Effect of forest biomass on airborne snow water equivalent estimates obtained by measuring terrestrial gamma radiation

Estimates of snow water equivalent derived from measurements of the attenuation of terrestrial gamma radiation emitted by potassium are systematically biased downward if substantial amounts of forest biomass exist in the region where the radiation measurements are obtained. The degree of underestimation is a function of the amount and type of biomass. The effects of these factors on the snow water equivalent estimate are examined, and a means of correcting for the downward bias is given. The methodology presented can aid National Weather Service hydrologists in improving river and flood forecasts, water supply forecasts, and spring flood outlooks for large areas of the United States and Canada