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Now showing items 1 - 16 of 861

  • Risk-based decision making to evaluate pollutant reduction scenarios

    Ahmadisharaf, Ebrahim   Benham, Brian L.  

    A total maximum daily load (TMDL) is required for water bodies in the U.S. that do not meet applicable water quality standards. Computational watershed models are often used to develop TMDL pollutant reduction scenarios. Uncertainty is inherent in the modeling process. An explicit uncertainty analysis would improve model performance and result in more robust decision making when comparing alternative pollutant reduction scenarios. This paper presents a risk-based framework for evaluating alternative pollutant allocation scenarios considering reliability in achieving water quality goals. We demonstrate a generic routine for the application of Generalized Likelihood Uncertainty Estimation (GLUE) to Hydrological Simulation Program-FORTRAN (HSPF) using existing softwares to evaluate two bacteria reduction scenarios from a recently developed TMDL that addressed a bacterial impairment in a mixed land use watershed in Virginia, U.S. Our probabilistic analysis showed that for reliability levels <25%, the recommended TMDL bacterial load reduction scenario had the same exceedance rate as the full reduction scenario (fully reducing all bacterial loads except wildlife), while for reliability levels between 25% and 50%, the exceedance rates for the two pollutant reduction scenarios were similar, with the TMDL recommended scenario violating the water quality criteria only slightly more often. The full reduction scenario performed better in higher reliability levels, although it could not meet the water quality criteria. Our results indicated that, in this case, achieving water quality goals with very high reliability was not possible, even with extreme levels of pollutant reduction. The risk-based framework presented here illustrates a method to propagate watershed model uncertainty and assess performance of alternative pollutant reduction scenarios using existing tools, thereby enabling decision makers to understand the reliability of a given scenario in achieving water quality goals. (C) 2019 The Author(s). Published by Elsevier B.V.
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  • Incidence of waterborne lead in private drinking water systems in Virginia

    Pieper, Kelsey J.   Krometis, Leigh-Anne H.   Gallagher, Daniel L.   Benham, Brian L.   Edwards, Marc  

    Although recent studies suggest contamination by bacteria and nitrate in private drinking water systems is of increasing concern, data describing contaminants associated with the corrosion of onsite plumbing are scarce. This study reports on the analysis of 2,146 samples submitted by private system homeowners. Almost 20% of first draw samples submitted contained lead concentrations above the United States Environmental Protection Agency action level of 15 mu g/L, suggesting that corrosion may be a significant public health problem. Correlations between lead, copper, and zinc suggested brass components as a likely lead source, and dug/bored wells had significantly higher lead concentrations as compared to drilled wells. A random subset of samples selected to quantify particulate lead indicated that, on average, 47% of lead in the first draws was in the particulate form, although the occurrence was highly variable. While flushing the tap reduced lead below 15 mu g/L for most systems, some systems experienced an increase, perhaps attributable to particulate lead or lead-bearing components upstream of the faucet (e.g., valves, pumps). Results suggest that without including a focus on private as well as municipal systems it will be very difficult to meet the existing national public health goal to eliminate elevated blood lead levels in children.
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  • Comparison of Two Alternative Methods for Developing TMDLs to Address Sediment Impairments

    Wallace, Carlington W.   Benham, Brian L.   Yagow, Eugene R.   Gallagher, Daniel L.  

    While excessive sediment is a leading cause of aquatic life use impairments in free-flowing rivers in Virginia, there is no numeric sediment-water quality criterion. As a result, total maximum daily load (TMDL) sediment loads are often established using a comparable, nonimpaired reference watershed. Selecting a suitable reference watershed can be problematic. This case study compared the reference watershed approach (RWA) which uses the Generalized Watershed Loading Function and the disaggregate method (DM) which uses output from Phase 5.3 of the Chesapeake Bay Watershed Model. In this case study, the two methods were used to develop sediment TMDLs for three impaired watersheds in Virginia (Taylor Creek, Turley Creek, and Long Meadow Run). In this case study comparison, the RWA required between 12.8 and 14.7 times greater sediment load reductions (t/year) to reach the TMDL load (Taylor Creek > Long Meadow Run > Turley Creek) when compared to the reductions called for using the DM. While each TMDL development method has inherent limitations, the DM uses output from the Chesapeake Bay Watershed Model to establish TMDL target loads. This means that the application of the DM is restricted to the Chesapeake Bay Watershed.
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  • Bacterial transport from agricultural lands fertilized with animal manure

    Mishra, Anurag   Benham, Brian L.   Mostaghimi, Saied  

    A plot scale study was conducted to determine bacterial transport in runoff from cropland treated with poultry litter and dairy manure applied at phosphorus (P) agronomic rates. Treatments included surface application of dairy manure, surface application of poultry litter, incorporation of dairy manure and control. A rainfall simulator was used to induce runoff 1 and 2 days after manure application. Runoff was analyzed to determine the concentration of indicator bacteria-fecal coliform, Escherichia coli, and Enterococcus. Observed edge-of-field bacterial concentrations were 10(2) to 10(5) times higher than Virginia's in-stream bacteria criteria for primary contact recreation waters. No significant treatment effects were observed on edge-of-field bacteria concentration or yield. Results suggest that the manure application based on agronomic P rates may yield significant bacterial loading to downstream waterbodies if rainfall occurs soon after manure application. This research underscores the need for BMPs that reduce runoff volumes and filter pollutants associated with animal manures.
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  • Scale-dependent impacts of urban and agricultural land use on nutrients,sediment,and runoff

    Lacher, Iara L.   Ahmadisharaf, Ebrahim   Fergus, Craig   Akre, Thomas   Mcshea, William J.   Benham, Brian L.   Kline, Karen S.  

    We coupled a spatially-explicit land use/land cover (LULC) change model, Dinamica EGO, (Environment for Geoprocessing Objects), with the Chesapeake Bay Watershed Model (CBWM) to project the impact of future LULC change on loading of total nitrogen (TN), total phosphorous (TP) and total suspended solids (TSS) as well as runoff volume in the watersheds surrounding Virginia's Shenandoah National Park in the eastern United States. We allowed for the dynamic transition of four LULC classes, Developed, Forest, Grasses (including both pasture and hayfields) and Crops. Using 2011 as a baseline scenario and observed differences in LULC between 2001 and 2011, we estimated the temporal and spatial patterns of LULC change as influenced by physiographic and socio-economic drivers 50 years in the future (2061). Between transitions of the four LULC classes, the greatest absolute change occurred between the gain in total Developed land and loss in total Forest. New Developed land was driven primarily by distance to existing Developed land and population density. Major findings on the effect of LULC change on watershed model outputs were that: the impact of LULC change on pollutant loading and runoff volume is more pronounced at finer spatial scales; increases in the area of Grasses produced the greatest increase in TP loading, while loss of Forest increased TN, TSS, and runoff volume the most; and land-river segments with a greater proportion of Developed or a smaller proportion of Forest in the 2011 scenario experienced a greater change in runoff than other land-river segments. Results of this study illustrate the potential impact of projected LULC change on nutrient and sediment loads which can adversely impact water quality. Studies like this contribute to a broader understanding of how ecosystem services such as freshwater respond to LULC change, information relevant to those in planning and watershed management. (C) 2018 Published by Elsevier B.V.
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  • Application of the Analytical Hierarchical Process for Improved Selection of Storm-Water BMPs

    Young, Kevin D.   Kibler, David F.   Benham, Brian L.   Loganathan, G. V.  

    Engineers and planners responsible for the selection and design of storm-water best management practices (BMPs) face a formidable array of practices and techniques for managing the quality of urban runoff. Primary factors affecting the choice of BMP invariably include the performance capability of a given class of BMPs and the new impervious cover fraction arising from development projects. We introduce the analytical hierarchal process (AHP) as an analytical framework for BMP selection, through priority ranking of storm water control objectives and BMP performance metrics. Using the AHP, a BMP priority ranking is accomplished through the construction of pairwise relative rankings of the selection criteria and then of the BMPs themselves against the respective selection criteria. The use of normalized ranking vectors, obtained through eigenvector approximation, is employed to provide a final ranking of BMP choices that then can be carefully reviewed by the design engineer. Two BMP selection applications are included in the context of a residential/commercial development and a linear highway project.
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  • FTABLE generation method effects on instream fecal bacteria concentrations simulated with HSPF1

    Hall, Kyle M.   Zeckoski, Rebecca W.   Brannan, Kevin M.   Benham, Brian L.  

    Computer simulation models are used extensively for the development of total maximum daily loads (TMDLs). Specifically, the Hydrological Simulation Program-FORTRAN (HSPF) is used in Virginia for the development of TMDLs for bacteria impairments. HSPF estimates discharge from a reach using function tables (FTABLES). The FTABLE relates stream stage, surface area, and volume to discharge from a reach. In this study, five FTABLE estimation methods were assessed by comparing their effect on various simulation outputs. Four "field-based" methods used detailed cross-sectional data collected via site surveys. A fifth "digital-based" method used digital elevation data in combination with the Natural Resources Conservation Service Regional Hydraulic Geometry Curves. Sets of FTABLEs created using each method were used in simulations of instrearn bacteria concentration for a Virginia watershed. Several statistics relating to instrearn bacteria including longterm average concentration, die-off, and the violation rate of Virginia's bacteria criterion were compared. The pair-wise Student's t-test was used for the comparison. The HSPF simulations that used FTABLES estimated from digitally based data consistently produced significantly higher long-term average instream fecal bacteria concentrations, significantly lower instrearn fecal bacteria die-off, which is related to differences in residence time in the streams, and significantly higher water quality criterion violation rates.
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  • Assessment of wastewater reuse effects on nutrient loads from paddy field using field-scale water quality model

    Kim, Sang Min   Im, Sang June   Park, Seung Woo   Lee, Jeong Jae   Benham, Brian L.   Il Jang, Tae  

    CREAMS-PADDY, a modified version of the field-scale CREAMS model, simulates the hydrologic, sediment, and nutrient cycles in paddy fields. The CREAMS-PADDY model was applied to estimate the effects of using wastewater for irrigation on nutrient loads from paddy fields in Republic of Korea. The model was calibrated and validated using data from two rice paddy fields. The coefficient of determination between observed and simulated total nitrogen and total phosphorus were 0.92 and 0.57, respectively, for the calibration period and 0.84 and 0.73 for the validation period. Simulations showed that when using wastewater for irrigation, the total nitrogen loads increased by 210% and total phosphorus by 1,270% when compared with conventional water irrigation. The total nitrogen and total phosphorus concentration in the ponded water increased by 254 and 534%, respectively, when compared with conventional water irrigation. The effect of reducing N and P fertilizer application rates by 10, 30, and 50% on nutrient loads exiting a paddy field were also simulated using the validated CREAMS-PADDY model. These simulations indicated that total phosphorus loads from the paddy were reduced only slightly by reducing the fertilizer, while total nitrogen loads were reduced by as much as 8.8, 16.6, and 24.4% when N ferlitizer rates were reduced by 10, 30, and 50%, respectively.
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  • Two-Phase Monte Carlo Simulation for Partitioning the Effects of Epistemic and Aleatory Uncertainty in TMDL Modeling

    Mishra, Anurag   Ahmadisharaf, Ebrahim   Benham, Brian L.   Gallagher, Daniel L.   Reckhow, Kenneth H.   Smith, Eric P.  

    A two-phase Monte Carlo simulation (TPMCS) uncertainty analysis framework is used to analyze epistemic and aleatory uncertainty associated with simulated exceedances of an in-stream fecal coliform (FC) water quality criterion when using the Hydrological Simulation Program-FORTRAN (HSPF). The TPMCS framework is compared with a single-phase or standard Monte Carlo simulation (SPMCS) analysis. Both techniques are used to assess two total maximum daily load (TMDL) pollutant allocation scenarios. The application of TPMCS illustrates that cattle directly depositing FC in the stream is a greater source of epistemic uncertainty than FC loading from cropland overland runoff, the two sources specifically targeted for reduction in the allocation scenario. This distinction is not possible using SPMCS. Although applying the TPMCS framework involves subjective decisions about how selected model parameters are considered within the framework, this uncertainty analysis approach is transparent and the results provide information that can be used by decision makers when considering pollution control measure implementation alternatives, including quantifying the level of confidence in achieving applicable water quality standards.
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  • Two-Phase Monte Carlo Simulation for Partitioning the Effects of Epistemic and Aleatory Uncertainty in TMDL Modeling

    Mishra, Anurag   Ahmadisharaf, Ebrahim   Benham, Brian L.   Gallagher, Daniel L.   Reckhow, Kenneth H.   Smith, Eric P.  

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  • Generalized Likelihood Uncertainty Estimation and Markov Chain Monte Carlo Simulation to Prioritize TMDL Pollutant Allocations

    Mishra, Anurag   Ahmadisharaf, Ebrahim   Benham, Brian L.   Wolfe, Mary Leigh   Leman, Scotland C.   Gallagher, Daniel L.   Reckhow, Kenneth H.   Smith, Eric P.  

    This study presents a probabilistic framework that considers both the water quality improvement capability and reliability of alternative total maximum daily load (TMDL) pollutant allocations. Generalized likelihood uncertainty estimation and Markov chain Monte Carlo techniques were used to assess the relative uncertainty and reliability of two alternative TMDL pollutant allocations that were developed to address a fecal coliform (FC) bacteria impairment in a rural watershed in western Virginia. The allocation alternatives, developed using the Hydrological Simulation Program-FORTRAN, specified differing levels of FC bacteria reduction from different sources. While both allocations met the applicable water-quality criteria, the approved TMDL allocation called for less reduction in the FC source that produced the greatest uncertainty (cattle directly depositing feces in the stream), suggesting that it would be less reliable than the alternative, which called for a greater reduction from that same source. The approach presented in this paper illustrates a method to incorporate uncertainty assessment into TMDL development, thereby enabling stakeholders to engage in more informed decision making.
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  • Assessment of Wastewater Reuse Effects on Nutrient Loads from Paddy Field Using Field-Scale Water Quality Model (vol 13, pg 305, 2008)

    Kim, Sang Min   Im, Sang June   Park, Seung Woo   Lee, Jeong Jae   Benham, Brian L.   Il Jang, Tae  

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  • Brian L. Davies,

    Victor Taki  

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  • , by Mary L. Gray, Brian J. Gilley, & Colin R. Johnson (Eds.)

    Blake Hawkins  

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  • Warfare in Eastern Europe, 1500–1800by Ed. Brian L. Davies

    Review by: Lawrence Sondhaus  

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  • Warfare in Eastern Europe, 1500–1800by Ed. Brian L. Davies

    Review by: Lawrence Sondhaus  

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