Climate change is unbalancing the hydrological cycle in Latin America, causing more extreme floods and droughts. This is shifting hydroelectric power capacity and changing river flows. The Earth Simulator model projects further intensification of rainfall and longer dry periods under climate change. This will compromise the ability of mountain basins to regulate water flows as glaciers recede and fires reduce vegetation. To adapt, impacts must be assessed at the basin level to strengthen systems' resiliency and minimize reliability impacts.

1. Climate change impacts
on hydrological cycle
ADVANCING
SUSTAINABLE
HYDROPOWER
IN LATIN AMERIC
A
NOVEMBER 12 2012
WALTER VERGARA AND SIMONE
BAUCH
CLIMATE CHANGE AND
SUSTAINABILITY DIVISION

2. Will future climate affect the
integrity and stability of hydrology?
 Climate trends may be unbalancing the hydrological cycle in
major regions of Latin America; extreme floods and period of
severe droughts are being registered with increased
frequency;
 and, in association with land use changes, may be shifting
existing hydro power firm capacity and changing its structure
and behavior.
 These changes could also have implications for regional and
global carbon and water cycles.
 Use of the Earth Simulator (high speed, high resolution nested
model) could discern projected changes in hydrology in large
basins

3. Extreme hydrology:
Grijalva Basin in Mexico
• 40% of all runoff in Mexico
and 30% of all hydro power
generation.
• The hydrology in the basin is
destabilizing: 4 100 year
floods in the last 20 years.
• Impacts on settlements and
economic activities are not
controlled.
• The costs to the States of
Tabasco and the border area
with Guatemala have
exceeded 4% of GDP

4. Loss of Glaciers in the Andes
 Andean glaciers
retreat:
Impacts from loss of
water regulation
would affect human
water supply,
agriculture, power
generation and
ecosystem integrity

5. Temperature increase and fire events
in the central range of the Andes(Las Brisas)

6. The Earth Simulator
 IPCC 5th assessment report
 MRI Global circulation model
http://www.jamstec.go.jp/es/en/index.html 819.2 Gflops x 160 = 131 Tera flops

7. Projection of changes in hydrology with the Earth Simulator
Atmosphere- High-resolution Regional cloud
Ocean model global atmospheric resolving model
model by nesting
180km mesh 20km mesh 5km & 1km
mesh
Atmos Predicted
Atmos Boundar
phere SST phere y
condition
SST SST
Boundary
Ocean condition Future
100-50km mesh
Near
Future
Present
SST=Sea Surface SST
Temperature Year
7
1979-2003 2015-2039 2075-2099

8. Projected intensification of
rainfall (future-present 5 day max)

9. Projected increases in length of dry
periods in days (future-present)

10. Projected seasonal changes in top
soil moisture (%)

11. Projected changes in dry season
rain in the Amazon basin

12. Projected changes in stream-flows

13. Changes in river flows: a) current annual flows (mm) and b) change between the present
and the end of the century (%)
Note: The picture a) presents the absolute annual flow and therefore the scale is in mm. The picture b) presents the
change, and the scale is in percentage.

14. Conclusions and next steps
Ability of upper-shed basins to regulate water Need to assess the impacts at a
flows may also be compromised by loss of basin level so that adaptation
glacier cover and mountain wetlands responses can be designed;
Fire events will further reduce water retention by
vegetation in mountain areas. Need to strengthen resiliency of
Future climate may bring increased frequency of water supply and power
extreme rain and also lengthen the duration generation systems to minimize
of dry periods net impacts in reliability of
Future climate is likely to be associated with service
reductions in moisture in top soil layers
In the aggregate all of these changes can affect
the stability of hydrology and thus have
impacts in all depending services, including
firm capacity of hydro power reservoirs,
water supply for agriculture and human
settlements and others