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

Figure VI.C.4. Mean temperature increase across Europe (Alcamo et al., 1996).
Precipitation and river flows
The statistical analysis of rain intensity during the period 1940-2000 using data from
2150 meteorological stations in the Ebro basin, applying the non parametric Mann-
Kendall trend test, does not yield a significant trend (PHN, 2000). Studies analyzing
precipitation series across Europe indicate that, for all locations in Spain, no
significant trend exists (Klein Tank et al., 2002, Figure VI.C.5). In light of such
findings, it is difficult to derive meaningful projections for future precipitation trends in
the Ebro watershed.
GCM simulations and climate change scenarios estimate air temperature increases
and precipitation reductions, accompanied by a significant change in precipitation
patterns, with a higher frequency of extreme events (dry periods, torrential rains).
Possible reductions from 5% to 20% have been foreseen (PHN, 2000; 2003), in
agreement with prediction from international models. However, the impacts of
changes in precipitation in the Ebro river basin are difficult to assess due to the
heterogeneity of the watershed. For example, Batalla et al. (2004) divide the Ebro
river basin into four main climatic zones:
• the Atlantic headwaters, 23% runoff, 900 mm/year;
• the west–central Pyrenees, 31% runoff, 950 mm/year;
• the eastern Pyrenees, 41% runoff, 800 mm/year;
• and the southern Mediterranean zone, 5% runoff, 500 mm/year.
Mean average precipitation is ~ 670 mm/year (PNH, 2000) and results from different
contributions from each of the four zones. Considering such a subdivision,
projections presented by IPCC (2001) for the year 2050, using the coupled model of
the Hadley Centre, foresee a reduction between 0 and 25 mm/year for the main part
of the Ebro watershed with the exception of the Pyrenees where reductions of up to
25-150 mm/year may be expected.
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