Towards a Baltic Sea Region Strategy in Critical ... - Helsinki.fi

CRITICAL INFRASTRUCTURE PROTECTION IN THE BALTIC SEA REGION
This observed data shows that the sea level changes have a direct, remarkable and
very fast effect on the groundwater level. The time lag between the seawater rise
and groundwater level rise seems to be only a few hours in this highly permeable
aquifer. Thus, based on this data and according to the climate change scenarios, it
can be concluded that the significant rise of sea level in the Hanko coastal area
could cause problems to the water supply managements and infrastructure
planning in the Hanko and in many other coast aquifer areas.
6.4 RISK ASSESSMENT IN THE HANKO AREA
Threats to shallow groundwater aquifer and water supply
Threats to the Hanko shallow groundwater aquifer and water supply are below
classified into two main categories: (1) threats from human activities and (2)
threats from climate change. The groundwater based water supply is part of the
most important critical infrastructures (e.g. distribution network, pipe network),
because shallow groundwater is the main water source available, with easy
abstraction methods, and the communities and industries in the Hanko area rely on
it for both domestic consumption and industrial use.
Risks, either anthropogenic or natural, can affect groundwater quantity or
quality. Often, the changes in groundwater quantity – increase or decrease of
groundwater table – affect changes in groundwater quality.
Basically, it is a good situation if the amount of groundwater increases, but
this can affect significantly the groundwater quality. The infiltration time will be
shorter, and that means that the water will not be purified well before it reaches the
groundwater table. During the infiltration the quality of the water improves; the
unsaturated zone works like a refiner by different geochemical processes. If the
span of water in this zone is too short, all the geochemical processes have only a
short time to complete and such things as the risk of groundwater contamination
by microbes will increase. The hydrogeological processes in the unsaturated zone
are not yet well known in Finland. The corrosion of different materials in buildings
and constructions will increase if the groundwater table varies greatly.
If the water table decreases, the most remarkable result is that wells may no
longer reach the groundwater when the water quantity diminishes. Sometimes, it is
possible to dig deeper wells, but small aquifers may dry up.
The rise in sea level rise has the long-term high potential risk of the intrusion
of seawater, which would increase the corrosion of the water pipe system,
resulting in high operation costs and possibly groundwater contamination. Capital
costs of infrastructure, such as the rebuilding of wells and water pipe line networks
or water treatment of contaminated groundwater would increase. In addition, the
rise of the sea level will push the groundwater level up and in long term, it could
cause reductions of infiltration interval of water because of thinner infiltration
zone. The thinner infiltration zone could worsen the groundwater quality,
especially in the area of high permeable sand and gravel zones.
All the changes in groundwater circumstances may, however, have economic
effects, for example due to the necessities of rebuilding wells or pipelines or by
204 NORDREGIO REPORT 2007:5