QUALIDADE DA ÁGUA SUPERFICIAL DA BACIA HIDROGRÁFICA DA LAGOA MIRIM.

O presente trabalho foi realizado no estado de Rio Grande do Sul e teve por objetivo avaliar a qualidade das águas dos principais afluentes da Lagoa Mirim entre os anos de 1996 e 1998, utilizando-se o Índice de Qualidade de Água de Bascarán (IQAb). Como resultados finais, verificou-se que a qualidade hídrica dos afluentes da Lagoa Mirim avaliados foi, no geral, aceitável, tendo como poluente mais impactante em relação à qualidade das águas o fósforo. Além disso, o índice refletiu a realidade ambiental verificada na região, onde é realizada a agricultura intensiva e o lançamento de grande parte dos efluentes domésticos e industriais sem prévio tratamento nos mananciais. Palavras-chave: Índice de Qualidade de Água; Bascarán; monitoramento; rios ABSTRACT Superficial Water Quality of the watershed of the Mirim lake. This study was conducted in the state of Rio Grande of Sul, and had as its objective to evaluate the water quality of the principal tributaries of the Mirim Lake between the years 1996 and 1998, using the Quality Water Index of Bascarán (IQAb). As final results, it was found that the quality of the water of the tributaries of the Mirim Lake was in general acceptable with and the most impressive pollutant regarding the water quality was phosphorus. Moreover, the index reflected the environmental reality found in the region, which has intensive agriculture, and the release of most household and industrial waste without prior treatment in the springs. Key words: Water Quality Index, Bascarán, monitoring, river

Trophic state of water in the watershed of Lake Mirim, RS, Brazil

The objective of this work was to analyze the spacetime variations in the trophic characteristics of the principal water bodies feeding Lake Mirim, in the state of Rio Grande do Sul, by determination of the Trophic State Index proposed by Toledo Jr. (IETT) and Lamparelli (IETL), to assess water quality data between 1996 and 1998. It was verified that the lotic environments presented greater eutrophication conditions when evaluated by the Toledo Jr. methodology, in which the IETT varied from Eutrophic to Hypereutrophic. However, the evaluated environments showed variations from Mesotrophic to Hypereutrophic for the IETL when evaluated according to the Lamparelli methodology. From the classification proposed by Toledo Jr., lentic water bodies were considered Mesotrophic (IETT > 44) and Hypereutrophic (IETT > 74), while the Lamparelli method classified them as Eutrophic (IETL > 59) and Hypereutrophic (IETL > 67). Concentrations of phosphorus encountered in all water samples were greater than the limits established by the CONAMA Resolution n. 357, 2005, for class 2 water bodies, probably due to the discharge of untreated domestic and industrial wastes into the waters