FLOW-INTEGRATED LOAD REDUCTION ESTIMATION TECHNIQUE FOR TMDLS
Abstract:The New Jersey Department of Environmental Protection (Department) has developed an analytical technique that uses instantaneous measurements, or grab samples, to estimate load reductions for TMDLs (Total Maximum Daily Loads). This technique, less complex than most load reduction models, uses linear regression to develop a flow-integrated relationship between measured pollutant loadings and the associated flows at a single monitoring site. The method, known as the Flow-Integrated Reduction of Exceedances (FIRE), provides an accurate estimation of the load capacity that will not cause an exceedance of the water quality standard while remaining relatively simple to use. Point source loadings and the associated load allocations should not be assessed with this method. However, non-point loadings stemming from agricultural and residential land uses, and other non-point sources that can be controlled with structural or non-structural best management practices (BMPs) are appropriate for analysis with this technique. Since most BMPs for nutrients have a wide range of removal efficiencies, a complex modeling technique to determine loading reductions would likely not provide a more effective result for implementation of the TMDL than a less-sophisticated approach such as FIRE.
The U.S. Environmental Protection Agency has approved the flow-integrated method. The Department has applied this technique to develop three TMDLs for total phosphorus and is considering expanding its use for other water quality parameters, including metals, when applicable.
This report presents the setup and application of the flow-integrated method, and comparison to the PLOAD model, and to the Load Duration and geometric average methods. Results of estimated load reductions from the PLOAD, Load-Duration, and statistical applications were up to 81, 124, and 53 percent greater than the flow-integrated technique, respectively. When loading reduction estimates using the FIRE method were applied to the measured exceedances, resulting loadings were all within the loading target to attain the water quality standard.
Document Type: Research Article
Publication date: January 1, 2005
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