Transport of Cryptosporidium and Giardia in Massachusetts Watersheds During Storm Events

It is widely known that micro-organisms such as bacteria (for example, E. coli), Giardia (often associated with beaver), and Cryptosporidium (sometimes associated with pets, livestock, and wildlife) can enter streams during rain and snowmelt events. It is difficult, however, to accurately determine the magnitude and timing of transport during such events. In addition, accurately identifying the sources of these contaminants is a challenge. Hence, the organizations responsible for public water supplies, outdoor recreation, and environmental quality face substantial challenges in their efforts to protect public health. Microbial and water-quality measurements were collected during storm events under a variety of meteorological and land-use conditions in order to 1) identify risk of Cryptosporidium oocysts, Giardia cysts and other constituents, including microbial indicator organisms, entering surface waters from various land uses during periods of surface runoff; and 2) optimize storm sampling procedures for these parameters. The resulting database consists of wet weather transport data for twenty-one distinct storm events and three dry weather spatial basin sampling events. Insights gained on the prevalence and transport characteristics of the monitored parameters are discussed.