Salinity behavior and intrusion in Kelantan River Estuary.

Abstract

An estuary is a unique environment influenced by tidal and freshwater mixing. Saltwater intrusion during the wet season is less studied in Kelantan River despite occasional flooding from high tides. Thus, this study presents one month’s water level measurements at three locations and two days horizontal, vertical and longitudinal salinity profile measurements at seven cross-sections along approximately 11 km upstream of the Kelantan River estuary. Salinity measurements were taken using the YSI Water Quality meter by moving boat method before the North-East Monsoon in October 2015. The maximum tidal range computed from water level data is around 1.32 m on average and can be classified as microtide, characterised by delta formation from upland discharged sediments. The vertical salinity profile was measured every 0.5 m water depth and the inflexion point where mixing starts to occur increases from around 2 m at the river mouth to 4.5 m at 8.3 km upstream. The longitudinal salinity structure indicates Kelantan estuary as salt wedge maximum saltwater intrusion around 9 km upstream. The data provides a preliminary understanding of longitudinal and vertical salinity structure. During wet and dry seasons, higher or lower river discharge may alter the mixing process and saltwater intrusion length.