WATER QUALITY ANALYSIS USING MULTI´-VARIATE STATISTICAL METHODOLOGY IN THE VELHA RESERVOIR (CEPTA/IBAMA/PIRASSUNUNGA/SP)

Abstract

Innumerable difficult questions appear during the planning, construction and post-construction phases of reservoirs which must be approached from an interdisciplinary perspective, with the sediment deposition process being particularly important. With the purpose of analyzing the limnological depositional behavior of a set of variables, this study was carried out during the years 1998 and 2000, in the “Velha” reservoir, the Center for Research and Management of Continental Fishing Resources (CEPTA/IBAMA), in the city of Pirassununga (SP). This dam supplies 128 tanks and fisheries for pisciculture, where 6 water sampling points were established; samples were collected in dry as well as the rainy seasons. Some water quality variables were determined in the samples collected. The data was submitted to the statistical multivariate method of cluster analysis demonstrating that in the dry season, the parameters behaved differently when compared to the same parameters in the rainy season. In the latter, although the number of groupings was the same as for the dry period, alterations in the nature of the grouped parameters were observed. Thus, the phosphate radicals and total phosphorus were directly related to the suspended material in the water of the reservoir studied in the dry season, while the same was not observed in the rainy season. The depositional effect in the rainy season was more disperse among the collection points compared to that verified in the dry period.