Groundwater processes in a sandbar-regulated estuary, Mengabang Telipot, Peninsular Malaysia

A study of groundwater processes in a sandbar-regulated estuary has been conducted at Mengabang Telipot, located in Terengganu State, Peninsular Malaysia. Beach groundwater level, salinity and dissolved phosphate (PO4 3-) were investigated at high spatial and temporal resolutions. Establishment of distinctive hydrodynamic characteristics in the beach groundwater system were observed as the mouth of the estuary varied between an open sea connection and closure resulting from sandbar development. Sandbar and tidal dynamics regulate the interactions between beach groundwater, estuary and sea. When the estuary was closed, intertidal activities had minor effects on groundwater level. The groundwater level increased through time due to rainfall infiltration and seepage from barrier bar and inland sand ridges. When the sandbar opened, the beach groundwater level was tidally-controlled and the interactions between groundwater, estuary and sea were dependent on the tidal-induced hydraulic gradient. Hydraulic head difference between the beach groundwater system and the inland water table aquifer, which was controlled by the closing and opening of the estuary, strongly influenced salinity and PO4 3distributions. High PO4 3concentrations in beach groundwater was attributed to density-driven circulation and low seepage velocity.