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Addressing Infrequent, Brief, and Small Excursions of Water Quality

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Watershed ManWatershed Management to Meet Water Quality Standards and TMDLS (Total Maximum Daily Load) Proceedings of the 10-14 March 2007, San Antonio, Texas  701P0207.(doi:10.13031/2013.22435)
Authors:   George G Ice, Jay P Unwin, Timothy J Hall, Paul Wiegand, Douglas B McLaughlin
Keywords:   criteria, dissolved oxygen, forest, sediment, standard, temperature, water quality, watershed

Water resource managers must assess how variations in water quality impact designated uses. If streams are listed as water-quality impaired when they experience natural or very modest excursions from listed water quality criteria then there is a dilution of resources directed at streams that are legitimately listed. Here we discuss infrequent, brief, and small excursions to water quality criteria and how some states are trying to factor minor or natural water quality excursions into assessments. We further discuss water quality variability in time, space, and scale, and how this variability affects the biological response of organisms. This review shows that frequency, duration, and extent of water quality exceedances all combine to influence biological responses. Many aquatic organisms are adapted to avoid or tolerate infrequent, short-duration, and minor excursions. Recognizing when and where excursions from water quality criteria will have minor biological and/or designated use impacts allows water resource managers to focus on more serious water quality problems.

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