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Hydro Geo-Electrical Investigation in Gombe Town and Environs, Northeastern Nigeria
Abstract
Thirty three vertical electrical soundings (VES) were conducted around Gombe and environs, employing Schlumberger array with a maximum electrode separation of AB/2 = 200m to determine locations
favorable for sitting boreholes. The data obtained were interpreted using the partial curve matching technique and software (offix) for resistivity data interpretation. From the result, it was found that twenty one of the VES points are three layers while twelve are four layers. The first layers have thicknesses ranging from 0.8m to 16.1m, the second
and third layer have thicknesses ranging from 0.994m to 149m and 11.7m to 108.2m, respectively while the fourth layer had thickness that extended beyond the probing depth. A correlation of the curves with existing lithologic log from boreholes in the study area suggests that the major lithologic units penetrated by the sounding curves were
laterite, clay, shale, sandstone and sandy clays. The sandy clay and sandstone constitute the aquifer zones with resistivity range of 28 ohm-m to 84 ohm-m for clay, 240 ohm-m to 501 ohm-m for sandstone, 967 ohm-m to 1008 ohm-m for sandy clay. Others are 2069 ohm-m to 9607 ohm-m for the calcareous and the laterite units and 17456
0hm-m for the compacted sands. The direction of groundwater flow in the area was found to be northwest-southeast, average fitting error, pH and conductivity are 6.138 percent, 7.02 and 72.16ohm cmP-1Prespectively.
favorable for sitting boreholes. The data obtained were interpreted using the partial curve matching technique and software (offix) for resistivity data interpretation. From the result, it was found that twenty one of the VES points are three layers while twelve are four layers. The first layers have thicknesses ranging from 0.8m to 16.1m, the second
and third layer have thicknesses ranging from 0.994m to 149m and 11.7m to 108.2m, respectively while the fourth layer had thickness that extended beyond the probing depth. A correlation of the curves with existing lithologic log from boreholes in the study area suggests that the major lithologic units penetrated by the sounding curves were
laterite, clay, shale, sandstone and sandy clays. The sandy clay and sandstone constitute the aquifer zones with resistivity range of 28 ohm-m to 84 ohm-m for clay, 240 ohm-m to 501 ohm-m for sandstone, 967 ohm-m to 1008 ohm-m for sandy clay. Others are 2069 ohm-m to 9607 ohm-m for the calcareous and the laterite units and 17456
0hm-m for the compacted sands. The direction of groundwater flow in the area was found to be northwest-southeast, average fitting error, pH and conductivity are 6.138 percent, 7.02 and 72.16ohm cmP-1Prespectively.
