Abstract:
The gravity supply of water to irrigation fields can be achieved by impounding
schemes or diversion schemes. Unlike impounding dams, diversion structures
for irrigation are usually exposed to the overflow action of water and sediments.
Hence, they are liable to exhibit problems & predicting their performance under
this condition is very difficult.
Accordingly, irrigation structures demand the multi-faceted considerations of
hydrologic, structural, sediment and hydraulic analysis, geotechnical &
agronomic considerations and if not properly designed, often end up in
consequential problems. Thus, practicing engineer in the field often faces to
make sure this problem will not happen in the designs even if there is very
limited or no actual data in the field.
A case study considering 26 existing small scale irrigation works (1/3 of the total
schemes) in the south region is carried out for this research work and attempt is
made to understand the causes of the major problems that are related to the
design consideration of the different components of the structure and identify
the gap in knowledge between the current design practices and performance of
the structures. The pre and post construction institutional aspects and water
management problems are also given due attention. Some of the many
structural problems in the existing irrigation structures are problems of
sedimentation at the headwork and main canal, downstream scouring,
upstream flooding, damage on impervious and flexible apron, change of river
course, clogging of intake and under sluice outlets. Likewise, some of the
institutional & management problems are water right conflict among up
streamers and down streamers, market problems, proper handing over
problem, lack of proper training and the like. The causes for these problems are
attributed to the problems in study, design, implementation and utilization of the
schemes.
