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N.E. Spahr

Publications and source records attributed to N.E. Spahr.

13 recordsLinked to original sources
USGS2009

Identifying pathways and processes affecting nitrate and orthophosphate inputs to streams in agricultural watersheds

Understanding nutrient pathways to streams will improve nutrient management strategies and estimates of the time lag between when changes in land use practices occur and when water quality effects that result from these changes are observed. Nitrate and orthophosphate (OP) concentrations in several environmental compartments were examined in watersheds having a range of base flow index (BFI) values across the continental United States to determine the dominant pathways for water and nutrient inputs to streams. Estimates of the proportion of stream nitrate that was derived from groundwater increased as BFI increased. Nitrate concentration gradients between groundwater and surface water further supported the groundwater source of nitrate in these high BFI streams. However, nitrate concentrations in stream-bed pore water in all settings were typically lower than stream or upland groundwater concentrations, suggesting that nitrate discharge to streams was not uniform through the bed. Rather, preferential pathways (e.g., springs, seeps) may allow high nitrate groundwater to bypass sites of high biogeochemical transformation. Rapid pathway compartments (e.g., overland flow, tile drains) had OP concentrations that were typically higher than in streams and were important OP conveyers in most of these watersheds. In contrast to nitrate, the proportion of stream OP that is derived from ground water did not systematically increase as BFI increased. While typically not the dominant source of OP, groundwater discharge was an important pathway of OP transport to streams when BFI values were very high and when geochemical conditions favored OP mobility in groundwater. Copyright ?? 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Journal of Environmental Quality↗
USGS2008

Efficacy of algal metrics for assessing nutrient and organic enrichment in flowing waters

1. Algal-community metrics were calculated for periphyton samples collected from 976 streams and rivers by the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Programme during 1993–2001 to evaluate national and regional relations with water chemistry and to compare whether algal-metric values differ significantly among undeveloped and developed land-use classifications. 2. Algal metrics with significant positive correlations with nutrient concentrations included indicators of trophic condition, organic enrichment, salinity, motility and taxa richness. The relative abundance of nitrogen-fixing algae was negatively correlated with nitrogen concentrations, and the abundance of diatom species associated with high dissolved oxygen concentrations was negatively correlated with both nitrogen and phosphorus concentrations. Median algal-metric values and nutrient concentrations were significantly lower at undeveloped sites than those draining agricultural or urban catchments. 3. Total algal biovolume did not differ significantly among major river catchments or land-use classifications, and was only weakly correlated with nitrate (positive) and suspended-sediment (negative) concentrations. Estimates of periphyton chlorophyll a indicated an oligotrophic–mesotrophic boundary of about 21 mg m −2 and a mesotrophic–eutrophic boundary of about 55 mg m −2 based on upper and lower quartiles of the biovolume data distribution. 4. Although algal species tolerance to nutrient and organic enrichment is well documented, additional taxonomic and autecological research on sensitive, endemic algal species would further enhance water-quality assessments.

Freshwater Biology↗
USGS2003

Comparison of 2002 Water Year and Historical Water-Quality Data, Upper Gunnison River Basin, Colorado

Introduction: Population growth and changes in land-use practices have the potential to affect water quality and quantity in the upper Gunnison River basin. In 1995, the U.S. Geological Survey (USGS), in cooperation with local sponsors, City of Gunnison, Colorado River Water Conservation District, Crested Butte South Metropolitan District, Gunnison County, Mount Crested Butte Water and Sanitation District, National Park Service, Town of Crested Butte, and Upper Gunnison River Water Conservancy District, established a water-quality monitoring program in the upper Gunnison River basin to characterize current water-quality conditions and to assess the effects of increased urban development and other land-use changes on water quality. The monitoring network has evolved into two groups of stations, stations that are considered as long term and stations that are rotational. The long-term stations are monitored to assist in defining temporal changes in water quality (how conditions have changed over time). The rotational stations are monitored to assist in the spatial definition of water-quality conditions (how conditions differ throughout the basin) and to address local and short term concerns. Another group of stations (rotational group 2) will be chosen and sampled beginning in water year 2004. Annual summaries of the water-quality data from the monitoring network provide a point of reference for discussions regarding water-quality sampling in the upper Gunnison River basin. This summary includes data collected during water year 2002. The introduction provides a map of the sampling locations, definitions of terms, and a one-page summary of selected water-quality conditions at the network stations. The remainder of the summary is organized around the data collected at individual stations. Data collected during water year 2002 are compared to historical data (data collected for this network since 1995), state water-quality standards, and federal water-quality guidelines. Data were collected during water year 2002 following USGS protocols (U.S. Geological Survey, variously dated).

Data Series↗
USGS1998

Salinity trends in surface waters of the Upper Colorado River Basin, Colorado

Dissolved-solids data collected in the Upper Colorado River Basin upstream from Cameo, Colorado, and in the Gunnison River Basin were analyzed for trends in flow-adjusted dissolved-solids concentrations and loads for water years 1970 to 1993, 1980 to 1993, and 1986 to 1993. Trend results for flow-adjusted periodic dissolved-solids concentrations for the Colorado River Basin upstream from Cameo, CO, generally were downward or no trend was indicated. Trends in flow-adjusted monthly and annual dissolved-solids loads primarily were downward or absent. These trend results partly agree with the downward trends reported by a previous investigation for the Colorado River near Cameo site. In the Gunnison River Basin, trends in flow-adjusted dissolved-solids concentrations and loads were not detected for more than one-half of the site/analysis-period combinations. Of the trends that were present, most indicated decreases in concentrations and loads rather than increases. In both the Colorado River Basin upstream from Cameo, CO, and the Gunnison River Basin, trends in flow-adjusted dissolved-solids concentrations and flow-adjusted monthly and annual dissolved-solids loads may be affected by a variety of factors. These include channel evolution and hydrologic variation, water quality and flow rate of groundwater discharges and springs, sample size and period of record of dissolved-solids data, and changes in land use in the basin.

Journal of Environmental Quality↗
USGS1998

Water-quality characteristics of the Slate and East rivers, Colorado, during the winter recreational season, December 1996

Periods of population influxes during winter recreation occur simultaneously with periods of extreme low flow in many Rocky Mountain areas. The ability of streams to assimilate additional nutrient loading is reduced by the low-flow conditions. Low-flow water-quality characteristics of the Slate and East Rivers, which drain the Crested Butte area, were investigated in December 1996. Six sites were chosen for evaluation-four on the Slate River and two on the East River-to assess water-quality conditions, including nutrient (nitrogen and phosphorus) concentrations and algal biomass, during a 24-hour period. Discharge in the Slate River ranged from about 18 to 30 cubic feet per second, and discharge in the East River downstream from the mouth of the Slate River was about 80 cubic feet per second. Chemical concentrations in water in the Slate and East Rivers generally were dilute with specific-conductance values of 175 to 300 microsiemens per centimeter and alkalinity values of 40 to 110 milligrams per liter during low-flow conditions. Dissolved oxygen was at or near saturation at all measurements sites. Ammonia nitrogen concentrations increased downstream from Crested Butte and Mount Crested Butte in the Slate River and then returned to background concentrations in the East River. Concentrations of nitrite plus nitrate nitrogen increased downstream from the Crested Butte area, probably associated with the nitrification of the ammonia to nitrate, and concentrations then were diluted in the East River downstream from the confluence of the Slate River. Phosphorus concentrations also increased slightly in the reach downstream from Crested Butte and Mount Crested Butte. Algal biomass values increased downstream from the Crested Butte area, decreased to low values in a subsequent reach, and then returned to higher values downstream. Biomass values were similar to those found in unenriched to moderately enriched streams. The lower biomass and higher phosphorus values occurred in a reach that was covered completely with ice and snow. Algal biomass in this reach was extremely low, probably due to the absence of light. The biomass values upstream and downstream from this reach were moderately high and probably resulted in the lower phosphorus and possibly somewhat lower nitrogen, which suggests that benthic algae may be partially controlling the nutrient levels through assimilation and uptake. When light conditions restrict algal growth and subsequent loading occurs, the concentrations of phosphorus increase slightly. Once the physical limitation (absence of light) is removed, the biomass responds with a corresponding decrease in phosphorus. The nutrient concentrations were low and well below stream standards. Nutrient increases were measured downstream from Crested Butte and Mount Crested Butte, and these increases resulted in an increase of algal biomass. Overall results indicate that, at the present time, the Slate and East Rivers can assimilate winter low-flow nutrient loads.

Colorado↗
USGS1997

Nitrogen and phosphorus data for surface water in the Upper Colorado River basin, Colorado, 1980-94

This report documents, summarizes, and provides on 3.5-in. diskette the surface-water data collected from January 1980 through August 1994 for nitrogen and phosphorus in the Upper Colorado River Basin from the Colorado-Utah State line to the Continental Divide. Ancillary data for parameters, such as water temperature, streamflow, specific conductance, dissolved oxygen, pH, and alkalinity, also are compiled, if available. Data were retrieved from the U.S. Geological Survey National Water Information System and the U.S. Environmental Protection Agency STORET (STOrage and RETrieval) system. The water-quality data are presented for sites having five or more nutrient analyses that reflect ambient stream conditions. The compiled data base contains 4,927 samples from 123 sites. The median sample period of record for individual sites is 2.5 years, and the seventy-fifth percentile is about 12 years. Sixteen sites have only five samples each. The median number of samples per site is 14 samples, whereas the seventy-fifth percentile is 65 samples. The compiled data set was used in the design of a basinwide sampling network that incorporates sites that lack historic surface-water-quality data.

Colorado↗
USGS1997

Interim results of quality-control sampling of surface water for the Upper Colorado River National Water-Quality Assessment Study Unit, water years 1995-96

Quality-control samples provide part of the information needed to estimate the bias and variability that result from sample collection, processing, and analysis. Quality-control samples of surface water collected for the Upper Colorado River National Water-Quality Assessment study unit for water years 1995?96 are presented and analyzed in this report. The types of quality-control samples collected include pre-processing split replicates, concurrent replicates, sequential replicates, post-processing split replicates, and field blanks. Analysis of the pre-processing split replicates, concurrent replicates, sequential replicates, and post-processing split replicates is based on differences between analytical results of the environmental samples and analytical results of the quality-control samples. Results of these comparisons indicate that variability introduced by sample collection, processing, and handling is low and will not affect interpretation of the environmental data. The differences for most water-quality constituents is on the order of plus or minus 1 or 2 lowest rounding units. A lowest rounding unit is equivalent to the magnitude of the least significant figure reported for analytical results. The use of lowest rounding units avoids some of the difficulty in comparing differences between pairs of samples when concentrations span orders of magnitude and provides a measure of the practical significance of the effect of variability. Analysis of field-blank quality-control samples indicates that with the exception of chloride and silica, no systematic contamination of samples is apparent. Chloride contamination probably was the result of incomplete rinsing of the dilute cleaning solution from the outlet ports of the decaport sample splitter. Silica contamination seems to have been introduced by the blank water. Sampling and processing procedures for water year 1997 have been modified as a result of these analyses.

Water-Resources Investigations Report↗
USGS1985

Selected hydrologic data for the south Platte River through Denver, Colorado

The U.S. Geological Survey, in cooperation with the cities of Littleton and Englewood, Colorado, studied the effects of the discharge of treated effluent from the Bi-City Waste Water Treatment Plant on low-flow conditions of the South Platte River. An 18-mile reach of the South Platte River, beginning below Chatfield Reservoir, through the Denver metropolitan area was studied. Chatfield Reservoir was used to regulate the flow of the South Platte River on four occasions between October 1982 and January 1984. Each flow-regulation period was used to achieve a stable, low-flow condition. Data collection during low flow allowed for the study of waste assimilation during both warm- and cold-water conditions. Water quality, streamflow, channel geometry, traveltime, mixing-zone, reaeration, and benthic-oxygen demand data were collected at selected instream, tributary, and effluent sites. This report presents data collected during four periods of low flow along the South Platte River. (USGS)

Open-File Report↗
USGS1985

Traveltime, longitudinal-dispersion, reaeration, and basin characteristics of the White River, Colorado and Utah

Traveltime and longitudinal-dispersion characteristics were measured for the White River using dye tracers. Discharges ranged from 281 to 1,840 cubic feet per second and velocities ranged from 1.26 to 3.17 miles per hour. Traveltimes were determined for discharges other than measured discharges by a graphical method and a linear-regression method. Longitudinal-dispersion coefficients ranged from 284 square feet per second at a discharge of 539 cubic feet per second to 5,430 square feet per second at a discharge of 1,580 cubic feet per second. Reaeration was measured in four reaches of the White River during a medium-flow period in August 1982. Reaeration coefficients at 20 degrees Celsius ranged from 5.3 to 25.3 per day. The results of a comparison with measured reaeration coefficients and reaeration coefficients predicted using empirical equations showed that the most accurate equations were by Bennett and Rathbun (1972) and Isaacs and Gaudy (1968). Basin characteristics were computed using U.S. Geological Survey topographic maps, precipitation data from the National Weather Service, and aerial photographs taken on September 11, 1981. (USGS)

Water-Resources Investigations Report↗
USGS1985

Effects of wastewater effluent on the South Platte River from Littleton to Denver

The U.S. Geological Survey 's one-dimensional steady-state water quality model was used to investigate the effects of the effluent from the Bi-City WWTP (Wastewater Treatment Plant) on the South Platte River. The Bi-City WWTP is operated by the Cities of Littleton and Englewood. The model was calibrated from a 14.5 mile reach for 5-day carbonaceous biochemical oxygen demand, organic, ammonia, nitrite and nitrate using data collected during September 1983. Model verification was completed using data collected during October 1982 and January 1984 for all constituents except nitrite nitrogen. Nitrite nitrogen could not be verified for the cold temperature conditions of January of 1984. Measured benthic sediment oxygen demand used in model ranged from 1.01 to 2.77 grams per square meter per day. Model simulations were made for an estimated 7-day, 10-year discharge of 18 cubic feet per second, upstream from the outfall of the WWTP. Two groups of simulations were made for both warm and cold temperature conditions. In the first group of simulation variations were made in effluent 5-day carbonaceous biochemical oxygen demand concentrations and flow rates. The second group of simulations varied the amount of nitrogen discharged as ammonia and nitrate. The extent of the mixing zone downstream of the WWTP outfall was determined by injecting Rhodamine WT dye into the effluent. The mixing zone was found to extend 0.8 miles during low-flow conditions. (USGS)

Water-Resources Investigations Report↗
USGS1985

Estimation of evaporation from Ned Wilson Lake, Flat Tops Wilderness Area, Colorado

As part of an effort to define the hydrology and water quality of Ned Wilson Lake, evaporation rates were estimated for the summer periods of 1983 and 1984. Mass-transfer and energy-budget techniques and the Morton model were used to estimate evaporation using data collected at the lake and data collected at a meteorological station 0.1 mile from the lake. The estimate of evaporation for July 29 through September 27, 1983, using the mass-transfer technique, was 9.50 inches; the estimate using the energy-budget technique was 8.10 inches; the estimate using the Morton model was 9.90 inches. The evaporation estimate for July 18 through September 25, 1984, using the mass-transfer technique was 8.71 inches; the estimate using the energy-budget technique was 7.88 inches; the estimate using the Moron model was 10.49 inches. These estimates will provide values to be used in future analyses of the interaction of lake and groundwater; however, refinement of data collection will be necessary to determine specifically the rate of evaporation. (USGS)

Water-Resources Investigations Report↗
USGS1983

Reservoir evaporation in central Colorado

Evaporation losses from seven reservoirs operated by the Denver Water Department in central Colorado were determined during various periods from 1974 to 1980. The reservoirs studies were Ralston, Cheesman, Antero, Williams Fork, Elevenmile Canyon, Dillon, and Gross. Energy-budget and mass-transfer methods were used to determine evaporation. Class-A pan data also were collected at each reservoir. The energy-budget method was the most accurate of the methods used to determine evaporation. At Ralston, Cheesman, Antero, and Williams Fork Reservoirs the energy-budget method was used to calibrate the mass-transfer coefficients. Calibrated coefficients already were available for Elevenmile Canyon, Dillon, and Gross Reservoirs. Using the calibrated coefficients, long-term mass-transfer evaporation rates were determined. Annual evaporation values were not determined because the instrumentation was not operated for the entire open-water season. Class-A pan data were used to determine pan coefficients for each season at each reservoir. The coefficients varied from season to season and between reservoirs, and the seasonal values ranged from 0.29 to 1.05. (USGS)

Water-Resources Investigations Report↗