Spatial and temporal variations in snowmelt runoff chemistry, Northwest Territories, Canada

Abstract

In order to demonstrate the spatial and temporal variations in meltwater chemistry at both the lysimeter (0.25 m2) and basin scale, field measurements of snowmelt were conducted in northern Canada. These observations show that microscale variations in flow volume are accompanied by variations in meltwater chemistry. For example, the solute concentrations were largest in areas with low flow, while the largest mass flux occurred in the areas with highest flow. The observed variations in both concentration and mass flux can be quantitatively described by the relationships described by Hibberd [1984). The field measurements clearly demonstrate that in order to estimate the average meltwater chemistry, it is necessary to sample the flow field at a scale similar to that required to average the lateral variations in meltwater volume. Variations in meltwater runoff chemistry also occur at the basin scale due to changes in snowcover depth and the resulting differences in the timing of meltwater release. For example, at this site, meltwater release occurs up to a week earlier from the shallow snow covers than for the deeper snow covers. It would be expected that this asynchronous meltwater runoff would result in a smoothing of the ionic pulse at the basin scale, with lower peak values and a more gradual decline in concentration when compared with meltwater at a point.