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

temperatures potentially lead to higher evaporation and evapotranspiration. Annual
precipitation trends for the period 1900–2000 show a contrasting picture between
northern Europe (10–50 % wetter) and southern Europe (up to 20 % drier). Changes
have been greatest in winter in most parts of Europe. Projections for Europe show a
1–2 % increase per decade in annual precipitation in northern Europe and an up to 1
% per decade decrease in southern Europe (in summer, decreases of 5% per
decade may occur) (EEA, 2004). Higher temperatures affect precipitation patterns
as well, even in those cases in which total annual rainfall may not display significant
changes. A higher frequency of weather extremes is likely to be observed (torrential
rains, leading to floods; dry periods, leading to droughts).
River discharges (being a function of precipitation and watershed characteristics,
among other factors) will in turn be affected; soil, in fact, acts as a storage buffer: in
winter and spring, increasing precipitation normally generates higher discharges
because the buffer is full and evaporation is low; during the summer, storage is
reduced by evaporation and transpiration, and the soil must be refilled before runoff
begins. As a consequence of increased precipitation intensities, peak runoff is
subject to increase, thus increasing the occurrence of flood events.
Groundwater recharge is also dependent on precipitation and soil moisture
conditions. Aquifers usually recharge slowly and mostly during the winter season.
Shortening of the wet season across Europe might negatively affect recharge rates.
Moreover, future reduced surface water availability during the dry season might
induce over-exploitation of groundwater resources, thus further deteriorating the
status of some aquifers.
There is a need for advancement in our capability to describe the interaction in time
and space between physical processes governing climate and the various
components of the hydrologic cycle. On a short time scale individual components of
the hydrological cycle are much more variable than climatic factors. Seasonal to
inter-annual variability in precipitations and temperatures accounts for some of the
shifts in hydrological characteristics in European river basins. However, accurate
predictions about the consequences of climate change on individual components of
the hydrologic cycle at European, regional or local scale are difficult to obtain
because of the bias introduced by anthropogenic factors (changes in land-use
patterns and the drainage conditions of rivers, increases in the proportion of
impermeable areas) (Beniston et al., 1994). There is a strong want for further
research, aiming at decoupling the effects of human activities (e.g. increased
population, expansion of irrigated land, industrial growth) and climate change on the
hydrological cycle, to avoid in the future catastrophic synergies and interactions.
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