Water quality and trophic state of a tropical urban reservoir for drinking water supply (Juiz de Fora, Brazil)

Abstract

The Dr. João Penido Reservoir is an 80-year-old tropical impoundment that serves as the main drinking water supply for the city of Juiz de Fora, Brazil. The reservoir is an important environment for the region, serving as a study site for the scientific community. The main objective of this research was to calculate quality indices for water and the trophic state of the reservoir. We performed physical–chemical and microbiological analyses on water samples collected at 5 points in the reservoir between July 2011 and March 2013, a period that characterizes both dry and rainy periods. The parameters analyzed were water temperature, dissolved oxygen, pH, turbidity, total solids, biochemical oxygen demand, nitrate, total phosphorus, chlorophyll a, thermotolerant coliforms and total coliforms. Indices modified for tropical waters, the Water Quality Index (WQIIgam) and the Trophic State Index (TSILamp, a variation of the Carlson Index typically used for temperate zones) were calculated for each sample. The results showed the prevalence of a “mesotrophic” state and a “medium” level of water quality in the Brazilian reservoir. It is likely that the age, forms of use, and occupation of the watershed have produced negative impacts on the aquatic ecosystem over the last 80 years. Water quality clearly demonstrates the safety and environmental health of a watershed. This study presents data on the water quality and trophic state of the Dr. João Penido Reservoir and provides guidelines for developing and implementing an integrated management plan for the preservation of its watershed.