|Abstract:|| We formalize the pointwise HiMod approach in an unsteady setting,
by resorting to a model discontinuous in time, continuous and hierarchically reduced in space.
The selection of the modal distribution and of the space-time discretization is automatically performed
via an a posteriori analysis of the global error.
The results of the numerical verification confirm the robustness of the proposed adaptive procedure
in terms of accuracy as well as of sensitivity with respect to the goal quantity.
The validation results in the groundwater experimental setting are actually more than satisfying,
with an improvement in the concentration predictions by means of the adaptive HiMod approximation.|