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

V.C.2. WFD implementation and adaptation to climate change
Although the influence of human activities on climate represents an adverse
environmental impact, the management of that impact is global rather than only a
European-scale issue. In the background paper evaluating the REFCOND guidance
Owen et al. (2002) wrote:”The benefits of recording global impacts through the
Directive’s classification scheme are likely to be outweighed by the increased
complexity of determining the relative significance of these pressures.” Although the
underlying causes of human effects on climate are beyond the scope of river basin
planning, the river basin management plans can be used as an istrument to mitigate
adverse effects of climate impact. However, there will be adverse effects of humaninduced
climate change that cannot be avoided, even with co-ordinated action at a
European level. As a consequence, classification scales and therefore the river basin
management plans need to be adapted taking into account the effects of climate
change.
Typology and type specific reference conditions of water bodies
Depending on geographic region, catchment geology and size, water bodies obtain
naturally different chemical and physical features and offer different habitats for biota.
Water bodies located in areas of fertile soils with rich mineral composition show
naturally higher nutrient concentrations and higher productivity compared, e.g. to
water bodies in silicious catchments. Trophic scales like that worked out by the
OECD (1982) are useful tools for describing these differences but do not allow
distinguishing between natural and anthropogenic eutrophication. To enable the
distinction between natural variability and anthropogenically caused changes, the
WFD introduced the requirement to work out a detailed typology of water bodies and
to specify type specific reference conditions (RC) that could serve as the basis for
water quality assessment. As the principle issues for the WFD implementation
related to typology of water bodies, Owen et al. (2001) pointed out the following
questions:
• how much natural variation can be accommodated within types?
• how can we differentiate between natural variation and impact?
• should we update the natural range of values to accommodate “natural”
changes, such as climate change?
The factors used to build up the typology are summarised in Table V.C.1. Several of
the typology factors suggested by the WFD are actually climatic variables (mean air
temperature, precipitation), have an intimate linkage to them (altitude, latitude,
longitude, river flow, water level, lake mixing) or may be influenced by climate in a
longer perspective (morphometric characteristics).
As a result of climate change, water bodies, especially those located near the
boundary of the type characteristics, may change in type. The most probable
changes, already observed in some cases, are the changes in lake mixing type. In
warmer climate cold monomictic lakes may stratify in summer and become dimictic
(Sorvari, 2001). The disappearance of ice-cover will cause a continuous mixing in
winter turning previously dimictic lakes into warm monomictic lakes. Higher stability
of the water column may prevent full mixing of deep lakes changing them from
holomictic to meromictic (Ambrosetti et al., 2003). Decrease in precipitation often
accompanied by increased summer temperatures in the future climate scenarios for
warm regions will consistently change river discharges, increase evaporation and
cause a shift from permanent to temporary water bodies. All these changes will have
a major impact on the ecosystems of these water bodies.
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