Bulletins, Virginia Water Resources Research Center

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  • A productivity study of the Roanoke River above Niagra Dam in Virginia
    Sherrard, Joseph H.; Hoyle, Joyce L. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1977)
    Deterioration of the water quality in the upper end of the Roanoke River of Smith Mountain Lake due to eutrophication has caused much concern. The Smith Mountain Lake impoundment was constructed in 1965 as a pump storage facility to generate electrical energy and has served as a major recreational area for Southwestern Virginia. Eight sampling stations were established along the length of the Roanoke River from an agricultural area in Montgomery County through the urban area of Roanoke-Salem to Niagra Dam above Smith Mountain Lake. On 12 different occasions, approximately once a month, grab samples. were taken at the sampling stations. Samples were analyzed for general chemical parameters and for nitrogen and phosphorus. The Algal Assay Procedure Bottle Test [Environmental Protection Agency, 1971] was conducted with the samples, and in addition, with samples in which phosphorus and/or nitrogen spikes were added to determine potential productivity and to determine which element was limiting productivity. ResuIts of this investigation demonstrate that the algal assay bottle test is usefuI in correlating phosphorus concentrations with algal growth rate. Phosphorus was found to limit the algal growth in the Roanoke River above the Roanoke wastewater treatment plant for Selenastrum capricornutum and Anabaena flos-aquae, the two algal species used in this study. Maximum specific growth rates tended to increase with in- creasing phosphorus concentration.
  • Restoration of the Lower Mississippi Delta bottomland hardwood forest : economic and policy considerations
    Amacher, Gregory S.; Sullivan, Jay; Shabman, Leonard A.; Zepp, Laura J. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1997-11)
    Historically, water and related land resources management has been accomplished by engineering controls over rivers and adjacent lands in order to advance the material prosperity of the nation. One result desired from these projects was that wetlands could be drained and cleared so that their fertile and cultivable soils would add to the nation's agricultural base. Today we recognize that these activities necessarily disrupted the existing ecosystems, often diminishing their capacity to provide environmental services (terrestrial and aquatic wildlife habitat, sediment and nutrient trapping, mediation of hydro logic extremes of flood and drought). Recent recognition of these environmental consequences of our water management history has resulted in calls for ecological "restoration" as a new objective for water management (National Research Council 1993). At some scales restoration may be quite costly and disruptive of current land and water management regimes. In the Lower Mississippi River delta states, however, an opportunity exists for wetlands restoration on flood prone agricultural lands that will not be disruptive of the economic conditions in the area. The return of frequently flooded agricultural lands in the Mississippi Alluvial Plain (the Delta) to their original condition as forested wetlands has the potential to be a wetlands restoration option that can provide significant environmental gains at low cost.
  • Development and evaluation of a colorimetric coliphage assay detection system
    Ijzerman, M. Marian; Hagedorn, Charles III; Reneau, Raymond B. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1994-03)
    A colorimetric coliphage assay detection system (CCADS), composed of a liquid colorimetric presence-absence (LCPA) method and a colorimetric agar-based (CAB) method, was developed to overcome the limitations imposed by the Standard Methods for the Examination of Water and Wastewater agar-based coli phage method (APHA method). Both CCADS methods are based on the induction of p-galactosidase in Escherichia coli and the release of the enzyme through a lytic cell infection. The released enzyme then cleaves a chromogenic substrate, which produces a colored reaction product. The CCADS was evaluated against the APHA method under laboratory conditions using a common sewage coliphage strain as a model (American Type Culture Collection-13706-B2), and under field conditions using water samples collected from four different sources. During thelaboratory evaluation, both the LCPA and CAB methods were found to be superior to the APHA method in coliphage detection because: 1) the LCPA and CAB methods were easier to read and interpret than the APHA method, 2) the LCPA and CAB methods were not subject to false positive results, 3) the ·LCPA method theoretically detected fewer coliphage particles than the APHA method, and 4) the CAB method detected roughly twice the number of coliphage particles detected with the APHA method. During the field evaluation, the results indicated: 1) the LCPA method was as reliable as either the CAB or APHA method in coliphage detection; 2) the LCPA and CAB methods were easier to read and interpret than the APHA method; 3) neither the LCPA method nor the CAB method were subject to false positive results; 4) the CAB method detected more coliphages than the APHA method under conditions of high fecal pollution, but both methods performed equally well in coliphage detection under conditions of low fecal contamination; and 5) the LCPA and CAB methods were equally as sensitive in coliphage detection as the APHA method. Finally, the coliphage group proved to be a useful indicator of fecal pollution in nonpotable water supplies exhibiting a high degree of fecal pollution, whereas they were not shown to be useful indicators in potable water supplies exhibiting low levels of fecal contamination. The lack of coliphage detection sensitivity under conditions of low fecal contamination does not appear to be method-limited, but the result of inefficiencies in processing environmental samples using the concentration methods currently available.
  • Investigations of eutrophication in Mountain Lake, Giles County, Virginia
    Beaty, Myron H., 1963-; Parker, Bruce C. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1994-07)
  • The concept of instream flow and its relevance to drought management in the James River Basin
    Vadas, Robert L.; Weigmann, Diana L. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1993-09)
  • Sediment-water column nutrient exchanges in southern Chesapeake Bay nearshore environments
    Reay, William G.; Gallagher, Daniel L.; Simmons, George M. Jr. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1993-08)
    Using field and modeling methodology, the effects of benthic microcommunities and physical transport mechanisms on sediment nutrient flux were investigated for two nearshore sediment types on Virginia's Eastern Shore. Subtidal sandy mineral sediments were conducive to water transport and influenced by groundwater discharge to a greater degree than less-permeable organic silt-clay sediments. Sediment ammonium and dissolved inorganic phosphorus (DIP) fluxes were strongly dependent on benthic aerobic respiration rates for silt-clay sediments as compared to sandy substrates. In-situ studies showed a significant decrease in ammonium and DIP fluxes as a result of nutrient uptake by benthic microalgal communities. The importance of advective solute transport mechanisms within nearshore sediments was demonstrated by a one-dimensional, steady-state model for a conservative substance. By incorporating dispersive and advective transport mechanisms, model predictability for chloride sediment flux was significantly improved as compared to a diffusion-based model. Model results indicate that velocity-associated transport of solutes, driven by elevated upland hydraulic heads, is significant and can dominate over diffusive flux in sandy sediment. In contrast, silt-clay sediment solute fluxes were dominated by dispersive processes. The importance of sedimentary nutrient flux in a shallow coastal embayment was demonstrated by short water column dissolved inorganic nitrogen (DIN) and DIP turnover times ·with respect to sediment nutrient fluxes, by the significance of ammonium and DIP sediment nutrient fluxes with respect to phytoplankton nutrient assimilation demands, and by the relative importance of benthic respiration with respect to water column primary productivity. To evaluate water quality impacts of groundwater discharge on a larger scale, a surface, groundwater, and in-situ groundwater discharge water quality survey was conducted in a shallow estuarine embayment. Sediment inorganic nitrogen fluxes were elevated adjacent to agricultural fields without benefit of a vegetative buffer. Nitrogen contributions from direct groundwater discharge and groundwater-derived creek contributions appear to be of significant importance in terms of water quality and phytoplankton nitrogen assimilation demands. In summary, this study highlights the importance of nearshore sediments with regard to estuarine nutrient water quality and ecological processes. Neglecting groundwater discharge as a nutrient source and transport mechanism and potential biotic effects occurring at the sediment-water interface may lead to misinterpretation of data and error in water quality strategies.
  • An assessment of the transferability of habitat suitability criteria for smallmouth bass
    Groshens, Thomas P.; Orth, Donald J. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1993-06)
  • Evaluation of the performance of five aerated package treatment systems
    Kellam, J. Lee; Boardman, Gregory D.; Hagedorn, Charles III; Reneau, Raymond B. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1993)
  • A model of nitrate leaching from agricultural systems in Virginia's Northern Neck
    Johnson, Terrence G.; Parker, Jack C. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1993-06)
    A model (VT-CROPS) was developed to simulate the long-term effects of nitrogen (N) leaching to groundwater in the Northern Neck region of Virginia and, ultimately, to the Chesapeake Bay. VT-CROPS simulates N fate and transport in a soil-plant-atmosphere continuum in a vertical slice between two crop rows, enabling consideration of nonuniform fertilizer placement and root growth patterns. VT-CROPS models atmospheric, soil and crop subsystems. Atmospheric conditions (rainfall, temperature, solar radiation) may be entered directly by the user or generated by using a stochastic climatic generator. The soil subsystem simulates runoff, infiltration, drainage and soil-water redistribution, N immobilization, nitrification, mineralization, denitrification, and advective N transport. The crop subsystem simulates plant N uptake, and vegetative and reproductive growth in response to soil and climatic factors, explicitly for maize or wheat. VT-CROPS simulates soybean in a crop rotation, empirically accounting for leaf area and root growth. The model is capable of simulating long-term cropping sequences under minimum and conventional tillage . practices for continuous maize or for rotations involving maize, wheat, soybean, and fallow. Critical internal model parameters were calibrated through comparison of output to field data. The sensitivity of output to input variables was determined. Model output is most sensitive to the climatic variables. Model-predicted crop performance variables-grain and total dry matter yields and N content-and soil N content were compared with available field data from two sites over a three-year period for maize. Data from six sites over a one-year period were tested for wheat. Predictions for maize and total N content were fairly accurate, with a tendency to greater error in dry years. Predictions for wheat were somewhat less accurate, but incomplete field data precluded determining the source of discrepancies. Long-term model predictions, for two-year crop rotations with minimum and conventional tillage, were evaluated by comparing performance variables with literature values. Appropriate responses were obtained for N transformation processes. Mass conservation for soil water and N were good. Maize performance variables were within the range of literature values, and were higher under minimum till. Wheat yields and N contents were somewhat higher than values reported in the literature. Nitrogen load is correlated to drainage and water use over the short run, and to rainfall and drainage over longer periods. Minimum tillage did not increase N load to groundwater. Over a year, nitrogen load was periodic, with most leaching taking place from January through April. More than 50% of the N load over a rotation was lost during an extended fallow period that followed soybeans. Nitrogen load increased with fertilizer rates; however, the N leaching fraction was optimal at rates of 150-200 kg/ha. The model was applied to the Virginia counties of Richmond, Westmoreland, Lancaster, King George, and Northumberland to assess the potential for long-term N leaching to groundwater. Soil surveys indicated that 34 soil map units occurred within 123,000 hectares of cultivated land. To reduce the number of simulations, principal component analysis and cluster analysis were used to subdivide the cultivated area into 10 land units based on different soil properties. Historical climatic data from the area were used to calibrate the stochastic climatic generator. Analyses were performed to determine long-term crop performance and N loads to groundwater and surface waters in the study area over a 26-year period (13 rotations). Two management systems were applied to the land units. The first management system consisted of a rotation of minimum-tilled maize, conventionally tilled wheat, minimum-tilled soybeans, and a fallow period. The second management system had a similar cropping sequence, but all crops were conventionally tilled. In both cases, fertilizer was applied at a rate of 150 kg-N/ha/crop. With the exception of two land units, mean yield, water use, and N uptake over the simulation were fairly uniform among the land units. Runoff and drainage were highly variable between land units and over time within units. Mineralization, denitrification, and N load were highly variable both between land units and over time. Nitrogen load ranged from 66 to 131 kg/ha/rotation between land units. Long-term average N loads and N concentrations from the cultivated area and from the total area of the study region were estimated. For this analysis, it was assumed that 80% of the cultivated area was under minimum till and 20% under conventional tillage. An area-weighted average of 5.4 million kg-N/ha/year, or 29% of total N applied, is discharged to groundwater, with an average drainage concentration of 9.9 mg/I. The average N concentration from the study area (including uncultivated areas) to groundwater is estimated at 5.1 mg/I. Average N concentration to the Chesapeake Bay from all sources, after dilution with runoff, is 4.5 mg/I, which is lower than the drinking water standard for nitrate N of 10 mg/I. The possibility of using sewage sludge as a replacement for, or in consort with, N fertilizer was investigated for a typical land unit, under a conventionally tilled maize-wheat-soybean-fallow rotation. Simulations were conducted with 100%, 50%, and 0% sludge (CN ratio of 12). With fertilizer N augmenting the sludge, the total N input (250 kg/ha) was the same for each treatment. Mean yields were similar for 50% and 0% sludge, but lowered by 10% and 16%, respectively, for maize and wheat with 100% sludge. Discrepancies in yields were attributed to the fact that mineralization rates of sludge are not high enough to supply the crop N requirement during periods of peak uptake. Nitrate leaching was reduced by 41 % and 25% with 100% and 50% sludge applications, respectively.
  • The influence of microbial ecology on subsurface degradation of petroleum contaminants
    Novak, John T.; Yeh, Carol; Eichenberger, John Joseph, 1964-; Benoit, Robert E. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1992-11)
  • Crop selection, tillage practices, and chemical and nutrient applications in two regions of the Chesapeake Bay Watershed
    Bosch, Darrell J.; Shanholtz, Vernon O. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1992-11)
    The objectives of this study were to obtain information on crop selection, tillage, and nutrient and chemical use on cropland having varying sediment loading and leaching potential. Additional objectives were the determination of economic, attitudinal, and demographic factors related to these agricultural practices. The study was carried out in Virginia in three counties of the Northern Neck region (Lancaster, Northumberland, and Westmoreland) and in Rockingham County. In each area, a stratified random sample of 120 sites with varying leaching and sediment loading potential was drawn from the Virginia Geographic Information System (VirGIS) database of cropland. Information on cultural practices on the sites as well as other farm and farmer characteristics was obtained through personal interviews with farm operators. Survey responses indicate that farmers are concerned about the effects of pollution on water quality-particularly drinking water. However, farmers tend not to see actions on their own farms as contributing to water quality damage. Most farmers do not agree that runoff and leaching of nutrients and chemicals from their farms contribute to water quality problems. When asked about the sampled sites on their farms, farmers generally responded that the potential for water quality damage caused by leaching and erosion was low. Their assessment of potential damage did not increase significantly on sites with high leaching or sediment loading potential. In the Northern Neck, farmers generally apply nitrogen and phosphorus at close to recommended rates. In Rockingham County, nitrogen is applied at below recommended rates, while phosphorus is overapplied due to heavy manure applications. Farmers' tillage practices, crop rotations, and nutrient and pesticide application rates generally do not vary according to site leaching and sediment loading potential. Thus, sites with higher leaching and/or sediment loading potential are likely to contribute a disproportionate share of potential loadings to groundwater and surface water. Further research is needed to determine whether targeting nonpoint pollution control to sites with higher leaching and sediment loading potential is a cost-effective way to achieve water quality protection goals.
  • Fate and transport of pesticides in a Virginia Coastal Plain soil
    Heatwole, Conrad D.; Zacharias, Sebastian; Mostaghimi, Saied; Dillaha, Theo A. III; Young, Roderick W. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1992)
    The fate and transport of atrazine, metolachlor, and bromide as a tracer, were characterized through surface runoff monitoring and soil core sampling on no-till and conventionally tilled field plots planted with corn. A rainfall simulator was used to generate a surface runoff event within 48 hours of pesticide application. In comparison with the conventional-tillage plot, the no-till plot yielded 32% of the runoff volume, 8% of the sediment, and 50% of the pesticide mass. Total losses of atrazine and metolachlor in surface runoff were 0.5-1 .5% of the amount applied, with the greatest losses associated with conventional tillage. Significant precipitation in the early stages of the study resulted in rapid leaching of the chemicals in both plots. Statistical tests show that chemicals moved deeper in the no-till plot, as compared to the conventional-tillage plot, in the first two weeks after application. However, statistical analysis of the remaining period shows no consistent differences in pesticide concentrations in the soil profile based on tillage practice. Atrazine dissipation was higher in the no-till plot, and there was a significant carryover of the pesticide in both plots at the end of the 157-day period.
  • Effect of land use management on flood predictions
    Smith, Rod W.; Jamison, Donald K.; Knapp, John W. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1977)
  • Interactions between surface water and groundwater in a Virginia coastal plain watershed
    Eshleman, Keith N.; Pollard, John S.; Kuebler, Anne (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1992-04)
  • Surface water quality trends in southwestern Virginia, 1970-1989. I, Seasonal Kendall analysis
    Zipper, Carl E.; Holtzman, Golde I.; Rheem, Sungsue, 1957-; Evanylo, Gregory K. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1992-02)
  • Denitrification in onsite wastewater treatment and disposal systems
    Degen, Marcia B.; Reneau, Raymond B.; Hagedorn, Charles III; Martens, David C. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1991-11)
    The effects of effluent type, effluent loading rate, dosing interval, and temperature on denitrification in onsite wastewater treatment and disposal systems (OSWTDSs) were evaluated in this study. The variables were soil horizon, effluent type, effluent loading rate, dosing interval, and temperature. Surface and subsurface soil cores were collected from a Groseclose silt loam soil (clayey, mixed, mesic Typic Hapludult) and subjected to the following treatments: aerobic and anaerobic effluent, loading rates of 0.5, 1.0, and 1.5 times the Virginia Department of Health (VDH)-recommended levels, 24-hour and 48-hour dosing rates, and summer and winter temperatures. The effects of the treatments on denitrification were evaluated based on analyses of leachate from the cores, soil chemical analyses, and microcosm studies to estimate actual denitrification activity. From the study, a model was developed that predicted the mean nitrous oxide (N20) production for each combination of the experimental treatments. The results of the study and the model indicate that denitrification can be enhanced in OSWTDSs by the application of anaerobic effluent at the VDH-recommended effluent loading rate to surface soil horizons using a 48-hour dosing interval. A field study was conducted on a Lowell silt loam soil (fine, mixed, mesic Typic Hapludalf). Denitrification was measured at this site using acetylene blocking, and the results compared to those predicted by the denitrification model developed from the laboratory data. The field measurements of denitrification based on N20 concentration in the soil atmosphere were almost three orders of magnitude higher than that predicted by the model.
  • The 1986 amendments to the Safe Drinking Water Act : impacts on Virginia's water supply industry
    Cox, William E.; Sherrard, Joseph H.; Gaw, Christopher D. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1991-10)
  • Biodegradability of atrazine, cyanazine, and dicamba in wetland soils
    Gu, Ji-Dong; Berry, Duane F.; Taraban, Ronald H.; Martens, David C.; Walker, H. Lynn; Edmonds, William J. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1992-02)
    Small amounts of applied pesticide chemicals eventually can end up in nontarget areas such as wetlands, sediments, and groundwater where anaerobic conditions often predominate. Runoff and leaching are major means by which pesticides move away from application sites. Pesticides also can find their way into nontarget areas as a result of inappropriate disposal and accidental spills. We evaluated the biodegradability of atrazine, cyanazine, and dicamba in wetland soils under nitratereducing and methanogenic conditions. Wetland soil samples were collected from three different sites in the Chesapeake Bay watershed region. These sites represented both tidal (Lawnes and Levy soils) and nontidal (Myatt soil) wetlands. Tidal wetlands are water-saturated throughout the year, whereas nontidal wetlands are saturated only during certain times of the year. Herbicide fate studies were conducted in wetland soil microcosms consisting of serum bottles filled with soil slurry and containing either atrazine, cyanazine, or dicamba. Atrazine was extremely stable in wetland soil microcosms regardless of incubation temperature, redox status (nitrate-reducing versus methanogenic conditions), or soil type. Neither temperature nor redox status affected cyanazine stability in Myatt wetland soil microcosms. We observed a significant decrease in cyanazine concentration in Lawnes wetland microcosms incubated under methanogenic and nitratereducing conditions. Losses were more pronounced at 25° than at 15°C. Results from enrichment culture studies suggest that cyanazine was cometabolized (i.e., cyanazine could not be used as a carbon and energy source by the microorganisms) in Lawnes soil microcosms. Dicamba was readily biodegraded in the wetland soils tested, although total mineralization was not achieved.
  • A Helium high efficiency microwave induced plasma for the atomic spectrometric determination of metals and nonmetals
    Perkins, Larry D.; Motley, Curtis Bobby; McCleary, Keith Alan; Long, Gary L. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1991)
  • Agricultural BMPs applicable to Virginia
    Heatwole, Conrad D.; Dillaha, Theo A. III; Mostaghimi, Saied (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1991-03)