Assessment of rating curve through entropy-based Manning’s equation

The rating curve is the most used methodology for river flow quality and quantity monitoring and control. Nevertheless, it is still difficult to obtain a reliable rating curve because it takes a long time and involves high costs, especially if the measurement cross-section is unstable. Besides, the difficulties faced by operators who carry out the measurements lead to water discharge values being calculated on a statistical basis or with numerical models, which could involve significant errors in rating curves. To overcome these difficulties, the use of a modified form of the Manning’s equation, which contains information about the geometric development of the cross-section and the hydraulic behaviour, is suggested here. This formulation, derived from the entropy velocity theory, allows assessing water discharge in an expeditive way, maintaining a sufficient level of reliability, through the use of global parameters which consider the geometric information and the roughness of the river or, more extensively, of the areas of fluvial pertinence. In a first step, the procedure is validated on four river sections in the Grand-Duchy of Luxembourg and in the Basilicata region of Southern Italy. The results seem to demonstrate the validity and potential of the proposed approach.