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Fluxes of suspended sediment, phosphorus and silicate in the Chao Phraya River at the
Pak Kret and Bang Sai Transects showed spatial and seasonal variations. They were mostly
transported towards the lower river during high discharge [Period 1] condition and back
transported during some tidal cycles during low discharge [Period 2] condition. The daily
net material fluxes changed both in magnitude and direction depending on the influences of
tidal currents and daily concentration of materials in the river. Variability in the
annual regime of material fluxes of suspended sediment, total phosphorus, and particulate
phosphorus corresponded to the flow patterns. The patterns of dissolved flux of phosphate
phosphorus and silicate depended on the interaction of solute and the flow regime of the
river. In the region of 0-18 % part of the river, dissolved phosphorus fluxes was removed
by phosphorus absorption onto the bottom sediment and river-borne suspended sediment, in
the region above 18% phosphorus was transported in the river conservatively. The behavior
of dissolved silicate was mostly conservative while the fluxes varied and were modified by
the influence of discharge. The annual mean of net transport during December 1987 to
December 1988 through the lower basin of the Chao Phraya River of discharge, suspended
sediment ,total phosphorus, particulate phosphorus, dissolved phosphorous and dissolved
silicate were 155 x 108 m3 yr-1, 1,566 x 103 tons yr-1 , 3.13 x 103 tons yr-1, 2.49 x 103
tons yr-1, 0.63 x 103 tons yr-1 and 69.48 x 103 tons yr-1 respectively.
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