A public-private partnership between Water Board Vallei & Eem, District Water Control Board De Stichtse Rijnlanden and Alterra Wageningen UR has led to the development of a new method of schematising the physical properties of soils in the Netherlands. It gives a detailed picture of the soil properties in individual soil horizons and is important for modelling studies.
“This new schematisation replaces the much-used PAWN schematisation devised in 1988,” project manager Henk Wösten said. “It provides important input data for modelling, for example, anti-desiccation, fertiliser and nutrient run-off, and pesticide behaviour in the soil. Water retention and saturated or unsaturated water permeability are crucial soil physical features as they determine the transport of water and nutrients in any soil type. We have improved data entry; this has led to a better correspondence between model outcomes and field observations. As a result, users are more willing to accept the model outcomes and it will also make policy implementation easier.”
Henk Wösten and colleagues have developed a new methodology to describe the 315 soil units in the Soil Map of the Netherlands, scale 1 : 50 000, in terms of soil physics. Calculations were then performed on these 315 units using a relatively simple hydrological model. The model outcomes were subsequently used to cluster the 315 soil units into 72 soil physics units that referred, for example, to groundwater depths, saturation deficiency, available water storage, C-value profile and the main soil types.
The end result is called BOFEK2012, which stands for ‘BOdemFysische EenhedenKaart’ (soil physics units map). In order to be able to use these data in models to calculate water and nutrient transport in the soil, a dataset has been compiled containing information about the GIS database with the geographic spread of the BOFEK units in the Netherlands, and profile diagrams showing the soil layers to 1.20 metres below ground level, together with the relevant soil physical characteristics.
This new schematisation of soil physical properties adds an important and reliable element to modelling studies involving, for example, ammonia and nutrient emissions, and the effects of changes in water and soil management.
Using the same methodology, a Hydrological Response Units map was also drawn up for the the Limpopo River in South Africa.