Assessing flow regime alterations in a temporary river - the River Celone case study

Abstract: In this paper, we present an approach to evaluate the hydrological alterations of a temporary river. In theserivers, it is expected that anthropogenic pressures largely modify low-flow components of the flow regime with consequencesfor aquatic habitat and diversity in invertebrate species. First, by using a simple hydrological index (IARI) riversegments of the Celone stream (southern Italy) whose hydrological regime is significantly influenced by anthropogenicactivities have been identified. Hydrological alteration has been further classified through the analysis of two metrics: thedegree (Mf) and the predictability of dry flow conditions (Sd6). Measured streamflow data were used to calculate the metricsin present conditions (impacted). Given the lack of data from pristine conditions, simulated streamflow time serieswere used to calculate the metrics in reference conditions. The Soil and Water Assessment Tool (SWAT) model wasused to estimate daily natural streamflow. Hydrological alterations associated with water abstractions, point dischargesand the presence of a reservoir were assessed by comparing the metrics (Mf, Sd6) before and after the impacts. The resultsshow that the hydrological regime of the river segment located in the upper part of the basin is slightly altered, while theregime of the river segment downstream of the reservoir is heavily altered. This approach is intended for use with ecologicalmetrics in defining the water quality status and in planning streamflow management activities.