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Climate Change Impacts on Water Availability in the Semiarid Elqui Valley, Chile

IWRA World Water Congress 2008 Montpellier France
3. Climate Change and Disasters
Author(s): Maxime Souvignet
Hartmut Gaese
Lars Ribbe
Ricardo Oyarzún
Nicole Kretschmer
Contact Author: Maxime Souvignet Institute for Technology in the Tropics Cologne University of Applied Sciences D 50769 Cologne Germany max.souvignet@gmx.net Tel: +49/221/82 752 125 Fax: +49/221/82 752 736 Additional Authors: - Hartmut Gaese, I

Keyword(s): Climate Change, Streamflow Simulation, Statistical Downscaling, Chile, Regional Impacts, Semiarid Watershed, HadCM3, HEC-HMS, SDSM

AbstractAlthough climate has been influenced by humans for centuries, the actual rate of climate change is greater than those recorded in the past. In the vulnerable central- northern Chile (Norte Chico), where agriculture still serves as a backbone of the economy as well as ensures the well being of people, the knowledge of water resources availability is essential. The region is characterised by a semiarid climate with a mean annual precipitation inferior to 100mm. Moreover, the local climate is also highly influenced by the ENSO phenomenon, which accounts for the strong inter-annual variability in precipitation patterns mainly occurring in high altitude areas. The objectives of this study are a) to develop climate change scenarios (2000-2059) for the Elqui watershed and b) to analyse the local outcomes in terms of temperatures and precipitations. In addition, this study aims at c) modelling the future impacts of local climate on streamflows in the Elqui valley and d) evaluate the possible impacts on agriculture and the local economy. The outputs of the HadCM3 A2a and B2a SRES scenarios were regionalised for the Elqui watershed for a 60-years period (2000- 2059) by means of the SDSM statistical downscaling technique. Thereafter, a previously calibrated hydrological model (HEC-HMS) was fed with downscaled future temperatures and precipitations. Accordingly, future streamflows were simulated for the studied period. Local temperatures are expected to rise in the region, whereas precipitations may decrease. However, minimum and maximum temperatures would increase with a faster rate in high altitude areas with an increase ranging from 1.1°C to 1.4°C by 2059. Furthermore, lower altitudes areas expect an increase from 0.5°C to 0.7°C. The Cordillera may encounter warmer and longer winters with a dramatic decrease of icing days (Tmax<0°C). As for precipitation, both SRES scenarios return a diminishing tendency of ca. 25%, though the A2a scenario results show a faster decrease rate. In addition, the region expects an augmentation of dry spell in middle altitudes areas during the six decades. Results indicate potential strong inter-seasonal and inter- annual perturbations in the region. These, in turn, would impact the pattern of streamflows. By 2059, both A2a and B2a scenarios return net variations in monthly and annual flows. Moreover, forecasted fluctuations of flows underline an increase in the sensitivity of the region in terms of hydrological responses to climatic variations. Hence, the hydrology of the Elqui valley could be strongly affected by climate change. At the same time, an insufficient number of high altitude stations does not allow to draw definitive conclusions on future climate variability. In addition, this work reveals the gap of knowledge concerning the simulation of future extreme rainfall events on a local level for mid- and long term prognosis. Accordingly, concrete suggestions are made for future research in order to fill these data gaps. Finally, some qualitative statements are made on the impacts on the local agriculture and economy, including the possible evolutions of water rights in the region. This research is a mere first step in analysing possible impacts of climate change in the Elqui watershed and hopefully contributes to set the basis for appropriate adaptation strategies.
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