Snow depth and snow water equivalent distribution in a high alpine basin: quantifying the length scales and magnitude of variation in Senator Beck Basin, Colorado

Estimating the distribution of seasonal snow is important for water resource management, as one-sixth of the world's population depends on snowmelt for their water supply. In addition, snow water equivalent (SWE) estimates are important for flood and hydropower forecasting, and are critical for understanding surface and groundwater systems. Because the snow cover has such a large effect on the global energy balance, accurate SWE estimates over large areas are necessary for evaluating future climate change scenarios. To adequately describe the correlation length scales of snow depth and SWE at the basin scale, however, measurements at 10 m resolution or less are required, which is impractical using traditional methods. Using an accurately calibrated, portable FMCW radar, coupled with a survey-grade kinematic GPS system, more than 700,000 independent radar measurements were made throughout Senator Beck Basin over a 3 day period in March 2007. These radar measurements are used to estimate snow depth and SWE, covering scales from 10 cm to several km. Due to the large number of estimates, the variogram of snow depth can be accurately calculated, and used to help interpolate between measurements. The length scales and magnitude of variation both above and below tree line are quantified, and uncertainties in the degree of variation are described. Due to the differences in environmental controls, optimum sampling and interpolation schemes vary with location in the basin.