Impacts of future climate on water ecosystem services in the watershed of Homem river (northwest Portugal)

Abstract

Ecosystems are under pressure, especially due to climate change, which reduces among others, the ability of ecosystems to provide water-related ecosystem services such as water supply and soil erosion control. The aim of this study, carried out in the Homem River basin (Northwest Portugal), was to assess how future climate alterations may influence the provision of these ecosystem services. The Soil and Water Assessment Tool (SWAT), a hydrological model, was calibrated and validated for local watershed conditions (river discharge and monthly reservoir volumes). Future climate projections (2020-2050) were forced into SWAT, based on four regional climate models and two climate change scenarios (RCP4.5 and RCP8.5). The results confirm that the SWAT model has a good performance in quantifying river discharge and reservoir water volume after calibration and validation. Climate change may affect water supply by reducing annual water yield in the basin by 7% under RCP8.5 scenario by 2050, when compared to the historical period (1970-2000). There will be less water in the river in spring, summer and autumn and more water during winter. The reservoir water volume should decrease considerably, therefore reducing the potential of hydropower production, especially during summer. The sediment exportation would increase, especially under RCP8.5 scenario. These results are of high relevance for building adaptation strategies to reduce the impacts of climate change on water ecosystem services provision, taking into account nature-based solutions, particularly at the local level to support sustainable river basin management strategies.