NUMERICAL SIMULATION ON FORMATION OF FRESH WATER LENS IN ATOLL ISLANDS

Abstract

 Atoll islands has resources of fresh water under the ground which called freshwater lens. Freshwater lens has been used traditionally by residents of island, however, the rapid urbanization and salinitation changed the freshwater lens as unusable resources. this study conducted that the numerical simulation on formation of freshwater lens forcused on the width of island, recharge rate and influence of tidal change of water surface. the results revealed that the volume of freshwater lens increase with direct proportion by recharge rate. Additionally the volume of freshwater lens increased exponentionally by width of island. It was estimated that the potential volume of freshwater lens formed Fongafale island of Funafuti atoll provides residents resource of freshwater for 40 to 90 years. Tidal change influenced to salinity concentrtion and shape of the edge of freshwater lens but the influence is locally.