Groundwater potential of Thika area, Kenya

Abstract

The area described in this report is Thika and its surroundings defined by the coordinates 37 00’00’’ to 37 06’50’’E and 1 00’00’ to 1 05’45’’ S covering about 110 km2.The main objective of the project is to determine the ground water potential of the area and make some recommendations. The area is about 45 km from Nairobi on eastern side of the rift valley. The average rainfall is about 900mm which presents itself in bi modal form. There are several streams draining eastwards. Geologically, the area is covered by rocks of the upper Athi series which formed from successive lava flows in the post rift valley formation. The stratigraphy is defined by Athi series which overlie the Kapiti phonolite which then overlie the basement rocks of the Mozambique belt. Aquifers in the area constitute the weathered, the fractured and the contact zones between different layers. Analysis of data from boreholes in the area showed that there are confined aquifers positioned at different levels. There are also varied ground water potentials in the aquifers supplying different wells with some showing high, others moderate while others had low potential. It will be important to manage the environment and well abstraction rates so as to maintain a desired quality and quantity of the ground water. Possibilities of artificial recharge should also be considered. Details are contained in the rest of the report.