IONIC TRACER MOVEMENT THROUGH A WYOMING SNOWPACK

A meltwater ionic pulse with initial concentrations of 5-10 or more times the average was observed in lysimeters set at the base of a 2-m snowpack in an unpolluted, alpine watershed. Both background chemical species and added tracers exhibited the initial pulse. About 10 days after the onset of meltwater release, solute concentrations collected in the lysimeters dropped to near the average snowpack level. Silica was elevated more than major ions in some initial lysimeter samples, which is evidence of a soil-water or overland-flow contribution. Lysimeter flow rates were equivalent to about 2 cm of melted snow per day, approximately equal to the daily melt estimated from a temperature-index model. Less than 10 per cent of the ionic-tracer mass applied to snow directly above the lysimeters was present in the meltwater. Snow pits dug in an area adjacent to the lysimeters showed that ice lenses played a significant role in solute movement through the pack, influencing both solute depletion and horizontal vs vertical flow. Snow pits also showed depletion of at least 25-35 per cent of the solute mass during release of the first 10 per cent of meltwater. © 1990.