Description and application of the combined surface and groundwater flow model MOGROW

In the Netherlands shallow groundwater tables prevail in many parts, such that groundwater and surface water are closely interlinked. Thus the use of a combined groundwater and surface water model is necessary to predict the effect of certain measures on a regional scale. Therefore the model MOGROW was developed to simulate the flow of water in the saturated zone, the unsaturated zone and the surface water. The model is physically based and therefore suitable to be used in situations with changing hydrological conditions. The model has been kept fairly simple to handle practical applications. The saturated part consists of a quasi three-dimensional finite element model. The unsaturated zone is modelled one-dimensionally per type of land use. The following special phenomena were included in the unsaturated zone model: surface runoff, perched water tables, hysteresis and preferential flow. Some empirical parameters were introduced to simulate these processes. The major water courses in the model are considered as a network of sections. This network can also include special sections such as weirs, pumps, gates and culverts. The minor channels are considered as aggregated reservoirs connected to the network. The MOGROW model was verified on the Hupselse Beek drainage basin, an area of 6.5 kM2 with less pervious Tertiary deposits near the soil surface. It is relatively simple to simulate the variation in groundwater levels, but it is more difficult to correctly simulate peak discharges for such a basin. Incorporating the process of preferential flow and surface runoff in the model of the unsaturated zone gave more realistic discharge patterns