Author(s): D. Sengschmitt; R. Schmalfuss; A. P. Blaschke
Linked Author(s):
Keywords: Stream-aquifer interaction; Seepage rate; Clogging processes
Abstract: Stream-aquifer interactions are of fundamental importance for studies of natural groundwater recharge and to design irrigation and drainage systems or wells near streams. Field investigations between surface water and groundwater are normally a regional scale problem. In order to quantify the seepage rates of wells near rivers the stream-aquifer interaction at the local scale is becoming more important. For fundamental research on physical processes that control the stream-aquifer interaction the process scale (physical scale) has to be focused. To integrate fundamental microscopic research (e. g. : laboratory investigations) into practical river basin management the question if dominant processes in one scale can be found in another scale is of fundamental importance. This investigation presented here will compare seepage rates from an 11. 93 km long Danube River reach in the Vienna area (regional scale) starting with the impoundment of the river by the hydro-power dam„Freudenau “in March 1996 with linear upscaled seepage rates from a crosssection within this reach (local scale) until August 1998. Our comparison shows a good correspondence between the two scales during the impoundment phase 1. But we were able to show that linear upscaling is only possible if the following restrictions are taken into account: ·similar geohydraulic boundary conditions over the whole study site must be assumed, ·a calibration factor has to be found due to the possible spatial variability of geological and hydrological parameters and·the influence of the riverbed clogging processes have to be analysed with the help of a seepage model. The reason is that linear upscaling is only possible if the clogging processes have no substantial influence on the seepage rates. In our investigation a decrease in the leakage-factor of the streambed of 5 times during phase 1 at the local scale shows a reduction in the seepage rates of only 10% . We could also show that the change in the groundwater temperature from 2°C during winter to 20°C during summer caused a periodic change in the seepage rates of 50% .
Year: 1999