Publisher's Synopsis
Threats from pathogens such as Cryptosporidium and Giardia are difficult to protect against, particularly without a clear understanding of the variability of pathogen occurrence in space and time. A majority of data collected to date on pathogen occurrence in surface waters has concentrated on characterization of levels under average conditions. Data are lacking on pathogen variability in sub-basins characterized by different pathogen sources, during and following events such as rainfall, or following land use change.