“…Nevertheless, despite of the low values of the coefficient of determination (R 2 ), having a system that approximates the water level of a river's flow with a mean error of 1 cm, is considered as a fair enough approximator for the purposes of this document. While in many studies, such as, e.g., in [12,14,15], only the past time series are used in order to forecast the water level of rivers, and some others use the weather data of the past days together with the time series (e.g., in [16]), the present study follows a completely different approach. The present study uses data provided by sensors installed on areas of the river, together with weather data which can be provided in real-time by national organizations; this methodology was followed because the authors believe that the rainfall in areas near the river is a parameter easy to retrieve, is of crucial importance on the resulting water level, but other studies usually do not use it.…”