Setting an ecological flow regime in a Mediterranean basin with limited data availability: The Locone River case study (S-E Italy)

The Environmental Flow regime (E-Flows) was defined as the flow regime necessary to support river ecosystems, which in turn support crops, the economy, sustainable livelihoods, and human well-being. Although a large number of methods for setting an E-Flow regime have been developed, E-Flows science is still an emerging discipline in non-perennial rivers because of the lack of specific guidelines at the European and national level and the limited data availability (i.e., hydrological/biological). The aim of the present work was to define a methodology for setting an E-Flow regime in a region with limited data availability. The proposed approach was tested in the Locone basin (S Italy). A long time series (1971 to 2020) of daily streamflow in un-impacted conditions were simulated by using the SWAT+ model, a new release of the Soil and Water Assessment Tool. The flow regime was characterized in un-impacted conditions by means of the Indicators of Hydrological Alterations (IHAs) based on modeled daily streamflow. The E-Flow regime was defined by adopting the Range of Variability Approach and assuming the interquartile range (25 - 75 percentile) as an acceptable range of variation of each IHA. For the Locone reservoir, the monthly water release pattern, magnitude, and duration of high and low flow were defined as well as the timing and frequency of floods, and dry conditions.