Canal Monitoring Algorithm

Abstract

One of the main problems in the water management of irrigation canals is the control of water distribution among users’ outlets. This is because of the difficulty of measuring the removing flows correctly because they are highly variable in both time and space. To help solve this problem, a mathematical algorithm, the so-called canal monitoring algorithm, which determines the history of lateral extractions, is propounded. It uses the water depth measurements at checkpoints and the gate and other control device trajectories, which are implemented on the canal during a past period of time, and then obtains water withdrawals that happened at the outlets. The method also gives an estimation of the current state of the canal for model predictive control purposes. The algorithm solves the classical inverse problem, in which the unknowns are the parameters that define the flow rate trajectories of canal outlets, which are defined as piecewise functions of time in this paper. The algorithm is on the basis of the Gauss-Newton method and uses the complete Saint-Venant equations for the computation of the least-squared function. Numerical tests with excellent results have highlighted its computational efficiency, converging in a few iterations to the exact final results. These properties make the algorithm adequate to operate in real time. A laboratory canal test for verification shows accuracy in detecting water withdrawals at canal outlets when the Manning roughness coefficients are known. The test also reveals a functional relationship between the discharge removed and the empirical coefficients.