Water balance in karstic hidrogeologic system, region of Lagoa Santa, Minas Gerais

Abstract

The studied area, APA Lagoa Santa Karst and its surroundings, is located 35 km north from Belo Horizonte and it covers around 505 km². The region has been a target to many enterprises that demand an increase on water request. Having as a scenario this growth and the fragility of the Karst system, it becomes necessary to know the hydrological system, as well as to understand the hydric balance. Geologically, the area is represented by metacalcarium and neoproterozoic metapelitic rocks from The Bambuí Group, with rich density of features of karstic dissolution that make the recharge and the fast conduction of the flows water. The drainage of the region is affluent by the left bank of Das Velhas river that functions as its base level. The objective of this project was to perform the water balance, with emphasis on the aquifer recharge, considering the complex underground drainage network with inputs and outputs of the system. Available information about hydric connections have helped on the adopted circulation model used to equate hydric balance. 6 fluviometric stations were installed in 6 basins, having monitored the hydrological year of 2016/2017, whose data was used to calculate its recharge using the methodology of Rutledge and Daniel (1994). The average flow of the basin in 91% of the total confirms the importance of underground water to the hydrological system and the recharge of 12% of the annual precipitation (1010 mm) can be adopted as minimum value, once there are other hydric outputs that are not analysed in this work.