Predicting subsurface rocks’ storage properties is a fundamental problem of groundwater prospecting and potential evaluation for planning of long term abstraction wells. Water in aquifers is stored and or released from elastic storage and gravity drainage. Aquifer storage parameters are traditionally determined from pumping tests data which are seldom available until wells have been drilled. Confined aquifer storativity (S) is estimated as a function of rock lithology and thickness of the aquifer using the rule of thumb equation S = 3.0 × 10-6b, but S = Ssb neglecting the effect of porosity and compressibility. The storativity equation assumes that all aquiferous rocks have a constant specific storage even though specific storage is directly dependent on rock porosity and most importantly rock grain compressibility which differs with lithology. In this study, apparent resistivity data derived from field resistance measurements in 31 locations were interpreted to infer geolectric layers lithologies and thicknesses. To determine the rock grain compressibility for computation of the specific storage, vertical stress at the aquifer depth was estimated using average densities of the interpreted subcrustal rocks. Results show that rock mineral grain compressibility varies from 7.915 × 10-7 to 9.235 × 10-5/Pa, porosity from 0.08 to 1.64 with the weathered overburden and sandstones having the higher porosities; specific storage vary from 8.32 × 10-6 to 1.80 × 10-3 and storativity ranges from 3.161 × 10-6 to 1.96 × 10-3. Clearly, results indicates that the specific storage differ predictably with rock type and consequently the storativity of the different aquifers.