Mwaniki S. Ngari, Wanjau T. Wangui, Njeru S. Ngoci, Mavura J. W
Abstract: Gichugu division has numerous springs, which are a manifestation of potentially high volumes of groundwater. This water is characteristically different from river water in terms of physical parameters like fizzling, characteristic taste and clarity. Its chemistry was studied to explain the above differences. The study established that groundwater in Gichugu area is slightly acidic (pH 6.48), moderately hard (126.1 mg/l CaCO3) and NaHCO3 / NaCl type (357.7 mg/l Na, 155.6 mg/l HCO3-, 4.67 mg/l Cl- ). These salts and the pH explained the taste of the water. Also, NaCl electrolyte accounted for the relatively higher conductivity (2.888 Ec S/cm) while such ions as Ca2+ and Mg2+ explained the moderate hardness of this ground water. The percolation of this water through the surface soils of recharge areas generally results in significant purification hence the clarity. Fizzling was as a result of dissolved gases such as carbon dioxide and oxygen as they escaped. It was also established that a common groundwater aquifer underlies the area. Iron (0.6762 mg/1) and manganese (0.2972 mg/1) were found in excess of WHO recommended limits (0.3 mg/1 and 0.1 mg/1 respectively) for potable water quality while fluoride was in relatively low amounts (0.497 mg/1). However, their levels in this water do not make this water unsuitable for drinking since they are still within the acceptable tolerance levels.