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Daily Load (daily + load)
Kinds of Daily Load Selected AbstractsThe Watershed Deposition Tool: A Tool for Incorporating Atmospheric Deposition in Water-Quality Analyses,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2009Donna B. Schwede Abstract:, A tool for providing the linkage between air and water-quality modeling needed for determining the Total Maximum Daily Load (TMDL) and for analyzing related nonpoint-source impacts on watersheds has been developed. Using gridded output of atmospheric deposition from the Community Multiscale Air Quality (CMAQ) model, the Watershed Deposition Tool (WDT) calculates average per unit area and total deposition to selected watersheds and subwatersheds. CMAQ estimates the wet and dry deposition for all of its gaseous and particulate chemical species, including ozone, sulfur species, nitrogen species, secondary organic aerosols, and hazardous air pollutants at grid scale sizes ranging from 4 to 36 km. An overview of the CMAQ model is provided. The somewhat specialized format of the CMAQ files is not easily imported into standard spatial analysis tools. The WDT provides a graphical user interface that allows users to visualize CMAQ gridded data and perform further analyses on selected watersheds or simply convert CMAQ gridded data to a shapefile for use in other programs. Shapefiles for the 8-digit (cataloging unit) hydrologic unit code polygons for the United States are provided with the WDT; however, other user-supplied closed polygons may be used. An example application of the WDT for assessing the contributions of different source categories to deposition estimates, the contributions of wet and dry deposition to total deposition, and the potential reductions in total nitrogen deposition to the Albemarle-Pamlico basin stemming from future air emissions reductions is used to illustrate the WDT capabilities. [source] EPA'S BASINS MODEL: GOOD SCIENCE OR SERENDIPITOUS MODELING?,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 3 2000Ray C. Whittemore ABSTRACT: Better Assessment Science Integrating Point and Non-point Sources (BASINS) is a geographic-based watershed assessment tool developed by EPA's Office of Water to help states more efficiently target and evaluate water-bodies that are not meeting water quality standards. BASINS (EPA, 1996a, 1998) brings together data on water quality and quantity, land uses, point source loadings, and other related spatial data with supporting nonpoint and water quality models at a quicker and more effective pace. EPA developed BASINS, to better integrate point and nonpoint source water quality assessments for the Nation's 2100+ watersheds. In its zeal to achieve this endpoint, EPA has initiated a simplistic approach that was expected to grow through scientific enhancements as TMDL developers become more familiar with modeling requirements. BASINS builds upon federal databases of water quality conditions and point source loadings for numerous parameters where quality assurance is suspect in some cases. Its design allows comprehensive assessments and modeling in typical Total Maximum Daily Load (TMDL) computations. While the TMDL utility is the primary reason BASINS was developed, other longer-range water quality assessments will become possible as the Agency expands the suite of assessment models and databases in future releases. The simplistic approach to modeling and user-friendly tools gives rise, however, to technical and philosophical concerns related to default data usage. Seamless generation of model input files and the failure of some utilities to work properly suggest to NCASI that serious problems may still exist and prompts the need for a more rigorous peer-review. Furthermore, sustainable training becomes paramount, as some older modelers will be unfamiliar with Geographic Information System (GIS) technology and associated computer skills. Overall, however, BASINS was judged to be an excellent beginning tool to meet the complex environmental modeling needs in the 21st Century. [source] Evaluation of water quality using acceptance sampling by variablesENVIRONMETRICS, Issue 4 2003Eric P. Smith Abstract Under section 303(d) of the Clean Water Act, states must identify water segments where loads of pollutants are violating numeric water quality standards. Consequences of misidentification are quite important. A decision that water quality is impaired initiates the total maximum daily load or TMDL planning requirement. Falsely concluding that a water segment is impaired results in unnecessary TMDL planning and pollution control implementation costs. On the other hand, falsely concluding that a segment is not impaired may pose a risk to human health or to the services of the aquatic environment. Because of the consequences, a method is desired that minimizes or controls the error rates. The most commonly applied approach is to use the Environmental Protection Agency (EPA)'s raw score approach in which a stream segment is listed as impaired when greater than 10 per cent of the measurements of water quality conditions exceed a numeric criteria. An alternative to the EPA approach is the binomial test that the proportion exceeding the standard is 0.10 or less. This approach uses the number of samples exceeding the criteria as a test statistic along with the binomial distribution for evaluation and estimation of error rates. Both approaches treat measurements as binary; the values either exceed or do not exceed the standard. An alternative approach is to use the actual numerical values to evaluate standard. This method is referred to as variables acceptance sampling in quality control literature. The methods are compared on the basis of error rates. If certain assumptions are met then the variables acceptance method is superior in the sense that the variables acceptance method requires smaller sample sizes to achieve the same error rates as the raw score method or the binomial method. Issues associated with potential problems with environmental measurements and adjustments for their effects are discussed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Advances in the application of the SWAT model for water resources managementHYDROLOGICAL PROCESSES, Issue 3 2005R. Jayakrishnan Abstract Developments in computer technology have revolutionized the study of hydrologic systems and water resources management. Several computer-based hydrologic/water quality models have been developed for applications in hydrologic modelling and water resources studies. Distributed parameter models, necessary for basin-scale studies, have large input data requirements. Geographic information systems (GIS) and model,GIS interfaces aid the efficient creation of input data files required by such models. One such model available for the water resources professional is the Soil and Water Assessment Tool (SWAT), a distributed parameter model developed by the United States Department of Agriculture. This paper describes some recent advances made in the application of SWAT and the SWAT,GIS interface for water resources management. Four case studies are presented. The Hydrologic Unit Model for the United States (HUMUS) project used SWAT to conduct a national-scale analysis of the effect of management scenarios on water quantity and quality. Integration of the SWAT model with rainfall data available from the WSR-88D radar network helps us to incorporate the spatial variability of rainfall into the modelling process. This study demonstrates the usefulness of radar rainfall data in distributed hydrologic studies and the potential of SWAT for application in flood analysis and prediction. A hydrologic modelling study of the Sondu river basin in Kenya using SWAT indicates the potential for application of the model in African watersheds and points to the need for development of better model input data sets in Africa, which are critical for detailed water resources studies. The application of SWAT for water quality analysis in the Bosque river basin, Texas demonstrates the strength of the model for analysing different management scenarios to minimize point and non-point pollution, and its potential for application in total maximum daily load (TMDL) studies. Copyright © 2005 John Wiley & Sons, Ltd. [source] GROUPWISE MODELING STUDY OF BACTERIALLY IMPAIRED WATERSHEDS IN TEXAS: CLUSTERING ANALYSIS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2006Sabu Paul ABSTRACT: Under the Clean Water Act (CWA) program, the Texas Commission on Environmental Quality (TCEQ) listed 110 stream segments in the year 2000 with pathogenic bacteria impairment. A study was conducted to evaluate the probable sources of pollution and characterize the watersheds associated with these impaired water bodies. The primary aim of the study was to group the water bodies into clusters having similar watershed characteristics and to examine the possibility of studying them as a group by choosing models for total maximum daily load (TMDL) development based on their characteristics. This approach will help to identify possible sources and determine appropriate models and hence reduce the number of required TMDL studies. This in turn will help in reducing the effort required to restore the health of the impaired water bodies in Texas. The main characteristics considered for the classification of water bodies were land use distribution within the watershed, density of stream network, average distance of land of a particular use to the closest stream, household population, density of on-site sewage facilities (OSSFs), bacterial loading from different types of farm animals and wildlife, and average climatic conditions. The climatic data and observed instream fecal coliform bacteria concentrations were analyzed to evaluate seasonal variability of instream water quality. The grouping of water bodies was carried out using the multivariate statistical techniques of factor analysis/principal component analysis, cluster analysis, and discriminant analysis. The multivariate statistical analysis resulted in six clusters of water bodies. The main factors that differentiated the clusters were found to be bacterial contribution from farm animals and wildlife, density of OSSFs, density of households connected to public sewers, and land use distribution. [source] CONTROLLING PHOSPHORUS IN RUNOFF FROM LONG TERM DAIRY WASTE APPLICATION FIELDS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2004Anne M.S. McFarland ABSTRACT: Phosphorus (P) in runoff from long term animal waste application fields can contribute to accelerated eutrophication of surface waters. Manure when applied at nitrogen (N) agronomic rates generally increases soil P concentrations, which can increase runoff of soluble P. Along the North Bosque River in central Texas, dairy waste application fields are identified as the most controllable nonpoint source of soluble P in a total maximum daily load. To evaluate P reduction practices for fields high in soil extractable P, edge-of-field runoff was measured from paired plots of Coastal bermudagrass (Cynodon dactylon) and sorghum (Sorghum bicolor)/ winter wheat (Triticum spp.). Plots (about 0.4 ha) received manure at P agronomic rates following Texas permit guidelines and commercial N during the pretreatment period. During the post-treatment period, control plots continued to receive manure at P agronomic rates and commercial N. Treatment plots received only commercial N during the post-treatment period. Use of only commercial N on soils with high extractable P levels significantly decreased P loadings in edge-of-field runoff by at least 40 percent, but runoff concentrations sometimes increased. No notable changes in extractable soil P concentrations were observed after five years of monitoring due to drought conditions limiting forage uptake and removal. [source] Use of turbidometry to characterize suspended sediment and phosphorus fluxes in the Lake Tahoe basin, California, USAHYDROLOGICAL PROCESSES, Issue 3 2007Andrew P. Stubblefield Abstract The efficacy of in-stream nephelometric turbidometry as a surrogate for total suspended solids (TSS) and total phosphorus (TP) concentrations was evaluated for use in low turbidity (<50 NTU) subalpine watersheds at Lake Tahoe, California,Nevada, USA. Continuous turbidity records for the 1999, 2000 and 2001 snowmelt seasons and data from water quality samples (1982,2000) were examined to determine watershed sediment delivery dynamics. Strong correlations were found between turbidity and both TSS and TP concentration. The strong correlation indicates that turbidity can serve as a good surrogate for direct measurement in these watersheds. The watersheds displayed clockwise hysteresis: sediment flushing and depletion, on daily, seasonal and decadal time-scales. The hysteresis curves had strong concave shapes, indicating a sensitive response to peak flow. A pronounced seasonal trend was observed for the ratio of suspended sediment concentration (SSC)/discharge over time, indicating early season flushing of available sediment. Significant linear relationships (p < 0·05) were found for 12 of 17 years. Comparison of annual sediment rating curve coefficients indicated smaller coefficients during high sediment loading years and in the years following. The smaller coefficients are evidence of sediment depletion during high flow years. The effect of hysteresis on monitoring methods was illustrated by comparing turbidity estimates of TSS load with sediment rating curve estimates of SSC. After accounting for differences in SSC/TSS methods of analysis, daily loads calculated with turbidity methods were 58,98% of rating curve estimates for the spring snowmelt seasons of 1999,2001. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||