Title: Modeling Water Quality Impacts of Stormwater Runoff. Why Hydrologic Models Aren't Sufficient
Abstract: Although hydrology-based stormwater runoff models are often used to estimate total concentrations of chemical contaminants at a particular location in runoff and receiving waters, this paper argues that the results from these models do not properly assess water quality impacts. An evaluation monitoring approach is proposed to more reliably evaluate the water quality impacts of pollutants in runoff/discharges. This approach focuses monitoring on chemical impacts rather than on chemical concentrations. If toxicity is found in laboratory tests of an effluent or receiving water, an assessment is made as to whether such toxicity is manifested in the water of concern and whether that toxicity significantly adversely affects the water body's beneficial uses. It should not be assumed that toxicity measured in a standard laboratory toxicity test necessarily translates to toxicity that is significantly altering the numbers, types, or characteristics of desirable forms of aquatic life in a water body. This is especially true for situations such as urban-area and highway stormwater runoff, where there can be short-term pulses of contaminants associated with runoff events that are not of sufficient magnitude and duration to exceed the critical magnitude. In the evaluation monitoring studies conducted, samples of stormwater runoff were collected from 10 watersheds covering urban, highway, and agricultural areas. The studies showed that stormwater runoff from urban areas and highways frequently contained heavy metals in concentrations above EPA water quality criteria. They also showed that that runoff was toxic to the zooplankton, Ceriodaphnia. Toxicity identification evaluations involving the addition of ethylene diamine tetra acetic acid to the toxicity tests to render copper and other heavy metals non-toxic, however, revealed that the toxicity was not due to heavy metals. Rather, the toxicity was due to pesticides used in the watersheds studied. These studies demonstrate the appropriateness of using the evaluation monitoring approach to evaluate the potential water quality impacts of stormwater runoff-associated potential pollutants.
Publication Year: 2008
Publication Date: 2008-02-01
Language: en
Type: article
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Cited By Count: 2
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