Abstract

Kenya is implementing Integrated Water Resources Management (IWRM) policies. The water policy provides for mandatory reserve (environmental flow) which should be sustained in a water resource. Four out of the six main catchments in Kenya face water scarcity. Further water resource quality objectives for many rivers are yet to be determined. This study applied Water Evaluation and Planning System (WEAP21) to study the implications of implementing the water reserve in Perkerra River which is among the few rivers that drain into Lake Baringo.  The Tennant method was used to determine minimum environmental flows that should be sustained into the lake. WEAP21 was used to perform hydrological and water management analysis of the catchment. Mean monthly discharge time series of the catchment monitoring stations indicate that Perkerra River is becoming seasonal. The results further show that implementing the reserve with the present level of water management and development will increase the demand by more than 50%. With good regulation policies Chemususu dam project will reduce the impact of the reserve on abstractive uses by 20 to 40% and ensure that Perkerra River does not dry up.

Key words: WEAP21, environmental flows, sustainable management, demand, allocation.