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.