Non-equilibrium processes during infiltration into structured soil

• Applicant: Professor Dr. Hans-Jörg Vogel
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2008 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 66234063

• Final Report Year: 2017

Final Report Abstract

This project demonstrated the importance of hydraulic non-equilibrium during transient flow in unsaturated porous media. An experimental setup was developed which allowed for investigating non-equlibrium phenomena under well defined conditions. An ultimate goal was to predict the observed non-equilibrium based on structural properties of the materials. Thus, we analyzed the structure of porous media at the continuum scale and at the pore scale. At the continuum scale we found that a segmentation of a heterogenous sample into discrete classes of hydrologically different materials is not possible even for artificial simple composites. This is because the hydraulic behavior can only be understood based on the complete spatial setting. At the pore scale we separated different pore domains based on connectivity criteria to distinguish between pore volumes that are easily accessible for drainage and imbibition processes and others that are less accessible. It was possible to relate these sub-volumes to the varying magnitude of non-equilibrium at different water saturations. The non-equilibrium dynamics as measure using the new experimental approach could be described by a 1D effective model after separating the pore domain into accessible and less accessible sub-volumes. Thereby the characteristic timescale of the non-equilibrium dynamics was assumed to be a fixed material property. However it could be demonstrated that non-equilibrium dynamics depends on the specific range of water potential across a drainage or imbibition front and the structure of the pore space which is drained or filled respectively. The corresponding coupling of structural properties and model parameters will be subject of future research.

Publications

• 2012: Conductivity and hydraulic non-equilibrium across drainage and infiltration fronts, Vadose Zone Journal, 11/3
  Weller, U., and Vogel, H.-J.
  
• 2015: Modelling dynamic non-equilibrium water flow observations under various boundary conditions. J. Hydrol., 529, 1851-1858
  Diamantopoulos, E., W. Durner, S. C. Iden, U. Weller, and H.-J. Vogel
  
• 2015: Water ow and solute transport ¨ in unsaturated sand – a comprehensive experimental approach, Vadose Zone Journal, 14(2)
  Kumahor, S., Schlüter, S., de Rooij, G., and H.-J. Vogel