In connection with water acidification and the subsequent disappearance of fish populations and also massive fish kills during spring floods, particular interest has been focused upon the fate and effects of ions released from the snowpack during melting.

Meltwater, enriched in ions, leaves the snowpack during melting episodes in winter. These (often small) amounts of water may via the ground-water reservoir have a long term influence upon the quality of winter runoff.

Data from catchments ranging from 0.04 to 232 km2 indicate that, during spring snowmelt in Tovdal, South Norway, the equivalent sum of ions in runoff is mainly governed by the release from the snowpack of sulphate and chloride, which move more or less directly into the watercourses, carrying with them cations directly from the snowpack or from biological and geological material within the catchment.

The concentrations in bulk snow decrease during melting and, therefore, during early snowmelt, the concentrations of sulphate and chloride are 2–5 times higher in the runoff than in the snowpack, well in accordance with polyethylene lysimeter experiments. The composition of the cationic counterparts of these anions in the runoff varies with the runoff rate, with high runoff rate yielding the most acid water.