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Cooby Dam
Cooby Dam
	Boat ramp, 2014
	Location of the Cooby Dam in Queensland
Country	Australia
Location	Darling Downs, Queensland
Coordinates	27°23′09″S 151°56′24″E / 27.38583°S 151.94000°E
Purpose	Potable water supply;
Status	Operational
Construction began	1938;
Opening date	1942;
Operator(s)	Toowoomba Region Council
Dam and spillways
Type of dam	Embankment dam
Impounds	Cooby Creek
Height	32 m (105 ft)
Length	207 m (679 ft)
Dam volume	71×103 m3 (2.5×106 cu ft)
Spillway type	Uncontrolled
Spillway capacity	680 m3/s (24,000 cu ft/s)
Reservoir
Creates	Cooby Creek Reservoir
Total capacity	23,100 ML (5.1×109 imp gal; 6.1×109 US gal)
Active capacity	19,703 ML (4.334×109 imp gal; 5.205×109 US gal)
Inactive capacity	1,462 ML (0.322×109 imp gal; 0.386×109 US gal)
Catchment area	159–169 km2 (61–65 sq mi)
Surface area	301 ha (740 acres)
Maximum water depth	12.5 m (41 ft)
Normal elevation	482 m (1,581 ft) AHD

The Cooby Dam is a rock–fill embankment dam with an un–gated spillway across the Cooby Creek, a tributary of Condamine River, at Groomsville in the Toowoomba Region on the Darling Downs, Queensland, Australia. The main purpose of the dam is for potable water supply of the Toowoomba region.^[1]^[3] The impounded reservoir is called the Cooby Creek Reservoir.^[4]

Location and features

The dam is located approximately 17 kilometres (11 mi) north of Toowoomba.^[5] The other two storages used for Toowoomba are Perseverance Dam and Cressbrook Dam.

Completed in 1942, the rock–fill dam structure is 32 metres (105 ft) high and 207 metres (679 ft) long. The 71-thousand-cubic-metre (2.5×10^⁶ cu ft) dam wall holds back the 23,100-megalitre (5.1×10^⁹ imp gal; 6.1×10^⁹ US gal) reservoir when at full capacity. From a catchment area of 169 square kilometres (65 sq mi), the dam creates an unnamed reservoir, with a surface area of 301 hectares (740 acres) at a maximum depth of 12.5 metres (41 ft) when at full capacity. The uncontrolled un-gated spillway has a discharge capacity of 680 cubic metres per second (24,000 cu ft/s).^[1] The dam is managed by the Toowoomba Region Council.^[3]

Cooby Dam's lowest usable storage volume was recorded at 8% in January 2010.^[2]

In July 2006, public outcry and a referendum with winning "No" vote rejected plans to place recycled water into Cooby Dam.^{[citation needed]} In 2007, the idea was again resurrected when plans for an advanced water treatment plant to be built near Cooby Dam by the Toowoomba City Council were suggested.^[6] The trial would test the re-use of recycled water into Toowoomba's drinking water supply. In 2008, an emergency bore was used to extract water from the Great Artesian Basin to supplement water supplies for the dam as drought conditions reduced supply to critical levels.^[7]