Watercourses may be defined by line-elements in multiple layers. In combination with the TOPSYSTEM triwaco can simulate virtually any water system. On a regional scale from a delta to karstic terrain and on a local scale from complex drainage systems to entire artificial recharge & recovery schemes.

As part of this it is sometimes useful or even necessary to calculate changes in the surface water system together with changes in groundwater flow.

Overland flow and lakes

triwaco offers the possibility to simulate infiltration from lakes or hollows in the dunes and superficial discharge with the SF-module. In these cases the user defines de areas which are to be considered as (sub) surface water units. Such an area may be a catchment, slope or just a hollow in the landscape.

The surface water level is assumed to be the same over the entire area of a valley. The water level can change through time under influence of rainfall, evaporation, seepage and infiltration. Seepage occurring along a slope is discharged to an adjoining valley (surface run-off).

Surface water flow

The SF-module can also consider surface water flow to and from adjacent areas (valleys) defined by line-elements (watercourse). The module TRIFLOW is more advanced and is able to calculate flow rate in canals and surface water levels simultaneously.

The module can be used in steady state as well as in transient simulations. In transient simulations the module can account for inundation of watercourses and rivers.

Coupling with surface water models

triwaco offers an open structure for easy linkage between different models within or outside the triwaco working environment . The interaction between groundwater and individual watercourses (defined as line elements) can easily be linked to the branches of a hydraulic surface water model. This link is defined conceptually and will work for any numerical discretization.

For on-line coupling of a groundwater model (MODFLOW or FLAIRS) with a surface water model Royal Haskoning has developed an interface with DUFLOW and SOBEK. more >>