Dr. Jan FleckensteinDepartment of Hydrology, University of Bayreuth, Germanyhttp://www.bayceer.uni-bayreuth.de/geooek/ |
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Simulation of groundwater-surface water exchange - heterogeneity and scale |
| In hydrology and water management exchange between groundwater (GW) and surface water (SW) has traditionally been treated in simplified ways or even been neglected all together. Large scale questions of conjunctive use and river recharge to regional aquifers were often the main concerns. With the growing awareness of the significance of GW-SW exchange for the ecological health of riparian zones and other groundwater dependent ecosystems smaller scale dynamics and patterns of exchange have become a new focus of research. GW-SW exchange is often highly variable in space, usually caused by geologic heterogeneities, and time, due to variability in the hydrologic forcing. Hence the resulting zone of mixing between GW and SW (hyporheic zone), which is important for nutrient cycling and the retention of pollutants, is dynamic. New regulations such as the EU Water Framework and Groundwater directives require linkages between GW and SW to be addressed in order to ensure the good status of water bodies and resources with respect to quantity and quality. Results from field and modeling studies to assess exchange dynamics and patterns in an alluvial river-aquifer system with intermittent flow and deep water table in California and a lake-aquifer system in Eastern Germany will be presented. Geostatistical simulations of subsurface heterogeneity at different scales were used to parameterize several integrated surface-subsurface, numerical flow models for the river-aquifer site. In addition to hydrologic data temperature data were used at both sites to qualitatively and quantitatively assess exchange patterns and fluxes and to constrain model calibration. Simulated surfacesubsurface exchange at the river site showed large spatial and temporal variations with impacts on local water tables and minimum river flows. Simulated patterns of soil moisture in the riparian zone (e.g. perched saturated zones) correlated with the distribution of riparian plants, suggesting that such features can sustain phreatophytes even when the regional water table is far below the river channel. Temperature measurements using traditional sensors were successfully used at both sites to obtain additional insights into the dynamics and patterns of exchange. New technologies such as DTS (distributed temperature sensing) may provide even better data sets at higher spatial and temporal resolution to characterize and quantify small scale dynamics and patterns of GW-SW exchange. |
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Ort |
| 27.11.2008 15:00 Uhr Großer Hörsaal |
© IGB |