Abstract:
Irrigation enhances agricultural production, improves the food supply and income of rural
population in Ethiopia. From this important viewpoint irrigation projects were widely
studied, planned and implemented throughout the country. However, little or no attention
was given to the monitoring and evaluation of the performance of already established
schemes. This study was done during off season of rain in Gedeb Asasa district, West Arsi
Zone on Mada Batu Small Scale Irrigation Scheme to characterize the scheme in terms of
capacity, dimensions and functionality of reservoir, main and secondary canal, to evaluate
the performance of scheme using performance indices such as conveyance efficiency (Ec),
application efficiency (Ea), runoff ratio (ROR), deepercolation fraction (DPF), water
storage efficiency (Es), overall efficiency (Eo) and distribution uniformity (DU), along
with water productivity and finally identifying problems of the scheme. For this study three
farmers’ fields were selected each from the upper, middle and lower stream of the
irrigation scheme. The scheme has trapezoidal shape of reservoir with a capacity of 2604
m3 live storage along with trapezoidal shape of main canal with average size of 161, 59,
38.2 cm at the top, bottom and depth respectively and maximum discharge capacity when
gate was full opened at off take was 70 l/sec. Most of the secondary canals were not
functioning due to some part of canal like water closing gate and division box were
damaged. Due to this water being diverted to its own way by farmer from division box
reaching to their farms. Parameters like Ec, Ea, ROR, DPF, Es, Eo and DU were
determined and their average values of scheme were found to be 64.77%, 64.54%,
12.10%, 23.29%, 82.47%, 41.47%, and 93.10% respectively. Water productivities (in
terms of water use efficiency) was 0.74 kg/m3 for the upper and middle and 1.61 kg/m3 for
lower irrigation scheme whereas, the productivity (in terms of irrigation use efficiency)
had values of 1.34 kg/m3 for the upper and middle and 3.68 kg/m3 for lower stream of the
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irrigation scheme. The redesign of scheme was needed due to discharge of main canal to
command area size not compatible.
