Tidal Weir

What is it?

The Clyde Tidal Weir is an important part of Glasgow's infrastructure network and is essential to maintaining the water level of the River Clyde. The Weir stabilises the upstream banking of the River Clyde by maintaining a fixed water level, creating a deep, wide channel of water through Glasgow Green.

Function

The Tidal Weir's purpose is to stabilise the upstream banking, by maintaining a fixed water level, creating a deep, wide channel of water through Glasgow Green. Downstream of the Weir is entirely tidal, alternating between fresh and sea water.

The change from fresh water to salt water within river estuaries usually happens gradually over a number of miles. The Weir creates an unnatural situation: two distinct ecosystems separated by a barrier. This mix provides an important habitat for a range of birds, fish and mammals.

Facts

• The Weir was built by Glasgow Corporation and opened in 1901.
• In engineering terms the Weir is an underflow tidal sluice.
• It has three adjustable gates. Each is 80 feet long and 12 feet high.
• The gates move vertically in guides contained within the two masonry abutments and two intermediate masonry piers; and are connected by chains to counteract movement within the abutments and piers.
• Electrical motors are used to assist with the movement of the gates.
• Three steel arches linking the abutments and piers, assist with the lifting mechanism and support a footpath (no public access).
• The structure also supports two large water main pipes which cross the Clyde at this point.

History

Built in 1901, the Weir needed major repairs in 1943, due to damage sustained in the catastrophic floods of 1941, when both the Weir and the riverside tenements on Adelphi Street on the south bank were demolished. The north side of the Weir is within Glasgow Green near Jocelyn or Jail Square, an area once used for public executions and public speaking. The Weir is now a Category B Listed Structure due to its design and appearance.

The Weir underwent the first major refurbishment works since 1946. This included:

• installation of a new deck and handrails;
• grit blasting of steelwork;
• repair and painting of steelwork to a standard that will last several decades;
• complete rewiring;
• installation of period light fittings to restore original character