Influence of cattle ranching and agricultural activities on physical chemical parameters of water.

Water Quality Index (WQI) was used during summer and winter of 1994 and 1995 in the final section of Onca and Feijao streams, downstream Broa Reservoir (Sao Carlos/SP) to evaluate agricultural and catlleman effects. In Onca stream water quality was "acceptable" in winter and "inappropriate to conventional treatment" in the summer. In Feijao stream the water had an "excellent" quality in winter and "good" in the summer. A MANOVA (Multivariate Analysis of Variance) has used to discriminate seasons and streams. Correlation (p<0,05) among the variables was tested. Water temperature, turbidity, pH and fecal bacteria are highly correlated and can be one of the factors that cause WQI change hy seasons.