Uso do modelo qual2e no estudo da qualidade da água e da capacidade de autodepuração do Rio Araguari-AP (Amazônia)
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Data
2006-12-12
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Universidade Federal de Goiás
Resumo
The current investigation presents a characterization of the hydraulics and water
quality of the medium course of the Araguari River, State of Amapá, Brazil, which has an
approximate extension of 120 km. The Araguari River is the main water resource of the State of
Amapá, located in the domains of the Amazon (the greatest tropical forest of the planet) in a
region with great hydropower potential. In the studied river stretch, there is a hydropower
generation station called Coaracy Nunes (UHECN), the first barrage build in the Amazon for
electrical generation. A model for DO and BOD has been built with the help of the QUAL2E
modeling system, developed by the United States Environmental Protection Agency. For this
purpose, during one and a half year, field trips have been conducted with the intent of
characterizing spacially and seasonally the hydraulics, kinetics and water quality of the Araguari
River. The modeling stages involved model construction, sensitivity analisys and calibration.
After model calibration, three hypothetic cenarios were simulated: (1) the introduction of a new
barrage upstream of the UHECN; (2) municipal untreated wastewater inflow from Porto Grande
and Ferreira Gomes into the waterbody, including populational growth, during the high flow
period; (3) the same cenario as before but during the low flow period. The carbonaceous organic
matter present in water hás shown to decompose, in average, in the first five days of incubation.
The values obtained for the BOD first order reaction coefficient layed between 0,13 d-1 and 0,90
d-1. The reaeration coefficient, K2, estimated based on hydraulic characteristics, layed between
0,01 d-1 and 1,40 d-1. The results of the sample collections in the river stretch has shown that,
amongst the parameters measured, the following were mostly altered: pH, electric conductivity,
total solids, suspended solids, fecal coliforms, ammonium, nitrate, BOD and DO. Fecal
coliforms, pH, nitrate and BOD were in disagreement with limits defined by Brazilian Legislation
on water quality (CONAMA 357/2005). The river impoundment has shown not to significantly
alter the DO and BOD concentrations, however, the same statement can not be made for other
water characteristics. The water characteristics mostly altered by the UHECN were: hydraulic
(flow, velocity, breadth, cross-sectional area) and water quality (pH, electric conductivity, water
temperature, total solids, suspended solids, fecal coliforms, nitrate, chloride, BOD and DO). The
simulated scenario with municipal untreated wastewater inflow from Porto Grande and Ferreira
Gomes (including population growth) into the waterbody during low flow period showed the
most critical results in terms of the water quality. The worst simulated situation happened in the
dry period in which the river flows decreased significantly and so did the river dilution capacity.
In this period the greatest OD depletion occurred and achieved concentrations bellow 4.0 mg/L,
in disagreement with Brazilian Water Quality Legislation (CONAMA 357/2005).
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BÁRBARA, Viníciu Fagundes. Using the model QUAL2E in the study of water quality and self-purification capacity of Rio Araguari-AP (Amazon). 2006. 174 f. Dissertação (Mestrado em Engenharias) - Universidade Federal de Goiás, Goiânia, 2006.