Modelling stage-discharge relationship with single inflection point non-linear functions

The problem of using a non-linear function with only one inflection point for modelling hydrological phenomena is addressed. We present the examples of such functions and retain values of their parameters giving increasing function with one inflection point. For a set of data from one river, their least squares adjustments are compared for the stage-discharge relationship, namely the flow and the height of the water of a river. Finally we raise the problem of classifying rivers in terms of their best non-linear fitting model.