An object-oriented groundwater/river model

In this paper we present a model for coupled groundwater and river flow which is developed based on object-oriented programming concepts. The groundwater model is three dimensional (3-D) and accounts for confined as well as unconfined flow. Additionally density effects resulting from salinity and heat variations can be taken into consideration. The river model is based on averaged I-D Saint-Venant equations. The coupling between the two hydraulic systems can be treated in two different ways. First, in the framework of finite element technology, the groundwater body (represented by 3-D prismatic elements for aquifers/aquitards and 2-D quad elements for faults) and the river stream (represented by I-D line elements) are coupled directly, i.e. having common mesh nodes. Second, groundwater and river systems can be coupled in the framework of the multi-continuum concept (i.e. each hydraulic system is represented by an individual continuum which are coupled via transfer functions). The second approach has advantages concerning numerical stability, but transfer functions must be given for water exchange between both compartments, which are difficult to obtain experimentally. Here the direct coupling concept is presented. The groundwater-river model is based on data from the Jordan Valley area. The focus of this paper is the technical background for coupled hydrosystem modelling, such as data import, consistent geometric modelling, meshing of heterogeneous systems, objectorientation for coupled processes and user interfaces.