Setting an E-Flow regime under climate change

The E-Flow regime is defined as “the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-being that depend on these ecosystems" (Brisbane Declaration, 2007). The natural flow regime of rivers can be greatly altered by human activities and climate change, which can strongly impact habitats and biotic communities. The present work aims to establish an E-Flow regime for the temporary river Locone (S-E Italy) for the near future under climate change. Temporary rivers are typical for Mediterranean climate areas. Yet, as it is the case for the Locone river, they are often poorly monitored and only few historic observations of river discharge are available. With the limited data that is available, a SWAT+ model was set up for the Locone catchment and was calibrated based on the daily discharges observed in the year 1971. 5000 model parameter combinations were sampled and three criteria with thresholds were defined to select acceptable model parametrizations, which are the Kling Gupta Efficiency for daily discharge of the entire time series (KGE_q > 0.75), the absolute percentage bias (abd(pbias_lf) < 5%), and as the major focus is on low flows the mean absolute error of daily discharges in the extended low flow period of the year 1971 (mae_lf < sd(qobs_lf)). The validation conducted based on the flows observed in the year 1972 returned good KGE values ​​for the selected runs between 0.46 and 0.67. Weather data from GCMs were used for simulating daily streamflow in the near future (2020-2049). The downscaling was carried out over the historical period (1971-2005). Daily streamflows predicted by the model were used to calculate the Indicators of Hydrological Alteration and, finally, the application of the hydrological method Range of Variability Approach allowed to set the E-Flow regime by fixing the variability of each indicator in the interquartile range.