Monitoring snow water equivalent using the phase of RFID signals

Abstract. The amount of water contained in a snowpack, known as snow equivalent (SWE), is used to anticipate the snowmelt that could supply hydroelectric power plants, fill reservoirs, or sometimes cause flooding. This work introduces wireless, non-destructive method for monitoring SWE dry snowpack. system based on an array low-cost passive radiofrequency identification (RFID) tags, placed under and read at 865–868 MHz by reader located above snow. was deduced from phase delay tag's backscattered response, which increases with traversed wave. Measurements taken laboratory, during snowfall events over 4.5 months Col de Porte test field, were consistent reference measurements cosmic rays, precipitation pits. accuracy ±18 kg m−2 throughout season (averaged three tags) ±3 data two antennas four five tags). overall uncertainty compared weighing ±10 % density range 61–390 m−3. main limitations observed measurement bias caused wet (biased discarded) need unwrapping. has number advantages: it allows continuous (1 min sampling rate snow), can provide complementary tag temperature, does not require reception external data, opens way towards spatialized measurements. results presented also demonstrate RFID propagation-based sensing remotely monitor permittivity low-loss dielectric material scientific-level accuracy.