Localized recharge in semi-arid region: a case study of sinkholes in the Verde Grande River Basin, Minas Gerais – Brazil

Abstract

Localized recharge from sinkholes is very important in karst environment and especially in arid and semiarid regions, where it contributes to the recharge on karst fissured aquifers because these geomorphic structures favor the concentration of water runoff in areas with shortage of water. The study area is located in sub-basins of the Rio Verde Grande, in the Verdelândia and Varzelândia cities and it is part of the semi-arid climate (average regional rainfall = 790 mm), and is strongly marked by the presence of sinkholes in Neoproterozoic pelitic-carbonate of karst Bambuí Group. To understand the processes of this kind of recharge and quantify it in the study area, we used the automated identification in ArcGIS to select two sinkholes and the following methodological procedure was adopted: soil texture characterization; soil infiltration tests; permeability tests of aquitard/aquiclude from the bottom of the sinkhole; automated monitoring of rainfall and underground water level; hydric balance, estimated with the hydric balance and water level variation methods. The results showed local recharge values between 7,8% and 19,5% of the precipitation, demonstrating the importance of preserving these features in the region.