Avaliação do impacto da expansão urbana sobre a infiltração superficial e recarga potencial subterrânea no município de São Leopoldo, Estado do Rio Grande do Sul - Brasil

Abstract

The assessment of urbanization impact on potential groundwater recharge variation in São Leopoldo, Rio Grande do Sul State - Brazil, concerning the 1950-2012 period, was carried out by multicriteria analysis. During this period, the population had a 860% growth, ranging from 25.794 to 214.210 inhabitants. At the same time, urban area changed from 20 km² to 71 km² , what means an increasing rate of 252%. Due to this urban expansion, a reducing of surficial infiltration was expected. In fact, by multicriteria analysis of several steps of urban expansion, it was detected a reduction around 75% of high potential infiltration areas. The potential groundwater recharge in São Leopoldo was assessed through quantifiable and non-quantifiable criteria. A comparison of the results showed a rate of coincidence of 73.5% excluding the urban area, for which, it was considered extremely low values. As for deviations estimation of the order of 26.5%, the CN (Runoff Curve Number) technique presented predominantly higher results. The trend of deviation occurs towards the CN technique because of Geological criteria not be used in this method, which was however considered in the Multicriteria technique.