The highest removal efficiency rates of water (mainly
mass removal) occurred in the dry season. The concentrations
and mass loading rates of the majority of the
inlet metals were higher during the rainy season than
those during the dry season. As the mass loading rates
account for the quantify effect of water in which the
metal is in solution, the measure of mass removal is
more accurate than the concentration removal (Kadlec
and Wallace 2009). Therefore, additional loading from
runoff and other sources such as rain may have reduced
the removal efficiencies during the rainy season by
increasing the HLR. It is likely that the higher detention
time in the dry season increased the metal removal
of the water because it allowed for longer contact
between the water, sediment, and macrophytes and
promoted metal retention by precipitation and
sedimentation..