Groundwater Potential on the Jos – Bukuru Plateau, North Central Nigeria. Using Lineaments from Gravity Measurements

The rocks of the Jos – Bukuru area in North Central Nigeria is characterized by negative and positive gravity residual anomalies ranging from –25 to +20 mGals. Lineaments were extracted from the gravity residual anomaly map for the purpose of assessing the groundwater resources in the area. The region is marked by more than one set of lineaments, each with its distinctive orientation and probably spacing. Lineaments shorter than 20 km in length are shallow structures suitable for this exercise because of their importance in groundwater recharge, transmission and discharge. In a bin size of 15^oone major and one minimum striking directions between 000^o and 030^o were obtained. The major type lies between 000^o and 015^o, while the minimum one is oriented within the 015^o and 030^o direction. These directions correspond to the stress axis of the essentially north – south trending geological structures of Nigeria. Invasions of mineralizing fluids might had sealed some of the joints and other fractures, however where the open spaces are not sealed, weathering and erosion widen and deepened the joints paving routes for surface water flows and direct seepage into the underlying strata. On the lineament density and lineament intersection maps the closures suggest probable discontinuity of the aquifer units. On this basis of the lineament density and the lineament intersection results, the area was divided into three hydrogeological zones. Site 1 is considered most favourable for water well development, while site 3 may result in low yields or even in abortive water wells