectonic movement (uplift and subsidence), but were also influenced by eustasy. Deposition of the 70-kilometer long and 3- to 8-kilometer wide fan-delta plain that covers much of the South Coast ground-water province occurred largely in response to glacially-induced changes in sea level and climate during the Quaternary period. Tectonic movement played a much less important role during the Quaternary. The North Coast ground-water province of Puerto Rico is underlain by homoclinal coastal plain wedge of carbonate and siliciclastic rocks that infill the North Coast Tertiary Basin and thicken to more than 1,700 meters. A thin basal siliciclastic sequence of late Oligocene age is overlain by a thick section of mostly carbonate rocks of Oligocene to middle Miocene age. Globigerinid limestone of late Miocene to Pliocene age crops out and lies in the shallow subsurface areas of northwestern Puerto Rico. Oligocene to middle Miocene age rocks tentatively can be divided into five depositional sequences and associated systems tracts; these rocks record carbonate and minor siliciclastic deposition that occurred in response to changes in relative sea level. The Cibao Formation represents the most complex of these sequences and contains a varied facies of carbonate, mixed carbonate-siliciclastic, and siliciclastic rocks that reflect differential uplift, subsidence, and transgression of the sea. Uplift, graben formation, and gradual shallowing of the sea are reflected within the bathyal-dominated sedimentary facies of the Kingshill Limestone in St. Croix, U.S. Virgin Islands. Reef-tract limestone beds of Pliocene age were subject to exposure, resubmergence, and meteoric leaching of aragonitic skeletal debris; these beds contain patchy lenses of dolomite that are restricted to a small, structurally-controlled embayment. The South Coast aquifer, the principal water-bearing unit of Puerto Rico's South Coast ground-water province, consists of boulder- to silt-size detritus formed by large and small coalescing fan deltas of Pleistocene to Holocene age. Deep well data indicates that it is possible to vertically separate and group a highly complex and irregular-bedded detrital sequence that underlies distal parts of the fan-delta plain into discrete water-bearing units if correlated with 30- to 40-meter thick, eustatically-controlled depositional cycles. Lithofacies maps show that greatest hydraulic conductivity within the fan-delta plain is generally associated with proximal fan and midfan areas. Distal and interfan areas are least permeable. Alluvial valley aquifers located in the western part of the South Coast ground-water province are important local sources of water supply and appear to contain some of the same physical and hydraulic characteristics as the South Coast aquifer. Older sedimentary rocks within the basin are poor aquifers; conglomeratic beds are well-cemented, and carbonate beds do not contain well-developed solution features, except locally where the beds are overlain by alluvium. Ground-water occurs under unconfined conditions in proximal and midfan areas. Confined conditions within deeper parts of the system and in interfan and some midfan areas are created largely by the intercalated nature of discontinuous fine-grained beds that retard vertical ground-water movement. The development of water resources in southern Puerto Rico has modified the hydrologic system of the South Coast aquifer considerably. Under predevelopment conditions, the South Coast aquifer was recharged in the unconfined, proximal fan and some midfan areas by infrequent rainfall and seepage from streams near the fan apex. Discharge occurred as seabed seepage, baseflow discharge along the lower coastal reach of streams, seepage to coastal wetlands, or evapotranspiration in areas underlain by a shallow water table. Under development conditions, seepage from irrigation canals and areal recharge from furrow irrigation represented a principal mechanism for recharge to the aquifer. Increased ground-water withdrawals in the 1960's and 1970's resulted in declines in the water table to below sea level in some places and intrusion of salt water into the aquifer. By the middle 1980's, a reduction in ground-water withdrawals and a shift from furrow irrigation to drip-irrigation techniques resulted in the recovery of water levels. Under present-day (1986) conditions, regional ground-water flow is coastward but with local movement to some well fields. In addition to the discharge mechanisms described above, ground-water discharges also to coastal canals. The North Coast limestone aquifer system consists of limestone, lesser amounts of dolomite, and minor clastic detritus of Oligocene to Pliocene age that form an unconfined upper aquifer and a confined lower aquifer; these aquifers are separated by a clay, mudstone, and marl confining unit. Topographic relief and incision of carbonate coastal plain rocks by streams are the principal factors controlling the direction of ground-water flow. The North Coast limestone aquifer system is recharged principally by precipitation that enters the upper and lower aquifers where they crop out. Regional groundwater movement from the upper aquifer is to the major rivers, wells, coastal wetlands, coastal, nearshore, and offshore springs, or as seabed seepage. Regional discharge from the lower aquifer is to the major rivers along its unconfined parts or where the confining unit has been breached by streams. Discharge from the lower aquifer also occurs in the San Juan area where the Mucarabones Sand provides an avenue for diffuse upward ground-water flow. Transmissivity within the upper limestone aquifer appears to be largely regulated by the thickness of the freshwater lens. The lens is thickest and transmissivity is greatest in interstream areas that lie in a zone that closely corresponds to the landwardmost extent of the underlying saltwater wedge. Hydraulic conductivity of the upper aquifer generally increases in a coastward direction and reflects lithologic control, karstification in the upper 30 to 100 meters of the section, and enhanced permeability in a zone of freshwater and saltwater mixing. Transmissivity of the lower aquifer is an order of magnitude smaller than that of the upper aquifer; highest transmissivities in the lower aquifer largely correspond to a coarse grainstone-packstone and coral-patch-reef depositional facies contained within the outcropping parts of the Montebello Limestone Member and its subsurface equivalents. Porosity within the North Coast limestone aquifer system is high in grainstone-packstones and low in wackestone and marl. Dolomitized zones and moldic grainstone-packstone strata are the most porous carbonate rocks, but occur in thin beds that usually are only a few meters thick. Processes of karstification that include the development of caverous zones and large vugs, and dissolution along possible regional fracture sets has enhanced permeability within the upper part of the aquifer system. Stratigraphic and lithologic control play an important role controlling permeability within the lower part of the system. The Kingshill aquifer of St. Croix, in large part, is composed of deepwater limestone that contains only microscopic pores and is poorly permeable; however, the upper part of the aquifer, a shallow-water skeletal and reef limestone, is fairly permeable, but restricted in areal extent. Permeability within these uppermost beds of the aquifer has been enhanced by meteoric leaching, dissolution within a mixing zone of saltwater and fresh water, and dolomitization. However, most large-yield wells completed in the Kingshill aquifer are also screened in alluvium that overlies or infills incised channels. The alluvial deposits serve as a temporary storage zone for rainfall, runoff, and ground water slowly entering the Kingshill aquifer.

Puerto Rico↗

Hydrodynamic modeling of juvenile mussel dispersal in a large river: The potential effects of bed shear stress and other parameters

Because unionid mussels have a parasitic larval stage, they are able to disperse upstream and downstream as larvae while attached to their host fish and with flow as juveniles after excystment from the host. Understanding unionid population ecology requires knowledge of the processes that affect juvenile dispersal prior to establishment. We examined presettlement (transport and dispersion with flow) and early postsettlement (bed shear stress) hydraulic processes as negative censoring mechanisms. Our approach was to model dispersal using particle tracking through a 3-dimensional flow field output from hydrodynamic models of a reach of the Upper Mississippi River. We tested the potential effects of bed shear stress (??b) at 5 flow rates on juvenile mussel dispersal and quantified the magnitude of these effects as a function of flow rate. We explored the reach-scale relationships of Froude number (Fr), water depth (H), local bed slope (S), and unit stream power (QS) with the likelihood of juvenile settling (??). We ran multiple dispersal simulations at each flow rate to estimate ??, the parameter of a Poisson distribution, from the number of juveniles settling in each grid cell, and calculated dispersal distances. Virtual juveniles that settled in areas of the river where b > critical shear stress (c) were resuspended in the flow and transported further downstream, so we ran simulations at 3 different conditions for ??c (??c = ??? no resuspension, 0.1, and 0.05 N/m2). Differences in virtual juvenile dispersal distance were significantly dependent upon c and flow rate, and effects of b on settling distribution were dependent upon c. Most simulations resulted in positive correlations between ?? and ??b, results suggesting that during early postsettlement, ??b might be the primary determinant of juvenile settling distribution. Negative correlations between ?? and ??b occurred in some simulations, a result suggesting that physical or biological presettlement processes might determine juvenile settling distributions. Field data are needed to test these hypotheses. Results support the idea that flow patterns and b can act as negative censoring mechanisms controlling settling distributions. Furthermore, a river reach probably has a quantifiable threshold range of flow rates. Above the upper threshold, ??b probably is the primary determinant of juvenile settling distribution. Relationships of ?? with H, Fr, S, and QS were relatively weak. Important physical processes that affect dispersal probably are not captured by approximations based on large-scale hydraulic parameters, such as Fr and H. ?? 2010 The North American Benthological Society.

Conference Paper↗

Nitrate fate and transport through current and former depressional wetlands in an agricultural landscape, Choptank Watershed, Maryland, United States

Understanding local groundwater hydrology and geochemistry is critical for evaluating the effectiveness of wetlands at mitigating agricultural impacts on surface waters. The effectiveness of depressional wetlands at mitigating nitrate (NO 3 ) transport from fertilized row crops, through groundwater, to local streams was examined in the watershed of the upper Choptank River, a tributary of Chesapeake Bay on the Atlantic Coastal Plain. Hydrologic, geochemical, and water quality data were collected from January of 2008 through December of 2009 from surface waters and networks of piezometers installed in and around current or former depressional wetlands of three major types along a gradient of anthropogenic alteration: (1) natural wetlands with native vegetation (i.e., forested); (2) prior-converted croplands, which are former wetlands located in cultivated fields; and (3) hydrologically restored wetlands, including one wetland restoration and one shallow water management area. These data were collected to estimate the orientation of groundwater flow paths and likely interactions of groundwater containing NO 3 from agricultural sources with reducing conditions associated with wetlands of different types. Natural wetlands were found to have longer periods of soil saturation and reducing conditions conducive to denitrification compared to the other wetland types studied. Because natural wetlands are typically located in groundwater recharge areas along watershed divides, nitrogen (N) from nearby agriculture was not intercepted. However, these wetlands likely improve water quality in adjacent streams via dilution. Soil and geochemical conditions conducive to denitrification were also present in restored wetlands and prior-converted croplands, and substantial losses of agricultural NO 3 were observed in groundwater flowing through these wetland sediments. However, delivery of NO 3 from agricultural areas through groundwater to these wetlands resulting in opportunities for denitrification were limited, particularly where reducing conditions did not extend throughout the entire thickness of the surficial aquifer allowing NO 3 to pass conservatively beneath a wetland along deeper groundwater flow paths. The complexity of N fate and transport associated with depressional wetlands complicates the understanding of their importance to water quality in adjacent streams. Although depressional wetlands often contribute low NO 3 water to local streams, their effectiveness as landscape sinks, for N from adjacent agriculture varies with natural conditions, such as the thickness of the aquifer and the extent of reducing conditions. Measurement of such natural geologic, hydrologic, and geochemical conditions are therefore fundamental to understanding N mitigation in individual wetlands.

Maryl↗

Biomonitoring of Environmental Status and Trends (BEST) Program: Environmental contaminants and their effects on fish in the Mississippi River Basin

We collected, examined, and analyzed 1378 fish of 22 species from 47 sites in the Mississippi River basin (MRB) during 1995 and from a reference site in 1996. The sampling sites in the MRB represented National Contaminant Biomonitoring Program (NCBP) stations situated at key points on major rivers and National Water- Quality Assessment Program (NAWQA) stations located on lower-order rivers and streams in the Eastern Iowa Basins (EIB) and Mississippi Embayment (MSE) Study Units. The reference site was the water supply system of the USGS-Leetown Science Center in rural Jefferson County, WV. Common carp (Cyprinus carpio; carp) and black basses (Micropterus spp.; bass), the targeted species, together represented 82% of the fish collected. Each fish was examined in the field for externally and internally visible gross lesions, selected organs were weighed to compute various ponderal and organo-somatic indices, and selected tissues and fluids were obtained and preserved for analysis of biomarkers. Fish health indicators included splenic macrophage aggregates, lysozyme activity, and hispathological analysis of liver, kidney, and other tissues. Reproductive biomarkers included analysis of plasma concentrations of vitellogenin (vtg) and the sex steroid hormones 17-estradiol (E2) and 11-ketotestosterone (11- kt); and the histological determination of percent oocyte atresia (in female fish) and gonadal stage. Hepatic ethoxyresorufin O-deethylase (EROD) activity was also measured. Composite samples of whole fish from each station were grouped by species and gender and analyzed for persistent organochlorine and elemental contaminants and for dioxin-like activity (TCDD-EQ) using the H4IIE rat hepatoma cell bioassay. Organochlorine and inorganic contaminant concentrations in fish were generally low relative to historical levels at most sites, but remained present at concentrations representing threats to piscivorous wildlife in some locations. Toxaphene and DDT (mostly as p,p?-DDE) concentrations remained elevated in fish from the cottongrowing regions of the lower Mississippi valley, and were generally greater in the smaller streams draining agricultural areas (that is, in the MSE Study Unit) than at large river sites. Cyclodiene pesticide concentrations were also greatest in the EIB Study Unit and elsewhere in the corn-growing regions of the mid-MRB. Former point-sources of organochlorine pesticides also remained evident, especially in the Mississippi River near Memphis, TN. Consistent with previous findings, total PCB concentrations tended to be greatest (1-3 g/g) in the industrialized and urbanized Ohio River and Upper Mississippi sub-basins and at Memphis, TN, and were generally correlated with TCDD-EQ and EROD activity. Conversely, PCB concentrations were low (<0.1 g/g) in the more agricultural parts of the MRB. Concentrations of inorganic contaminants were also relatively low and stable or declining relative to past levels at most sites. Exceptions were Hg and Se; Hg concentrations were slightly elevated (>0.3 g/g) in bass from the Mississippi River at Memphis and several other sites and in carp from one MSE site. Concentrations of Se were also great enough to constitute a hazard to piscivorous wildlife (>0.6 g/g) at several MRB sites in the western parts of the MRB and were especially high (4-5 g/g) in fish from John Martin Reservoir, CO, where elevated concentrations were reported previously. Biomarker results indicated that fish from many stations had been exposed to contaminants, but at no sites did findings indicate exposure to high concentrations of toxic chemicals. Noteworthy among biomarker findings was that 73% of the male smallmouth bass (Micropterus dolomieui) from the Mississippi River at Lake City, MN (Lake Pepin) were intersex as indicated by the histological detection of ovotestes; and the combined EROD and H4IIE results indicated that fish from several rural sites in the

Mississippi River basin↗

Flow and sediment suspension events on the inner shelf of central California

The US Geological Survey conducted a field experiment in the late spring and early summer of 1998 off northern Santa Cruz County, California, to study sediment fluxes along the central California shelf. As part of this study, a bottom-mounted instrument package was deployed in a sediment-filled paleo-stream channel (h=12 m) off a pocket beach to measure waves, currents, suspended-sediment concentration, temperature, salinity, and seabed-level changes. The observations of suspended-sediment concentration revealed intermittent, intense periods of sediment suspension near the bed that were associated with the passage of individual large waves or wave groups. We used an ensemble averaging technique to characterize the temporal structure of near-bed sediment suspension events (SSEs) defined as when the near-bed instantaneous concentration exceeded the mean by three standard deviations. During the 800 h of deployment, over 9500 SSEs occurred. The 3917 SSEs that began under onshore flow were found to have a different temporal structure than the 5650 events that began during offshore flow. The longer mean duration of the onshore flow events caused an average of 83% of the sediment suspended during the course of the events to be carried offshore after the reversal of flow. All of the sediment suspended during the offshore events was carried offshore due to the shorter mean duration of these events. SSEs are shown to contribute 12% on average and up to 95% of the total sediment suspended by mass, demonstrating the importance of these events to sediment transport in this type of environment. Suspended-sediment transport models developed for the shelf, which use the product of the mean current and the mean suspended-sediment concentration, cannot accurately model the magnitude and direction of suspended-sediment transport on this energetic inner shelf due to the lack of information regarding the instantaneous coupling between fluid flow and sediment suspension. We conclude that time-variant models must be used to accurately model suspended-sediment transport in this type of environment.

California↗

A watershed approach to ecosystem monitoring in Denali National Park and preserve, Alaska

The National Park Service and the National Biological Service initiated research in Denali National Park and Preserve, a 2.4 million-hectare park in southcentral Alaska, to develop ecological monitoring protocols for national parks in the Arctic/Subarctic biogeographic area. We are focusing pilot studies on design questions, on scaling issues and regionalization, ecosystem structure and function, indicator selection and evaluation, and monitoring technologies. Rock Creek, a headwater stream near Denali headquarters, is the ecological scale for initial testing of a watershed ecosystem approach. Our conceptual model embraces principles of the hydrological cycle, hypotheses of global climate change, and biological interactions of organisms occupying intermediate, but poorly studied, positions in Alaskan food webs. The field approach includes hydrological and depositional considerations and a suite of integrated measures linking key aquatic and terrestrial biota, environmental variables, or defined ecological processes, in order to establish ecological conditions and detect, track, and understand mechanisms of environmental change. Our sampling activities include corresponding measures of physical, chemical, and biological attributes in four Rock Creek habitats believed characteristic of the greater system diversity of Denali. This paper gives examples of data sets, program integration and scaling, and research needs.

Journal of the American Water Resources Associatio↗

Water temperature in the Lower Quinault River, Olympic Peninsula, Washington, June 2016 - August 2017

The availability of cold-water refugia during summertime river-water temperature maximums is important for cold-water fish species including Endangered Species Act listed salmonids since water temperature influences metabolism, growth, and phenology. The U.S. Geological Survey monitored water temperature at 10 sites approximately evenly-spaced along the lower Quinault River on the Olympic Peninsula, Washington, from June 2016 to August 2017 to assess thermal conditions in the lower river. During this 15-month period, there was a near-continuous, 15-minute record at 7 of the sites; complications with thermistors at 3 of the 10 sites limited the temperature dataset to include only summer 2016. In addition, near-streambed and water-surface temperatures were measured along the lower river during a longitudinal survey from August 9 to 12, 2016, during summer baseflow conditions to potentially identify cold or cooler water regions. Measured August water temperatures were warmer than model-predicted August temperatures for the period, 1993–2011. Summertime (July–September) daily minimum temperatures exceeded established salmon habitat threshold temperatures of 16 °C (core summer season) and 17.5 °C (spawning, rearing, and migration periods) for 122 and 65 days, respectively, on average at all monitoring sites with a complete 15-month record that included two summer baseflow periods. Summertime water temperatures at those sites were generally cooler in the downstream direction along the lower Quinault River but became warmer in the downstream direction during the rest of the year, suggesting the river was influenced by diffuse discharge of groundwater with a relatively constant annual temperature. The August longitudinal temperature survey did not detect cold-water refugia (features more than 3 °C cooler than ambient stream water), although it did identify 11 cooler water features (CWF) approximately 100–800 m in length that were 0.1 °C cooler than adjacent upstream or downstream water. The CWFs appeared to correspond to local geomorphic conditions. In August 2017, 10 of the 11 CWFs were field surveyed, and 5 appeared to be influenced by shading from solar radiation by riparian vegetation or steep cliff banks. In addition, field observations suggest that finer scale (that is, less than 10 m) CWFs, specifically individual side pools associated with large, in-channel wood, increased in frequency in the downstream direction along the lower Quinault River. However, this study did not quantify the density or water temperatures associated with these fine-scale features that may serve as cool- or cold-water pockets or patches.

Washington↗

Water availability of Choctaw County, Alabama

Large quantities of ground water and surface water are available in Choctaw County. Major sources of ground water are the Nanafalia Formation, Tuscahoma Sand, Hatchetigbee Formation, and Gosport Sand and Lisbon Formation. The Nanafalia Formation is the most productive source of ground water, and individual wells will yield as much as 1.0 mgd (million gallons per day). The depths to aquifers and the quality of ground water in the south half of the county are governed in part by geologic structures. The average flow of the Tombigbee River at the southeast corner of the county is 16,500 mgd and the 7-day Q2 exceeds 1,000 mgd. Kinterbish, Tuckabum, and Okatuppa Creeks have average flows that range from 115 to 265 mgd at their confluences with the Tombigbee River and 7-day Q2's that exceed 10 mgd in their downstream reaches. Average runoff originating in the county is about 786 mgd or 0.8 mgd per square mile. Water in aquifers tapped by wells generally contains less than 500 mg/1 (milligrams per liter) dissolved solids and is soft to moderately hard. In southeastern parts of the county, in the vicinity of the Hatchetigbee anticline, wells have been abandoned because of the poor quality of water. Water in streams, with the exception of that in Okatuppa Creek and some of its tributaries near Gilbertown and Barrytown, is generally soft and contains less than 140 mg/1 dissolved solids. The quality of water in Okatuppa Creek and some of its tributaries reflects contamination by oil-field brines. Biweekly samples collected from Okatuppa Creek from September 1965 to May 1967 show an average chloride content of 312 mg/1 and specific conductances indicate an average dissolved solids content of 630 mg/ 1.

Alabama↗

Geologic map of the Simcoe Mountains Volcanic Field, main central segment, Yakama Nation, Washington

Mountainous parts of the Yakama Nation lands in south-central Washington are mostly covered by basaltic lava flows and cinder cones that make up the Simcoe Mountains volcanic field. The accompanying geologic map of the central part of the volcanic field has been produced by the U.S. Geological Survey (USGS) on behalf of the Water Resources Program of the Yakama Nation. The volcanic terrain stretches continuously from Mount Adams eastward as far as Satus Pass and Mill Creek Guard Station. Most of the many hills and buttes are volcanic cones where cinders and spatter piled up around erupting vents while lava flows spread downslope. All of these small volcanoes are now extinct, and, even during their active lifetimes, most of them erupted for no more than a few years. On the Yakama Nation lands, the only large long-lived volcano capable of erupting again in the future is Mount Adams, on the western boundary. The geologic map presented here extends, east-west, from Satus Creek to the Klickitat River and, north-south, from Signal Peak to Indian Rock. In various colors, the map shows the areas covered by about 223 different eruptive units, mostly lava flows and cinder cones, while stars mark vents where many of them erupted. Shown in plain gray, the basement beneath the Simcoe Mountains volcanic field is the Columbia River Basalt Group, regional &ldquo;flood basalts&rdquo; of enormous volume and extent that erupted far to the east and long before the Simcoe volcanics. Although the number of past eruptions is large, few were great explosions that fed towering eruption plumes or spread ash over huge areas downwind. Most were localized basaltic lava fountains (like some in Hawaii) where showers of molten fragments reached heights of a few hundred feet. Most of them also poured out tongues of lava that were channelled along stream valleys for a few miles downstream or, occasionally, as far as 10 miles. Because the basalt so common here is one of the most fluid kinds of lava, it tends to flow farther and faster than most other types of lava before it cools and solidifies. Lava compositions other than various types of basalt are uncommon here. Andesite is abundant on and around Mount Adams but is very rare east of the Klickitat River. The only important nonbasaltic composition in the map area is rhyolite, which crops out in several patches around the central highland of the volcanic field, mainly in the upper canyons of Satus and Kusshi Creeks and Wilson Charley canyon. Because the rhyolites were some of the earliest lavas erupted here, they are widely concealed by later basalts and therefore crop out only in local windows eroded by canyons that cut through the overlying basalts.

Washington↗