LARGE-SCALE IRRIGATION DEVELOPMENT IN KENYA Pastst Performance and Future Prospects
The costs of an irrigation scheme are a function of the size of the project, the technology
applied, ecological setting, the crops produced and marketing and pricing policy. A gravity
scheme is likely to be cheaper than a pumping scheme. Except for Mwea and Perkerra all
the other large-scale schemes are pumping schemes. Drainage is by gravity except for West
Kano where pumping is necessary to get rid of excess water. In Mwea water is conveyed
by gravitation and distributed through canals to flood the farms. The black cotton soils have
high retention rates and little infiltration. High efficiency rates are achieved (i.e. 85%). The
water flow is reliable since the rivers feed the head works with sufficient quantities all the
year round. (Manig, 1973). This contrasts sharply with Bura where water has to
pumped and conveyed over 40km canal to reach the scheme. Just like in the other NIB
projects poor distribution sometimes occurs due to several factors including pump
breakdown (as occured in Bura in 1986), shortage of diesel, insufficient water from source
and excessive loss during conveyance. The Perkerra Scheme, for instance, experiences an
irregular flow and shortage during the peak season.8
be
The planning, design and construction also has important implications for the final scheme
costs. Mwea was constructed in four phases, with each phase being funded separately. As
Gitonga (1985) argues this approach is to be preferred since it provides ample time for
investigative planning, design, construction and training of personnel. Appropriate cost
savings could be achieved through construction in successive stages. The experience gained
can be replicated in later phases and machinery and equipment which are acquired in the
earlier phases could be utilized more effectively..
Article source: https://scispace.com/pdf/large-scale-irrigation-development-in-kenya-past-performance-2wog80k1ps.pdf
