Performance Evaluation of Karfe Small-Scale Irrigation Scheme: (A case Study of Karfe Small Scale Irrigation Scheme East Shoa Bishoftu,
No Thumbnail Available
Date
2026-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The performance of small-scale irrigation schemes is necessary for increasing agricultural productivity
and ensuring sustainable water resources management. This study assessed the hydraulic, agronomic,
and structural performance of the Karfe Small-Scale Irrigation Scheme (65 ha), which diverts water
from the Mojo River using a broad-crested weir and serves 162 households through right (2,250 m) and
left (1,503 m) main canals. The evaluation was conducted during the main wheat cropping season (07
January–30 April 2026), considering spatial variability across head, middle, and tail sections of the
command area. A mixed-methods approach was applied, combining field measurements, laboratory soil
analysis, and farmer interviews. Soil were analysed for texture, bulk density, and soil moisture
characteristics using standard laboratory equipment, while irrigation performance parameters were
measured using bucket–stopwatch flow measurement techniques and canal observations. Performance
indicators were computed based on FAO, IWMI, Bos et al. Khosla, and Terzaghi standards. The results
show that the soils are dominantly clay (average 55.39%), with bulk density ranging from 1.10–1.13
g/cm³, field capacity of 0.37–0.41 m³/m³, and total available water of 130–170 mm/m. Application
efficiency averaged 54.82% (moderate), while storage efficiency averaged 89.10%. Water supply
indicators shown spatial imbalance, with SAR (1.08), RI (50% at tail), and DPR (0.58) confirming
over-supply at the head and deficits at the tail. Conveyance efficiency averaged 76.09% (moderate),
while distribution uniformity was 75%. Structural evaluation showed poor conditions with an average
SCI of 2.36 and EI of 33.93%, indicating significant infrastructure deterioration. Major hydraulic
failures were also observed, including misaligned weir (12.4° deviation), insufficient stilling basin
length (2.19m deficit), floor length (1.55m) ,Froude number (3.93m) and FS Sliding(1.45),FS
Overturning 1.88 the retaining wall instability under seismic loading and water Pressure. Based on
these findings, mitigation measures including redesigned the retaining wall in two options (option1) is
Masonry, option 2 reinforced concrete retaining wall) as alternative, canal rehabilitation, structural
repair, improved irrigation scheduling, and strengthening of water user management are recommended
to enhance overall system performance and sustainability.
Description
Keywords
Small-scale irrigation, Water supply, Conveyance efficiency, Karfe, IWMI