Abstract. This paper presents WHETGEO and its 1D deployment: a new physically based
model simulating the water and energy budgets in a soil column. The purpose of
this contribution is twofold. First, we discuss the mathematical and numerical
issues involved in solving the Richardson–Richards equation, conventionally
known as the Richards equation, and the heat equation in heterogeneous soils. In
particular, for the Richardson–Richards equation (R2) we take advantage of
the nested Newton–Casulli–Zanolli (NCZ) algorithm that ensures the convergence
of the numerical solution in any condition. Second, starting from numerical
and modelling needs, we present the design of software that is intended to
be the first building block of a new customizable land-surface model that is
integrated with process-based hydrology. WHETGEO is developed as an
open-source code, adopting the object-oriented paradigm and a generic
programming approach in order to improve its usability and
expandability. WHETGEO is fully integrated into the GEOframe/OMS3 system,
allowing the use of the many ancillary tools it provides. Finally, the paper
presents the 1D deployment of WHETGEO, WHETGEO-1D, which has been tested
against the available analytical solutions presented in the Appendix.
Generic programming with combinators and objects
