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Institut für Wasserbau - IWS

Selected Topics and International Network Lectures

16:00 Uhr
Dr. C. Kuells
Institut für Hydrologie
Universität Freiburg

The role of snow-melt events on runoff generation and groundwater recharge -- how isotopes reveal scale effects and climate impacts


Time series analysis of environmental tracers combined with hydrological observations and models provides insight into processes of runoff generation and groundwater recharge. The natural integration of temporal and spatial variability of stable isotope data (oxygen-18, deuterium) at different scales of hydrological systems can be used as a basis for the study of catchment response to climate variability and change. This approach is demonstrated using monitoring data of runoff, groundwater levels, stable isotope and chemical composition at the meso-scale Dreisam catchment (Black Forrest, Germany). The observations reveal that the serious hydrologic drought in summer 2003 was preceded by deviations from the hydrologic and isotopic regime. The departure from a regular seasonal variation started already during winter and spring 2002/2003 - half a year before the hydrological drought became obvious. Isotope data suggest that the lack of intense groundwater recharge from snow-melt due to a warmer than average winter season aggravated the drought of 2003. Further investigations showed a scale-dependent and event-dependent percentage of snow-melt contributions to runoff and groundwater recharge. As a result the role of snow-melt for groundwater regimes needs to be reviewed. Climate changes resulting in different snow-melt conditions might have non-linear impacts on the water balance of catchments and aquifers. Environmental tracers provide methods for the integrated study of these processes at different scales.