English Abstract A number of two- and three-dimensional Galerkin finite
element simulations have been carried out with the geohydrological model
METROPOL-3 to evaluate flow and transport in the vicinity of a selected
rock-salt diapir in the Netherlands. With METROPOL-3, variable density flow
and solute transport can be modelled. In those studies, special emphasis
was placed on the subrosion of the salt dome. Besides simulations
reflecting the present conditions, attempts were made to investigate flow
and transport for six Late Quaternary periods (Late Saalian, Eemian, Early
Weichselian, Middle Weichselian, Atlanticum and Roman Time). A dissolving
salt dome boundary condition was implemented into METROPOL-3 to simulate the
subrosion process. Using realistic permeabilities, the calculated subrosion
rates for two 2-D cross sections at y=568 km and x=258 km were about 0.08
and 0.12 mm/year. The subrosion rates during the Late Saalian glacial were
considerably higher then for all other geological periods because during the
Late Saalian the pressure gradients and groundwater velocities were much
larger than for the other periods, including the Weichselian glacial. The
3-D local geohydrological model was used for two simulations, one with
realistic heterogeneous permeabilities and the other with homogeneous
permeabilities. After 50,000 years the subrosion rate of the realistic
simulation was 0.119 mm/year, while the subrosion rate of the homogeneous
case was almost twice as high. By using uniform permeabilities, the clay
layer that covers the salt dome could not effectively restrict groundwater
flow and transport of the dissolved salt, resulting in larger salt mass
fraction gradients near the dome and higher subrosion
rates.
