Based on the maximization of entropy, microwave sensors are becoming standard approaches for converting point surface velocity measurements into discharge. Unfortunately, this conversion is conditioned by cross-section regularity and by the need to take the surface measures above the vertical where the maximum velocity occurs. Cross-section irregularities and the presence of floodplains, vegetation and/or local bed depressions can change the theoretical applicability conditions of the proposed methods and, due to the wandering of the current, the microwave sensor must be continuously moved to track the maximum velocity. We describe the theoretical development and practical application of a new approach to operationally convert surface velocity and water level, measured using a fixed installation, into discharge. The resulting equation that links the surface point velocity measurement to the discharge is a function of two parameters describing the velocity distribution within the cross-section plus an additional correction factor which describes the non-homogeneity of the different vertical slices into which the cross-section is divided. Interesting results of the approach are shown for the gauging section of Tavagnasco on the Dora Baltea River in Italy with high performances both in terms of calibration and validation.

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