RD&D-Programme 2004 - SKB

Newfound knowledge since RD&D 2001
The water exchange model’s sensitivity to different climatic changes (temperature and ice
formation), salinity changes and a change in land uplift was evaluated for Öregrundsgrepen
/20-32/. The model has also been used by the Swedish Environmental Protection Agency and
the Finnish Meteorological Institute to study water exchange in coastal waters. It is fundamental
for water exchange calculations in the Stockholm archipelago. Results and applications have
been published in scientific journals /20-33, 20-34/. In the site investigations and the analysis
work, the model will be applied after calibration with site-specific measurements and improved
depth data from the sea bays at the sites.
Certain interactions in the boundary layer between rock and surface water were studied in the
Safe project /20-35/. It has, for example, been found that water flowing out of the rock is to a
great extent diluted by the groundwater in the Quaternary deposits by a factor of about 100.
The study showed that it is possible that the water may follow conductive layers in Quaternary
deposits and discharge near the shoreline. A follow-up of this study was done with a better
resolution of the near-surface strata /20-36/. It confirms previous results that discharge takes
place at low points in the terrain, preferably lakes, sea and wetlands. Depending on the hydraulic
conductivity, the water will discharge through the bottom layers or against the shoreline, see
further sections 19.2.11 and 19.2.12. The site investigations will provide more information on
how hydraulic conductivity varies in the lake and sea beds at the site. Radionuclide transport
can also be affected by diffusion through bottom layers /20-37/.
Surface hydrology calculations were performed at KTH for two lakes in northern Uppland
/20-38, 20-39/. Different studies have been conducted with simple Gis tools to calculate the
surface runoff in a catchment, for example PCRaster /20-40/. The site investigation programme
has identified several important hydrological studies and measurements that should be conducted
to facilitate the biosphere modelling /20-5/. These data will also be used to develop
the models. The studies are being coordinated with the programmes for hydromodelling and
hydrogeochemistry, see section 19.2.11.
Preliminary results from model studies to identify discharge areas from existing map material
with the aid of Gis show that approximately 80 percent of the areas (wetlands, lakes, sea) can be
identified with the aid of morphometric data (topography, elevation differences, slope, convex
or concave surfaces). This means that it may be possible to predict which ecosystems discharge
takes place to without knowing exactly where they are located in the future. The systems
ecology models that are being developed describe the flow of particles (as organic matter) in
a coastal area /20-20 to 20-22, 20-41, 20-42/. The net transport of sedimenting materials can
be calculated from the studies of sediments /20-43 to 20-46/. Flow rates and the quantity of
particulate matter are obtained from the hydrological measurements and chemistry samplings
in surface water in the site investigations.
Programme
The projects described above will continue and can be summarized in the following main topics:
• In-depth surface hydrology with evaluation of surface hydrology models or simplified
Gis tools, for example Shetran topographical indices.
• In-depth model studies of nuclide transport at discharge points from the rock. Particular
attention is being given to how nuclides move near lake and sea basins.
• Continued model and literature studies of particle transport as described above,
supplemented with field data from the site investigations.
• A model and literature study of human transport activities under various conditions as
a delimitation of how large a population can be affected by a contaminated area, which
facilitates a judgement of the representativeness of the most heavily exposed group, in
accordance with SSI’s regulations.
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