Avaliação temporal e espacial da qualidade da água no lago da Usina Hidrelétrica de Miranda, região do Triângulo, Minas Gerais

Abstract

This work aims to evaluate in time and space the quality of the lake water of the Miranda hydroelectric power plant by means of physicochemical and bacteriologic analyses. The collections of samples were made in two distinct seasons of the year : dry and rainy in the years of 2003, 2004, 2005, 2006 and 2007. Results of the analyses indicated considerable variations in the biochemical demand of oxygen, of the chemical demand of oxygen, of the dissolved oxygen, of oils and grease, of total dissolved solid, of the transparency, of the turbidness and of the bacteria presence of the coliform group. The values of the samples were interpreted in function of the limits of acceptance established by the Resolut ion 357 of CONAMA (2005). To help in the understanding of the results of the physicochemical and bacteriologic analyses, the area of study was mapped in what concerns the usage and occupation of the lands. This mapping identif ied the presence of 70,55% of antropic usage, 26,77% of natural vegetation cover and 2,68% occupied by water bodies. The map with dist ribution of the Water Quality Indices (WQI) points out that the major varies f rom great (79< WQI<100) to regular (36< WQI<51). The evaluation of physical, chemical and biological variations of the water of Miranda Lake allied to techniques of geoprocessing, allowed a better knowledge of the envi ronmental condi tions of the study area, and the results obtained can be used as sources of primary data to promote the planning and local and regional envi ronmental gestalt.