Sandbar Regulated Hydrodynamic Influences On Hydrochemistry Of Mengabang Telipot Estuary, Peninsular Malaysia

Abstract

Influences of river and groundwater hydrodynamic behaviours (water level, flow velocity and flow rate) on hydrochemistry (salinity, pH, dissolved oxygen (DO) saturations and dissolved phosphate (DP)) were evaluated through high spatial and temporal resolution study at sandbar-regulated Mengabang Telipot estuary. River and groundwater levels were measured using stick gauge and pressure transducer sensor. River flow velocity was measured using Valeport flow meter. River flow rate was calculated from stage-area curve. River and groundwater were sampled sub-daily at high tide and low tide. Salinity, pH and DO were measured in-situ using YSI Multi-parameter probe. DP was determined using ascorbic acid method.

River hydrodynamic during sandbar closed event was characterized by minor dependency on tidal fluctuations, gradual increase of water level, continual low flow velocity and flow rate. These hydrodynamic behaviours established a hydrochemistry equilibrium, in which water properties generally were characterized by virtual absence of horizontal gradients while vertical stratifications were significant. In addition, the river was in high trophic status as algae blooms were visible. Conversely, river hydrodynamic in sandbar opened event was tidal-controlled and showed higher flow velocity. Horizontal gradients of water properties became significant while vertically more homogenised and with lower trophic status. Groundwater hydrodynamic during sandbar closed event was less controlled by tides and the water level gradually increased through time. On the contrary, groundwater level during sandbar opened event was tide controlled.