The system of weirs and locks on the Murray River was designed to
provide stable pools
for irrigation diversions and enable navigation of the river
throughout the year.
The construction of Mildura Weir in particular created some
significant advantages; water quality was vastly improved because of the prevention of
undue percolation of affected water, and the suction lift of the Mildura and Red Cliffs
Pumping Stations was substantially reduced.
Construction of the Mildura Weir began in August 1923 and was
completed four years later,
at a total of 370,250 pounds. An estimate was made in 1984
that the weir would cost approximately 12 million dollars to replace.
The weir comprises of 24 steel trestles, each weighing approximately
11 tonnes. The weir can
be removed from the river by means of an electrically driven
winch, to allow flood flow to pass
and enable maintenance to be carried out on the
trestles.
It is the river's eleventh weir, and is situated 878km from the
mouth of the Murray. The weir
pool is 34.5m above sea level and it has a storage capacity
of 36,200ML.
Lock 11 is a concrete chamber 61.5m long, 17.1m wide and 7.6m deep.
Each of the four steel lock gates is 9.4m long, 6.9m high and weighs 18 tonnes. The lock
is filled by opening the four butterfly valves (1.8m x 0.9m) that are located upstream of
the two upstream lock gates. Water enters the lock chamber via two 2.4m x 1.5m tunnels and
the chamber can accommodate approximately 4.5ML. The lock chamber is drained by opening
four butterfly valves near the downstream gates which are operated by hydraulic cylinders.
The difference between the river levels upstream and downstream of the weir is normally
3.7m.
The weir and lock is a Dethridge type concept (named after
Commissioner Dethridge) but was actually designed by Commission engineers E.D. Shaw and
G.A. Baker. In fact, it was E.D. Shaw's father Ebenezer Shaw, who was largely responsible
for the establishing of the Wimmera-Mallee Domestic Stock Supply System - the largest
scheme of its type in the world.
Interesting Facts
- The Mildura Weir Set-up is rather unique in that it is the only site
on the Murray
where a lock and weir are separated by an island. The island is comprised of
some
15 hectares of bushland.
- There is a constant flow of boating along the river, with between
3,000 and 3,500
vessels passing through the lock each year.
- The downstream side of the weir provides locals and tourists with
ample fishing
opportunities for mainly perch, bream and carp.
- The weir and lock were completed in 1927, and on 2nd August, 1927,
the first
river steamer passed through the lock.
- 1,000,000 Gallons or 4.5ML of water is required to change the levels
in the lock chamber.
