Comportamento hidrodinâmico de sistemas cársticos na bacia do rio Betari, Município de Iporanga - SP

Abstract

Time series analyses of spring hydrographs and pluviometric data are applied in order to characterize the groundwater flow in a karst aquifer of a highland plateau in the Upper Ribeira Valley (Alto Vale do Ribeira). Two kinds of karst spring behavior were revealed based on their contrasting statistical characteristics: one is extremely inertial (the Lago spring) while the other (the Areias spring) has a fast response to rainfall events, returning quickly to the pre-impulse stage. The differences are explained on the basis of system geometry together with flow dynamics (investigated by qualitative and quantitative fluorescent dye tracer tests), by recharge volume and mechanisms (identified through the mapping of catchment areas and surface karst features) and conceptual models which relate spring flow and discharge characteristics with the internal structure of the groundwater drainage. The spring with inertial behavior is part of a distributive drainage system, and the meteoric recharge is made by small catchment basins. On the other hand, the Areias spring corresponds to a convergent drainage system (which is observed along the Areais cave system) with meteoric recharge characterized by large inputs at discrete points connected to the largest allogenic recharge areas.