Integration of geophysical methods and aerophotogrammetry applied to groundwater exploration in fissured environments in Cedro, Ceará (CE), Brazil

Abstract

In Northeastern Brazil, the semi-arid region is known for its periodic natural drought phenomenon and the predominant fissured aquifer system, which is recognized for its low cost/benefit ratio concerning the construction of tubular wells for using groundwater. This work, therefore, aims at improving prospecting efficacy when exploring these natural resources using the available historical geological and structural data on the existing wells, integrated geophysical methods (resistivity and electromagnetic), and drone imaging. The proposed methodology was applied in a controlled environment in Cedro, Ceará/CE, using electromagnetism as a preliminary method followed by electroresistivity as a detailing technique. The analysis allowed us to recommend minimum values for the studied parameters in the research area. The dipole-dipole and Wenner-Schlumberger arrays with an electrode spacing of 10 m were the best suited for the study conditions. These results integrated with the structural geology can explain the failing wells observed in several areas as well as the successful wells associated with brittle structures found in the area. Thus, the proposed methodology allowed us to evaluate different responses and, consequently, define a set of basic steps to improve the accuracy of the studied procedures.