Use of 2D/3D Models for Cohesive and Noncohesive Sediments in Irrigation Canals

Abstract

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.