Sediments cause serious problems in irrigation systems, adversely affecting canal performance, driving up maintenance costs and, in extreme cases, threatening system sustainability. Multiple studies were done on the deposition of non-cohesive sediment and implications for canal design, the use of canal operation in handling sedimentation problems is relatively under-studied, particularly for cohesive sediments. In this manuscript, several scenarios regarding weirs and gate operation were tested, using the Delft3D model, applied to a case study from the Gezira scheme in Sudan. Findings show that weirs play a modest role in sedimentation patterns, where their location influences their effectiveness. On the contrary, gate operation plays a significant role in sedimentation patterns. Reduced gate openings may cause canal blockage while intermittently fully opening and closing of gates can reduce sediment deposition in the canal by 54% even under conditions of heavy sediment load. Proper location of weirs and proper adjusting of the branch canal’s gate can substantially reduce sedimentation problems while ensuring sufficient water delivery to crops. The use of 2D/3D models provides useful insights into spatial and temporal patterns of deposition and erosion but has challenges related to running time imposing a rather coarse modelling resolution to keep running times acceptable.

In order to cover the crop water requirements, flow control structures such as gates and weirs are used to transfer the desired amount of water from the canals to the field canals. This paper examines the impact of gate operation and the selection of gates on the deposition of non-cohesive sediment. The Delft3D model is used to simulate the effects of different scenarios regarding gate operation and the location of the gate that is opened. The model results showed that the gate selection affects not only hydraulic parameters but also morphological parameters. It was found that opening the gates closer to the offtake resulted in less sediment deposition at the entrance of the branch canal when compared to opening the gates further away. Gate selection can be used as a tool in sediment management. By alternating the opening of different gates sediments that are already deposited after opening one gate can be eroded when another gate is operated, thus minimizing the additional cost of sediment removal. The use of Delft3D proved beneficial as the selection of different gates leads to asymmetric sediment deposition patterns which would be missed when using a 1D model.

Sediment deposition in irrigation systems results in the disruption of water distribution and thereby high maintenance costs. The vast majority of studies on the behavior of cohesive and noncohesive sediments have been done in rivers and estuaries. Modeling studies on sediments in irrigation systems have mainly dealt with noncohesive sediments mostly using one-dimensional (1D) models. In practice, irrigation systems diverting from natural rivers often face a mix of cohesive and noncohesive sediments. Sediment deposition is usually asymmetric, especially around offtakes and structures, and cannot be resolved using 1D models. Therefore, the authors used Delft3D version 4.02.03—a two- and three-dimensional (2D/3D) model commonly applied to rivers and estuaries—adapting it for use in irrigation canals to test different scenarios of uniform and mixed cohesive and noncohesive sediments of varying concentration and water discharge. The authors found that the model was able to provide additional insights into the behavior of cohesive and noncohesive sediments in irrigation canals, thus showing the importance of using 2D/3D models. Also, they found that cohesive sediments are more sensitive to variations in discharge and velocity compared with noncohesive sediments. Simulations revealed that where noncohesive sediments are present in a mixture with cohesive sediments, deposition is slower than in the case of pure noncohesive sediments of the same concentration.