Effect of a reservoir in the water quality of the Reconquista River, Buenos Aires, Argentina

Abstract

The lower portion of the Reconquista River is highly polluted. However, little is know about the state of high and middle basin. The aim of this work was to assess the water quality on high and middle Reconquista River basin and to determinate of the presence of a reservoir in the river has a positive effect on the water quality. We conducted a seasonal study between August 2009 and November 2010 at the mouth of La Choza, Durazno, and La Horqueta streams, at the Roggero reservoir - which receives the water from the former streams-, at the origin of the Reconquista River, and 17 km downstream from the reservoir. We measured twenty five physical and chemical parameters, including six heavy metal concentrations, and performed a multivariate statistical analysis to summarize the information and allow the interpretation of the whole data set. We found that Durazno and La Horqueta streams had better quality than La Choza, and the presence of the reservoir contributed to the improvement of the water quality allowing oxygenation of the water body and processing of organic matter and ammonia. The water quality of the Reconquista River at its origin is good and similar to the reservoir, but a few kilometers dowstream water quality declines as a consequence of the presence of industries and human settlements. Therefore, Roggero reservoir produces a significant improvement of water quality of the RIver but the discharge of contaminants downstream quickly reverses this effect.