Downstream Control Algorithm for Irrigation Canals

Abstract

A downstream control algorithm for on‐demand operation of irrigation canal systems is presented. A constant water level is maintained at the downstream end of the pool. The approach is based on an explicit finite‐difference solution procedure of the St. Venant equations. The upstream gate settings are corrected according to the water level and the flow rate at the information nodes along the canal. The method is illustrated for the control of a canal pool bounded by an upstream gate and a downstream gate or pump. The effectiveness of the control has been tested using an unsteady‐flow simulation model that is based on the complete St. Venant equations and the implicit Preissmann scheme. The simulation results show that the proposed control method can cope with rapid variations of water demand and unknown disturbances in the system. The influence of the number of information nodes and the assessment of the physical parameters of the system on the response of the system has been investigated. Unless the estimated physical parameters of the system are too far from their actual values, an effective control can be achieved by measuring the water level and estimating the flow rate only at the most upstream and downstream ends of the pool.