ALO docView - Study of the Discharge of Alpine Glaciers by means of Environmental Isotopes and dye Tracers (1971)

											/ 6 pages
Study of the Discharge of Alpine Glaciers by... (1971)

	tt^::T%AA Snow and Ice-Symposium-Neiges et Glaces (Proceedings of the Moscow Symposium, August 1971 ; Actes du Colloque de Moscou, aoüt 1971): IAHS-AISH Publ. No. 104, 1975. Study of the discharge of Alpine glaciers by means of environmental isotopes and dye tracers H. Behrens, H. Bergmann, H. Moser, W. Rauert, W. Stichler, W. Ambach, H. Eisner and K. Pessel Abstract. To gain a deeper insight into the water budgets of temperate glaciers, a model has been used in which the total discharge of a glacier is a combination of three runoff components, namely, ice and snow melt water runoff during the summer ablation period and water discharge sub- glacially. This model has been applied to the runoffs of the Kesselwand ferner and the Hintereisferner in the drainage area of the Rofenache (Ötztal Alps. Austria). Measurement of total runoff was made with the aid of a tracer method using the fluorescent dye rhodamine WT. The method was improved in particular by a simple apparatus for continuous samplirig during tracer passage at the measuring point. To determine the runoff proportions of the total flow, balance equations of the natural isotope levels of tritium and deuterium (or oxygen-18) were used in the water; these isotope levels are subject to significant annual variations, and also to daily fluctuations during the summer ablation period. The premise of the method is that a correlation exists between the separate runoff proportions and the specific tritium and deuterium contents. It was found also that spring water and melt water are characterized by distinct conductivity values. Measurements on the Hintereisbach, the Kesselwandbach and the Rofenache, using a quantitative model calculation of the daily variations of the runoff proportions gave meaningful glacio-hydrological results. In addition, the isotope contents of the glacier runoffs monitored in part for periods of more than five years provided valuable insights into glacier melting processes, their correlation with weather conditions, and the runoff phenomena of melt water in summer and winter. Resume. Pour arriver ä une connaissance plus approfondie du regime hydrologique des glaciers temperes, on a realise un modele de glacier: l'eau qui vient de ce glacier modele a trois origines, ä savoir: eau venant de la fönte des neiges et eau venant de la fönte de la glace, en ete; eau venant des sources situees sous le glacier. Ce modele de glacier a ete applique aux eaux d'ecoulement du glacier de la Kesselwand et du glacier du Hintereis dans le bassin de la Rofenache (ötztaler Alpen, Autriche). La mesure de l'ecoulement total fut realisee par la methode colorimetrique avec, pour traceur, le colorant fluorescent rhodamin WT. Pour prelever un echantillonnage integral durant le passage du traceur ä l'endroit de la mesure, on a realise un instrument simple. Pour la determination des differentes composantes de l'eau d'ecoulement du glacier, on a pose des equations de bilan relatives ä la teneur isotopique de l'eau en tritium et deuterium (ou meme oxygene-18). Cette teneur en isotopes montre d'importantes variations saisonnieres. Pendant la periode estivale de fönte en surface de l'eau du glacier, eile montre aussi des variations diurnes. II y a relation etroite entre les differentes composantes des eaux d'ecoulement ayant des contenus specifiques de tritium et de deuterium. On a constate d'autre part que l'eau de source et l'eau de fönte se distinguent l'une de l'autre par leur conductibilite electrique differente. En pre.nant comme base les mesures realisees sur les variations journalieres des differents ecoulements du ruisseau venant du glacier du Hintereis, du ruisseau du glacier de la Kesselwand et du ton-ent Rofenache, on a constate que l'utilisation quantitative du calcul fait sur le modele donnait de precieuses indications hydro-glaciaires. Les resultats des mesures faites durant cinq ans sur le contenu en isotopes de l'eau d'ecoulement des glaciers apporterant en outre des apercus sur les phenomenes d'ecoulement de l'eau de fönte en ete et en hiver. INTRODUCTION In the catchment area of the Rofenache (Vent, Ötztal Alps, Austria), glacio- hydrological investigations were carried out during 1969 and 1970 to determine the