Increasingly severe wildfires at high elevations are impacting snowpack - an important reservoir for the U.S. West. The altered landscape makes it more challenging to predict when snow will melt and how much water will be available for use. Colorado State University researchers studied the 2020 Cameron Peak Fire's effects on snowpack across mountainous terrain and found that location is key to melt rate and timing. Snowmelt rates vary from slope to slope, based on how much sun the slope receives and vegetation. Snow generally melts faster on south-facing slopes, which get more sun. The researchers found that the amount of water in the snow on a burned south aspect peaks earlier in the season than other snowpack locations, and south aspect snow melts sooner. The maximum water in the snowpack occurred 22 days earlier at burned south-facing locations than at burned north-facing sites at the same elevation, because of the increased solar radiation absorbed at the south-facing burned sites and lack of trees to intercept it. Snow on the burned south-facing slopes also melted completely 11 days sooner than snow on burned north-facing slopes. "This is an advance from previous understanding, because we've captured this spatial variability across complex mountainous terrain in a way that hasn't been done before," said Dan McGrath, a co-author of the study and Geosciences associate professor in the Warner College of Natural Resources. The study, published in Water Resources Research, is the first to quantify the impact of the full energy balance - both long- and shortwave energy - on snowpack in burned areas. Thermal energy is emitted by anything that absorbs solar energy, including the Earth's surface, trees and even cold substances, like snow. Loss of the forest canopy lowers this source of energy in burned areas, so the snowpack stays colder in winter. In spring, however, the energy balance flips, and the tree canopy in unburned... |