Snowmelt during rain-on-snow in coastal British Columbia

A study was conducted in Jamieson Creek Experimental watershed near Vancouver, B. C. to determine differences in melt rates during rain-on-snow events between a cutover and a Coastal Western Hemlock old-growth forest. An evergy balance approach was used to quantify the energy fluxes involved in the snowmelting process. Each site was equipped with two independent lysimeters; a pair of small (0.3 sq m) barrel lysimeters and a large (28 sq m) plastic sheet lysimeter recording through tipping bucket arrangements. Wind speed, relative humidity and air temperatures were measured at .6 meters and 1.5 meters above the snow pack to evaluate turbulent fluxes. Snowpack and ground heat exchange was measured with a profile of 6 thermocouples at 0, 0.3, 0.6, and 1.0 meter above ground surface and 0.05 and 0.1 meter below the ground surface. Radiation was monitored with net all-wave radiometers (1 in cutover, 3 in forest). Lysimeter results are compared to U.S. Corps of Engineers equations and theoretical calculations.