Recharge and hydraulic connection between porous and fissural aquifer units of the Campus Pampulha aquifer system, Belo Horizonte, MG

Abstract

The aim of this study was estimate the recharge and hydraulic connection between the granular and fissured aquifers of the aquifer system in the Pampulha campus of the UFMG, in Belo Horizonte, Minas Gerais, was analyzed.In the area, the granular aquifer is unconfined, overlaps the fissural, and consists of alluvium, colluvium and residual soil, while the fissured aquifer is unconfined to semiconfined, represented by gneisses, granites and dikes of the Belo Horizonte Complex. The mean annual rainfall is 1,404.8 mm, with the highest incidence between October and March. An automated and manual monitoring of the water level for 8.5 months was carried out that completely involved the rainy season, from August/2012 to April/2013. The automated measurements were performed by installing pressure transducers in 3 piezometers and 3 inactive deep wells, with readings every 15 minutes, while manual monitoring was performed weekly in other 2 deep inactive wells and a piezometer. The characterization of the hydraulic connection was made by estimating the response time of the water level of each aquifer to the precipitation and the time elapsed between the direct recharge of the granular medium and the indirect recharge of this to the fissural medium. Cross-correlation function analysis techniques was used to calculate the hydraulic connection. The results indicated that the response time to recharge of the fissural aquifer from the granular was less than 24 h. The recharge for the granular aquifer, calculated by the variation of the water level, was 264 to 390 mm (average of 775,000 m³), 28% to 41% of the precipitation, respectively. Of this total, it was preliminarily estimated that about 14% (109,200 m³) recharge the fissural aquifer.