Geophysical methods to constrain sediment and water transport models at Alpine Catchments
Complementary Chinese topic:
Alpine catchments in Tibet have a large impact on the water quality and on the sediment budget of downstream regions. Climate change may lead to dramatic changes within these Alpine Catchments, through degradation of permafrost or the modification of alpine meadows. The understanding of the impact of Climate change on the water and sediment transport is often based on numerical simulation. Numerical simulation requires information on physical properties, as well as ground truth for validation of the results, which can be provided by geophysical methods.
In this project, we will apply geophysical methods in an alpine catchment in Tibet in order to constrain models of water and/or sediment transport processes. Electrical resistivity methods are particularly suitable to characterize frozen ground, since resistivity depends on grain size distribution, and becomes extremely large if the ground is frozen. In order to reduce the inherent ambiguity when interpreting resistivity, it is useful to measure the frequency-dependent resistivity, using the induced polarization or the capacitive resistivity method. The methods may be used to detect and quantify permafrost, as well as for the characterization of freeze-thaw cycles. The techniques are also suitable to estimate hydraulic conductivity, which enters as an essential parameter into groundwater flow models. The electrical resistivity measurements shall be complemented by ground-penetrating radar (GPR) surveys. GPR is particularly suitable to delineate different lithological units and is also sensitive to ice content and grain size distributions. Innovative joint interpretation techniques will be used in order to reduce the ambiguity of the interpretation and to provide the best possible input for numerical simulations.
Cooperation within TransTiP
close collaboration with project W4 dealing with groundwater modeling
Sino-German complementarity of research
The project of our Chinese partners will focus on soil erosion and sediment transport observation. They are using models in order to trace the sediment transport to the rivers and to the lakes on the Tibetan Plateau. The existing models will be enhanced to model the runoff generation process under the influence of soil freezing/thawing. Project S6 will therefore provide input for validation and information on the distribution of permafrost in the research area. Project W4 will provide a model to simulate the freeze-thaw cycle.
Prof. Dr. Andreas Hördt, TU Braunschweig Prof. Dr. Thomas Graf, LU Hannover Prof. Dr. Fan Zhang, ITP-CAS