Abstract:
The Oromia regional state undertook the construction of 173 schemes from
1984 G.C to 2006 G.C. for meeting demands of about 31940 HH by developing
12456.97ha
1
of land in the region. This IWMl-financed research, "Evaluation of
Failures and Design Practices of River Diversion Structures for Irrigation", was
made on schemes with objectives of assessing problems and drawing set of
recommendations for the design, implementation and operation of existing river
diversion structures.
The GIS arcview data base showing all the features and the problems was
prepared for \he schemes. Furthermore, a detail data for the region with respect
to total area developed, total investment, total number of beneficiaries benefited
from the scheme was prepared on branch and zonal basis. The hydraulic
problems considered for the analysis on 36 schemes were sedimentation
upstream of weir, main canal siltation, damage on farm lands, damage on the
Intake, clogging of the under sluice, damage on scouring sluice, downstream
scouring, damage on the retaining wall, damage on downstream apron, damage
on the downstream cut off, damage on the sill, damage on weir proper, change
in the river course and upstream flooding. All these problems could be created
because of inappropriate design procedure, knowledge gap in utilizing data and
use of empirical formula. The problems, sedimentation upstream of weir and
main canal siltation were found the most critical for the schemes considered. A
case study of a sample project was taken for detail analysis on which problems
of sedimentation upstream of weir, clogging on the under sluice, downstream
scouring and damage on the sill exist together. Analysis on problems other than hydraulic i.e . planning, institutional, social,
economic and operational was also made on 17 schemes for which full data
was obtained. And accordingly lack of selective crop production system, lack of
storage facilities, presence of crop disease, malaria case, lack of land
redistribution, lack of credit were found the upper most critical out of 20
problems considered. All of the above problems are critically analyzed for each
scheme from which important conclusion and recommendation could be drawn.
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