Groundwater Potentials Of The Nanka Sands Around Nanka-Oko And Its Environs, Anambra State

                                                         ABSTRACT

Investigations were carried out for groundwater potentials and hydro-geochemical characteristics of the Nanka-Oko area and environs, southeastern, Nigeria. The areas are underlain by the Nanka Sands Formation. Data from 14 vertical electrical soundings were interpreted using computer aided techniques (IPI2win software). A total of 16 borehole groundwater samples, were also analyzed for their physiochemical and biological properties with the aim of assessing their characteristics and quality for domestic and agricultural purposes. The results of the interpretation of the geophysical data show that the area is characterized by variable subsurface layering ranging from six layers to eight layers.Lithologic logs, geoelectric sections and static water levels data reveal that the area is characterized by two aquifer horizons (upper and lower) and two aquifer types (confined and unconfined).Based on the estimated hydraulic conductivity, transmissivity and specific yield, two groundwater potentials zones (low and high) were defined.  Results also show that the order of magnitude of the ionic species of groundwater of the area is > Na+> Ca2+>> Cl-> Mg2+>> Fe2-/3-.  Only  among the major ions (, Cl-,,Ca2+,Mg2+ and Na+) shows a pronounced difference in concentrations from the two aquifer types. The chemical composition of the groundwater is controlled mainly by weathering processes with little contribution from dilution processes. Three hydro-geochemical facies were deduced from the Piper diagram namely, CaHCO3, mixed CaMgCl and CaCl2.  The geochemical data also reveal that the groundwater from the area is potable as drinking water and suitable for irrigation purposes.