One thing I learn from Aldo Fiori at CATHY's meeting in Padua on Monday, Jan. 17, was that having a water table at the base of a hillslope is changing the way that the hillslope responds to the rainfall input. This is particularly important for getting the right residence time of water, that through this water table is recirculated and resides more time.
The assumption seems to me reasonable. This has also clear implications on the setting of the initial conditions. In fact, it seems reasonable to put a water table at the same level where there are surface water, at least for most of the year, interpolating the water levels of the blue lines.
This obviously does not mean that the spin-out runs can be avoided (see previous posts), which should be performed to gain a dynamical equilibrium level of the water tables.
Certainly this implies a radical change with respect to the habit to assume an impermeable bedrock a few meters below the terrain surface, and imposes the necessity of a more deep discussion of the hydraulic properties of the bedrock itself.
Notable References to Aldo's work
Fiori, A., M. Romanelli, D.J. Cavalli, D.Russo, Numerical experiments of streamflow generation in steep catchments, JOURNAL OF HYDROLOGY, 339, 183-192, 2007.
Fiori, A., D. Russo, Numerical Analyses of Subsurface Flow in a Steep Hillslope under Rainfall: The Role of the Spatial Heterogeneity of the Formation Hydraulic Properties, WATER RESOURCES RESEARCH, 43, W07445, doi:10.1029/2006WR005365, 2007
Russo, D., A. Fiori. Equivalent Vadose Zone Steady-State Flow: An Assessment of its Capability to Predict Transport in a Realistic Combined Vadose Zone - Groundwater Flow System. WATER RESOURCES RESEARCH, 44, W09436, doi:10.1029/ 2007WR006170, 2008.
Fiori, A., D. Russo, Travel Time Distribution in a Hillslope: Insight from Numerical Simulations. WATER RESOURCES RESEARCH, 44, W12426, doi:10.1029/2008WR007135, 2008.
Russo, D., and A. Fiori, Stochastic analysis of transport in a combined heterogeneous vadose zone–groundwater flow system. WATER RESOURCES RESEARCH, 45, W03426, doi:10.1029/2008WR007157, 2009.
Fiori, A., D. Russo, M. Di Lazzaro. Stochastic analysis of transport in hillslopes: Travel time distribution and source zone dispersion. WATER RESOURCES RESEARCH, 45, W08435, 2009.