Copyright © 2018, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 3 51 DOI: 10.4018/978-1-5225-2719-0.ch003 ABSTRACT Lack of water allocation plans in semi-arid river basins increases the risks of hydrological droughts. The Mukurumudzi river basin was experiencing extremely low fows which led to a water allocation assessment to quantify the available resource amidst competing demands from domestic, commercial and environmental needs. An abstraction survey was conducted along the entire length of the river followed by a low fow study and water balance modelling using rainfall-runof Model. Observed fows at source and mouth were 0.028 m 3 /sand 0.043 m 3 /s respectively. Simulated fows estimated an environmental fow (Q95) defcit of0.023 m 3 /s and 0.010 m 3 /s in July and August respectively. Normal fow (Q80) of 0.190 m 3 /s and food fow (Q50) of 0.520 m 3 /s were estimated. Compensating the environmental fow defcit in July and August was recommended. A more detailed hydrogeological study should be conducted to elucidate the potential of the groundwater resource in meeting current demands. Water Allocation Assessment and Hydrological Simulation on Mukurumudzi River Basin in Kenya Jacob Mutua Katuva University of Nairobi, Kenya Christian Thine Omuto University of Nairobi, Kenya John P. O. Obiero University of Nairobi, Kenya