The Biobío River basin is of high strategic importance for Chilean development, at both the regional and the national levels. For this reason, advances in the general understanding of, and in the capacity to describe and predict, in a spatially explicit way, the impact of climate and anthropogenic forcing on the hydrology of the Biobío basin are urgently needed. The work presented here attempts to set the basis for future modelling applications within the Biobío basin by analysing the applicability of a readily available modelling tool, the SWAT model, to one of its sub-basins. Modelling results show that the model performs well in most parts of the study basin. The SWAT model application for the Vergara basin confirms that SWAT is a useful tool and can already be used to make a preliminary assessments of the potential impacts of land-use and climate changes on basin hydrology.Key words hydrological modelling; SWAT; calibration; Chile; Biobío Modélisation hydrologique avec SWAT en conditions de données peu disponibles: évaluation des résultats d'une application au ChiliRésumé Les eaux du bassin du Biobío sont d'une importance stratégique pour le développement du Chili, au niveau régional comme au niveau national. Pour cette raison, il est urgent d'avancer dans la compréhension générale de l'hydrologie du bassin, afin de pouvoir décrire et prévoir, d'une manière spatialement explicite, l'impact du forçage climatique et anthropique. Le travail présenté ici prétend établir la base pour les futurs efforts de modélisation du bassin du Biobío, en analysant l'applicabilité d'un outil de modélisation existant, le modèle SWAT, à un de ses sous-bassins. Les résultats indiquent que le modèle a une bonne performance dans la presque totalité du bassin étudié. L'application du modèle SWAT au bassin de Vergara confirme qu'il est un outil utile, qui peut d'ores et déjà être utilisé pour faire des évaluations préliminaires des impacts potentiels des changements d'occupation du sol et de climat sur l'hydrologie du bassin.

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2Patagonia is commonly seen as an exceptionally pristine area because of its wildlife and practically unpolluted 3 waters. However, during the twentieth century the burning of natural forests was one of the most important 4 human activities in Northern Chilean Patagonia. Some estimations indicate that three million hectares were 5 burned during the first three decades of the century being its impacts rarely assessed. Hence the objective of this 6 study was to evaluate the impacts of the historical fires in Lake Burgos (45º42'S) and Lake Thompson (45º38'S) 7 in Chilean Patagonia. The impact was measured by evaluating chironomid assemblage since they are sensitive 8 enough to be used as an indicator of aquatic ecosystem health. Fires have a direct and drastic effect on a lake 9 watershed but also indirectly affect a lake ecosystem, changing sedimentation patterns or increasing nutrient 10 inputs. In the studied lakes the periods with higher prevalence of fires were identified by charcoal analysis, 11 while organic matter and magnetic susceptibility allowed to confirm the pre-fire and post-fire periods. The 12 chironomid composition was evaluated through a PCA and an analysis of similarity (ANOSIM) to test the 13 significance among periods while a DCA was applied to the chironomid assemblage downcore to assess 14 compositional structure and taxa turnover. In Lake Burgos the ANOSIM test indicated significant differences 15 between the pre-fire and fire periods (p<0.05), while in Lake Thompson differences were not significant.

Several impacts over ecosystem services have been produced by land use/cover changes, placing it as one of the main factors driving global environmental change. In the present study, the SWAT model was used to assess the effect of land use/cover changes on the hydrology response in the Andalien river basin from the south-central zone of Chile. Three land use/cover scenarios (LU_1986, LU_2001, and LU_2011) were compared over a period of 30 years (1984–2013) to remove the effect of climate variability on hydrology. The results show a significant decrease in total annual flows among the three LU scenarios. The greater differences in the annual flows of 25.05 m3/s were observed between LU_1986 and LU_2011 scenarios. The hydrological cycle dynamics in the basin show an increasing trend of evapotranspiration and surface flows with a significant decrease in percolation and lateral flow on a monthly and seasonal scale. This behavior can be explained by the increasing percentage of the basin area covered by exotic plantations, from 35.22% to 63.93% during the period. The evidence of these changes and the evaluation of their effects are particularly relevant for the long-term sustainable management of water resources.

Abstract. A multidisciplinary approach is followed for analysis of the effect of changes in land use patterns on the hydrologic response of the Vergara watershed (4340 km 2 ) located in central Chile. Probable future land use scenarios were generated using heuristic rules and logistic regression models, in order to identify and represent the main pressure on the watershed, namely forestation of extensive areas used for agriculture with rapid growing exotic species. The hydrologic response of the watershed was computed with a physically based distributed precipitation-runoff model, which was calibrated and validated for the current period. Results show that mean annual discharge increase with agricultural land use and diminish with introduced forest coverage. Thus, forestation of areas with introduced species like Pinus radiata and Eucalyptus globulus might be regulated in order to protect the water resources of the watershed.