Staustufe Obernau, Lock and barrage system in Aschaffenburg, Germany

Staustufe Obernau is a lock and weir system on the Main River in Aschaffenburg with a fish passage and chamber for river navigation. The facility raises and lowers water levels to allow boats to pass safely between sections of the river.

The Obernau barrage was built between 1926 and 1929 without a raft channel. Its power plant, run by the Rhein-Main-Donau AG, was erected in 1926–1930 with two Kaplan turbines. From 2008 the structure was renovated after concrete damage appeared in the lock chamber walls. Because frost damage left the core concrete porous, a replacement weir and lock are planned about 160 metres downstream, with planning approval proceedings opened in July 2017.

The weir drums are raised and lowered by gears and chains that remain largely exposed to view, unlike at most barrages on the Main. Visitors can also see the untreated concrete sections, with their honeycombed pockets and leaching, which still show how the structure was poured in the late 1920s.

The site is easily visible from the riverbank and accessible by foot or bicycle. You can walk around the grounds to watch boats passing through the lock system.

The weir's gears and chains that raise and lower the three drum gates are largely exposed to view, unlike at most barrages on the Main. The untreated concrete sections, with their voids and leaching stains, still show how the structure was poured in the late 1920s.