Surface water chemistry characteristics in the Lake Storgronningen drainage area, Hoylandet, during periods of high and low discharge

The surface water chemistry of Hoylandet has been studied by performing two synoptic surveys, during high runoff in the autumn of 1986 and during a low flow period in the summer of 1988. Based on water samples of up to 38 chemical variables from 75 sites, analyses show considerable variation in the chemical composition. There is a strong altitude gradient, i.e. very dilute poorly buffered waters dominate at higher elevations near the timberline while progressively higher salt content and alkalinities are characteristic at lower altitudes more dominated by forests. The influence of mires is less pronounced. The overall water quality is of oligotrophic nature with low concentrations of strong acid anions and metals known to be enriched under acidified conditions. The natural pH gradients are considerable but with no indication of anthropogenic acidification. The data provide little support for the hypothesis that in-catchment production of organically derived acidity leads to acid runoff, which in these catchments appears compensated by increased weathering. The findings are in general accordance with other Hoylandet catchment studies. It is concluded that this area may serve as a representative pristine surface runoff analogue for catchments currently affected by atmospheric deposition of strong mineral acids.