Abstract:
Integrated water resources management (IWRM) is being embraced by many
countries. Kenya is implementing a new water policy formulated along IWRM
principles. The newly formed river basin organisations grapple with issues of
sustainability, water allocation, resource quality objectives, equity,
environmental flows among others. Kenya experiences water scarcity and stress.
This research applied the Water Evaluation and Planning System (WEAP21)
model to test a systems approach in evaluating the impact of changes in water
policy and water development in Perkerra catchment in Kenya. The upper
catchment has humid to semi-humid climatic conditions while the lower
catchment experiences semi-arid to arid climatic conditions. Biophysical and
human interventions were modelled in WEAP21. The scenarios analysed the
impact of the new water policy of equitable water allocation, maintaining the
reserve and ecological flows. The impact of increasing water storage and
irrigation efficiency was evaluated. The reference scenario was validated using
flows at the catchment observation station 2EE7B. The Tennant method was
used to determine minimum environmental flows. From the analyses, one dam
project will reduce water deficit by 5%. However, higher irrigation efficiency
reduces the deficit by 15%. The implementation of two dam projects improves demand coverage by 20%, including environmental flows. The findings indicate
that more efforts should be directed towards improving irrigation efficiency
