Water Governance in the Context of IWRM: Chile - Climate Change and Water Governance: Adaptive Capacity in Chile and Switzerland - page 160

both a warming and a drying trend throughout the rest of the twenty-first century
(Christensen et al. 2007 ). Winter months (June-August) feature both minimum
temperatures and maximum precipitation, namely about 80% of annual total precipi-
tation between May and August (Vicuña et al. 2011a ) . Summer months (Dec-Feb)
feature minimum precipitation and tend to be snow or glacier melt dominated, with
the main proportion of stream flow taking place in late spring and summer (Sep-Jan)
(Vicuña et al. 2011a ). This leads to almost total reliance on glacier and snow pack
melt for water during the growing season, in areas where there is no storage capac-
ity. Climate change associated reductions in run-off, hydrograph timing and
enhanced evapo-transpiration will have significant impacts on agriculture in the
semi-arid areas of northern and central Chile (Vicuña et al. 2011b ) .
Furthermore, precipitation and temperature are both strongly influenced by
different large scale natural phenomena such as ENSO as well as, the Pacific
Decadal Oscillation (PDO) (Garreaud et al. 2009 ; Souvignet and Heinrich 2011 ;
Verbist et al. 2010 ), leading to high inter-annual variability (Vicuña et al. 2011a ) .
ENSO is a coupled ocean-atmosphere phenomenon, tied to the tropical Pacific
Ocean, that is characterised by fluctuations (periodicity between 2 and 7 years)
between a warm phase (El Niño), generally associated with higher than average
precipitation in central Chile, and a cold phase (La Niña), associated with lower
than average precipitation (Garreaud et al. 2009 ). While ENSO is observed as the
primary driver of inter-annual variability, PDO has been suggested to force decadal
and inter-decadal variability, with temperature and precipitation anomalies related
to ENSO, but with smaller amplitude (Garreaud et al. 2009 ) . In the preceding
decades, ENSO events have become increasingly frequent, but high levels of uncer-
tainty mean that projecting its development according to climate change scenarios
is still poorly understood (Kim and An 2011 ) .
While glacier shrinkage in the Dry Andes (generally between 20 and 35 S) has
been relatively well captured (Le Quesne et al. 2009 ), the impacts on stream flow
have been less well documented, in part due to the challenges of data collection
(Gascoin et al. 2010 ). Despite high uncertainty and general lack of data on climate
change impacts in the central Chilean region, studies and observation show that in
the Aconcagua Basin, there has been a significant decrease in the annual and
seasonal trend of streamflow from the Aconcagua basin glaciers, related to decreasing
contributions from glaciers and snow cover (Casassa et al. 2009 ; Pellicciotti et al.
2007 ) . Pellicciotti et al. ( 2007 ) suggest that melting rates tend to be higher in the
Central Andes, since the glacier ablation area occurs at lower elevations and so
higher temperatures in summer have increased melting. Furthermore, simulations in
northern central Chile suggest that the Dry Andean mountain range is likely to
encounter warmer winters, decreasing precipitation, changes in snowpack, changes
in snow and glacier melt and generally increasing dry periods, though as mentioned
earlier, this is still poorly modelled by GCMs (Souvignet et al. 2008 ; Vicuña et al.
2011b ). As Vicuna et al. ( 2011b , p 482) clarify 'increase in temperature leads to a
reduction in snowpack accumulation during the rainy season and an earlier, faster
snowmelt process during spring and summer'.