Exploring hydrological system performance for alpine low flows in local and continental prediction systems

Study region: The European alpine space.<br />Study focus: Despite the advancements in hydrological modeling, there is a lack of comparative studies quantifying the performance differences between local and large-scale models, particularly in the context of drought and low flow assessment. This study addresses this gap by designing a framework to evaluate the European Flood Awareness System (EFAS), a continental system, in simulating low flow events across 101 alpine stations from 1999–2018, with detailed comparisons to two local systems — GR6J in France and PREVAH in Switzerland — at 34 of these stations.<br />New hydrological insights for the region: The results show that the local systems, PREVAH and GR6J, generally outperform the continental system EFAS for almost all stations. The performance gap between the systems increases as low flow conditions intensify, highlighting the importance of local systems for extreme low flow events. Despite EFAS not being specifically set up for low flows, it has shown an overall acceptable performance compared to the local hydrological systems, especially at locations that are not calibrated within the EFAS system, indicating its potential in ungauged areas. This study lays a foundation for understanding how a continental hydrological system like EFAS can complement local systems or fill the gap when a local system is unavailable to provide reliable predictions of low flow conditions.