The present study attempts to define the relationship between groundwater flow systems and the distribution of chemical facies with the aid of Geographical Information System (GIS). The study also identifies the different geochemical processes responsible for the chemical evolution of groundwater chemistry. Analytical results of 23 groundwater samples reveal mean values of cations as Na⁺ (84.2 mg/l), K⁺ (4.2 mg/l), Ca²⁺ (27 mg/l), Mg²⁺ (11.5 mg/l) and Fe²⁺ (0.6 mg/l). The anion mean values are HCO₃<sup style="margin-left:-7px;">– </sup> (4.5 mg/l), SO₄<sup style="margin-left:-7px;">2– </sup> (3.7 mg/l), Cl^– (22.5 mg/l) and NO₃<sup style="margin-left:-7px;">– </sup> (2.2 mg/l). Based on mean values, the cations are in order of abundance as Na⁺ > Ca²⁺> Mg²⁺ > K⁺ > Fe²⁺ while the anions reveal order of abundance as Cl^– > HCO₃<sup style="margin-left:-7px;">– </sup> > SO₄<sup style="margin-left:-7px;">2– </sup> > NO₃<sup style="margin-left:-7px;">– </sup>. The geographical information system (GIS) using Inverse Distance Weighted (IDW) delineate two groundwater zones into: Ca-Mg-SO₄-Cl and Na-SO₄-Cl water types. The Ca-Mg-SO₄-Cl constitutes about 35% of the chemical facies and its evolutionary trend is due to simple hydrochemical mixing between Ca-Mg-HCO₃ and Na-SO₄-Cl facies and reverse cation exchange. The Na-SO₄-Cl facies constitutes about 65% of the chemical facies and represents fossil groundwater. The Ca-Mg-SO₄-Cl facies is dominant in the recharge areas while Na-SO₄-Cl facies prevails in discharge areas. Rock-water interaction diagrams indicate precipitation induced chemical weathering along with dissolution of rock-forming minerals. The scattered plots among ions revealed geochemical processes as carbonate weathering, silicate weathering, cation exchange and sulphate reduction. HCA identified effects of rock-water interaction and anthropogenic effects as responsible for the modification of groundwater chemistry in the area

Twenty-two Vertical Electrical Sounding (VES) were carried out to evaluate groundwater potential and aquifer protective capacity of the overburden units using Schlumberger configuration. It was observed that H-curve is the dominant curve type in the study area. The Geo-electro stratigraphic section revealed that the geologic sequence beneath the study area is composed of topsoil, highly weather basement, partly fractured basement and fresh basement. The first layer has an average thickness and resistivity of 1 m and 130 Ωm, respectively. The second layer has an average thickness of 14 m and an average resistivity of 53 Ωm. The third layer is partly fracture basement with an average resistivity of 747 Ωm while at some VES point represents fresh basement. The highly weathered basement and partly fracture basement layer make up the water bearing formation of the area. Dar-Zarrouk parameter revealed that the area under study has protective capacity range from weak to good capacity of the overburden material. Areas that are classified as poor and weak are indicative areas are thus vulnerable to infiltration of leachate and other surface contaminations. The groundwater potential of the area ranges from low to moderate potential; the moderate zone constitutes 86% while the low potential constitutes 14% of the study area. The transverse resistance within the study area ranges from 119.6 to 6983.7 ohms-m2 with an average value of 1024.59 ohms-m2. Hydraulic conductivity values determined from geoelectrical technique range from 3.05 to 38.04 m/day with an average value of 14.86 m/day.

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 -1P respectively. @ JASEM Resistivity survey was employed in this work to determine locations suitable for borehole construction because it can favorably locate water-bearing layer. The area is bounded by Latitude

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