Assessment of future hydrologic alteration due to climate change in the Aracthos River basin (NW Greece).

Climate change is a worldwide reality with significant effects on hydrological processes. It has already produce alterations in streamflow regime and is expected to continue in the future. To counteract the climate change impact, a better understanding of its effects is necessary. Hydrological models in combination with Indicators of Hydrologic Alteration (IHA) suppose an up-to-date approach to analyze in detail the impacts of climate change on rivers. In this study, the Soil and Water Assessment Tool (SWAT) model and Indicators of Hydrologic Alteration in Rivers (IAHRIS) software were successfully applied in Aracthos River basin, an agricultural watershed located in the north-western area of Greece. Statistical indices showed an acceptable performance of the SWAT model in both calibration (R = 0.74, NSE = 0.54, PBIAS = 17.06%) and validation (R = 0.64, NSE = 0.36, PBIAS = 12.31%) periods on a daily basis. To assess the future hydrologic alteration due to climate change in Aracthos River basin, five Global Climate Models (GFDL-ESM2, HadGEM2-ES, IPSL-CM5A-LR, MIROC-ESM-CHEM and NorESM1-M) were selected and analyzed under two different emission scenarios (RCP 4.5 and RCP 8.5) for a long-term period (2070-2099). Results indicate that precipitation and flow is expected to be reduced and maximum and minimum temperature to be increased, compared to the historical period (1970-1999). IHA, obtained from IAHRIS software, revealed that flow regime can undergo a severe alteration, mainly on droughts that are expected to be more significant and longer. All these future hydrologic alterations could have negative consequences on the Aracthos River and its surroundings. The increase of droughts duration in combination with the reduction of flows and the alteration of seasonality can affect the resilience of riverine species and it can produce the loss of hydraulic and environmental diversity. Therefore, this study provides a useful tool for decision makers to develop strategies against the impact of climate change.