Het ecohydrologisch voorspellingsmodel DEMNAT-2 : conceptuele modelbeschrijving

VakpublicatieInstitute of Environmental Science

Het ecohydrologisch voorspellingsmodel DEMNAT-2; interpretatie van de rekenresultaten.

The Dose-Effect Model for terrestrial NATure (DEMNAT) is a model for the nationwide prediction of effects of water management measures on vegetation. For scenario analyses with DEMNAT geographical data on vegetation (ecotope groups), soil and groundwater (ecoseries) and hydrological doses are combined. Effects can either be expressed as changes in the completeness (or relative species richness) of ecotope groups, or as changes in nature value. This allows combining changes in various ecotope groups, weighed relative to their significance for nature conservation. With DEMNAT both damage and recovery due to water management measures can be calculated. To this end, separate dosis-effect functions for damage and recovery were defined, as recovery is often less rapid or incomplete. For the National Policy Plan on Drinking Water and Industrial Water Supply which was to be accompanied by an Environmental Impact Assessment eight basic scenarios were evaluated. A scenario is defined by a percentual change in the amount of groundwater withdrawn in a certain way (e.g. from phreatic groundwater) and for a pre-defined application. As substantial amounts of groundwater are withdrawn from ice-pushed ridges, the largest effects occur around the ridges. Smaller effects occur over larger surfaces, especially at the Holocene alluvial plains along the boundary of the elevated Pleistocene parts of the Netherlands. Ecotope groups of nutrient-poor, weakly acid sites are the most severely influenced by most scenarios. A comparison of the results of each scenario with the reference situation shows that various scenarios may add substantially to the recovery of wet and moist ecotope groups