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Climate change and water availability in North-West Algeria: investigation by dendrochronology and stable water isotopes

Congress: 2008
Author(s): Luc Lambs(1), Mohamed Labiod(2)
Luc Lambs 1 and Mohamed Labiod 1,2 1: Ecolab – CNRS, Toulouse 2: Université de Tlemcen, Algérie

Keyword(s): water need, dendrochronology, stable water isotope
AbstractSince the seventies, the rainfalls incomest are getting lower along the North African coast, while the demographic pressure increase, and such the water need increases. We present here the situation of the Tafna river basin, centre around the city of Tlemcen, in the North-West of Algeria. Many poplar plantations in the lower part of this basin present enhanced die-back and insects attacks, while many wells have no more water during summer. The study reveals that the main cause of this die-back is the lack of water. Wood cores have been extracted from these trees to quantified the change in growth. To complete the limited available rain data, the tree- rings of the century old Alep pine forest over Tlemcen could be used to have a better knowledge of the local climate change. Also isotopic samplings (18Oxygen and Deuterium) of the water in this basin were performed to better understand the water circulation. The objectives of this work is to compile all the data available on the climate (rainfalls, river discharge, lake level), trying to make a dendrochronology reference curve, compare with the previous data and to see how to extrapolate for longer time period. The first stable isotopes results have shown no seasonal variation for the ground water, which confirm the wide karstic buffer. Also the isotopic signal is different between the ground water of the higher and the lower Tafna basin, suggesting a bad connection between the two levels. Now a more global surface water sampling is in progress to better understand the water fluxes in this area, and also the impact of the dams, the other water puncture and used for domestic and industrial purposes. In conclusion, this local climate change is followed by many tools to better understand the impact of these lack of water, the consequence on the underground water buffer and the influence on the local vegetation and the behaviour of the human water uses. References: -Devenir du peuplier blanc (Populus alba l.) dans le Nord-Ouest Algérien. Diagnostic sanitaire de quelques peuplements sur la région de Tlemcen. M. Labiod, A. Haddad, R. Bouhraoua, A. Khelil Mohamed et Luc Lambs Foret Méditerranéenne, soumis en Février 2007 -Etude hydrologique et dendrochronologique du haut bassin de la Tafna, NW Algérie L. Lambs et M. Labiod 4 e Journées de la société Francaise des Isotopes Stables, Nantes, 11-14 septembre 2006.
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