Water Resources Research Act Program

Details for Project ID 2020GU275B

Geospatial-temporal Analysis of Patterns and Trends of Salinity in Finegayan

Institute: Guam
Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $13,524 Total Non-Federal Funds: Not available

Principal Investigators: Dr. Yuming Wen

Abstract: Guam, a strategic U.S. territory in the western Pacific, 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 attracts over 1.5 million tourists annually. About 5000 marines will be relocated to Guam from Okinawa in the next few years. With the marines and their dependents moving to Guam, and the importation of foreign labor to assist with the buildup activities and infrastructure needs of the military, the island’s population is expected to soar in the next few years. Groundwater from a karst limestone aquifer in the northern Guam currently 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 especially susceptible to contamination from urban runoff, chemical spills, effluents from septic tanks and sewage overflows. Guam Waterworks Authority (GWA) is the custodian of Guam’s public water supply and is responsible for ensuring that it meets all appropriate standards as mandated under the Safe Drinking Water Act and Clean Water Act of US EPA. To this end, GWA regularly evaluates the physical, chemical and biological integrity of the island’s drinking water in accordance with US EPA requirements. While the agency has maintained a considerable amount of monitoring data over the years, only values that approach or exceed the water quality standards are paid attention. The rest, which account for well over 99% of all monitoring data collected so far, falls well below critical thresholds of concern and is of little immediate interest or attention. As a consequence, these data are simply stored on file for reference purposes. They are just paid attention only when they need be used to identify subtle changes in contaminant abundances and distributions within the aquifer or changes for a long term basis. Because of projected increase of population, and relocation of around 5000 marines from Okinawa to Gaum in the next few years, water quantity and quality, particularly groundwater quantity and quality will be crucial to the sustainable development of resources and environment in Guam. Since the Finegayan area will be involved in lots of buildup activities due to relocation of marines, it’s very important to evaluate whether the related activities will affect the quantity and quality of the water resources, especially groundwater resources. Concerning water quality problems in the northern Guam lens aquifer (NGLA), salinity is of serious consideration. Based on this concern, the project will focus on salinity problem in Finegayan. The foci of the project will aim to evaluate the patterns of salinity levels from individual wells and all wells in the basin in space and over time, and to analyze the trends of salinity change of individual wells and overall trends of salinity in the basin spatially and temporally.