Analysis of Groundwater Flows Using Geophysics and Tracer Tests in a Karst Area of Minas Gerais, Brazil

The mapping of hydrogeological continuities in heterogeneous aquifer systems presents significant challenges in understanding and managing groundwater resources. The studied area is part of the central portion of the state of Minas Gerais, Brazil, and covers the northern portion of the Lagoa Santa Karst Environmental Protection Area (EPA) and surroundings, a region that holds important archaeological and paleontological sites, as well as karst-fissural aquifers responsible for a large part of the urban and industrial supply of the area. In order to analyse the main underground flows and prove the hydrogeological connectivity between the Lagoa Santa Karst EPA and adjacent areas to the west, electroresistivity tests and application of a dye tracer were conducted around important karst springs in the region. The electroresistivity profiles indicate W-E direction flows, consistent with the regional flow, as well as contributions from S to N and NW to SE flows. The dye tracer test proved the underground connection of a sinkhole located to the west of the EPA with aquifers inserted in this conservation unit. Hydrogeological sections also indicate the continuity of the karst-fissural aquifers from west to east, towards the Velhas river. In addition, the probable areas of contribution of karst springs located near the western edge of the Lagoa Santa Karst EPA indicate that the current conservation unit does not cover a significant portion of the recharge areas of the local hydrogeological system. Therefore, it was proposed to either expand the Lagoa Santa Karst EPA or create a new environmental conservation unit in the area.