Uncertainty of modelled flow regime for flow-ecological assessment in Southern Europe

Olga Vigiak, Stefanie Lutz, Angeliki Mentzafou, Gabriele Chiogna, Ye Tuo, Bruno Majone, Hylke Beck, Ad de Roo, Anna Malagó, Fayçal Bouraoui, Rohini Kumar, Luis Samaniego, Ralf Merz, Christos Gamvroudis, Nikolaos Skoulikidis, Nikolaos P. Nikolaidis, Alberto Bellin, Vicenç Acuňa, Nataša Mori, Ralf LudwigAlberto Pistocchi

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


Sustainable water basin management requires characterization of flow regime in river networks impacted by anthropogenic pressures. Flow regime in ungauged catchments under current, future, or natural conditions can be assessed with hydrological models. Developing hydrological models is, however, resource demanding such that decision makers might revert to models that have been developed for other purposes and are made available to them (‘off-the-shelf’ models). In this study, the impact of epistemic uncertainty of flow regime indicators on flow-ecological assessment was assessed at selected stations with drainage areas ranging from about 400 to almost 90,000 km2 in four South European basins (Adige, Ebro, Evrotas and Sava). For each basin, at least two models were employed. Models differed in structure, data input, spatio-temporal resolution, and calibration strategy, reflecting the variety of conditions and purposes for which they were initially developed. The uncertainty of modelled flow regime was assessed by comparing the modelled hydrologic indicators of magnitude, timing, duration, frequency and rate of change to those obtained from observed flow. The results showed that modelled flow magnitude indicators at medium and high flows were generally reliable, whereas indicators for flow timing, duration, and rate of change were affected by large uncertainties, with correlation coefficients mostly below 0.50. These findings mirror uncertainty in flow regime indicators assessed with other methods, including from measured streamflow. The large indicator uncertainty may significantly affect assessment of ecological status in freshwater systems, particularly in ungauged catchments. Finally, flow-ecological assessments proved very sensitive to reference flow regime (i.e., without anthropogenic pressures). Model simulations could not adequately capture flow regime in the reference sites comprised in this study. The lack of reliable reference conditions may seriously hamper flow-ecological assessments. This study shows the pressing need for improving assessment of natural flow regime at pan-European scale.
Original languageEnglish (US)
Pages (from-to)1028-1047
Number of pages20
JournalScience of the Total Environment
StatePublished - Feb 15 2018
Externally publishedYes

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