Evolução do índice de qualidade da água ao longo do córrego São João, Tocantins, para os anos de 2004 e 2005.

Abstract

The São João river, bound for Porto Nacional and Palmas, in the State of Tocantins, receives contribuition from agricultural, cattle and urban uses (the latter in a lower scale). Two series of Water Quality Index (WQI) were measured along the river, for the years of 2004 and 2005. WQI values are highly sensitive to circumstances, which produces low correlation between time series (charts 1 and 2). Eventhoug, spacial series are highly correlated, with r² over 90%. It is understood that frequency of sampling is more important than spacial coverage if the intention is to track water quality in the São João river using the WQI.