Inicio  /  Water  /  Vol: 9 Núm: 2 Par: 0 (2017)  /  Artículo
ARTÍCULO
TITULO

Borehole Logging and Slug Tests for Evaluating the Applicability of Electrical Resistivity Tomography for Groundwater Exploration in Nampula Complex, Mozambique

Farisse Chirindja    
Jan-Erik Rosberg    
Torleif Dahlin    

Resumen

In Nampula province, Mozambique, there is a high number of water wells considered as having failed for having too low a pumping yield. Two Electrical Resistivity Tomography (ERT) measurement campaigns were conducted in the area for evaluating the reasons of failures. However, in some cases it was difficult to verify and interpret the ERT results by only using the inadequate lithological description presented in drilling reports. In this paper the integration of borehole logging and slug testing is presented as a solution to add more information and to enhance the interpretation of ERT models. The borehole logging tool measured resistivity, magnetic susceptibility and natural gamma. The logging results proved that the ERT models are accurate in estimating the resistivity for basement (>1400 ?m), fractured layer (220?1400 ?m), semi-weathered layer with clay accumulation (10?220 ?m), and weathered and leached layer (220?2700 ?m). The slug testing gave results of high hydraulic conductivity (K) values where the ERT indicates well-developed weathered and fractured layers, and low K values where these are less developed. The borehole interpretation can be extrapolated using the ERT model to give a geometric characterization of the aquifer. Therefore, the implementation of the ERT method in groundwater exploration is encouraged.

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Revista: Water