Setting an environmental flow regime under climate change in a data-limited Mediterranean basin with temporary river

Catchment in Southern Italy. Mediterranean waterways are commonly non-perennial; they are vulnerable to climate change (CC). Their management is particularly complex due to limited data availability. This work aims to develop a methodology for setting an Environmental Flow regime (E-Flows) for a temporary river (Locone, Italy) under limited data availability and under CC. As observed long-term time series of streamflow under natural conditions were not available, the Soil and Water Assessment Tool model (SWAT+) was applied to simulate the daily streamflow for the baseline period (1980–2010) and future (2020–2050) based on observed and model climate projections, respectively. A specific workflow was developed for model calibration focusing on the low flows. The hydrological regime was characterized by means of Indicators of Hydrological Alteration (IHAs), whereas the Range of Variability Approach (RVA) was applied to define the E-Flows. The basin is experiencing a statistically significant increase in the air temperatures observed from 1971 to 2020, which is also predicted to continue in the future. Consequently, the average annual streamflow and monthly streamflow in winter and spring is expected to decrease. The calibration, based on a multi-objective model evaluation, improved the low-flow simulation. The detected differences in IHAs for the predicted periods should be considered in future water management when setting E-Flows for temporary rivers. [Display omitted] •A reduction in rainfall is expected in winter and spring by up to 25% (2020-2050).•Models predict an increase in average summer temperatures of more than 1 °C.•To improve the simulation of zero flows a Zero-Flow threshold was introduced.•The workflow set up in the R environment improves SWAT+ calibration of low flows.•CC produces alterations of the flow regime that must be considered when setting Eflows.