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

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, altering the dynamics of the hydrological process within the watershed. As part of a multi-year R&D program examining the impacts of surface mining on watershed hydrology in the Elk Valley, British Columbia, this study investigates how surface vegetation atop waste rock influences snow accumulation and ablation, and the ability of a physically based model to simulate these hydrological processes. During the 2014 melt season, meteorological observations, eddy covariance turbulent fluxes 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. Variations of meteorological data, turbulent fluxes and measured snow conditions between sites were assessed. Elevation was the dominant control of snow accumulation, with the upper elevation site recording a maximum snow water equivalent of 67 cm, whereas the lower elevation site had a maximum snow water equivalent of 17 cm. Ablation was driven largely by incoming short-wave radiation, which at the bare waste rock and grass covered waste rock sites was greater than the forested site. Turbulent flux contributions to snow ablation were limited in 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 effectively simulate the influence of vegetated waste-rock surfaces on the hydrological system. However, model parameters regarding vegetation cover and blowing snow required careful calibration to obtain a suitable model output. Results of this study can be used to more accurately model the influence of vegetated waste-rock on the timing and magnitude of the spring freshet in the Elk Valley, British Columbia.