Climate Change and the European Water Dimension - Agri ...

An example of this kind of relationships is given in Figure V.C.2. Chlorophyll
concentration in the large shallow Lake Võrtsjärv (see Case Study) shows a marked
seasonal variation. Water level in this lake carries the signal of the North Atlantic
Oscillation and is the main driving factor in the ecosystem. Dropping of the water
level below a certain threshold (-50 cm on the relative scale) results in an enormous
increase of chlorophyll. The reasons for this increase are the improvement of light
conditions (as the water layer becomes thinner), and stronger resuspension of the
surface sediment. Resuspension has a dual effect on chlorophyll concentration: it
has a direct effect by stirring up the microbenthic algae living on the sediment surface
and the planktonic algae already settled out, but also an indirect effect by releasing
the nutrients from the sediment to the water layer where they support new algal
production. Including this natural variability already to RC of this lake substantially
decreased the variability in ecological quality estimates and allowed chlorophyll
values measured in different seasons to be used for quality assessment purposes.
This method can most easily be used for working out site specific RC for water
bodies which have a long investigation record. At the moment, a similar system of
flexible RC has been applied on the 5 th largest lake in Europe, the transboundary
Lake Peipsi shared between Estonia and Russia (Nõges and Nõges, 2003).
Climate Change sets new requirements to the monitoring process.
The methods currently used to monitor and model water bodies were developed
when weather patterns were different from those experienced today. Most are based
on a deterministic rather than a probabilistic approach and do not properly represent
the ‘cascade of uncertainty’ associated with recent climate-change scenarios
(CLIME, 2001). The future surveillance monitoring must be capable of detecting longterm
changes in the water environment. For example, long-term climate changes and
land cover changes could affect the condition of aquatic plants and animals in
surface waters by increasing the frequency of droughts and floods. Information on
such changes will be needed to avoid wrongly attributing their affects to other
pressures.
Climate change effects on aquatic ecosystems are not fully understood, and in many
cases inherently unpredictable. Long-term monitoring of minimally impacted sites is
highly important to measure and understand climate change effects on reference
conditions. To advance our understanding of ecosystem responses to climate
change, basic ecological research, especially sensitivity analyses at site-specific or
sub-regional scales would still be needed. Direct extrapolation of observed species
distributions in relation to present climate as a means for projecting future responses
is inappropriate; such projections must include consideration of physiological
tolerances, competition, and dispersal mechanisms (Halpina 1997). There is an
urgent need to develop modelling tools to analyse and understand regional climatic
changes, the underlying changes within these catchment systems, and the
hydrochemical and ecological behaviour occurring in aquatic ecosystems. Better
knowledge of these mechanisms would help to work out methods of mitigating the
impacts of environmental change across Europe.
V.C.3. European Research Projects Addressing Climate Change Impact
on Implementation of the WFD
In order to support the implementation of the Water Framework Directive, the
European Commission has established a cluster on Integrated Catchment Water
Modelling (CatchMod). The objective of this cluster is the development of common
harmonised modelling tools and methodologies for the integrated management of
water at river basin scales based on scenarios of climate change and other expected
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