Accuracy and repeatability of in situ snow wetness measurements using the newly developed twin-disc capacitance sensor

If water from snowmelt and rain-on-snow can be tracked as it moves through the snowpack, streamflow forecasters could be informed of the potential for excessive snowpack outflow before actual outflow occurred and gain time to apply mitigation procedures to accommodate the extra water. During the winter of 1985-1986, eight twin-disc capacitance sensors, used to track changes in the liquid water content of snow (wetness) at the USDA Forest Service’s Central Sierra Snow Laboratory, in northern California, were calibrated and tested for their ability to repeat measurements. For all sensors, snow volume wetness varied less than 0.06%, indicating low 'between measurement' variability. To assess accuracy, twin-disc sensor wetness was compared with wetness measured by the Denoth-Fogler snow moisture meter. For all sensors, the difference between the measurement means of the two methods was 0.25% snow volume wetness.