Snow depth evolution in the Pyrenees shows spatial variability, but overall we
observed a negative trend of snow depth during the study period. Moreover, we
found that in the snow depth sites located at higher elevations (2100–2600 m a.s.l.),
snow variability correlated inversely with the frequency of dry-warm days in spring,
indicating that only in years when exceptionally warm days predominate, snowpack
will be reduced, whereas the frequency of cold days is not a limiting factor. On the
contrary, in snow measurement sites at lower elevations (1800–2400 m a.s.l.), snow
variability correlated with the frequency of dry-cold and wet-cold days in spring,
meaning that spring temperature begins to be a limiting factor at this lower sites.
The consequence of the above mentioned trends over water resources has been,
so far, a change in the timing of flows, particularly on the occurrence of the spring
peak that results from snowmelt. On the studied rivers, there is an earlier occurrence
of spring flows during recent years than four decades ago. The increase of spring
temperatures triggers an earlier snowmelt, an overall decrease in the duration of the
snowpack and an earlier and lower spring peak flow. When projecting future
hydrological changes by coupling RCMs outputs and hydrological modelling, we
observe that the detected changes are likely to be enhanced if temperatures grow as
estimated by climate models: winter flows will augment due to fewer snowfalls and
snow accumulation and consequently spring flows will decrease. The amount of
water resources available will not suffer big changes, except if a large decrease in
precipitation occurs.
Such changes must be acknowledged by water managers and water users from
downstream territories and incorporated in long-term water management policies
that promote a sustainable use of the water resource in this sensitive territory.
References
Adam JC, Hamlet AF, Lettenmaier DP (2009) Implications of global climate change for snowmelt
hydrology in the twenty-first century. Hydrol Process 23:962–972
Arnell NW (1999) The effect of climate change on hydrological regimes in Europe: a continental
perspective. Glob Environ Chang-Hum Policy Dimens 9:5–23
Barnett TP, Adam J, Lettenmaier DP (2005) Potential impacts of a warming climate on water
availability in snow-dominated regions. Nature 438:303–309
Beguería S, López-Moreno JI, Lorente A, Seeger M, García-Ruiz JM (2003) Assessing the effect
of climate oscillations and land-use changes on streamflow in the Central Spanish Pyrenees.
Ambio 32:283–286
Bejarano MD, Marchamalo M, de Jalón DG, del Tánago MG (2010) Flow regime patterns and
their controlling factors in the Ebro basin (Spain). J Hydrol 385:323–335
Beniston M (2003) Climatic change in mountain regions: a review of possible impacts. Clim
Change 59:5–31
Beniston M (2012) Is snow in the Alps receding or disappearing?, WIREs climate change (wiley
interdisciplinary reviews/climate change). doi:10.1002/wcc.179
Beniston M, Goyette S (2007) Changes in variability and persistence of climate in Switzerland:
exploring 20th century observations and 21st century simulations. Glob Planet Chang 57:1–15
Birsan MV, Molnar P, Burlando P, Pfaundler M (2005) Streamflow trends in Switzerland.
J Hydrol 314:312–329
320
E. Morán-Tejeda et al.
observed a negative trend of snow depth during the study period. Moreover, we
found that in the snow depth sites located at higher elevations (2100–2600 m a.s.l.),
snow variability correlated inversely with the frequency of dry-warm days in spring,
indicating that only in years when exceptionally warm days predominate, snowpack
will be reduced, whereas the frequency of cold days is not a limiting factor. On the
contrary, in snow measurement sites at lower elevations (1800–2400 m a.s.l.), snow
variability correlated with the frequency of dry-cold and wet-cold days in spring,
meaning that spring temperature begins to be a limiting factor at this lower sites.
The consequence of the above mentioned trends over water resources has been,
so far, a change in the timing of flows, particularly on the occurrence of the spring
peak that results from snowmelt. On the studied rivers, there is an earlier occurrence
of spring flows during recent years than four decades ago. The increase of spring
temperatures triggers an earlier snowmelt, an overall decrease in the duration of the
snowpack and an earlier and lower spring peak flow. When projecting future
hydrological changes by coupling RCMs outputs and hydrological modelling, we
observe that the detected changes are likely to be enhanced if temperatures grow as
estimated by climate models: winter flows will augment due to fewer snowfalls and
snow accumulation and consequently spring flows will decrease. The amount of
water resources available will not suffer big changes, except if a large decrease in
precipitation occurs.
Such changes must be acknowledged by water managers and water users from
downstream territories and incorporated in long-term water management policies
that promote a sustainable use of the water resource in this sensitive territory.
References
Adam JC, Hamlet AF, Lettenmaier DP (2009) Implications of global climate change for snowmelt
hydrology in the twenty-first century. Hydrol Process 23:962–972
Arnell NW (1999) The effect of climate change on hydrological regimes in Europe: a continental
perspective. Glob Environ Chang-Hum Policy Dimens 9:5–23
Barnett TP, Adam J, Lettenmaier DP (2005) Potential impacts of a warming climate on water
availability in snow-dominated regions. Nature 438:303–309
Beguería S, López-Moreno JI, Lorente A, Seeger M, García-Ruiz JM (2003) Assessing the effect
of climate oscillations and land-use changes on streamflow in the Central Spanish Pyrenees.
Ambio 32:283–286
Bejarano MD, Marchamalo M, de Jalón DG, del Tánago MG (2010) Flow regime patterns and
their controlling factors in the Ebro basin (Spain). J Hydrol 385:323–335
Beniston M (2003) Climatic change in mountain regions: a review of possible impacts. Clim
Change 59:5–31
Beniston M (2012) Is snow in the Alps receding or disappearing?, WIREs climate change (wiley
interdisciplinary reviews/climate change). doi:10.1002/wcc.179
Beniston M, Goyette S (2007) Changes in variability and persistence of climate in Switzerland:
exploring 20th century observations and 21st century simulations. Glob Planet Chang 57:1–15
Birsan MV, Molnar P, Burlando P, Pfaundler M (2005) Streamflow trends in Switzerland.
J Hydrol 314:312–329
320
E. Morán-Tejeda et al.