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Cowwarr Weir

 

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Cowwar Weir History and Operations

History
Cowwarr Weir is a concrete gravity structure with three steel vertical lift spillway gates for regulating water supply from the Thomson River to the MID.

During an exceptional flood in 1952, the Thomson River formed a breakaway course through a series of depressions beginning at the point where the river emerges from the foothills on to the river plains. The new course continues east to rejoin the original course near Heyfield. The distance of the new course between the breakaway and rejoining points is much less than that of the former course, while the fall between the two points remains the same.

In 1959 the Cowwarr Weir and diversion channel were constructed at the point where the breakaway course of the Rainbow Creek begins. The weir allows control of water flow along the breakaway and to divert water to the area south of the Thomson River along the Cowwarr Channel to supplement water from Lake Glenmaggie for irrigation in the Nambrok-Denison area.


Purpose
Cowwarr Weir was built to service the Macalister Irrigation District (MID) in Gippsland.

Thomson River water is diverted via the Cowwarr Weir channel generally at the beginning of the spring months to irrigate the Nambrok-Denison Area. This enables water to be conserved in Lake Glenmaggie for as long as possible, thus maximising the water available to the irrigation district. Under normal conditions during the irrigation season the Cowwarr Weir Pool is maintained at or near the full supply level.

Statistics

RESERVOIR
Capacity 387 ML
Surface area 14.1 ha
Full supply level 40.50 m AHD
Full supply level 77.1 m AHD
Catchment area 1,942 km2
EMBANKMENT
Maximum height 5 m
Length 120 m
SPILLWAY
Crest length 120 m
Discharge capacity 500,000 ML per day
Location


Cowwarr Weir is located on Rainbow Creek, which is a breakaway section of the Thomson River near the Cowwarr township in Gippsland – Melway reference Map 82 C9.