An alternative approach to the coupling of flow and

1
An alternative approach to the coupling of flow
and reactive transport at a regional scale Marc
J.M. Vissers, Paulien F.M. van Gaans, Marcel van
der Perk Centre for Geo-Ecological Research,
Faculty of Geographical Sciences, Utrecht
University P.O. Box 80115, 3508 TC Utrecht, The
Netherlands
Introduction From a viewpoint of spatial
planning, a general knowledge of groundwater
quality is needed, which includes the spatial
variation of major element chemistry and
contaminant background concentrations. Approach Th
e approach we use is based on the two factors
that determine groundwater quality. 1) Quality of
the water at the time and place of
infiltration 2) Processes that occurred within
the aquifer along the flow path.
Concentration depth profiles of a multilevel
well from the Salland section These two processes
are recognized when looking at groundwater
quality in detail, as can be seen in the
following graphs. While input variations are very
dynamic over time and space, redox and buffering
processes can be considered as a more static
process taking place in the aquifer.
Essential steps in this approach are summarized
as 1) Conventional groundwater flow modeling,
including paleo flow. 2) Linking observed
hydrochemical well data to the time and location
of infiltration (land use). 3) Identification
and statistical characterization of the main
water types. 4) Location of the boundaries
between the main water types (hydrochemical and
borehole data). 5) Assessment of the forward
relation of land use and aquifer reactivity with
groundwater chemistry.
Elevation and coordinates of the study area in
meters
Land use in the study area
Different observation wells in the city of
Hengelo and surrounding areas
Why this approach? 1) The position of the various
chemical boundaries cannot be modeled 2) Regional
input data is not available at the required
scale 3) Reactive transport modeling is not
possible on a regional scale, because of
discretization requirements 4) What would be your
motivation?
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Groundwater quality depending on the infiltration
water quality
A5
A10
Clay
2
Clay
2 km
Boring with mini well screens Calcite saturated
waters NO3/Fe redox boundary SO4 redox boundary
Groundwater level Streamlines Pine / deciduous
forest Arable land (mostly corn)
Enschede
Nijverdal
Hengelo
Almelo
Point sources In urban areas, point source
pollution has a great impact on spatial planning
and legal permits. We use a different approach
for indicating the extent of point source
pollution, by constructing a plume-map. Data
from different governmental authorities are
combined, to provide them all with a consistent
information base.
Boulder clay Young clay Old Clay Loam and
peat Sand
Groundwater flow and reaction boundaries in an
example area
Distance in km
Geological transect of the study area
Example plume-map of an urban area
m.vissers_at_geog.uu.nl