The snowmelt hydrology of a small alpine watershed
A study of the mass and energy balance of a small alpine watershed was conducted in the summer of 1976, with the aim of applying snow hydrology theory at a watershed scale in a remote environment. The field area is in the Coast Mountains near Bralorne, B.C. The study concentrates on the measurement of snow ablation, the movement of meltwater within the snowpack, the generation of stream runoff during and following snowmelt, and the energy balance at the snow surface. Standard methods for
... methods for measuring snow ablation, used in the fields of glaciology and snow surveying, are analysed in terms of their accuracy and precision, and the sampling densities required for their application. Simple field instrumentation is used to study the movement of meltwater in the snowpack, and this is analysed in terms of the theory of flow through a porous medium. The movement of meltwater through the snow is found to be the most important process affecting the shape and timing of the stream hydrograph. The movement of water along the base of the snowpack and through the soil also has an influence on the shape of the hydrograph. In the alpine meadow environment studied, saturated soil and ice covering ground beneath the snow contribute to a rapid stream response. A water balance is calculated for the watershed, based on measurement of stream discharge, snow ablation, and precipitation, and on climatological estimates of evaporation. An energy balance for the season is also calculated, supported by microclimatological measurements for part of the season. Radiation is found to contribute 90% of the energy required for snowmelt, and a simple model for the calculation of net radiation from solar radiation is developed. Empirical methods are found to be suitable for the calculation of turbulent energy transfer over snow. Some observations are made of the water balance in the late summer, and these indicate that water stored in the soil during snowmelt is important in maintaining streamflow later in the season.