Factors influencing groundwater sources under the direct influence of surface waters

The objective of this study was to identify preliminary and other factors that could be used to screen surface waters before embarking on the expensive laboratory procedure. In order to determine which public water systems that are groundwater under the direct influence (GWUDI), a total of 62 wells at public water supplies suspected of being GWUDI were investigated. The wells sampled were distributed across seven counties in the Central Florida region. Water samples were collected and analyzed at the Department of Health Laboratory in Tampa, Florida using the Microscopic Particulate Analysis (MPA). The study investigated the well and hydrogeologic characteristics, and land use within the vicinity of the well locations. The results showed that 13% of the wells sampled were in the high-risk range while 29% and 58% of the wells sampled were within the moderate and low risk ranges, respectively. It was also observed that some well characteristics and the hydrogeology of an area generally influence the MPA risk index. Karst regions were observed to be susceptible to a higher risk than sandy areas. The results also suggested that older wells tend to have higher risk index.