Groundwater resources of river Kan Gimi Basin, north-central, Nigeria

Abstract.

The groundwater resources of the Kan Gimi drainage basin were evaluated to aid in their planning, development and management. The principal sources of groundwater in this basin are the fractured crystalline and unconsolidated overburden aquifers. The overburden unit has an average thickness of about 50 m. Groundwater occurs at shallow depths under unconfined to semi-confined conditions. Water levels in wells dropped to about 19 m below the ground surface at the peak of the dry season. Well yields for the fractured crystalline aquifer may be up to 2.7 m³ h^–1 whereas those of the unconsolidated overburden unit may average about 2.0 m³ h^–1 or more. These values are higher than the 0.72 m³ h^–1 (0.2 l s^–1) yield required for successful operation of hand pumps for lifts (depths) of less than 25 m. Sodium and bicarbonate are the dominant ions in the groundwater in this basin. Concentrations of the major cations and anions are very low compared with their permissible levels in potable water. The total dissolved solids is 230 mg l^–1 and below, which indicates fresh water. The water is soft, has a low electrical conductivity (20–329 µS Cm^–1) and a pH below 7. The concentration of total iron exceeds the recommended optimum limit for drinking water and some industrial usage, but falls below the maximum permissible limit of 1 mg l^–1. The low sodium adsorption ratio (0.08–2.3), coupled with low electrical conductivity, make the water have very low sodicity and salinity hazards. Thus, the groundwater is generally of suitable chemical quality for domestic, agricultural and most industrial uses.