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Zeitschrift für Gletscherkunde und Glazialgeologie, Bd.
VII,
Heft 1—2, 1971
STUDY OF THE DISCHARGE OF ALPINE GLACIERS
BY MEANS OF EiWIRONMENTAL ISOTOPES AND
DYE TRACERS*
ByH. BEHRENS, H. BERGMANN, H. MOSER, W. RAUERT, W. STICHLER
München, and
W. AMBACH, H. EISNER, K. PESSL, Innsbruck
Wifch 12 Figures
SUMMARY
In order to gain a deeper insight into the water budget of temperate glaciers, a model was
used in which total discharge of the glacier consists of three runoff components, namely,
ice and snow melt water running off during Summer ablation, and subglacial water. This
model was applied to the runoffs of Kesselwandferner and Hintereisferner in the catchment
area of the Rofenache (ötztal Alps, Austria).
The total runoff was measured by tracer methods using the f luorescent dye Rhodamin WT.
It proved advantageous to employ tracer methods particularly on glacier streams, since
current meter measurements in these flow Channels with their changing flow cross sections
and turbulent currents are very difficult. In view of the given terrain conditions and for
reasons of expediency, the instantaneous injection of tracer, combined with continuous
sampling, must be preferred to a continuous injection of tracer. This method is facilitated
in particular by a simple apparatus for continuous sampling during tracer passage at the
site of measurement. Comparison between the results of tracer measurements and those of
current meter measurements at Vent-Rofenache revealed that the accuracy of tracer measure¬
ments is at least equal to that of measurements by current meter.
For determining the runoff portions making up total flow, balance equations were used of
the natural isotope contents in the water of tritium and deuterium (or oxygen-18). The isotope
Contents are subjected to significant annual variations and in the summer ablation period
also to daily f luctuations. The premise of this method is that there exists a correlation between
the individual runoff portions and specific tritium and deuterium contents, respectively.
Thus, melt water from old glacier ice is practically free of tritium, whereas snow melt water
and subglacial water are marked by high tritium contents. As regards deuterium levels, sub¬
glacial water differs in its low values from the surface melt waters with higher values. It
was found, moreover, that spring water and melt water are characterized by distinct
conductivity values.
Based on the results obtained for the Hintereisbach, the Kesselwandbach and the Rofenache,
the quantitative model calculation of the daily variations of the runoff proportions furnished
meaningful glacio-hydrological results. In addition, the discussion of the isotope content of
glacier runoffs observed in part for periods of more than five years, provided valuable insight
into glacier melting processes, their correlation with weather conditions, and the runoff
phenomena of melt water in summer and in winter.
ZUSAMMENFASSUNG: UNTERSUCHUNG DES ABFLUSSES VON ALPENGLETSOHERN MIT
UMWELT-ISOTOPEN UND FARBSTOFF-TRACERN
Um einen vertieften Einblick in den Wasserhaushalt von temperierten Gletschern zu ge¬
winnen, wird ein Modell verwendet, bei dem sich der Gesamtabfluß des Gletschers aus drei
Abflußanteilen, nämlich dem während der sommerlichen Ablation abfließenden Eis- und
Schneeschmelzwasser und dem subglazial abfließenden Quellwasser zusammensetzt. Dieses
* Paper presented at
XV.
General Assembly of IUGG, Moscow, USSR, Commission of Snow
and Ice, Symposium on Interdisciplinary Studies of Snow and Ice in Mountain Regions,
9-13 August 1971.
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