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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Urban Ecology I
EFFECTS OF URBANIZATION ON WATER QUALITY IN THREE MERCER ISLAND DRAINAGE BASINS, KING COUNTY, WASHINGTON.
E.A. Ritzenthaler. King County Department of Natural Resources, Seattle, Washington, USA 98104
Mercer Island has implemented drainage basin improvement projects to control erosion in steep ravines and to minimize water quality degradation in the receiving waterbody, Lake Washington. Since 1999, King County's Water and Land Resources Division has provided technical assistance to evaluate acute water quality conditions in three basins. Water quality samples from storm events were analyzed for conventional parameters, metals, ten chlorinated herbicides, and seven organo-phosphorus pesticides. Excessively turbid stormflows have been quantified in each basin. Diazinon, 2,4-D, and MCPP have been found in each drainage. Diazinon has been seen as high as 0.332 ppb. Chlorpyrifos, MCPA, and dicamba have also been detected more than once. Three of the most common pollutants, 2,4-D, dicamba, and MCPP are routinely found in lawn care products. The highest levels and greatest variety of herbicides were found in the most residential basins. Drainage from the commercial district has exceeded the state's acute criteria for Copper and Zinc. Total Oil and Grease transport has been detected later in the fall than other pollutants. Benthic samples were collected annually during summer baseflows. BIBI scores of 14 to 18, some of the lowest in the County, further demonstrate the biological implications of poor water quality and urbanization.
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