ESTIMATION OF TOTAL GROUNDWATER RESERVES AND DELINEATION OF
WEATHERED/FAULT ZONES FOR AQUIFER POTENTIAL: A CASE STUDY FROM FEDERAL
DISTRICT -BRAZIL
Abstract
Unplanned urban growth exerts significant stresses on the underlying
aquifers in terms of increasing the groundwater extraction and reducing
the surface area for aquifer recharge. This situation has led to a more
difficult process in the search for new locations of productive tubular
wells, particularly in the Federal District of Brazil. In this region,
the groundwater extraction is challenged by fractured aquifers with
difficult identification of hydraulic tarps and significant uncertainty
in the estimation of recharge potential. The aim of the present study is
to optimize the demarcation of new locations of tubular wells by
conducting geophysical investigations. In the first stage, based on the
information of the physical environment and data from the existing
wells, the total exploitable amount of groundwater was calculated. Then
Electrical Resistivity Tomography (ERT) was carried out along specific
sites, which were selected based on the surficial characteristics. The
resistivity values obtained from the dipole-dipole array were inverted
and the resultant conducting zones (weathered rocks and fractures) were
delineated, which represent possible hydraulic traps where groundwater
may exist. Based on the results, the suitability of the selected sites
for deep tubular wells installation was prioritized on a linear scale
varying from 1 to 5, where 1 is the highest and 5 is the least suitable.
Based on this approach, eight new deep tubular well sites were proposed
and classified. The study provides a promising framework for
investigating groundwater in fractured aquifers.