EVALUATION Of GROUNDWATER VULNERABILITY IN FRACTURED AQUIFER USING GEOELECTRIC LAYER SUSCEPTIBILITY INDEX AT OJU, SOUTHERN BENUE TROUGH NIGERIA

Abstract

A combination of geoelectric and hydrogeologic concept was used in the assessment of groundwater vulnerability in fractured aquifers of Oju and environs. The study area is underlain by the sediments of the Asu River Group, Southern Benue Trough Nigeria. A total of twenty-seven (27) Vertical Electrical Sounding (VES) was carried out within the study area. Geoelectric parameters (layer, resistivity and thickness) of the overlying layers across the study area were determined and used to evaluate the vulnerability of the underlying aquifers. Three charts were compared using geo-electrically derived models; LC (Longitudinal Conductance), GLSI (geoelectric layer susceptibility indexing) and GOD (groundwater occurrence, overlying lithology and depth to the aquifer. Results obtained from LC revealed that the study area fell within the moderate category, GLSI showed that aquifer vulnerability were categorize within negligible to low category and GOD fell within low to moderate category. On the average, groundwater within the study area is considered moderate vulnerable to groundwater contamination.

Integrated Geophysical and Hydrogeochemical Characterization and Assessment of Groundwater Studies in Adum West Area of Benue State,Nigeria

“…From Table 6 6 revealed that sample locations GT-1 and 21 is classified to be of deep meteoric water percolation type that implies that the groundwater is influenced by precipitation [47] . While sample locations GT-2, 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,22,23,24,25,26,27,28,29,30,31,32,33 and 34 fell within shallow meteoric water.…”

“…Report from previous authors revealed that the delineation and characterization of groundwater potential within the Benue Trough becomes necessary as water samples from some existing wells and boreholes in the study area were below acceptable limits, especially during the dry season when most of the well and boreholes most have drop to a minimum yield and sometimes get dried up. Due to lack of hydrogeological information of the Benue Trough and improper delineation of the water bearing unit to facilitate the precise identification of desired water bearing unit before drilling and well completion for sustainable supply of potable water to the inhabitant of the study area [15,16] . [12] were of the opinion that basic resistivity parameters such as thickness, depth and resistivity of rock unit are vital in the determination of secondary aquifer which in turn help in the assessment of aquifer vulnerability.…”