Assessment of groundwater under direct influence of surface water.

Waterborne pathogens are known to reside in surface water systems throughout the U.S. Cryptosporidium outbreaks over recent years are the result of drinking water supplied from such sources. Contamination of aquifers has also led to several reported cases from drinking water wells. With high resistance to typical groundwater treatment procedures, aquifer infiltration by Cryptosporidium poses a serious threat. As groundwater wells are the main source of drinking water supply in the State of Florida, understanding factors that affect the presence of Cryptosporidium would prevent future outbreaks. This study examines karst geology, land use, and hydrogeology in the State of Florida as they influence the risk of groundwater contamination. Microscopic Particulate Analysis (MPA) sampling was performed on 719 wells distributed across Florida. The results of the sampling described each well as having high, moderate, or low risk to surface water influence. The results of this study indicated that the hydrogeology of an area tends to influence the MPA Risk Index (RI) of a well. Certain geologic formations were present for the majority of the high risk wells. Residential land use contained nearly half of the wells sampled. The results also suggested that areas more prone to sinkhole development are likely to contain wells with a positive RI.