'The Graduate School of the Humanities, Utrecht University'
Abstract
This thesis deals with solute transport by groundwater flow and the way in
which solute transport is affected by human activities. This in relation to
wetland ecosystems.
Wetlands in the eastern part of the Vecht river plain in The Netherlands are
historically renown for their great variety of aquatic and fen vegetation. Over
the past decades a marked deterioration of wetland vegetation has been
observed. In particular species of the alliance Caricion davalianae disappeared.
It is generally believed that the Caricion davalianae are dependent on
rather nutrient-poor (mesotrophic) calcium-rich groundwater. In the Vecht
river plain this type of water naturally originates from the adjacent sandy
ice-pushed ridge 'Het Gooi'. Upward seepage of ridge water in the river plain
has decreased over the past decades as an effect of increasing groundwater
extraction for public water supply on the ridge. The resulting water shortages
on the Vecht river plain in summer are met by import of external polluted
surface water. This eutrophic water has negative effects on the mesotrophic
aquatic and fen vegetation. Provincial groundwater management is
therefore directed towards regeneration of upward seepage of groundwater
from the ridge.
At the same time groundwater pollution on the ridge has increased. In time
this may affect the vegetation on the river plain through solute transport by
groundwater flow. Increased upward seepage from the ridge may thus have
adverse effects. Specific research questions related to the vegetation on the
river plain are:
- to what extent is the groundwater under the ridge polluted?
- are pollutants transported towards the river plain?
- are pollutants retarded or chemically altered during flow?
- is regeneration of upward seepage a good restoration measure; are there
alternatives