An Engineering Design Study of Electronic Snow Water Equivalent Sensor Performance

The USA ERDC CRREL and the USDA NRCS developed an electronic SWE sensor based on the results of field and theoretical studies of SWE pressure sensor performance. The CRREL/NRCS sensor is about 3 m square and is modular consisting of nine perforated panels, a center panel and eight outer surrounding panels that allow water to percolate through the sensor. Water percolation minimizes thermal differences between the sensor and surrounding soil and the eight surrounding panels act to buffer the center panel, where SWE is measured, from stress concentrations that develop along the perimeter of the sensor. Two years of field-tests (winters of 2005-2006 and 2006-2007) at Hogg Pass, OR, demonstrate that the CRREL/NRCS sensor's center panel accurately measures SWE variations even when stress concentrations are observed on the sensor's outer panels. During the first winter, stress concentrations occurred on the outer panels during periods of rapid snow settlement following large snow accumulations and when the rate of snowmelt at the sensor/snow interface was significantly different from the snowmelt rate at the soil/snow interface of the surrounding ground. SWE measurement performance is optimal when the sensor has no freeboard.