Hydrodynamic of the Bambuí Karst Aquifer System, with the use of dye tracers, in the Lagoa Santa region, Minas Gerais
Abstract
The study area is located 30 km to the north of Belo Horizonte and encompasses the Environmental Protection Area (APA, in the Portuguese acronym) Karst of Lagoa Santa. The Sete Lagoas Formation is the main outcropping unit, configuring a diverse karst geomorphology, characterized by canyons, blind valleys, dolines and caves. In the subsurface, a network of conduits forms karst aquifers that shelters important water reserves, which have been suffering qualitative and quantitative risks due to the intense pressure of demographic and industrial expansion. Employing the dye tracer injection technique, it has been an attempt to stablish the hydraulic interconnections, flowpath hydrodynamic conditions, configurations of recharge, circulation and discharge of these aquifers. Ten qualitative-quantitative assays were executed using the Fluorescein and Rhodamine WT. Positive results for water interconnections were observed in seven assays, revealing the provenance of 68.3%, 13.0%, 70.2%, and 41.3% of the outflows in four springs. The average apparent velocities ranged from 9.5x10-3 m/s to 4.49x10-2 m/s and 1.43x10-2 m/s to 6.27x10-2 m/s considering the sinuosity factor of the route, the which evidence the high velocity of the flows.
