Abstract:
The purpose of performance assessment of an irrigation scheme is to achieve an efficient
and effective use of available water resources, to sustain the scheme and to increase farm
productivity of the scheme. However, in the Ethiopia performance evaluation of irrigation
schemes is rarely conducted. This study was conducted to assess the performance of
community managed irrigation scheme found in the Awash basin during October to
December, 2016. Secondary data such as climate, design document were taken from
Shewarobit meteorological station and from Amara National, Regional State Water
Resource Development Bureau respectively. Primary data which were collected through
field measurements and field survey (field observation) were also taken. The conveyance
efficiency and losses were measured using inflow-outflow method in the main, secondary,
and tertiary canal. Flow of main and secondary canals were determined using Area-Velocity
method via determining canal cross-sectional area and flow velocity using current meter.
Discharge of field canal off-takes and tertiary canals were determined using Parshall flume.
To evaluate conveyance efficiency of the system 16 canal segments were taken. To
determine the water delivery indicators 15 field canal off-takes were also taken. Field
canal off-takes measurements were taken two times a month and canals three times over
the months. CROPWAT 8.0 and Geographical Information System (GIS) software were
used to analyze the collected data. The performance level of the scheme was assessed
using different indicators such as: adequacy, dependability, efficiency, effectiveness of
infrastructure and conveyance efficiency of the scheme. The result of this study revealed
that, adequacy, dependability, efficiency, equity and effectiveness of infrastructure were
0.62, 0.24, 0.94, 0.43 and 42.86% respectively. Those values indicate poor performance
level of the scheme except efficiency which was good. The overall average main, secondary
and tertiary canals conveyance efficiency was 89.9, 87.4, and 56.3% and conveyance loss of
1.33, 1.46 and 2.43ls
-1
100m-1
respectively which were below standards. This revealed
that, overall, maintenance and repair work on the conveyance canals were not sufficient.
Generally performance level of the scheme was poor. So, to use the water resources
effectively, efficiently and equitably water allocation to the farm should be carried out based
on crop water demand with irrigation scheduling. The conveyance systems should be
improved through regular canal cleaning and maintenance of infrastructures and
constructing silt entrance controlling structures are basic remedial measures.
