Time-lapse electrical resistivity tomography applied to cave sustainability (Barbados) and groundwater exploration (Saint Lucia)

Abstract

In this work we apply the method of two-dimensional time-lapse electrical resistivity tomography (2D time-lapse ERT) for two different problems. In the first problem, we monitor the structural stability of the roof of the Great Hall cavern in the Harrison's cave system, Barbados. We present an interpretation and comparison of two sets of resistivity data collected over the Great Hall: one set collected by us in 2010, the other in 1996. Our results show that fracturing and degradation had progressed since 1996, indicating a gradual weakening of the structural stability of the roof of the Great Hall cavern. In the second problem, we conduct 2D ERT surveys during dry and rainy seasons to evaluate the potential and feasibility of groundwater exploration next to the Thomazo River in the Fond D'Or watershed in Saint Lucia. Interpretation of the ERT data sets reveals a lens of a porous rock that has a high potential to be a productive aquifer. We use the ERT time-lapse approach to evaluate the change in water content between dry and wet seasons in the potential aquifer.