Hydrochemistry of Meltwaters Draining from an Alpine Glacier

Electrical conductivity, a measure of total ionic concentration, was determined for samples of meltwaters draining from the snout of Gornergletscher, Switzerland, during the summer ablation season of 1974 and continuously recorded in summer 1975. Samples of meltwaters from the snout meltstream and glacier surface were analyzed for Na+, K+, Ca2+, and Mg2+.Meltwaters from the glacier surface have low solute contents (electrical conductivity 2.7-5.4 μS cm−1; Na+ < 0.4 mg L−1; K+ 0.1-0.4 mg L−1; Ca2+ 0.1-0.7 mg L−1; Mg ≤ 0.1 mg L−1) of atmospheric origins whereas after passage through the glacier, waters are chemically enriched (conductivity 6.5-44.0 μS cm−1; Na+ 0.1-1.0 mg L−1; K+ 0.1-2.7 mg L−1; Ca2+ 1.8-9.0 mg L−1; Mg2+ 0.1-2.3 mg L−1). A marked, diurnal variation of solute concentration in meltwaters at the snout occurs inversely with that of discharge, as a result of a two-component system of englacial and sub-glacial routing of water within Gornergletscher. A trapezoidal distribution of discharge-concentration relationships in glacier meltwaters results. Clockwise hysteretic loops of electrical conductivity with discharge were observed to have a diurnal cycle. The dominant ion (45.0-90.9% of determined cations) in meltwaters draining from the snout is Ca2+.A comparison of meltwater composition from the meltstreams of Gornergletscher and other glaciers is presented. Intensive sampling or continuous monitoring is shown to be essential in characterizing daily and seasonal temporal variations in Alpine water quality.