International Journal of Environmental Sciences ISSN 2519-5549 (online) Vol.3, Issue 1, No.2. pp 21 - 41, 2020 www.iprjb.org 20 SPATIAL-TEMPORAL VARIATION OF GROUNDWATER RECHARGE FROM PRECIPITATION IN THE STONY ATHI SUB-CATCHMENT, KENYA Morris W. Mathenge, Dr. Gladys M. Gathuru and Dr. Esther L. Kitur