Land use and its impacts on the water quality of the Cachoeirinha Invernada Watershed, Guarulhos (SP)

Abstract

The urbanization process through which large urban centers have been passing has drastically affected the availability and especially the quality of water. The Cachoeirinha Invernada Watershed (CIW), located in the municipality of Guarulhos (State of São Paulo, Brazil), includes areas with different land use classes. This paper aims to correlate the spatial and temporal effects of land use and land cover on the water quality of the Cachoeirinha Invernada Watershed. In a period of 12 months and at six sampling points along the watershed, the physicochemical parameters temperature (T), pH, turbidity (TU), total solids (TS), electrical conductivity (EC), total phosphorus (TP), biochemical oxygen demand (BOD), as well as microbiological analysis (E. coli) were measured. Water quality was assessed using a modified version (WQI_M) of the Water Quality Index (WQI) and the Trophic State Index (TSI). The areas surrounded by urban development presented a marked worsening in water quality, with the downstream point most affected and ranked as ‘POOR’. From the evaluated parameters, what contributed most to water quality degradation of the Cachoeirinha Invernada Watershed (CIW) was E. coli, followed by BOD, and TP, all parameters related to the presence of sewage in the water. The need for the construction of sewerage and waste treatment, protection and recovery of riparian forests, and environmental education regarding waste disposal are necessary to significantly improve the environmental quality of the Cachoeirinha Invernada Watershed.