Forest Canopy Reduction and Snowpack Dynamics in a Northern Idaho Watershed of the Continental-Maritime Region, United States

• Published in: Forest science Vol. 61; no. 5; pp. 882 - 894
• Main Authors: Hubbart, Jason A, Link, Timothy E, Gravelle, John A
• Format: Journal Article
• Language: English
• Published: Bethesda Oxford University Press 01-10-2015
• Subjects: Forest management; Forests; Precipitation; River ecology; Snow; Studies; Topography; Watersheds; Idaho; USA, Idaho
• ISSN: 0015-749X; 1938-3738
• DOI: 10.5849/forsci.14-025

Full understanding of snowpack dynamics in forested mountainous terrain of the western United States remains one of the greatest uncertainties in forest and water management in the region. The effect of forest canopy removal (i.e., 100% clearcut, 50% partial cut) on snow deposition and ablation dynamics was studied in a northern Idaho watershed. For the water year tested, results indicate that 85% of the annual precipitation (132 cm) occurred during the snow deposition and ablation months (October-May). Peak snow water equivalent (SWE) was approximately 57, 30, 17, and 34 cm in clearcut, 50% basal area partial cut, undisturbed, and riparian valley bottom forest sites, respectively. The number of days to melt-out from peak SWE ranged from 53 to 36 days in the clearcut and full forest, respectively. Clearcutting resulted in almost 3 times the snowpack as full forest and prolonged snowpack depletion by 3 weeks. Snow interception in the full forest, partial cut, and valley bottom forested sites was approximately 60, 43, and 32% of annual snow deposition, respectively, assuming negligible meltwater drip. Results indicate high variability in snowpack dynamics at snow course sites, suggesting that site-specific microclimate variations within treatments (due to canopy cover, aspect, elevation, and other factors) are important. Ultimately, assuming snow cover uniformity may lead to considerable errors in the computed quantity and timing of runoff pre- and postharvest in the climatologically complex and topographically diverse landscapes of the continental-maritime region of the United States.