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

Abstract

Abstract. In order to demonstrate the spatial and temporal variations in meltwater chemistry at both the lysimeter (0.25 m 2) 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. With these deficiencies in mind, the objective of this paper is to outline the spatial and temporal variations in meltwater flow volume and chemistry within natural snowpacks at both microscale and basin scale. Specifically, we will investigate the impact of flow variability on the CF and mass flux of meltwater and finally consider the potential role that the spatial variations in snow depth play in controlling the timing of meltwater runoff chemistry.

Biogeochemical cycling in forest soils of the eastern Sierra Nevada Mountains, USA

“…At the smallest scale, temporal uncoupling of the N cycle can occur during snowmelt if the release of N from snowpack, litter, and soil does not coincide with the period of maximum tree uptake. In most snow-dominated systems, the majority of nutrient release occurs during the early parts of snowmelt (Berg, 1992;Bownam, 1992;Creed et al, 1996;Fahey and Knight, 1986;Marsh and Pomeroy, 1999;Peters and Leavesley, 1995;Stottlemeyer and Toczydlowski, 1990;Williams and Melack, 1991;Williams et al, 1995). In our studies in Little Valley, however, we find the opposite: that is, the majority of nutrient release occurs during the latter stages of snowmelt .…”

Ion enrichment of snowmelt runoff water caused by basal ice formation

“…The preferential flow paths are an important mechanism for rapid delivery of meltwater to the bottom of the snowpack while it is still below 0°C (Woo et al, 1982). The ion-mass flux in these flow fingers is higher than that in the matrix flow (Marsh and Pomeroy, 1999); implying that the basal ice will be primarily comprised of enriched water from preferential flow paths.…”

“…Fractionation is influenced by ion distribution within the parent snowpack, melt-freeze cycles, rain-on-snow events, snow depth, and preferential flow through the snowpack (e.g. Colbeck, 1981;Davies et al, 1982;Marsh and Pomeroy, 1999). Consequently, snow meltwater chemistry may be strongly influenced by processes occurring weeks or months prior to melt (Cragin et al, 1996).…”

Transformations of runoff chemistry in the Arctic tundra, Northwest Territories, Canada

“…The Ca 2C SO 4 2 signal was attributed to interaction with lake sediments and mixing with sediment pore water, and the Ca 2C HCO 3 signal was attributed to interaction with the Quaternary sediments underlying the stream channels (Teare, 1998). The ion composition of the streams contrasted strongly with the early melt peak in the primary chemical fluxes of Na C , Cl , SO 4 2 , and NO 3 and the very low levels of K C and organic acids observed by Marsh and Pomeroy (1999) in nearby snowpacks. This suggests that the composition of the melt water that flowed through the soil to the stream changed markedly by mixing with soil water and interacting with the soils.…”