Jaz Wrocław II, Wrocław

Jaz Wrocław II is a historic flap weir with two control rooms, built in 1942. It is the northern weir of the Wrocław II hydroelectric-power complex, one of the principal elements of the City Barrage. This larger system controls the Oder on its central-city branch, at the beginning of the Lower Downtown Water Junction.

The barrage exists because an earlier barrage upstream had scoured the riverbed badly enough to endanger its own structures; the downstream works protected them while making new hydroelectric generation possible. Here, the machinery of urban river management has an unusually substantial effect: the water-level difference across the barrage is now five point six two metres. Before reconstruction and operating changes after 1959, it was three point seven four metres.

The nearby north power-station building was designed by Max Berg, and Jaroslav Vonka created its ornamental metalwork. What appears to be a compact river structure is part of a network that keeps Wrocław's canalised stretch of the Oder at its required level.