Role of sediment transport in operation and maintenance of supply and demand based irrigation canals : application to Machai Maira Branch canals; Dissertation, Wageningen University and UNESCO-IHE Institute for Water Education, Delft.

Abstract

Majority of the irrigation canals in Indus Basin Irrigation System (IBIS) are upstream controlled with supply based operation and now gradually moving towards demand based operation. The irrigation canals under study are automatically downstream controlled with demand based operation. Sedimentation is a major operation and maintenance problem in IBIS canals. Various techniques are applied to manage sediments which start with the silt exclusion, silt ejection, canal design and operation and finally end with the removal of deposited sediments. The story of sediment management becomes more complicated for downstream controlled demand based irrigation canals. In demand based operation the irrigation canals cannot run always at full supply discharge like in supply based irrigation canals, but instead the discharge keeps on changing depending upon the crop water requirements in the canal command area. Such type of canal operation is not always favourable for sediment transport as at small discharges, flow velocities fall quite low which lead to excessive sediment deposition in the canal prism. This study has been designed to investigate the hydrodynamic relationships which can prevent sediment deposition in downstream controlled demand based irrigation canals, while catering the crop water requirements of the command area. It has been found that the maintenance needs can be minimized by managing sediment transport through better canal operation and management