Evolution of erosive and hydrodynamic impacts on water quality in tidal
channels at the mouths of the Araguari and Amazon rivers
Abstract
An intense erosive process has recently caused progressive
hydrogeomorphological changes in the mouths of two large rivers
belonging to the Amazon River Delta, on the estuarine coast of Amapá
State, namely: Araguari and Amazonas. Consequently, Araguari River was
captured by the Amazon River and it influenced the sediment and water
quality dynamics when two tidal channels expanded in opposite
directions; this process affected both hydrographic basins and blocked
Araguari River mouth. The aim of the current study is to analyze the
space-seasonal variations of hydrodynamic and water quality parameters
influenced by the following factors: location (channels connected to
Araguari and Amazonas rivers), seasonality (dry/rainy) and spring tidal
phase (flood/ebb). The herein adopted methodological stages comprised a)
flow measurement with Doppler current profiler; b) water sampling
(physicochemical and suspended sediments); c) suspended solids transport
estimates; and d) multivariate statistical analysis of parameters.
Results have indicated significant space-seasonal variation in these
parameters (p<0.05). Water balance in the dry period has shown
that Urucurituba Channel absorbs 100% of Araguari River flow,
distributes 29% of it in the floodplain and discharges 71% of Araguari
River flow into the Amazon River. This channel received 86% of Araguari
River flow and absorbed 14% of the flow deriving from the floodplain in
the rainy season, which totaled 100% of its flow at Amazon River mouth-
solid discharge was proportional to 107,982 t of tidal cycle-1.
Multivariate analyses have shown significant variations in 90% of the
investigated parameters, which were influenced by such as location,
seasonality and tidal phase (p<0.05). It was possible
concluding that the recent channels have significantly affected the
hydrodynamics, sediment transport processes and water quality of both
basins. This phenomenon is currently in intense and irreversible
hydrogeomorphological evolution, and it mainly affects the Araguari
River estuary