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SAMPLING DESIGN FOR ASSESSING RECREATIONAL WATER QUALITY
Citation:
Wymer, L J. SAMPLING DESIGN FOR ASSESSING RECREATIONAL WATER QUALITY. Presented at The International Environmetrics Society Conference 2001, Portland, OR, August 13-17, 2001.
Impact/Purpose:
Develop new bathing beach monitoring protocols and new approaches for communicating risks associated with swimming and other recreational water activities.
Description:
Current U.S. EPA guidelines for monitoring recreatoinal water quality refer to the geometric mean density of indicator organisms, enterococci and E. coli in marine and fresh water, respectively, from at least five samples collected over a four-week period. In order to expand this guidance to account for spatial and temporal variation in the contamination of bathing waters, sampling studies were conducted at five marine and freshwater beaches during the summer of 2000, these studies invovling twice-a-day, and sometimes hourly, sampling at several locations in the water at each beach. Implications for a sampling design for monitoring warer quality are examined, considering factors such as sample volume, number of locations sampled, and the compositing of samples. Variance components are estimated, and operating characteristic curves for sampling schemes designed to detect alternative in excess of some standard level of microbial contamination are constructed via generalized linear modeling and bootstrapping on the results from these studies. Principles of sampling design developed from these five bathing areas, all of which were limited to a fixed length of beach, may be adapted to varying stretches of beaches through consideration of spatial relationships of variation among sampling locations.