River discharge data availability is of crucial interest for a variety of practical hydro-logical applications, such as the implementation, calibration and validation of hydrological models, the monitoring of climate change impacts on water resources and runoff extremes, the identification of the best criteria for the hydraulic infrastructures design and evaluation, the strategic planning and policies developing for both civil protection and water management activities. Discharge estimation in natural rivers is traditionally conducted through a velocity-area method, based on the discrete point sampling of flow velocity by currentmeters. New methods based on doppler (ADCP) and optical techniques offer a great potential for river monitoring, allowing for massive, easy and low-cost acquisitions of a wide range of measures in real time, at any flow conditions and at high spatial resolution. Large-scale particle image velocimetry (LS-PIV) and particle tracking velocimetry (LS-PTV) techniques have gained wide consensus for natural rivers monitoring. The surface velocity field is indirectly obtained by measuring the velocity of floating tracer particles, naturally present or artificially introduced to the flow, which is assumed to move with the local flow velocity. The dynamics of the liquid surface are recorded by cameras, through a sequence of consecutive frames captured by digital permanent gauge-cams installed close to the river, mobile-devices with operators standing on the banks and on bridges, or cams installed on unmanned aerial vehicles. The sequence is then processed to reconstruct the local flow velocity starting from the identification of the tracer particles displacements between pairs of subsequent frames. HYCLIC-LAB is very active in rivers monitoring by currentometers, ADCP and optical techniques (PIV and PTV) and is currently involved in a field campaign for the monitoring of all the main rivers of Sicily (Italy) and the flow rating curve recalibrations for the regional hydrometric network. MAJOR INSTRUMENTATION AND SENSORS: 1. an electromagnetic current meter (Model 801 Electromagnetic Flow Meter – Valeport) 2. a StreamPro ADCP - Acoustic Doppler Current Profiler (Teledyne RD Instruments); 3. A drone (NT8 contras – Neutech);