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.
