Numerical and experimental investigations on aggradation and degradation in irrigation canals accounting for infiltration^*

Abstract

A numerical model was used in the present study to predict aggradation, degradation, and subsurface moisture content in irrigation canals. The numerical model solved Saint‐Venant and sediment continuity equations to analyse overland flow and sediment transport, whereas Richard's equation was used to analyse subsurface movement of water. Saint‐Venant and sediment continuity equations were solved by using the MacCormack scheme based on the finite difference method, and the Richard's equation was solved by using a mass‐conservative fully implicit finite difference method. Extensive irrigation canal experiments involving measurement of aggradation, degradation, and subsurface moisture content were conducted to assess the performance of the numerical model. The predicted aggradation and degradation represented a good agreement with data recorded in laboratory. Soil moisture profiles were estimated for sediment‐laden water and clear water conditions in irrigation canals. But the effect of sediment‐laden water on the moisture profiles was observed as insignificant. The observed and the model‐predicted soil moisture varied marginally as the observed moisture was attributed to errors during the collection of soil samples from the experimental field.