and García-Ruiz 2004), which is in turn related to the climate variability. The winter
snowpack acts as a natural water reservoir that further provides sustained water
during spring and summer. The south slopes of the Pyrenees drain to the Ebro
River, which flows through a region with semi-arid climatic conditions (low values
of precipitation, *350 mm yr
−1 and large rates of potential evapotranspiration, *1200 mm yr
−1 ) but with large irrigation area (9800 km
2 ) and agriculture
production, and high populated cities including Zaragoza or Lleida. Thus, the
melting waters draining from the Pyrenees are a strategic resource for the economy
and development of the downstream region. Moreover, the social development and
ecological value of the Pyrenees are highly related to water in solid form. The
permanent snowpack during winter months is a major source of economic income
for Pyrenean peoples through the touristic industry derived from the practice of ski
and other winter sports (Lasanta et al. 2007; Pons et al. 2015).
This work aims to present a general description of the interactions of climate
variability/trends, snow cover, and water resources during the last decades in the
Pyrenees, as well as to provide a simple but reliable projection in the availability of
water resources in the short-term future. For this, we focus our analysis in (1) trends
in climate indices that summarize far-from-normal conditions in temperature and
precipitation over the mountain chain; (2) temporal trends and spatial variability in
snow cover depth over the last decades; (3) changes in the timing of Pyrenean river
flows, related to the observed trends in climate indices and snow cover; (4) projection of future changes in river flows by means of hydrological modelling and
regional climate models output coupling.
13.2 Study Area
The Pyrenees is a mountain range located in SW Europe at the northern edge of the
Iberian Peninsula and constitutes the natural border between Spain and France
(Fig. 13.1). Altitude within the area ranges from 500 m to a maximum elevation of
3404 m a.s.l, and its extension is more than 50,000 km
2 . The relief is firmly split by
the river network due to the disposition of the main valleys (north–south), which are
perpendicular to the Pyrenean structures (west–east) (Peña and Lozano 2004).
The climate of the Pyrenees is influenced by its location between the Atlantic
Ocean to the west and the Mediterranean Sea to the east. The Central Pyrenees
shows a greater Continental influence. Moreover, topographic heterogeneity
introduces a noticeable variability to the distributions of precipitation and temperature (Del Barrio et al. 1990; García-Ruiz et al. 2001).
The temperature gradient proposed for the entire Pyrenean range varies
according to the author: 0.6 (García-Ruiz et al. 1986), 0.68 (Del Barrio et al. 1990)
and 0.63 °C/100 m (López-Moreno 2006). Based on these gradients, the annual
0 °C isotherm is located around 2900 m (Chueca-Cía et al. 2003). However,
13 Changes in Climate, Snow and Water Resources in the Spanish …
307
snowpack acts as a natural water reservoir that further provides sustained water
during spring and summer. The south slopes of the Pyrenees drain to the Ebro
River, which flows through a region with semi-arid climatic conditions (low values
of precipitation, *350 mm yr
−1 and large rates of potential evapotranspiration, *1200 mm yr
−1 ) but with large irrigation area (9800 km
2 ) and agriculture
production, and high populated cities including Zaragoza or Lleida. Thus, the
melting waters draining from the Pyrenees are a strategic resource for the economy
and development of the downstream region. Moreover, the social development and
ecological value of the Pyrenees are highly related to water in solid form. The
permanent snowpack during winter months is a major source of economic income
for Pyrenean peoples through the touristic industry derived from the practice of ski
and other winter sports (Lasanta et al. 2007; Pons et al. 2015).
This work aims to present a general description of the interactions of climate
variability/trends, snow cover, and water resources during the last decades in the
Pyrenees, as well as to provide a simple but reliable projection in the availability of
water resources in the short-term future. For this, we focus our analysis in (1) trends
in climate indices that summarize far-from-normal conditions in temperature and
precipitation over the mountain chain; (2) temporal trends and spatial variability in
snow cover depth over the last decades; (3) changes in the timing of Pyrenean river
flows, related to the observed trends in climate indices and snow cover; (4) projection of future changes in river flows by means of hydrological modelling and
regional climate models output coupling.
13.2 Study Area
The Pyrenees is a mountain range located in SW Europe at the northern edge of the
Iberian Peninsula and constitutes the natural border between Spain and France
(Fig. 13.1). Altitude within the area ranges from 500 m to a maximum elevation of
3404 m a.s.l, and its extension is more than 50,000 km
2 . The relief is firmly split by
the river network due to the disposition of the main valleys (north–south), which are
perpendicular to the Pyrenean structures (west–east) (Peña and Lozano 2004).
The climate of the Pyrenees is influenced by its location between the Atlantic
Ocean to the west and the Mediterranean Sea to the east. The Central Pyrenees
shows a greater Continental influence. Moreover, topographic heterogeneity
introduces a noticeable variability to the distributions of precipitation and temperature (Del Barrio et al. 1990; García-Ruiz et al. 2001).
The temperature gradient proposed for the entire Pyrenean range varies
according to the author: 0.6 (García-Ruiz et al. 1986), 0.68 (Del Barrio et al. 1990)
and 0.63 °C/100 m (López-Moreno 2006). Based on these gradients, the annual
0 °C isotherm is located around 2900 m (Chueca-Cía et al. 2003). However,
13 Changes in Climate, Snow and Water Resources in the Spanish …
307