A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1988

A simulation model for the operation of an irrigation canal system has been developed in this study. The method developed is applied to a hypothetical canal system consisting of main canal and branch canals. Vertical under sluice checks are provided to divide the main canal into reaches and to create higher water surface elevations so as to take out branch canal offtakes and also to control the flows to the branch canals and to the downstream of main canal reach. The model is developed to predict the discharge and depth hydrographs at vital locations in the system and to determine the final gate openings of in-line as well as off- line structures so as to allow predetermined discharge to pass through the check structures. The flow in the canal is considered unsteady and the complete Saint-Venant equations for unsteady flow in open channel is solved numerically by the implicit finite difference scheme with the help of the double sweep method. To start the computations for unsteady flow, initial condition is provided considering steady gradually varied flow and the Newton Raphson iterative procedure is adopted for profile computation. Sensitivity analyses are performed for t he model performance by varying the parameters both hydraulic and numerical . The results from the Newton Raphson method compares well with that of the constant step method. The unsteady flow simulation model is verified with the results of an analytical method and data from other sources. The verification confirms the validity of the model and the solution algorithm incorporated in this study. Lastly, the developed model is applied to a system with varying discharge condition (i.e discharge cutoff) and a solution strategy is presented. The programme developed in FORTRAN 77 is suitable for mainframe as well as for microcomputers.