The effect of the choice of the control variables of the water level control of open channels

The effect of the choice of the control action variables on centralized water level controllers for open channels is analyzed. Three models are compared. In the first model the control action variable is the discharge and then the inverse gate equation is used to calculate the gate openings. In the second case the control action variable is the gate opening and that is incorporated to the canal model - supposing that the upstream water levels of each pool are known. In the third case control variables are also the gate openings but the upstream water level of each canal pool is unknown, they are calculated by the models by using the hydraulic relationships between the variables. These three models are discussed and compared through an example of centralized Linear Quadratic Regulator (LQR) controller using as example the Test canal 2 of the ASCE.