Application of PID Controller for Water Level Tuning (Case Study: Main Canal of Alborz Irrigation Network)

Distribution of required water for irrigation purposes in agricultural farms is one of the main objectives of irrigation networks construction. In this research, a PID controller was used to improve the operational capability of the main canal of Alborz Irrigation Network. For this purpose, a PID controller was developed in upstream and downstream directions in FORTRAN language and was combined with a ICSS hydrodynamic model designed in order to simulate the hydraulic and hydrological conditions and to operate water transfer systems. The PID controller can minimize errors between the actual and target depths. The operation option was considered in order to investigate the ability of the controller in keeping the level of the water constant at the time of the simultaneous decrease and increase of water flow entering the canal and the need of pond canals. Two scenarios were used to compare the mentioned controllers. Results indicated that the water surface error in downstream controller was lower than that in upstream controller. In downstream controller, the water level error at the beginning of opeartion, compared to the status quo, was 87.5%, 87%, and 87% for each structure, and within 18 hours, 97%, 99.5%, and 99.7% improvement rates were obtained. Furthermore, in upstream controller, the water level error, compared to the status quo, gained some improvement the rate of which differed according to the time; in other words, at the beginning of simulation, it was 75%, 93%, and 92%, within 12 hours was 27%, 97%, and 96%, and within 18 hours was 77%, 94%, and 98% Moreover, the system response time in the upstream controller was less than that in downstream controller. A comparison of existing conditions results with those of application of controllers proved acceptable ability of the controller designed to control the water level.