Recent trends in Iberian streamflows (1945–2005)

12 páginas, 7 figurasThis paper analyzes streamflow trends in 187 sub-basins in the Iberian Peninsula for the period 1945– 2005. A database of monthly river discharges for the entire Iberian Peninsula including natural and regulated river regimes enabled assessment of the magnitude and spatial patterns and mechanisms of the hydrological trends. Annual and seasonal trend analyses were conducted. The results showed a marked decrease in annual, winter, and spring streamflows in most of the Iberian sub-basins, especially those in the south. In addition, changes in the seasonality of river regimes have occurred, most of them as consequence of dam regulation and water management strategies. We showed how river regulation by dams does not affect the sign of the trends, but its magnitude, by decreasing the releases during winter to meet the demand of water in summer creating important seasonal differences. The decrease of streamflows during the second half of the Twentieth Century in the Iberian Peninsula may accelerate in coming decades, as future climate projections show a generalized decrease in precipitation and more evapotranspiration induced by higher temperatures.We would like to thank the Centro de Estudios Hidrográficos (CEDEX), Sistema Nacional de Informaçâo de Recursos Hídricos (SNIRH), Agència Catalana de l’Aigua, Agencia Andaluza del Agua and Augas de Galicia for providing the hydrological data used in this study. This work has been supported by a pre-doctoral fellowship by the Aragón Government (Spain), and by the research projects CGL2006-11619/HID, CGL2008-01189/BTE, CGL2011-27574- CO2-02, CGL2011-27753-CO2-01 and CGL2011-27536 financed by the Spanish Commission of Science and Technology and FEDER, EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV- 2007-1- 212250) financed by the VII Framework Programme of the European Commission, ‘‘La nieve en el Pirineo Aragonés y su respuesta a la variabilidad climática’’ and ‘‘Efecto de los escenarios de cambio climático sobre la hidrología superficial y la gestión de embalses del Pirineo Aragonés’’ financed by ‘‘Obra Social La Caixa’’ and the Aragón Government and Influencia del cambio climático en el turismo de nieve. CTTP01/10, Financed by the Comisión de Trabajo de los Pirineos.Peer reviewe