English Abstract Groundwater is a very important source for public water
supply in the Netherlands since approximately 65% of total public water
supply relies on groundwater. Although fresh groundwater is available in
considerably large quantities, groundwater is becoming a scarce national
recource. Scarcity is mentioned with special reference to the effects of
groundwater withdrawal on agricultural production and the desiccation of
nature reserves. Groundwater withdrawal is one of the causes, but
intensified land drainage and the regulation of surface water levels also
contribute substantially to the lowering of groundwater levels. A study was
carried out to analyse the impact assessment for the next decades of
different groundwater extraction scenarios on the value and distribution of
terrestrial ecosystems (especially with regard to vegetation). Several
computer programmes have either been used or developed for this study.
Throughout the project intensive use was made of the features of the
Geographical Information System. The hydrological effects of changes in
groundwater withdrawal have been calculated with the RIVM National
Groundwater Model for the Netherlands (LGM). The changes in the amounts of
inlet water were calculated with the RWS/RIZA model, DEMand GENerator
(DEMGEN). The hydrological doses calculated with LGM and DEMGEN are input
for the eco-hydrological Dose-Effect Model for terrestrial NATure
(DEMNAT-2). With this model it is possible to predict changes in the
completeness of terrestrial ecosystems within a grid cell of 1 km2. The
results of this study are recorded in 15 separate reports, each covering one
or more specific topics. The overall results are summarized in this
particular report.