Depth‐based correlation analysis between the density of lineaments in the crystalline basement's weathered zones and groundwater occurrences within the Voltaian basin, Ghana

ABSTRACT

Geological structures have been shown by studies to have influence on the occurrence, storage and transportation of groundwater. Understanding the structural network of an area unearths a deep insight into the groundwater dynamics of the area. A geological structural analysis was carried out to reveal the geological structural network of Ghana's Voltaian Basin. Using aeromagnetic data, structural density models were generated using the Center for Exploration Targeting (CET) grid analysis technique for two depth ranges (that is up to 100 m and 300 m) over the Voltaian basin. The total length of geological structures (lineaments) delineated at depths up to 100 m and 300 m were more than 5 km and more than 8 km respectively. Given this, the study area was observed to be structurally dense at each of the aforementioned depths. The structural density models (SDM) were discretized into five classes (very low, low, moderate, moderately high and very high regions), each of which was evaluated to determine their spatial association with known locations of groundwater occurrences within the study area using the frequency ratio technique. Frequency ratio results for both SDM derived at 100 m and 300 m depths show the existence of a strong correlation between high SDM classes and the known groundwater occurrences. The structural density models were further evaluated using receiver operating characteristics (ROC) curve. The area under the ROC curve scores indicate that, although both SDM produced showed very good performance (with ROC scores greater than 0.7), the 300 m depth SDM produced performed better than the SDM generated at a depth of 100 m (with their ROC scores being 0.721 and 0.715 respectively). The results obtained corroborate with literature assertion that groundwater occurrence within the Voltaian basin is mainly associated with structural features. It is expected that, the outputs of this study would guide future groundwater exploration programmes within the study area.

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