Monitoring snowpack SWE and temperature Snow water equivalent can be monitored using RFID tags as wireless sensors signal propagation

This work shows that passive radio-frequency identification (RFID) tags can be used as low-cost contactless sensors, to measure the variations in snow water equivalent (SWE) of a snowpack. RFID tags are 15 produced massively to remotely identify industrial goods, hence are available commercially off-the-shelf at very low-cost. The introduced measurement system consists of a vertical profile of RFID tags installed before the first snowfall, interrogated continuously by a 865–868 MHz reader that remains above the snowpack. The system deduces the SWE variations from the increase of phase delay induced by the new layers of fresh snow which slows the propagation of the waves. The method is tested both in a controlled laboratory environment, and outdoors on 20 the French national reference center of Col de Porte, to cross-check the results against a solid reference dataset (cosmic rays, precipitation weighting, temperature monitoring, and snow pit surveys). The technical challenges solved concern multipathing interferences, snowmelt acceleration during reheats, measurement discontinuity, and wet snow influence. This non-contact and non-destructive RFID technique can estimate the SWE of dry snow, with the accuracy of ±3−30 kg/m2 depending on the number of tags and antennas. In addition, the system can 25 monitor the snow temperature with 1 °C accuracy and spatialization, using dedicated sensors embedded in the tags. 1 Abstract[MLB1].[TE2] The amount of water contained in a snowpack, known as snow water equivalent (SWE), is used to anticipate the amount of snowmelt water that could supply hydroelectric power plants, water reservoirs, or sometimes cause flooding. This work introduces a wireless, non-destructive method for monitoring the SWE of a dry snowpack. The system is based on an array of low-cost passive radiofrequency identification (RFID) tags, 30