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.
