Environmental Engineering Reference
In-Depth Information
river regimes (Beniston et al., 2003). For instance, Lopez-Moreno and Garcıa-Ruiz
(2004) reported a large effect of decreasing snowpack on changes in Pyrenean river
regimes, particularly a clear decrease in the spring high flows and the occurrence
of the high flows at least 1 month earlier than heretofore. Another important con-
sequence is that water reserves in headwaters are exhausted earlier, with declining
summer low flows forcing reservoir managers to reduce the discharge from dams
(Lopez-Moreno et al., 2008).
For the highest headwaters in a mountain range next to the Mediterranean Basin,
such as the Alps, an increase in temperature can result in rises for discharge related
to glacier melting, particularly in summer, as was observed in the southern French
Alps by Renard et al. (2008). These processes affect only small sectors of the river
basins, but jeopardize the sustainability of high mountain water resources.
Climate change projected for the region will severely impact river discharge and
water resource availability. Even if precipitation remains stable, an increase of tem-
perature may cause a noticeable decline in stream flow as a consequence of en-
hanced evapotranspiration (Nash and Gleick, 1993). Despite the uncertainty asso-
ciated with projections for precipitation, there is robust evidence for predicting a
decrease in this variable affecting the majority of the Mediterranean Basin. Less
precipitation will reinforce the likely effects of warming temperatures in reducing
water resources (Manabe et al., 2004).
Some studies based on hydrological models and the outputs from different sce-
narios obtained from climate change models point towards a diminution of sur-
face run-off and groundwater recharge (Younger et al., 2002; Nunes et al., 2008).
Fujihara et al. (2008) have shown that the drought return period for the Sayehan
River basin (Turkey) will change from 5.3 years under present conditions to
2.0 years under future conditions; that is, critical hydrological drought events will
occur more frequently as a consequence of climate change. Overall, climate change
scenarios suggest a marked increase of water resource stress in the Mediterranean
and the Middle East (Arnell, 2004).
9.5 Biosphere changes in the Mediterranean mountains
The Mediterranean Basin is one of the global biodiversity hotspots (Myers, 2003)
and it harbours, for example, more than 22 500 endemic vascular plant species:
more than four times the number found in all the rest of Europe. One of the main
reasons behind the high biological diversity in the Mediterranean Basin is the high
climate stability across different timescales. The Mediterranean Basin provided
refugia during the Pleistocene cycles, preventing species extinctions and likely sup-
porting speciation processes. Moreover, the Mediterranean mountains played a key
role in this, providing 36% (18 out of 52) of the recently proposed glacial refugia
within the Mediterranean Basin (Medail and Diadema, 2009), among which are the
Pyrenees, South Apennines, Taurus and Atlas.
Search WWH ::




Custom Search