We investigate groundwater from the minuscle pore scale to the grand regional scale for any feasible purpose. Our preferred approach is guided by a healthy mixture of experience, curiosity and our fondness of numerical modelling. We may cover all the necessary steps from borehole testing to the characterization of the hydrogeological domain, numerical simulations, special analyses of the results and detailed interpretations. Depending on the issues we either write our own codes or apply publicly available software. This combination of process understanding and modelling flexibility is our solid base for even the most complex projects.