Water Resources Research Act Program

Principal Investigators: Dr. Yuming Wen

Abstract: Guam is the largest (about 541.3 km2) and southernmost member of the Mariana Islands chain. It currently supports a local population of around 170,000 and receives over 1.5 million tourists annually. The relocation of around 5000 marines and their dependents in the next few years, and foreign labors hired to assist with buildup activities will impose impacts on water quantity and water quality in Guam. Groundwater from a karst limestone aquifer in the northern Guam supplies local residents and tourists with approximately 90% of their daily water needs. While estimates of the aquifer’s sustainable water resources remain adequate for the current population, there is serious concern that the projected population increase will severely compromise the island’s drinking water supplies and have an unprecedented impact on water quality and quantity. The high porosity and rapid recharge characteristics of the northern Guam lens aquifer make it vulnerable to contamination from urban runoff, chemical spills, effluents from septic tanks and sewage overflows. Guam Waterworks Authority (GWA) is in charge of Guam’s public water supply and ensures that it meets all appropriate standards as mandated under the Safe Drinking Water Act and Clean Water Act. While the agency has collected a considerable amount of monitoring data over the years, only values that approach or exceed the water quality standards are paid attention. Most of the data fall well below critical thresholds of concern and is paid little attention. However, these data may be useful for evaluation of changes of contaminants for a long term basis. Since groundwater in the Northern Guam Lens Aquifer (NGLA) supplies local residents and tourists with about 90% daily water use, it’s absolutely necessary to set up groundwater protection zones (GPZs) and make sure that water quality can be maintained so that the daily life of the people of the island will not be affected. The main purpose of the project will focus on a better way to create GPZs, particularly GPZs located in the parabasal zone in the NGLA.