Development and application for irrigation of hydraulic simulation model canal network

Improving the performance of the major irrigation projects is one of the economically viable options in meeting the growing water demands and sustaining the productivity of irrigated agriculture under present financial, environmental, and physical constraints. Hydraulic simulation models offer unlimited opportunities for improving the performance of the irrigation systems by studying the flow behavior in a large and complex canal network under a variety of design and management scenarios. This paper presents a hydraulic simulation model developed for steady and unsteady flow simulation in irrigation canal network. The model uses the implicit four-point Preissmann scheme for discretization of the Saint-Venant equations and solves the resulting equations using the sparse matrix solution technique. The model is applicable for simulating flow in a series of linearly connected reaches, and branched as well as looped canal networks. The different boundary conditions that can be modeled are discharge hydrograph at the source node(s) and stage hydrograph, rating curve, uniform flow, and discharge hydrograph at the terminus node(s). The model is capable of handling different hydraulic structures such as weirs, sluice gate, drops/falls, pipe outlet, and imposed discharge. It also allows computation of gate opening for a given full supply level and discharge at the cross-regulator and offtaking points, respectively. For entering and editing canal network description and boundary conditions, including different hydraulic parameters and displaying the results, a user friendly graphical user interface has been provided. Accuracy and numerical stability of the model tested using the mass conservation test and test with ramp discharge as inflow hydrograph, indicated that the model performs satisfactorily. Comparison of simulated and observed discharges at the tail regulator of the Right Bank Main Canal of Kangsabati Irrigation Project showed that the model performs satisfactorily for most of the irrigation events. Further, comparison of the model simulated stage and discharge with that of the HEC-RAS model showed that the results of both the models are almost identical. The different simulation results, thus, suggest that the developed model can be successfully used as a tool for hydraulic simulation of canal network.