#ralph lago

 Keywords: Langelier Saturation Index (LSI), groundwater, corrosion, pH, carbonate

by Ralph Lago1, Gerna Manatad2, Plormelinda Olet3,  Raymond Sucgang4, Jayvee Villagracia5 The application of isotope techniques in assessment of available freshwater resources in the shallow aquifer of San Narciso, Zambales was found to be practical and useful in the formulation of policies and in providing the scientific data for incorporation in the Comprehensive Land Use Plan of the province. Five scholars from the Middle Managers Class Batch 14 of the Development Academy of the Philippines  conducted a hydrological study in the Zambales basin. The study aims to determine the rate and mechanism of recharge, determine the vulnerability of the aquifer to pollution and establish base line data on the water quality parameters set forth by the Philippine National Standards for Drinking Water (PNSDW). Groundwater samples from deep wells, hand pumps and dug wells, and river water were collected within the study area from July 5, 2017 to July 7, 2017. At least 72% of the shallow wells in San Narciso were found to have total coliform plate counts of more than 1.1 MPN/100 mL. Wells in Siminublan showed iron (Fe) concentrations ranging from 3.2 ±0.2 ppm to 5.4±0.2 ppm which exceeded the limits set forth by the PNSDW. Organic Chemical Constituents (pesticides) of 2.0 ± 0.1 was observed in a well in Grullo (51 masl) Samples were analyzed for stable isotopes (δ2H and δ18O) using Laser Water Isotope Analyzer. In addition, estimation of mean residence time or groundwater age were done on some wells in Paite, La Paz, Dalipawen, Grullo, Siminublan, and Manatakan, using tritium-helium dating technique. Stable isotope values of groundwater from shallow and deep wells in the La Paz, Paite, Dalipawen, Siminublan, Grullo, and Manatakan laid within the Global meteoric water line (GMWL) and the Philippine meteoric water line (PMWL) which indicate that majority of the aquifers were being recharged locally by rain water. Water samples from shallow wells in La Paz were relatively more isotopically enriched as compared to majority of the wells. Chemical analysis of groundwater in San Narciso indicate a Ca-Mg-HCO3 water type which is a typical characteristic of groundwater with short mean residence time. The major source of active recharge to the San Narciso basin is rainfall. Recharge or infiltration of modern water to the groundwater happens mostly during the months of July to August, during the months of high waterlogging. Keywords: Water Resources Region 2, water stable isotopes, groundwater, mean residence time, groundwater age, groundwater chemistry, recharge, aquifer 1. Philippine Drug Enforcement Agency (PDEA). 2. Department of Health (DOH) 3. National Intelligence Coordinating Agency (NICA) 4. Philippine Nuclear Research Institute (PNRI) 5. Commission on Elections (COMELEC)