News

Weir workings to be on show

By Liz Mellino

Australia’s oldest irrigation structure, the Goulburn Weir, will be showcased in an upcoming exhibition at the National Museum in Canberra.

A delegation from the museum met Goulburn-Murray Water staff at the weir near Nagambie on Friday to learn more about the structure and the significant role it plays for irrigation districts.

Heralded as an engineering marvel of its time, construction began on the weir in the 1880s and it was later rebuilt to modern standards after close to a century of use.

One of the weir’s original gates, two pier supports and a complete set of lifting gear was donated to the museum eight years ago and will be housed in a new environmental history gallery set to open in 2020.

‘‘It is a very culturally, historically and economically significant piece of infrastructure as the first major intervention in the Murray-Darling Basin System for irrigation purposes,’’ Gallery Development Project lead curator George Main said.

‘‘We will be trying to give visitors a sense of what the weir is like and was like when it was first built and throughout its working life.’’

The structure was completed in 1891 and, under the management of G-MW, continues to supply properties in the Shepparton and Central Goulburn irrigation districts, as well as filling the Waranga Basin storage and forming Lake Nagambie.

The original elements of the weir will be installed in the museum to replicate exactly how they once worked, and will remain on display for 15 years.

G-MW dams operations manager Scott Wikman said the weir was refurbished in 1988 after it was discovered the original structure had sustained a significant amount of damage.

‘‘They did some investigation and found the original gates deteriorated to such a state they could no longer be maintained,’’ he said.

‘‘When they drained the weir to have a look at the damage there was a large cavity and they were concerned over time the whole structure could just fall forward.’’

The upgrade project saw the removal of the original iron gates which were replaced with mild steel replicas constructed according to the original plans.

The newly grafted gates were installed in front of the remaining ones, which were then cut and lifted from their position and transported away to be stored.

With each gate and accompanying cast iron piers weighing close to eight tonnes, Mr Main said a lot of preparation had to be done to ensure the museum could hold a structure of such size.

‘‘Installing such a big object inside the museum we’re not quite sure how it will all work just yet,’’ he said.

‘‘We have had an engineer do some assessments on the floor loadings and he identified two locations where the entire set of components could be assembled... if we can install it, it will be the largest object in the exhibition.’’

Goulburn Weir was the first major diversion structure built for irrigation in Australia, and in October last year was awarded international heritage status.

With an embankment 127m long and 15m high, the weir has a capacity of 25500Ml and covers a submerged area of 1130ha when full.

More than just concrete and cast iron, the Goulburn Weir quickly proved critical to the prosperity of central Victorian communities and incorporated one of the first hydro-electric turbines in the Southern Hemisphere.

G-MW managing director Pat Lennon said the weir was highly recognised for its advanced engineering, and appeared on the Australian half-sovereign and 10-shilling banknotes in the early 20th century.

‘‘It is an iconic structure and really important, not just for Victoria and our irrigation but it is recognised globally,’’ he said.

‘‘The weir services more than a quarter of our customers and about half the water we delivered to customers in the last year came through this infrastructure.

‘‘It is an impressive place and very important for us.’’

HISTORY OF GOULBURN WEIR

Construction of a weir on the Goulburn River started in 1887 and and was completed four years later.

Goulburn Weir is a concrete superstructure, founded on bedrock, with its downstream face stepped with granite blocks quarried from the nearby Mt Black.

The metal structure of the original weir included 21 cast iron and wrought iron gates mounted between cast iron piers.

The gates could be lowered into recesses in the weir crest to pass river and flood flows, with water-driven turbines providing power to lower and raise the gates.

‘‘In 1887 when they started construction there would have been a fairly significant commencement in the lead-up,’’ Goulburn-Murray Water managing director Pat Lennon said.

‘‘Back in those times it was all completed by manpower and the sort of speed they could have moved at is pretty slow.’’

Once completed, the weir was 212m long, 15m high, with nine radial gates and two overshot gates which could release up to 96000megalitres of water a day.

The structure also contained one of the first hydro-electric turbines in the Southern Hemisphere.

The electricity was used to illuminate the weir, and visitors came from across Victoria to see the steady bright electric light and floodlit water spray when the gates were operated at night.

Goulburn Weir has become an important social and recreational venue.

‘‘Its construction led to the development of this area, it enabled prosperity and agricultural production and exports,’’ Gallery Development Project lead curator George Main said.

‘‘One of the points of interest was that it had a hydro-electric generator, one of the first to generate electricity ... people would come for miles to see the lights.’’

After almost 100 years of use, work to stabilise the deteriorating weir structure was completed in 1983 and, in 1987, a major refurbishment was done.

The work included advice on agricultural and heritage matters from expert consultants and the engagement of specialist contractors.

As part of the works, the main weir superstructure was replaced with nine steel radial gates mounted between concrete piers.

Two of the original gates and lifting gear were retained to preserve part of the unique piece of engineering history.

In 1988, the refurbishment work was awarded the Engineering Excellence Award for stabilisation and reconstruction of a superstructure and retention of heritage value and charm.

Last year Goulburn Weir was listed as an official Heritage Irrigation Structure by the International Commission on Irrigation and Drainage.

‘‘It was really seen as a national icon soon after its construction and we are very aware of that heritage having national significance,’’ Mr Main said.