Water flow monitoring in open channels is widely employed in environmental and geotechnical field. Leakage measurement is one of the most important indicator of the overall performance of earth/rock-fill and concrete dam. The leakage rate is a function of the water level in the reservoir and depends either of the construction and of the behaviour of the dam. Consequently, leakage monitoring provides data for the evaluation of the long term stability of the dam constructions. Leakage water is usually impounded downstream of the dam and diverted to a basin in a weir-station.