During rainfall events, the aquifers in Puerto Rico capture a small fraction of the rainfall and sometimes can store it for years. Organic pollutants are degraded over time by microbial and chemical processes. The shorter the travel time between raindrop and aquifer recharge the greater is the risk of contamination. Existing data from non-pumping observation wells have been used to identify three areas at risk from superficial contamination. Highrisk areas have a high correlation between

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... o-water and temperature or respond quickly to rainfall events. The high-risk areas are in Florida and in the adjoining municipality of Quebradrillas/Camuy and Manatí/Vega Baja. It is proposed that production wells in the high-risk areas be instrumented to measure the rainfall and the temperature and specific conductance of the pumped water and the rainwater. The hypothesis of this proposed experiment is that in the high-risk areas the water pumped from the production well will show a reduction of temperature and specific conductance within 24 hours of a heavy rainfall event. In this manner the travel time from rain drop to aquifer recharge can be measured. The proposed paper will provide concrete data to improve the management of groundwater resources in Puerto Rico.