ABSTRACT
38Sediment deposition in irrigation systems results in disruption of water distribution and high maintenance costs. The vast majority of studies on the behaviour of cohesive and non-cohesive sediments have been done in rivers and estuaries. The relatively few studies on sediments in irrigation systems deal with non-cohesive sediments mostly using 1D models. In practice, irrigation systems that tapping from natural rivers often face a mix of cohesive and non-cohesive sediments. The sedimentation patterns usually are non-uniform, especially around offtakes and structures. Therefore, the authors used Delft3D, a hydro-dynamic 2D/3D model, and adapted it for use in irrigation canals to test different scenarios of pure and mixed sediments with varying concentrations and discharges. The authors found that Delft3D was able to provide additional insights in the behaviour of cohesive and non-cohesive sediments in irrigation canals and showed the importance of using 2D/3D models. Also, it is found that cohesive sediments are more sensitive to the variations in discharge and velocity compared to non-cohesive sediments. Simulations reveal that where non-cohesive sediments are present in a mixture with cohesive sediments, the deposition is slower than in the case of pure non-cohesive sediments of the same concentration.
