Statistisch-hydrologische Analyse der Abflusszeitreihe des Vernagtferners, Ötztaler Alpen, für den Zeitraum 1974 bis 2009 (Statistical-Hydrological Analysis of the Discharge Time Series of the Vernagtferner, Oetztal Alps, for the Period from 1974 to 2009)

摘要

This Bachelor’s Thesis deals with the consequences of climate change for runoff from the Vernagtferner glacier in the Oetztal Alps, Austria. Snow cover and glaciers provide the main sources of runoff during the ablation period. Furthermore, glaciers are important because of their long-term water storage. Varying climatic conditions cause glaciers to react in different ways. Discharge variations are caused by periods of sunny, warm weather as well as by snowfall, and bad weather. The Vernagtferner discharge time series for the interval between 1974 and 2009 describes the development of the glacier discharge as well as analyzes and identifies changes. These changes are measured at the 11.44 km**2 Vernagtferner drainage basin which is controlled by the 'Pegelstation Vernagtbach' (gauging station).udThe climatic pattern during these 36 years, of which 28 have negative mass balances, tends to increase runoff amounts and reduce the storage volume of the Vernagtferner. The impact of positive, negative, and balanced mass balance, resp., on glacier runoff is determined. The changes in climate conditions also affect the diurnal variations. The time series is discussed with special regard to both maxima and means based on daily, monthly and yearly values. Hourly and five-minute records are compared with respect to extreme runoff conditions. The Vernagtbach hydrograph is studied to identify seasonal shifts and to observe the varying influence of the respective months. In glaciated catchments, July and August typically contribute 60 to 70% of the yearly runoff amounts.udThe annual discharge amounts increase and reach their maxima in the decade 2000. These years show a total of 2200 mm of discharge, whereas in the years 1974 to 1979 it is only about 1200 mm. The strongest changes show up in June, where the increase of daily means is about 0.05 m**3/s per year. In July and August the hourly peak flows rise up to 14.76 m**3/s. The development in September and October is not as strong. The distribution of the discharge amounts varies as snow and ice begin to melt earlier in the year. Firn storage disappears and causes even stronger runoff in the summer. The ELA rises, and in some years is located above the glacier. The diurnal variations increase from 0.58 m³/s in 1978 to 7.38 m**3/s in 2003. The year 2003 is an extreme example for increasing glacier runoff and the consequences for the glacier. The ablation area covers 100% of the glacier, which causes extreme peak flows and the highest daily mean ever. The combination of a heavy rainfall and high ice melt culminates in a discharge of 6.87 m**3/s.udThis study highlights the changes of discharge for the Vernagtferner.