Snow wetness influence on impulse radar snow surveys theoretical and laboratory study

The snow-water equivalent of late-winter snowpack is of utmost importance f or hydropower production in areas where a large proportion of the reservoir water emanates from snowmelt. Impulse radar can be used to estimate the sn ow-water equivalent of the snowpack and thus the expected snowmelt discharg e. Impulse radar is now in operational use in some Scandinavian basins. Wit h radar technology the radar wave propagation time in the snowpack is conve rted into snowwater equivalent with help of a parameter usually termed the a-value. Use of radar technology during late winter brings about risk for m easurements on wet snow. The a-value for dry snow cannot be used directly f or wet snow. We have found that a liquid-water content of 5% (by volume) re duces the a-value by approximately 20%. In this paper an equation, based on snow density and snow liquid water content, for calculation of wet-snow a- value is presented.