Download Present and future water resources supply and demand

PROYECTO
GLACIARES
PRESENT AND FUTURE WATER RESOURCES SUPPLY AND DEMAND IN THE CENTRAL ANDES
A COMPREHENSIVE REVIEW WITH FOCUS ON THE CORDILLERA BLANCA, PERU
Fabian Drenkhan1, Christian Huggel1, Mark Carey2, Adam French3 & Luzmila Dávila4
1Geography
Department, University of Zurich, Switzerland
3Energy and Resources Group, University of California, Berkeley, USA
2Robert
D. Clark Honors College, University of Oregon, Eugene, USA
4Glaciology and Water Resources Unit, National Water Authority, Huaraz, Peru
Introduction
As virtual water towers, glaciers have been a crucial source for Andean societies and livelihoods. Peru’s mainly remote living population in the
Central Andes has to cope with a strong seasonal variation of precipitations and river runoff interannually superimposed by ENSO impacts.
Consequently, direct glacier and lake water runoff constitute a vital continuous water supply and represent a regulating buffer mitigating human
vulnerability to climatic-hydrological variability. This natural system is likely to deteriorate, triggered by accelerated glacier retreat and climatic
changes. This nourishes concerns about a sustainable water supply in the Cordillera Blanca (CB) area and even more so in the arid coastal
reaches of the lower Santa watershed while Ancash’s population, irrigation-intense agriculture and hydropower demand increase.
Here we present a comprehensive review of the actual situation and perspectives for water resources management in the Peruvian Andes.
Impacts in water supply: accelerated glacier retreat
First evidences of a crossed ‘peak water’
With 459 km2 glacier area at present the CB (Figure 1) represents the
largest glacierized mountain range of the tropics worldwide. Especially
as of the second half of the 1970s, it has been strongly affected by
massive ice loss with
blabla
Data from UGRH (ANA, 2010)
Data 1990: Georges, 2004
around 34% glacier
Data 1987, 1996:
Silverio & Jaquet, 2005
area decline from 1970
to 2010 (ANA, 2010;
Rabatel et al., 2013;
Figure
2).
More
frequent ENSO events
in the last decades and
the abrupt Pacific
climate shift with a Figure 2: Glacier area retreat in the CB area.
blbl
positive PDO phase and higher SST since 1976 could explain this
accelerated retreat (Rabatel et al., 2013; Vuille et al., 2008).
This constant water supply for human consumption especially during
the months of less precipitation is already decreasing. First evidences
corroborate a passed ‘peak water’ in 6 glacierized subcatchments of
the Santa river (Figure 3) from where on prior enhanced river runoff
will decrease and level out towards a new still unknown minimum
with higher discharge variability. This contradicts the general
consensus of a subsequent future discharge decline within a few
decades. Future annual water stream (Figure 3, Phase 4) will be much
lower than today with a dry season discharge decrease of up to 30%
(Baraer et al., 2012; Bury et al., 2013)).
Main characteristics of the Santa river basin
The 12,200 km² wide Santa basin receives about 675 mm/year
precipitation (34 station average), characterized by high seasonality.
Consequently, river flow has a high-level runoff in the wet season
(November-April: ~206 m³/s) and low-level runoff in the dry season
(May-October: ~62 m³/s). Glacial melt water contributes with 10-20%
in the wet and up to 40% in the dry season (Mark et al., 2005).
Phase 2
Phase 3
River discharge increase
driven
by
climateinduced glacier melt
Slowdown of discharge
increase
(accelerated
glacier retreat) reaching
the peak water
Pronounced decrease of
discharge and increase
of discharge variability
Phase 4
Discharge levels out until towards a new minimum
(negligible influence of retreated glacier bodies) with
high annual discharge variability
Agriculture accounts for 80% of the total water consumed in Peru.
ChaViMoChic, an emblematic project situated on the dry Pacific coast
(Santa effluent), is host to
74,000 ha export crops
including 60,000 jobs.
Recent expansion efforts
(Phase III, Figure 1) stand
in stark contrast and will
even trigger the declining
river runoff especially
during
dry
season
(cf. Carey et al., 2013).
Picture from: http://glaciers.uoregon.edu/Updates.html
Increasing water use: new hydropower schemes
Discharge
Phase 1
Increasing water demand: agriculture
Time
Hydropower, with 53% (5.3%) of whole power capacity nationwide
(Santa catchment) the energy pillar of Peru’s economy, might also be
heavily affected by diminishing water resources. The Cañon del Pato
central in the lower Santa river requires a minimum water discharge
of 72 m³/s at full capacity (263 MW). High runoff seasonality and the
current water resources decrease and increase of discharge variability
contain a strong conflict potential with high economic and social
impacts (cf. Vergara et al., 2007). Peru’s energy demand is increasing
by 7.5%/year (MINEM, 2013). Present and future hydropower
blschemes will need to take into account a lower river discharge.
Figure 3: Discharge impact phases of 9 subcatchments in the Santa river (after Bury et al., 2013).
Figure 1: Overview of the Santa basin and river with its main features in Peru (red rectangle defines dimensions of upper right detailed
map). Sources used: DEM (USGS SRTM v.3, 2013); National Topographic Map of Peru (Peruvian Ministry of Education, 2010)
Conclusions
The CB area and Santa basin have raised considerable
scientific interest but still represent an in-situ hydroclimatic and glacier data scarce region. Climate change
impacts are already altering natural water supply while
human water demand with needs for a year-round
constant minimum discharge is increasing.
References:
ANA (2010): Inventario de Glaciares – Cordillera Blanca. – Unidad de Glaciología y Recursos
Hídricos (UGRH, Huaraz), 81 pp., Autoridad Nacional del Agua, Lima.
Baraer, M., Mark, B. G., McKenzie, J. M., Condom, T., Bury, J., Huh, K.-I., Portocarrero, C., Gómez,
J. & S. Rathay (2012): Glacier recession and water resources in Peru’s Cordillera Blanca. –
Journal of Glaciology, 58 (207), pp. 134-150.
Bury, J., Mark, B. G., Carey, M., Young, K. R., McKenzie, J. M., Baraer, M., French, A. & M. H. Polk
(2013): New Geographies of Water and Climate change in Peru: Coupled Natural and Social
Transformations in the Santa River Watershed. – Annals of the Association of American
Geographers, 103 (2), pp. 363-374.
Carey, M., Baraer, M., Mark, B. G., French, A., Bury, J., Young, K. R. & J. M. McKenzie (2013):
Toward hydro-social modeling: Merging human variables and the social sciences with climateglacier runoff models (Santa River, Peru). – Journal of Hydrology, in press.
Mark, B.G., McKenzie, J.M. & J. Gómez (2005): Hydrochemical evaluation of changing glacier
meltwater contribution to stream discharge: Callejon de Huaylas, Peru. - Hydrological Sciences
Journal, 50 (6), pp. 975–987.
More comprehensive studies are imperative in order to
quantify and capture the complexity and links between MINEM (2013): Avance estadístico del subsector eléctrico: Cifras en octubre 2013. – Ministry
of Energy and Mining, Peru.
natural water supply and different water users. The use
Rabatel, A., Francou, B., Soruco, A., Gomez, J., Cáceres, B., Ceballos, J. L., Basantes, L., Vuille, M.,
of bias-corrected satellite data is imperative in order to Sicart, J.-E., Huggel, C., Scheel, M., Lejeune, Y., Arnaud, Y., Collet2, M., Condom, T., Consoli, G.,
Favier, V., Jomelli, V., Galarraga, R., Ginot, P., Maisincho, L., Mendoza, J., Ménégoz, M., Ramirez,
close data gaps in the remote and poorly gauged CB E., Ribstein, P., Suarez, W., Villacis, M. & P. Wagnon (2013): Current state of glaciers in the
tropical Andes: a multi-century perspective on glacier evolution and climate change. – The
area. More transdisciplinary efforts considering physical Cryosphere, 7, pp. 81-102, European Geosciences Union.
W., Deeb, A. M., Valencia, A. M., Bradley, R. S., Francou, B., Zarzar, A., Grünwaldt, A. &
and social key variables must be made to develop Vergara,
S. M. Haeussling (2007): Economic Impacts of Rapid Glacier Retreat in the Andes. – EOS
adaptation strategies to a rapidly changing water Tansactions, American Geophysical Union, pp. 261-268.
Vuille, M., Kaser, G. & I. Juen (2008): Glacier mass balance variability in the Cordillera Blanca,
Peru and its relationship with climate and the large-scale circulation. – Global and Planetary
balance in the Santa basin.
Change, 62 (1-2), pp. 14-28.
Acknowledgements
This study is part of the “Proyecto Glaciares” funded by the Swiss Agency for Development and
Cooperation (SDC).
Contact: Fabian Drenkhan [email protected]