Abstract

Over the last decades a progressive change in world-wide climatic conditions has been observed and described by the scientific community. Associated to these ongoing changes, reports on the devastating effects of floods and prolonged periods of droughts are increasingly brought to the attention of the public opinion. Also, for considerable parts of the Chilean territory, important changes in climatic conditions have been projected for the decades to come. This situation has encouraged society to take measures in order to attempt to control such changes, as well as to adapt to those changes that cannot eagerly be prevented through world-wide mitigation actions. From a water resources management perspective, the implementation of specific measures at the level of the river basin asks for the availability of tools that allow managers to take decisions in an informed way. Considering that the Biobío Basin (24.371 km 2) is of high strategic importance for Chilean development, advances in the general understanding and capacity to describe and predict, in a spatially explicit way, the impact of climate and climate change on (sub-)basin hydrology is urgently needed. The Soil and Water Assessment Tool (SWAT) was chosen to model the hydrology of two sub-basins of the Biobío, the Vergara Basin (4.265 km2), located in the south-eastern part of Biobío, and the Lonquimay Basin (455 km2), located within the Andean Mountain Range. First, the model was calibrated and validated for both sub-basins, and then, the response of basin hydrology to different plausible climate change scenarios was modelled. Even when results indicate a wide array of potential impacts in terms of the magnitude of a future reduction of monthly mean discharges, such reductions appear to be highly plausible as future conditions of river discharge. In the event of such reductions, important adaptation measures will be required.