Abstract

Three hundred and twenty two vertical electrical soundings (VES) have been used to evaluate the hydraulic properties of aquifers in Enugu State, Southeastern Nigeria.  The project domain lies within longitudes 7° 6’ E to 7° 54’E and latitudes 5° 56’N to 6 °52’N, and covers an area of about 7161 km² over eight main geological formations. The thickness, lateral extent and resistivity of the aquiferous layers were determined by the electrical survey. Also, zones of high yield potentials were inferred from the resistivity information. Transmissivity values were inferred using the empirical relationship between hydraulic conductivity and formation factor. Results show highly variable thickness of the main aquifer in the study area. Aggregate longitudinal conductance indicates greater depth of the substratum in the central part of the area, underlain by the Ajali and Nsukka Formations. High values of transmissivity, specific yield and moderate porosity also predominate, thus suggesting thick and prolific aquiferous zone. Lower average values of these parameters were obtained in southwestern and eastern parts underlain by the Imo and Ezeaku/ AwguNdeaboh/ Nkporo Formations, with the eastern part recording the lowest values, except porosity with the highest estimated average value. Maps of various geoelectrical and hydraulic parameters have been produced and the overall results can serve as a useful guide in planning a drilling program in the study area.

Key words: Formation factor, transmissivity, porosity, specific yield.