Abflusstrends in Österreichs Fließgewässern 1977–2020

This article analyses streamflow trends in Austria for 250 gauges (low flows and mean flows) and 331 gauges (floods) in the period 1977–2020. While the mean streamflow has changed little on average in Austria, regional shifts are observed, with significantly decreasing trends in the west, northwest (Innviertel, Mühlviertel) and southeast (about 20% in 43 years), and slightly increasing trends in the Alpine region. The increasing trends of floods have intensified in recent years. In particular, southern Lower Austria and Upper Styria, as well as areas along the main Alpine ridge, have experienced significant increases of up to more than +20% (+5% per decade). The increase is more pronounced in smaller catchments than in larger ones. In the East of Austria, there has also been a seasonal shift in annual floods from winter and spring to summer. With regard to low flows, decreasing trends are observed in about 16% of the catchments below 900m a.s.l., which are particularly pronounced in the southeast and in the Innviertel region with summer runoff decreases of more than –20% in 43 years (about –5% per decade). In these regions, the low flow situation is becoming more acute, a fact that should be taken into account in water management planning