Bulletin of the Geological Society of Malaysia, No. 66, December 2018, pp. 39 – 46

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

Mei Kee Koh1, Edlic Sathiamurthy2,* & Peter Robertson Parham3,4,5

1Institute of Oceanography and Environment, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Malaysia
2School of Marine and Environmental Sciences, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Malaysia
3Earth Observatory of Singapore, Nanyang Technological University, Singapore
4Southeast Asia Disaster Prevention Research Initiative (SEADPRI), Univ. Kebangsaan Malaysia, 43600 Bangi, Malaysia
5 Centre of Tropical Geoengineering, Universiti Teknologi Malaysia
*Corresponding author email address: edlic@umt.edu.my

Abstract: 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 PO₄^3- distributions. High PO₄^3- concentrations in beach groundwater was attributed to density-driven circulation and low seepage velocity.

Keywords: sandbar-regulated estuary, groundwater monitoring, groundwater/surface-water relations, fresh-saline water interface, density-driven circulation

https://doi.org/10.7186/bgsm66201806