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At least 1,333 records · Page 74Linked to original sources
USGS1986

Investigation of the need for discharge adjustments for unsteady flow at selected gaging stations on streams in Tennessee

Measured discharges made during rising or falling stages generally require adjustments to refine constant-stage rating curves (stage-discharge relations) for gaged sites. Measurements at 42 gaging stations on Tennessee streams were selected for adjustment. Two methods, generally accepted by the U.S. Geological Survey, were tested: (1) the slope method adjusts the discharge for changing slope during the measurement, and (2) the storage method adjusts for change in channel storage. Both methods are related to the rate of change in stage. The initial results of the storage method of adjustments were unsatisfactory because of uncertainty in determining channel storage at each site, and a specific trend in the results could not be defined. Consequently, the storage method of adjustment was deleted from successive analyses. Maximum adjustments in measured discharge using the slope method were less than 5 percent at 28 of the 42 stations and less than 10 percent at 39 of the 42 stations used in the analyses. The adjustments were small because most of the measurements were made during nearly stable stage. Adjustments of measurements made during stage changes of several feet per hour could be considerably larger than 10 percent. Stage records at 10 stations showed that maximum change in stage during rises were considerably higher than the change in stage observed during the measurements. Large adjustments are usually required for a short period of time on the rising side of a hydrograph and smaller adjustments are required for a longer period of time on the falling side. Maximum adjustments in discharge using the slope method were less than 5 percent at three of the 10 stations and less than 30 percent at eight of the 10 stations used in the analyses. The mean discharge for the adjusted and unadjusted hydrographs are about the same.

Tennessee↗
USGS1987

Geohydrologic framework of the coastal plain aquifers of South Carolina

The U.S. Geological Survey is conducting a series of investigations of aquifers throughout the United States as a part of the RASA (Regional Aquifer System Analysis) program. These investigations provide a comprehensive regional understanding of groundwater resources throughout the Nation. The Coastal Plain aquifers in South Carolina are being studied as a part of this program. An important part of a description of the groundwater resources is the development of a geohydrologic framework. Such a framework delineates the aquifers through which groundwater flows and the confining units which retard the flow of groundwater between aquifers. The Coastal Plain of South Carolina is underlain by a wedge of sediments that thickens from its inner margin, the Fall Line, to the coast and consists of sand, silt, clay, and limestone of Late Cretaceous to Holocene age. These sediments are underlain by pre-Cretaceous rocks consisting of consolidated sedimentary rocks of Triassic age and a complex of metamorphic and igneous rocks similar to those found near the surface in the Piedmont province of the State. The geohydrologic framework that divides the sediments of the South Carolina Coastal Plain into the Coastal Plain aquifer system is delineated by eleven geohydrologic sections and four maps showing the configuration of the top or base of individual aquifers. Although flow within the Coastal Plain aquifer system is three dimensional, simplifying the system by dividing it into a framework of discrete hydrologic units can aid significantly in understanding the hydrology of the system. This framework is the basis for the aquifers used in potentiometric mapping, transmissivity mapping, geochemical analysis, and groundwater flow modeling for the South Carolina RASA program. (Lantz-PTT)

South Carolina↗
USGS2001

Benthic invertebrate communities and their responses to selected environmental factors in the Kanawha River basin, West Virginia, Virginia, and North Carolina

The effects of selected environmental factors on the composition and structure of benthic invertebrate communities in the Kanawha River Basin of West Virginia, Virginia and North Carolina were investigated in 1997 and 1998. Environmental factors investigated include physiography, land-use pattern, streamwater chemistry, streambed- sediment chemistry, and habitat characteristics. Land-use patterns investigated include coal mining, agriculture, and low intensity rural-residential patterns, at four main stem and seven tributary sites throughout the basin. Of the 37 sites sampled, basin size and physiography most strongly affected benthic invertebrate-community structure. Land-use practices also affected invertebrate community structure in these basins. The basins that differed most from the minimally affected reference condition were those basins in which coal mining was the dominant nonforest land use, as determined by comparing invertebrate- community metric values among sites. Basins in which agriculture was important were more similar to the reference condition. The effect of coal mining upon benthic invertebrate communities was further studied at 29 sites and the relations among invertebrate communities and the selected environmental factors of land use, streamwater chemistry, streambed- sediment chemistry, and habitat characteristics analyzed. Division of coal-mining synoptic-survey sites based on invertebrate-community composition resulted in two groups?one with more than an average production of 9,000 tons of coal per square mile per year since 1980, and one with lesser or no recent coal production. The group with significant recent coal production showed higher levels of community impairment than the group with little or no recent coal production. Median particle size of streambed sediment, and specific conductance and sulfate concentration of streamwater were most strongly correlated with effects on invertebrate communities. These characteristics were related to mining intensity, as measured by thousands of tons of coal produced per square mile of drainage area.

North Carolina, Virginia, West Virginia↗
USGS2000

Selected organic compounds and trace elements in streambed sediments and fish tissues, Cook Inlet Basin, Alaska

Organochlorines, semivolatile organic compounds (SVOCs), and trace elements were investigated in streambed sediments and fish tissues at selected sites in the Cook Inlet Basin, Alaska, during 1998. At most sites, SVOCs and organochlorine compounds were either not detected or detected at very low concentrations. Chester Creek at Arctic Boulevard at Anchorage, which was the only site sampled with a significant degree of development in the watershed, had elevated levels of many SVOCs in streambed sediment. Coring of sediments from two ponds on Chester Creek confirmed the presence of elevated concentrations of a variety of organic compounds. Moose Creek, a stream with extensive coal deposits in its watershed, had low concentrations of numerous SVOCs in streambed sediment. Three sites located in national parks or in a national wildlife refuge had no detectable concentrations of SVOCs. Trace elements were analyzed in both streambed sediments and tissues of slimy sculpin. The two media provided similar evidence for elevated concentrations of cadmium, lead, and zinc at Chester Creek. In this study, 'probable effect levels '(PELs) were determined from sediments finer than 0.063 millimeters, where concentrations tend to be greatest. Arsenic and chromium concentrations exceeded the PEL at eight and six sites respectively. Zinc exceeded the PEL at one site. Cadmium and copper concentrations were smaller than the PEL at all sites. Mercury concentrations in streambed sediments from the Deshka River were near the PEL, and selenium concentrations at that site also appear to be elevated above background levels. At half the sites where slimy sculpin were sampled, selenium concentrations were at levels that may cause adverse effects in some species.

Alaska↗
USGS1997

Regional equations for estimation of peak-streamflow frequency for natural basins in Texas

Peak-streamflow frequency estimates are needed for flood-plain management; for objective assessment of flood risk; and for cost-effective design of dams, levees, other flood-control structures, roads, bridges, and culverts. Peak-streamflow frequency represents the peak discharges for recurrence intervals of 2, 5, 10, 25, 50, and 100 years. The U.S. Geological Survey, in cooperation with the Texas Department of Transportation, conducted an investigation to develop regional regression equations for the estimation of peak-streamflow frequency for ungaged sites in natural basins in Texas. Peak-streamflow frequency data from streamflow-gaging stations in natural drainage basins of Texas were used. Peak-streamflow frequency for 559 Texas stations with natural (unregulated and rural or nonurbanized) basins was estimated with annual peak-streamflow data through 1993. The peak-streamflow frequency and drainage-basin characteristics for the Texas stations were used to develop 16 sets of equations to estimate peak-streamflow frequency for ungaged natural stream sites in each of 11 regions in Texas. The relation between peak-streamflow frequency and contributing drainage area for 5 of the 11 regions is curvilinear, requiring that one set of equations be developed for drainage areas less than 32 square miles and another set be developed for drainage areas greater than 32 square miles. These equations, developed through multiple-regression analysis using weighted least squares, are based on the relation between peak-streamflow frequency and basin characteristics for streamflow-gaging stations. The regions represent areas with similar flood characteristics. The use and limitations of the regression equations also are discussed. Additionally, procedures are presented to compute the 50-, 67-, and 90-percent confidence limits for any estimation from the equations. Also, supplemental peak-streamflow frequency and basin characteristics for 105 selected stations bordering Texas are included in the report. This supplemental information will aid in interpretation of flood characteristics for sites near the state borders of Texas.

Texas↗
USGS1986

Effect of bank protection measures, Stehekin River, Chelan County, Washington

An investigation of the lower Stehekin River was conducted to study the effects on flood elevations and velocities from four bank protection and flood prevention measures that are being contemplated as a means of reducing erosional losses of river bank property. These measures are: bank armoring, armored revetment levees, spur dikes, and redevelopment of old cutoff channels. The banks at seven study sites could be armored without adverse effect on the flood velocities and elevations. The largest increases due to armoring--up to 1.6 ft/sec in velocity and 1 ft in elevation--occurred in the vicinity of sites 5, 6, and 7 where the gradient of the river channel is about 50 ft/mi and the velocities are high to begin with (about 6 to 13 ft/sec). The use of a levee in conjunction with armoring on the northeast bank from sites 5 to 7 would increase the velocities as much as 2.8 ft/sec and increase the elevation as much as 1 ft, but it would also provide some flood protection to the east bank, which is frequently inundated. Spur dikes were considered a practical alternative only at site 3, where reduced bank erosion may occur without aggravating flood inundation or erosion elsewhere. The rerouting of flood flow through an old cutoff channel near site 1 increased the velocity by 3.2 ft/sec and the elevation by 1 ft for the 100-year flood; however, it would move floodwater away from residential property where bank erosion is a problem. The few other old channels that shortcut river bends where much erosion occurs are apparently already part of the channel during floods. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1994

Investigation of bridge scour at selected sites on Missouri streams

Scour around bridge piers is a major concern in the design of a new bridge or the evaluation of the structural stability of an existing bridge. An adequate estimation of potential scour at bridge piers is essential to effective design, construction, and maintenance of hydraulic structures. Reasonably accurate estimates of scour depth are needed for safe, cost-effective bridge design. Although many equations have been developed on the basis of laboratory work that can be used to estimate local scour at piers, site-specific data have not previously been collected to verify the accuracy of these equations or applicability to Missouri streams. Scour data were collected during floods at 10 sites on streams in Missouri. The recurrence intervals of the floods ranged from less than 2 to more than 50 years. Local-scour holes near bridge piers ranged from 0.5 to 7.1 feet deep. Seven local-pier-scour equations were evaluated as to their usefulness in estimating the measured scour at the sites studied. Scour depths estimated using the Froehlich equatin without a safety factor had an interquartile range nearest in magnitude to the interquartile range of the measured scour depths. None of the medians of scour depths estimated using the seven equations were statistically equal to the median of the measured scour depths at a 0.05 level of significance. However, the Froehlich equation without a safety factor provided the "best fit" estimates of the equations considered. Contraction scour exceeded local scour by several times in some cases. Total scour of approximately 19 feet, largely becasue of contraction scour, was measured at the Chariton River near Prairie Hill during the flood of July 8, 1993. This large scour was, in part, the result of an accumulation of woody debris de- creasing the bridge-opening area. A bridge on State Highway 32 near Lebanon over North Cobb Creek (drainage area 52.5 square miles) was destroyed during the flood of May 26, 1990. Bridge scour attributable to contraction of the flood flow caused this loss.

Missouri↗
USGS1985

Cost effectiveness of stream-gaging program in Michigan

This report documents the results of a study of the cost effectiveness of the stream-gaging program in Michigan. Data uses and funding sources were identified for the 129 continuous gaging stations being operated in Michigan as of 1984. One gaging station was identified as having insufficient reason to continue its operation. Several stations were identified for reactivation, should funds become available, because of insufficiencies in the data network. Alternative methods of developing streamflow information based on routing and regression analyses were investigated for 10 stations. However, no station records were reproduced with sufficient accuracy to replace conventional gaging practices. A cost-effectiveness analysis of the data-collection procedure for the ice-free season was conducted using a Kalman-filter analysis. To define missing-record characteristics, cross-correlation coefficients and coefficients of variation were computed at stations on the basis of daily mean discharge. Discharge-measurement data were used to describe the gage/discharge rating stability at each station. The results of the cost-effectiveness analysis for a 9-month ice-free season show that the current policy of visiting most stations on a fixed servicing schedule once every 6 weeks results in an average standard error of 12.1 percent for the current $718,100 budget. By adopting a flexible servicing schedule, the average standard error could be reduced to 11.1 percent. Alternatively, the budget could be reduced to $700,200 while maintaining the current level of accuracy. A minimum budget of $680,200 is needed to operate the 129-gaging-station program; a budget less than this would not permit proper service and maintenance of stations. At the minimum budget, the average standard error would be 14.4 percent. A budget of $789,900 (the maximum analyzed) would result in a decrease in the average standard error to 9.07 percent. Owing to continual changes in the composition of the network and the changes in the uncertainties of streamflow accuracy at individual stations, the cost-effectiveness analysis will need to be updated regularly if it is to be used as a management tool. Cost of these updates need to be considered in decisions concerning the feasibility of flexible servicing schedules.

Michigan↗
USGS1998

Lithology and fracture characterization from drilling investigations in the Mirror Lake area, Grafton County, New Hampshire

The lithology and fracture network of the bedrock aquifer in the Mirror Lake area were characterized from hydrogeologic data collected from 1979-95 in Grafton County, N.H. The collection of these data is an integral part of an ongoing multidisciplinary study by the U.S. Geological Survey to characterize groundwater flow and solute transport in fractured rock. The data provide a physical framework and enable the characterization of the fractures and the rock types in the bedrock aquifer in the Mirror Lake study area. In addition, these data provide a detailed description of the subsurface intersected by boreholes that can be used to compare the results of other borehole testing. The Mirror Lake area is characterized by steep bedrock uplands that are mostly covered by colluvium, discontinuous stratified-drift deposits, and glacial till that varies locally in thickness from less than 10 meters to as much as 50 meters. The land-surface altitude ranges from 180 meters near the Pemigewasset River to 720 meters on the mountain top on the northwestern side of the study area. The bedrock in the area is predominantly sillimanite-grade pelitic schists that have been complexly folded and intruded by granitoids, pegmatites, and diabase dikes. The bedrock has been fractured in response to local and tectonic stress. The resulting interconnected network of fractures forms the bedrock aquifer. This report describes the lithologic units in the study area and provides a characterization of the lithology and fractures found in 40 boreholes, which range in depth from 60 to 305 meters, that were drilled for this study. Drilling logs and color video surveys were used to locate and characterize the fractures and rock types in the subsurface. Solid bedrock core was obtained from three of the boreholes. Petrographic thin-section, x-ray diffraction and scanning electron microscope with energy dispersive x-ray fluorescence spectrometry analyses were done on selected samples from boreholes and outcrops. Observations recorded at the time of drilling, descriptions of rock samples collected from the boreholes, interpretation of rock type and fractures based on boreholeimaging surveys, descriptions of rock core and petrographic analyses of selected rock samples are in tables and figures. Analysis of the data provided information on the distribution of fractures and lithology in the boreholes at Mirror Lake. The relative abundances of the rock types were computed for three groups of boreholes, including (1) the Forest Service Experimental (FSE) well field, (2) the Camp Osceola (CO) well field, and (3) the index boreholes, which are 15 boreholes distributed areally throughout the study area including the deepest borehole from each of the two well fields. The index boreholes are separated by hundreds of meters and are typically 100 meters deep. The FSE well field includes 13 boreholes that are separated by 10 to 40 meters. These 13 boreholes are approximately 100 meters deep, except for one borehole that is 230 meters deep. The rocks penetrated by the FSE wells are predominantly igneous. Approximately 70 percent of the rocks encountered in the boreholes in the FSE well field were granite, pegmatite, and aplite. The CO well field includes 9 boreholes that range from 60-70 meters deep and one borehole that is 175 meters deep. The rocks encountered in these boreholes were predominantly metamorphic. The distribution of rock types in the CO well field is similar to the distribution of rocks in highway roadcuts, that are approximately 90 to 150 meters east of the well field. Seventy percent of the roadcut exposures are schist. Collectively, in the 15 index boreholes, the metamorphic and igneous rocks are equally distributed. Analysis of the rock types in these boreholes indicates that the rock types tend to "change" every 5 to 9 meters. Although the metamorphic and igneous rocks each comprise approximately 50 percent of the rock types observed in the 15 index boreholes, 73 percent of the fractures were in the igneous rocks. This indicates that the granitoids tend to be more fractured than the metamorphic rocks. Pegmatite, diabase, quartzite, and gneissic rocks are relatively unfractured. Boreholes completed in bedrock generally have one or two water-bearing zones, which were identified during the drilling process. At the completion of drilling a borehole, the driller estimated the yield of the borehole with an air-lift test. Yields estimated by drillers ranged from less than 3 to 378 liters per minute. These yields are typical of the yields measured for domestic wells in Grafton County. Water levels measured in the open boreholes after the boreholes recovered from the hydraulic stresses of drilling were usually in the steel casing and were within 10 meters of the land surface. Water levels in eight of the boreholes were above the top of casing or above land surface.

New Hampshire↗
USGS2002

Results of Hydraulic Tests in Miocene Tuffaceous Rocks at the C-Hole Complex, 1995 to 1997, Yucca Mountain, Nye County, Nevada

Four hydraulic tests were conducted by the U.S. Geological Survey at the C-hole complex at Yucca Mountain, Nevada, between May 1995 and November 1997. These tests were conducted as part of ongoing investigations to determine the hydrologic and geologic suitability of Yucca Mountain as a potential site for permanent underground storage of high-level nuclear waste. The C-hole complex consists of three 900-meter-deep boreholes that are 30.4 to 76.6 meters apart. The C-holes are completed in fractured, variably welded tuffaceous rocks of Miocene age. Six hydrogeologic intervals occur within the saturated zone in these boreholes - the Calico Hills, Prow Pass, Upper Bullfrog, Lower Bullfrog, Upper Tram, and Lower Tram intervals. The Lower Bullfrog and Upper Tram intervals contributed about 90 percent of the flow during hydraulic tests. The four hydraulic tests conducted from 1995 to 1997 lasted 4 to 553 days. Discharge from the pumping well, UE-25 c #3, ranged from 8.49 to 22.5 liters per second in different tests. Two to seven observation wells, 30 to 3,526 meters from the pumping well, were used in different tests. Observation wells included UE-25 c #1, UE-25 c #2, UE-25 ONC-1, USW H-4, UE-25 WT #14, and UE-25 WT #3 in the tuffaceous rocks and UE-25 p #1 in Paleozoic carbonate rocks. In all hydraulic tests, drawdown in the pumping well was rapid and large (2.9-11 meters). Attributable mostly to frictional head loss and borehole-skin effects, this drawdown could not be used to analyze hydraulic properties. Drawdown and recovery in intervals of UE-25 c #1 and UE-25 c #2 and in other observation wells typically was less than 51 centimeters. These data were analyzed. Hydrogeologic intervals in the C-holes have layered heterogeneity related to faults and fracture zones. Transmissivity, hydraulic conductivity, and storativity generally increase downhole. Transmissivity ranges from 4 to 1,600 meters squared per day; hydraulic conductivity ranges from 0.1 to 50 meters per day; and storativity ranges from 0.00002 to 0.002. Transmissivity in the Miocene tuffaceous rocks decreases from 2,600 to 700 meters squared per day northwesterly across the 21-square-kilometer area affected by hydraulic tests at the C-hole complex. The average transmissivity of the tuffaceous rocks in this area, as determined from plots of drawdown in most or all observation wells as functions of time or distance from the pumping well, is 2,100 to 2,600 meters squared per day. Average storativity determined from these plot ranges is 0.0005 to 0.002. Hydraulic conductivity ranges from less than 2 to more than 10 meters per day; it is largest where prominent northerly trending faults are closely spaced or intersected by northwesterly trending faults. During hydraulic tests, the Miocene tuffaceous rocks functioned as a single aquifer. Drawdown occurred in all monitored intervals of the C-holes and other observation wells, regardless of the hydrogeologic interval being pumped. This hydraulic connection across geologic and lithostratigraphic contacts is believed to result from interconnected faults, fractures, and intervals with large matrix permeability. Samples of UE-25 c #3 water, analyzed from 1995 to 1997, seem to indicate that changes in the quality of the water pumped from that well are probably due solely to lateral variations in water quality within the tuffaceous rocks.

Water-Resources Investigations Report↗
USGS1999

Depth-Duration Frequency of Precipitation for Oklahoma

A regional frequency analysis was conducted to estimate the depth-duration frequency of precipitation for 12 durations in Oklahoma (15, 30, and 60 minutes; 1, 2, 3, 6, 12, and 24 hours; and 1, 3, and 7 days). Seven selected frequencies, expressed as recurrence intervals, were investigated (2, 5, 10, 25, 50, 100, and 500 years). L-moment statistics were used to summarize depth-duration data and to determine the appropriate statistical distributions. Three different rain-gage networks provided the data (15minute, 1-hour, and 1-day). The 60-minute, and 1-hour; and the 24-hour, and 1-day durations were analyzed separately. Data were used from rain-gage stations with at least 10-years of record and within Oklahoma or about 50 kilometers into bordering states. Precipitation annual maxima (depths) were determined from the data for 110 15-minute, 141 hourly, and 413 daily stations. The L-moment statistics for depths for all durations were calculated for each station using unbiased L-mo-ment estimators for the mean, L-scale, L-coefficient of variation, L-skew, and L-kur-tosis. The relation between L-skew and L-kurtosis (L-moment ratio diagram) and goodness-of-fit measures were used to select the frequency distributions. The three-parameter generalized logistic distribution was selected to model the frequencies of 15-, 30-, and 60-minute annual maxima; and the three-parameter generalized extreme-value distribution was selected to model the frequencies of 1-hour to 7-day annual maxima. The mean for each station and duration was corrected for the bias associated with fixed interval recording of precipitation amounts. The L-scale and spatially averaged L-skew statistics were used to compute the location, scale, and shape parameters of the selected distribution for each station and duration. The three parameters were used to calculate the depth-duration-frequency relations for each station. The precipitation depths for selected frequencies were contoured from weighted depth surfaces to produce maps from which the precipitation depth-duration-frequency curve for selected storm durations can be determined for any site in Oklahoma.

Water-Resources Investigations Report↗
USGS1998

Depth-duration frequency of precipitation for Texas

The U.S. Geological Survey, in cooperation with the Texas Department of Transportation, conducted a study of the depth-duration frequency of precipitation for Texas. Depth-duration frequency is an estimate of the depth of precipitation for a specified duration and frequency or recurrence interval. For this report, precipitation durations of 15, 30, and 60 minutes; 1, 2, 3, 6, 12, and 24 hours; and 1, 2, 3, 5, and 7 days were investigated. The recurrence intervals for the frequencies range from 2 to 500 years. The time series of precipitation annual maxima for 173 fifteen-minute, 274 hourly, and 865 daily National Weather Service precipitation stations with at least 10 years of record in Texas provide the basis of depth-duration frequency for each identified duration. In total, about 3,030; 10,160; and 38,120 cumulative years of record are available for the 15-minute, hourly, and daily stations, respectively. L-moment statistics of the precipitation annual maxima were calculated for each duration and for each station using unbiased L-moment estimators. The statistics calculated were the mean, L-scale, L-coefficient of variation, L-skew, and L-kurtosis. The mean for each station and duration was corrected for the bias associated with fixed-interval recording of precipitation. The generalized logistic distribution was determined, using L-moment ratio diagrams, as an appropriate probability distribution for modeling the frequency of annual maxima for durations of 15 minutes to 24 hours; whereas, the generalized extreme-value distribution was determined as appropriate for durations of 1 to 7 days. The location, scale, and shape parameters of the distributions for each duration and each station were calculated from the L-moments. These parameters were contoured using spatial interpolation, based on the geostatistical method of kriging, to produce 37 maps that depict the spatial variation and magnitude of each parameter. Contour maps of the shape parameter for the generalized extreme-value distribution for durations of 1 to 7 days are not presented; the root mean square errors of preliminary maps for 1- to 7-day shape parameters were not appreciably smaller than the statewide standard deviation. Therefore, a single statewide mean shape parameter was used for 1- to 7-day durations. The depth-duration frequency for any location in Texas can be estimated using the contour maps and the equation of the corresponding distribution.

Texas↗
USGS2003

August median streamflow on ungaged streams in eastern Aroostook County, Maine

Methods for estimating August median streamflow were developed for ungaged, unregulated streams in the eastern part of Aroostook County, Maine, with drainage areas from 0.38 to 43 square miles and mean basin elevations from 437 to 1,024 feet. Few long-term, continuous-record streamflow-gaging stations with small drainage areas were available from which to develop the equations; therefore, 24 partial-record gaging stations were established in this investigation. A mathematical technique for estimating a standard low-flow statistic, August median streamflow, at partial-record stations was applied by relating base-flow measurements at these stations to concurrent daily flows at nearby long-term, continuous-record streamflow- gaging stations (index stations). Generalized least-squares regression analysis (GLS) was used to relate estimates of August median streamflow at gaging stations to basin characteristics at these same stations to develop equations that can be applied to estimate August median streamflow on ungaged streams. GLS accounts for varying periods of record at the gaging stations and the cross correlation of concurrent streamflows among gaging stations. Twenty-three partial-record stations and one continuous-record station were used for the final regression equations. The basin characteristics of drainage area and mean basin elevation are used in the calculated regression equation for ungaged streams to estimate August median flow. The equation has an average standard error of prediction from -38 to 62 percent. A one-variable equation uses only drainage area to estimate August median streamflow when less accuracy is acceptable. This equation has an average standard error of prediction from -40 to 67 percent. Model error is larger than sampling error for both equations, indicating that additional basin characteristics could be important to improved estimates of low-flow statistics. Weighted estimates of August median streamflow, which can be used when making estimates at partial-record or continuous-record gaging stations, range from 0.03 to 11.7 cubic feet per second or from 0.1 to 0.4 cubic feet per second per square mile. Estimates of August median streamflow on ungaged streams in the eastern part of Aroostook County, within the range of acceptable explanatory variables, range from 0.03 to 30 cubic feet per second or 0.1 to 0.7 cubic feet per second per square mile. Estimates of August median streamflow per square mile of drainage area generally increase as mean elevation and drainage area increase.

Maine↗
USGS2009

DayCent-Chem simulations of ecological and biogeochemical processes of eight mountain ecosystems in the United States

Atmospheric deposition of nitrogen (N) and sulfur (S) cause complex responses in ecosystems, from fertilization to forest ecosystem decline, freshwater eutrophication to acidification, loss of soil base cations, and alterations of disturbance regimes. DayCent-Chem, an ecosystem simulation model that combines ecosystem nutrient cycling and plant dynamics with aqueous geochemical equilibrium calculations, was developed to address ecosystem responses to combined atmospheric N and S deposition. It is unique among geochemically-based models in its dynamic biological cycling of N and its daily timestep for investigating ecosystem and surface water chemical response to episodic events. The model was applied to eight mountainous watersheds in the United States. The sites represent a gradient of N deposition across locales, from relatively pristine to N-saturated, and a variety of ecosystem types and climates. Overall, the model performed best in predicting stream chemistry for snowmelt-dominated sites. It was more difficult to predict daily stream chemistry for watersheds with deep soils, high amounts of atmospheric deposition, and a large degree of spatial heterogeneity. DayCent-Chem did well in representing plant and soil carbon and nitrogen pools and fluxes. Modeled stream nitrate (NO 3 - ) and ammonium (NH 4 + ) concentrations compared well with measurements at all sites, with few exceptions. Simulated daily stream sulfate (SO 4 2- ) concentrations compared well to measured values for sites where SO 4 2- deposition has been low and where SO 4 2- adsorption/desorption reactions did not seem to be important. The concentrations of base cations and silica in streams are highly dependent on the geochemistry and weathering rates of minerals in each catchment, yet these were rarely, if ever, known. Thus, DayCent-Chem could not accurately predict weathering products for some catchments. Additionally, few data were available for exchangeable soil cations or the magnitude of base cation deposition as a result of dry and fog inputs. The uncertainties related to weathering reactions, deposition, soil cation exchange capacity, and groundwater contributions influenced how well the simulated acid neutralizing capacity (ANC) and pH estimates compared to observed values. Daily discharge was well represented by the model for most sites. The chapters of this report describe the parameterization for each site and summarize model results for ecosystem variables, stream discharge, and stream chemistry. This intersite comparison exercise provided insight about important and possibly not well understood processes.

Scientific Investigations Report↗
USGS2003

Sediment quantity and quality in three impoundments in Massachusetts

As part of a study with an overriding goal of providing information that would assist State and Federal agencies in developing screening protocols for managing sediments impounded behind dams that are potential candidates for removal, the U.S Geological Survey determined sediment quantity and quality at three locations: one on the French River and two on Yokum Brook, a tributary to the west branch of the Westfield River. Data collected with a global positioning system, a geographic information system, and sediment-thickness data aided in the creation of sediment maps and the calculation of sediment volumes at Perryville Pond on the French River in Webster, Massachusetts, and at the Silk Mill and Ballou Dams on Yokum Brook in Becket, Massachusetts. From these data the following sediment volumes were determined: Perryville Pond, 71,000 cubic yards, Silk Mill, 1,600 cubic yards, and Ballou, 800 cubic yards. Sediment characteristics were assessed in terms of grain size and concentrations of potentially hazardous organic compounds and metals. Assessment of the approaches and methods used at study sites indicated that ground-penetrating radar produced data that were extremely difficult and time-consuming to interpret for the three study sites. Because of these difficulties, a steel probe was ultimately used to determine sediment depth and extent for inclusion in the sediment maps. Use of these methods showed that, where sampling sites were accessible, a machine-driven coring device would be preferable to the physically exhausting, manual sediment-coring methods used in this investigation. Enzyme-linked immunosorbent assays were an effective tool for screening large numbers of samples for a range of organic contaminant compounds. An example calculation of the number of samples needed to characterize mean concentrations of contaminants indicated that the number of samples collected for most analytes was adequate; however, additional analyses for lead, copper, silver, arsenic, total petroleum hydrocarbons, and chlordane are needed to meet the criteria determined from the calculations. Particle-size analysis did not reveal a clear spatial distribution pattern at Perryville Pond. On average, less than 65 percent of each sample was greater in size than very fine sand. The sample with the highest percentage of clay-sized particles (24.3 percent) was collected just upstream from the dam and generally had the highest concentrations of contaminants determined here. In contrast, more than 90 percent of the sediment samples in the Becket impoundments had grain sizes larger than very fine sand; as determined by direct observation, rocks, cobbles, and boulders constituted a substantial amount of the material impounded at Becket. In general, the highest percentages of the finest particles, clays, occurred in association with the highest concentrations of contaminants. Enzyme-linked immunosorbent assays of the Perryville samples showed the widespread presence of petroleum hydrocarbons (16 out of 26 samples), polycyclic aromatic hydrocarbons (23 out of 26 samples), and chlordane (18 out of 26 samples); polychlorinated biphenyls were detected in five samples from four locations. Neither petroleum hydrocarbons nor polychlorinated biphenyls were detected at Becket, and chlordane was detected in only one sample. All 14 Becket samples contained polycyclic aromatic hydrocarbons. Replicate quality-control analyses revealed consistent results between paired samples. Samples from throughout Perryville Pond contained a number of metals at potentially toxic concentrations. These metals included arsenic, cadmium, copper, lead, nickel, and zinc. At Becket, no metals were found in elevated concentrations. In general, most of the concentrations of organic compounds and metals detected in Perryville Pond exceeded standards for benthic organisms, but only rarely exceeded standards for human contact. The most highly contaminated samples were

Water-Resources Investigations Report↗
USGS2002

An integrated geophysical and hydraulic investigation to characterize a fractured-rock aquifer, Norwalk, Connecticut

The U.S. Geological Survey conducted an integrated geophysical and hydraulic investigation at the Norden Systems, Inc. site in Norwalk, Connecticut, where chlorinated solvents have contaminated a fractured-rock aquifer. Borehole, borehole-to-borehole, surface-geophysical, and hydraulic methods were used to characterize the site bedrock lithology and structure, fractures, and transmissive zone hydraulic properties. The geophysical and hydraulic methods included conventional logs, borehole imagery, borehole radar, flowmeter under ambient and stressed hydraulic conditions, and azimuthal square-array direct-current resistivity soundings. Integrated interpretation of geophysical logs at borehole and borehole-to-borehole scales indicates that the bedrock foliation strikes northwest and dips northeast, and strikes north-northeast to northeast and dips both southeast and northwest. Although steeply dipping fractures that cross-cut foliation are observed, most fractures are parallel or sub-parallel to foliation. Steeply dipping reflectors observed in the radar reflection data from three boreholes near the main building delineate a north-northeast trending feature interpreted as a fracture zone. Results of radar tomography conducted close to a suspected contaminant source area indicate that a zone of low electromagnetic (EM) velocity and high EM attenuation is present above 50 ft in depth - the region containing the highest density of fractures. Flowmeter logging was used to estimate hydraulic properties in the boreholes. Thirty-three transmissive fracture zones were identified in 11 of the boreholes. The vertical separation between transmissive zones typically is 10 to 20 ft. Open-hole and discrete-zone transmissivity was estimated from heat-pulse flowmeter data acquired under ambient and stressed conditions. The open-hole transmissivity ranges from 2 to 86 ft2/d. The estimated transmissivity of individual transmissive zones ranges from 0.4 to 68 ft2/d. Drawdown monitoring in nearby boreholes under pumping conditions identified hydraulic connections along a northeast-southwest trend between boreholes as far as 560 ft apart. The vertical distribution of fractures can be described by power law functions, which suggest that the fracture network contains transmissive zones consisting of closely spaced fractures surrounded by a less fractured and much less permeable rock mass.

Connecticut↗
USGS1993

Brine contamination of ground water and streams in the Baxterville oil field area, Lamar and Marion Counties, Mississippi

A hydrologic investigation to define the extent of brine contamination in ground water and streams in the Baxterville oil field area was conducted from October 1984 through November 1985. The 260-square-mile study area includes the Baxterville oil field (approximately 12.5 square miles) in southwestern Lamar and southeastern Marion Counties, Mississippi. Since 1944, disposal of more than 1 billion barrels of brine pumped from the oil- producing zones has contaminated (increased chloride to greater than background concentrations) parts of the Citronelle and shallow Miocene aquifers and some streams that drain the oil field. Many domestic wells have been abandoned because of the presence of substantial quantities of brine in the ground water. Brine has moved laterally through the shallowest aquifers and discharged into Clear Creek and its tributaries. Although the presence of brine in surface water was greatest during periods of low flow when streamflow originated primarily from ground-water inflow, brine was also detected during high-flow periods when streamflow consisted largely of precipitation runoff.

Mississippi↗
USGS2003

Flow origin, drainage area, and hydrologic characteristics for headwater streams in the mountaintop coal-mining region of Southern West Virginia, 2000-01

Characteristics of perennial and intermittent headwater streams were documented in the mountaintop removal coal-mining region of southern West Virginia in 2000?01. The perennial-flow origin points were identified in autumn during low base-flow conditions. The intermittent-flow origin points were identified in late winter and early spring during high base-flow conditions. Results of this investigation indicate that the median drainage area upstream of the origin of intermittent flow was 14.5 acres, and varied by an absolute median of 3.4 acres between the late winter measurements of 2000 and early spring measurements of 2001. Median drainage area in the northeastern part of the study unit was generally larger (20.4 acres), with a lower median basin slope (322 feet per mile) than the southwestern part of the study unit (12.9 acres and 465 feet per mile, respectively). Both of the seasons preceding the annual intermittent flow visits were much drier than normal. The West Virginia Department of Environmental Protection reports that the median size of permitted valley fills in southern West Virginia is 12.0 acres, which is comparable to the median drainage area upstream of the ephemeralintermittent flow point (14.5 acres). The maximum size of permitted fills (480 acres), however, is more than 10 times the observed maximum drainage area upstream of the ephemeral-intermittent flow point (45.3 acres), although a single valley fill may cover more than one drainage area. The median drainage area upstream of the origin of perennial flow was 40.8 acres, and varied by an absolute median of 18.0 acres between two annual autumn measurements. Only basins underlain with mostly sandstone bedrock produced perennial flow. Perennial points in the northeast part of the study unit had a larger median drainage area (70.0 acres) and a smaller median basin slope (416 feet per mile) than perennial points in the southwest part of the study unit (35.5 acres and 567 feet per mile, respectively). Some streams were totally dry for one or both of the annual October visits. Both of the seasons preceding the October visits had near normal to higher than normal precipitation. These dry streams were adjacent to perennial streams draining similarly sized areas, suggesting that local conditions at a firstorder- stream scale determine whether or not there will be perennial flow. Headwater-flow rates varied little from year to year, but there was some variation between late winter and early spring and autumn. Flow rates at intermittent points of flow origin ranged from 0.001 to 0.032 cubic feet per second, with a median of 0.017 cubic feet per second. Flow rates at perennial points of flow origin ranged from 0.001 to 0.14 cubic feet per second, with a median of 0.003 cubic feet per second.

Water-Resources Investigations Report↗