Impacts of climate change on water resources: a case-study for Portugal

The paper briefly analyses the impacts of climate change on water resources and identifies, in general terms, the specific impacts related to different hydrological variables and different characteristics of the water systems. A case study of the impacts of climate change on Portuguese water resources developed within the SIAM project, is introduced. The climate scenarios considered, corresponding to selected climate models, show a small increase of annual precipitation for the northern region of Portugal and a decrease for the central and southern regions. The models also predict an increase of seasonal asymmetry with relevant decreases in summer precipitation. The annual average temperature appears to increase, particularly in southern Portugal. These climatic scenarios lead to a probable trend towards a concentration of river runoff in winter and an increase in the current seasonal asymmetry of water availability in Portugal. It also appears that the concentration of rainfall in winter and the estimated general increase in the frequency of heavy precipitation events is likely to augment the magnitude and frequency of flooding, particularly in the northern part of the country. The predicted decrease of river flow in southern Portugal, during the next century, associated with an increase in the spatial and temporal asymmetry of water resources distribution, may have very serious consequences and be a cause of major concern. It may, in fact, have strong implications for the water resources management strategies and policies to be designed for Portugal. Finally, how the consideration of climate change on water resources should influence the future planning and management of water resources, both in general terms and in the specific case of Portugal, is analysed. In particular, the joint study of climate change impacts on the water resources shared by Spain and Portugal is proposed as a major focus for scientific and technological co-operation of the two countries of the Iberian Peninsula.