Regulating weir Port, Regulating weir in Port, Switzerland

The regulating weir in Port is a water management structure built across the waterway to control water levels. The construction prevents flooding in the surrounding area and allows water flow to be adjusted as conditions change with the seasons.

The first Jura water correction (1875–1878) diverted the Aare into Lake Biel, and a dam built in 1885–1887 above the old Zihl confluence failed to prevent major floods, notably in 1910. During the second correction, the current weir was built between 1936 and 1939 below the confluence of the Nidau-Büren canal and the Zihl, with five gates and a navigation lock.

The weir's name is tied to the small town of Port, and its five sluice gates and navigation lock are the visible parts of a system steered from Bern's water and energy office. Since 2008 a forecast-based regulation lowers Lake Biel's level ahead of predicted floods; this pre-emptive drawdown was used during the 2013 flood.

A road bridge crosses the weir, linking Port and Brügg, so the structure and its five gates can be seen from the bridge deck. The lock beside the gates lets boats pass the roughly 3 m drop on the Aare. The gauge Aare Brügg sits at the weir, and the flow is set remotely from Bern.

The weir's five gates and its lock sit beside the Brügg hydroelectric plant, built by Bielersee Kraftwerk AG during the 1989-1992 overhaul and producing about 25 million kWh a year from 1995. The plant uses the same drop of 3.0 m at low water.