| Abstract |
The use of Chlorofluorocarbon (CFC) tracing technique in Dumaguete City provided significant information on the groundwater flow dynamics of the Okoy and Banica watersheds. Water district wells 54 and 55, located east of the Palinpinon thermal area, are tapping groundwater with 11% to 80% recent recharge aging from 10 to 36 years old, respectively. Towards the southeast in the area of well 47, the groundwater becomes older than 60 years old. CFC and geochemical data confirmed that the wells within 54 are hydrologically connected to the River waters of both Okoy and Banica while the wells to the south are recharged from a different location on the upper slope of the Banica watershed. Results of the initial application of the CFC technique in the Mt. Apo (MGPF) and Southern Negros Geothermal Production Field (SNGPF) suggest that there is about 7 to 42% recent groundwater recharge into the geothermal reservoirs having ages of 28 to 39 years old, respectively. The groundwater in the wells affected by injection fluid returns and cool water inflows were quantified using CFC data, which was correlated with existing geochemical, hydrological and stable isotope data. Based on initial results, 7% of the reservoir water at SNGPF is recent recharge while 19% comprise the recent recharge in the geothermal reservoir of MGPF. Further enhancement of data interpretation will provide more significant information that could be used as tool in reservoir management. |