Global changes in climate may have
large impacts on regional water resources and the
frequency of drought or flood events. Changes in
precipitation or temperature may also severely modify
the available water resources for users in several
sectors. Here, we examine climate change scenarios for
the Gállego river (a tributary of the larger Ebro river
in Spain) in the context of quantitative water resources
management for the basin. Projected changes to
precipitation and temperature are derived from an
ensemble of 6 Regional Climate Models (RCMs) run for the
period 2071–2100 under the SRES A2 emissions scenario
and are subsequently bias corrected before input into a
hydrological model. The use of RCM ensembles is
important for the incorporation of uncertainties derived
from different model structures, parameterizations and
boundary conditions into the hydrological modeling
process and subsequent climate change impact assessment.
All 6 RCMs project decreases in annual precipitation
with some RCMs projecting a slight increase between
December and February. Additionally, all models project
a >3°C increase in annual mean temperature over the
basin, with some models projecting a 9°C temperature
increase during summer months. Hydrological simulations
using the GEOTRANSF model, with the climate change
scenarios as input, show that projected water
availability for the Gállego is lower for the 2071–2100
period than for 1961–1990, with an increasing number of
dry years. During the water-storage period (October to
March), medium to low flows are reduced, while during
the irrigation period (April to September), streamflow
is reduced across the entire range of flows. The
projected changes vary across the basin and are also not
uniform throughout the year. Stronger drying occurs
during the summer with potentially important
implications for water resource management across many
sectors including agriculture, with a reduction in the
amount of water available for irrigation and hydropower
generation, due to projected seasonal reductions in
reservoir levels.