The purpose of this research is to evaluate the quality of the surface water of the Curuá river, classifying it according to the Resolution No. 357/05 of CONAMA and the Ordinance No. 518 of the Ministry of Health and to demonstrate the behavior of some meteorological variables and their influence on the functioning of this aquatic system. This research is being developed in the scope of the projects "Integration of approaches to environment, land use and social dynamics in the Amazon: human-environment relations and the challenge of sustainability - MillenniumLBA2 - subproject Aquatic Biogeochemistry" and "Study of riverine environment in the Eastern Amazon: hydro geochemical, climatic and plant physiology implications - PRONEX". The study region belongs to the Caxiuanã National Forest, municipality of Melgaço, Pará, where the Ferreira Penna Scientific Station (ECFPn) is located. Samples were manually collected at a depth of 0.30 m from January 2006 at six points in the Curuá River, one in the Caxiuanã Bay, one in the Caxiuanã River and one point at the ECFPn. Analyses were made of chloride (CI-1), alkalinity, calcium (Ca+2), magnesium (Mg+2), sodium (Na+1) and potassium (K+1), measured the parameters of temperature and pH, electrical conductivity, dissolved oxygen and wind speed. The average value of electrical conductivity is 17.8 i S . c m", The pH values obtained are predominantly acidic, mainly in the Curuá River. Dissolved oxygen reaches up to 90% saturation in the bay due to the action of the winds. The mean values of ions are higher in the ECFPn water supply samples (1.24 mg.L-1 Na+; 0.38 rnç.t,:' K+; 0.24 mç.L' Ca +2; 1.07 rnq. L' Mg+2; 3.53 rnq.L" Cj-), whose limits for color 15 (mgPt/Co) and turbidity (1.0 uT) were not exceeded, presenting color ° mgPt/Co and turbidity less than 0.84 uT. The waters of the Curuá River are sodic with a slight influence of magnesian calcitic waters and belong to the special class described in the 2005 CONAMA resolution No. 357.
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