Snow water equivalent (SWE) of snow is of great importance for hydropower production in areas where a large proportion of the reservoir water comes from snow. Impulse radar to estimate the SWE is now in operational use in some Scandinavian basins. With radar technology the radar wave propagation time in the snow pack is converted into SWE with the help of a parameter usually termed the a value. Use of radar technology during late winter brings about risk for measurements of wet snow. The a value for dry snow cannot be used directly for wet snow. A liquid-water content of 5% (by volume) reduces the a value by » 20%.