Evolução da eutrofização em uma represa nordestina de recente formação. Represa São Salvador - Sapé-PB.

Abstract

This work aimed the evaluation of sanitary aspects of water quality in the horizontal and vertical compartments of Sao Salvador reservoir, located in the municipal district of Sape (7°06'S; 35°14'5"W) state of Paralba and inserted in the micro region of the Agreste. Also compared this data with the existent in the order to evaluate the evolution of the dam trophic state, in three different climatic times. The analyzed data comprised the period of January of 1996 to July of 1998, inserted in different climatic times according to the precipitations. The periods were divided in three rainy season (Rain 1, Rain 2 and Rain 3) and two dry seasons (Dry 1 and Dry 2). The 7 points studied in the horizontal compartments (4 in the margins and 3 in the center of the dams) were analyzed in the Rain 1 (C1), Dry 1 (S1) and Dry 2 (S2). A grouping analysis using the software SPSS 8.0 for Windows was carried out to accompany the progress of eutrophication in the horizontal compartments. The results showed an alternative of water quality in those points near the entrance of the main tributary, the Sao Salvador stream, belonging to the Inferior Basin of the Paralba river which receives the influence of the final effluent of the Sape Wastewater Treatment Plant, with low efficiency for the removal of pathogens, organic material and suspend solids, contributing to tie dam water quality deterioration. Two indexes for trophic classification were used: modified Carlson index, which classified the dam as eutrophic in the dry season and as eu-hipereutrophic in the rainy season and the adapted Carlson index, which classified the dam as meso-eutrophic in the dry season and as eutrophic in the rainy season. It was also used the classification proposed by OECD (which uses limits values for the trophic classification) and this dam was considered as meso-eutrophic in the Dry Season 1 and went to eutrophic in Rain 1 reaching hipereutrophic level in the Dry Season 2. According to the CONAMA 20/86 classification the dam water Class 3 being suitable for human consumption after conventional treatment. These waters were classified as inappropriate for bathing due to the several human activities developed in the margins. The study of the submerged macrophyte Elodea canadensis in the deterioration of water quality in RS6 while in RS1, presented the best water quality because was better protected from the polluted pulses originated from of the margins.