The Influence of Site Conditions and Surface Vegetation on Snow Accumulation and Ablation in the Elk Valley, British Columbia, Canada

English Abstract:

Surface mining of coal in the Elk Valley, British Columbia involves the blasting of overburden rock to access the underlying coal formations. Waste rock is placed in adjacent valleys, which influences the timing and magnitude of hydrological fluxes within the watershed. As part of a multi-year R&D program examining the influence of surface mining on watershed hydrology in the Elk Valley, British Columbia, this study investigates how: 1) site conditions and surface vegetation atop waste rock influences snow accumulation and ablation, and 2) the ability of a physically based model to simulate these processes. During the 2014 melt season, meteorological observations, turbulent fluxes determined via eddy covariance, and snow conditions were measured at three sites: 1) a bare waste-rock surface, 2) a waste-rock surface covered with agronomic grass species, and 3) a mixed pine stand on waste-rock. Elevation was the dominant control of snow accumulation, with the upper elevation site recording a maximum snow water equivalent of 670 mm, that compared to the lower elevation site with a maximum snow water equivalent of 170 mm. Ablation was driven largely by incoming short-wave radiation, which at the bare waste-rock and grass covered waste rock sites was greater than at the forested site. Melt occurred at the forest site several weeks in advance of the bare and grass covered sites. Turbulent flux contributions to snow ablation were limited at the forested site relative to the bare waste-rock and grass covered waste rock sites. The physically based Cold Regions Hydrological Model (CRHM) was able to simulate the influence of surface vegetation on the accumulation and melt dynamics. Model results were sensitive to parameters quantifying vegetation cover and blowing snow. Results of this study assist our understanding of how surface vegetation on waste rock and site conditions can influence the timing and magnitude of melt and infiltration, and subsequent freshet response.