Qualidade da água em rios urbanos de Ouro Preto, MG

Abstract

This study investigated the interrelationship between physical characteristics and the environmental condition of urban watercourses in the Rio do Carmo basin, in Ouro Preto/MG. The research quantified the runoff dynamics of 189 channels through the analysis of linear morphometric parameters (bifurcation ratio, channel length, overland flow length, and channel gradient), aerial parameters (basin area, basin length, basin shape, stream and drainage density, and maintenance coefficient), and relief parameters (relief ratio, ruggedness index, and sinuosity index), which are fundamental for characterizing regional hydrological behavior (CHRISTOFOLETTI, 1980; CHEREM, 2008). Complementarily, longitudinal profiles integrated with lithological analysis were elaborated, correlating slope ruptures (knickpoints) with the resistance of local geological formations. To evaluate water quality, the Water Quality Index (WQI) was utilized based on a sampling campaign at four points selected by Strahler's hierarchy and the urban occupation gradient. Collections occurred after a precipitation event to capture the impact of surface runoff on parameters such as turbidity, pH, conductivity, temperature, and coliforms. The results demonstrate that the drainage network is strongly conditioned by resistant lithology and steep slopes, resulting in a fast hydrological response and high sediment transport potential. Field analysis revealed that precipitation acted ambiguously: while it promoted the dilution of E. coli at direct discharge points, it critically increased turbidity due to the wash-off of particulate matter from urban surfaces. Monitoring confirmed the worsening of contamination indices downstream, evidencing the cumulative effect of anthropogenic degradation. It is concluded that the vulnerability of fluvial systems in Ouro Preto is enhanced by the combination of natural geological factors and a lack of sanitation infrastructure, demanding integrated water management strategies.