Abstract:
Irrigation schemes are usually designed and implemented on the basis of assumed efficiencies in
water application, water conveyance, and water distribution. However, over time, physical changes
in the schemes such as poor maintenance of structures, soil property changes and deterioration of
equipment may alter these efficiencies. It is therefore imperative that the efficiencies are
periodically evaluated as a way of monitoring and evaluating the irrigation scheme. This study
identified the irrigation technologies the farmers were using and evaluated the water flow rates and
efficiencies of several smallholder schemes in Murang’a South District to ascertain whether these
schemes were operating at their design recommendations and efficiencies. Water flow rates were
measured using Parshall flumes, while soil water statuses were measured with tensiometers. Social
economic data was collected using structured questionnaires. The results showed that the sampled
schemes had high water conveyance efficiencies (95%). This was attributed to the use of pipes and
lined canals in the main conveyance systems. Distribution efficiencies ranged between 76% and 95%
while application efficiencies varied between 58% and 86%. The overall efficiency was between 44
and 77%. The water application uniformity was generally below acceptable limit, ranging between
41 and 71%. The low water application uniformity was attributed to the improper overlapping and
spacing of sprinklers. It was therefore recommended that the farmers be retrained on the proper
layout, spacing and overlapping of sprinklers in addition to water saving technologies in irrigation.
