Cotter River

Cotter River
The Cotter Dam in December 2005, surrounding country still showing the effects of the 2003 bushfires.
Origin	Scabby Range
Mouth	confluence with Murrumbidgee River
Basin countries	south-east Australia
Length	74 kilometres (46 mi)
Source elevation	1,912 metres (6,273 ft) (Bimberi Peak)
Mouth elevation	460 metres (1,510 ft)
Avg. discharge	2.21m³/s immediately downstream Corin Dam
Basin area	480.1 square kilometres (185.4 sq mi)

The Cotter River is a fresh water river in the Australian Capital Territory. It is a tributary of the Murrumbidgee River and part of Murray-Darling Basin. The Cotter River is one of two rivers—the Queanbeyan River is the other—that meet the water supply needs of the Canberra and Queanbeyan region. The river is named after a colonial convict Garrett Cotter who first settled and had a very long and continued association with the Cotter River region in the mid 19th century.

When the Government surveyor, Charles Scrivener, recommended Canberra as the best site for Australia's national capital, water catchment was a significant consideration. Of the total 2,358 square kilometres (910 sq mi) of the Australian Capital Territory, 480.1 square kilometres (185.4 sq mi) were reserved as the catchment area of the Cotter River.^[1] The catchment area was calculated to support a planned population of 100,000.^[2]

Dams

There are three reservoirs on the river, the Corin, Bendora and Cotter Dams which supply water to Canberra. Most of the Cotter catchment is in the Namadgi National Park.

• Cotter Dam is a concrete gravity dam built in 1912 when the city of Canberra was established. The height of the dam wall was raised in 1951 to increase capacity. The top water level of the dam is 501m above sea level. The dam has a capacity of 3,856 million litres; a review in October 2006 using more accurate mapping methods resulted in capacity being re-estimated downwards from the previous estimate of 4,700 million litres. Water was pumped from the dam to Mount Stromlo and from there the water flowed by gravity to fill the city's reservoirs. The dam water quality had deteriorated compared with Bendora and Corin dams and the dam was only used when water is in short supply. However, in December 2004, ActewAGL brought the dam back on line in response to the ongoing drought.^[3]

The Cotter Dam is currently having a new 76m dam wall built downstream of the current 26m dam wall, along with a couple of auxiliary dam walls along low-lying neighbouring valleys. This will increase storage capacity of the Cotter Dam from the current 3.9GL to 78GL. The old dam wall will remain and be inundated during extended periods of average to above average rainfall. Completion is expected in June 2012 .^[4]

• Bendora Dam, a double curvature concrete arch dam completed in 1961. It has a capacity of 11,540 million litres. The top water level of the dam is 778m above sea level.
• Corin Dam, an earth and rockfill embankment dam with a capacity of 70,900 million litres. This dam which was completed in 1967 is situated upstream of the Bendora Dam and controls the release of water into Bendora Dam. The top water level of the dam is 956m above sea level.

Corin Dam from west

Recreation

Cotter River picnic area

The Cotter Dam, like other dams and reservoirs within the Cotter Catchment supply domestic drinking water and is therefore closed to recreational watercraft use. The Cotter River Reserve located at the base of the dam wall is a very popular picnic area. The reserve has amenities such as barbecue facilities and tables. There are a number of areas that are suitable for swimming when there is sufficient water flowing in the river. There is also a short term camping site which can accommodate a very limited number of caravans and tents.

The Cotter Road, ACT tourist route 5, begins as a side road off Adelaide Avenue in the suburb of Deakin. The scenic drive stretches 17.6km from the centre of Canberra past the suburbs of Curtin, Holder and Duffy, in between Stromlo Forest and Narrabundah Hill Pine Plantation, and past Casuarina Sands into the Cotter Avenue river area. "The Cotter" and the adjoining 7.1km winding Brindabella Road (the beginning of "The Loop") are well known to motorcyclists, many of whom ride there in the evening after work or on weekends. The Cotter Hotel, which stood near the children's swings alongside the river, was burned down in the 2003 bushfires. It was a well known meeting place amongst motorcyclists on weekends.

The upper section of the Cotter River is also popular with white water kayakers. Featuring a fast flowing scenic grade 3 section. However the river requires high rainfalls for it to flow at a minimum level. There has been a push by local white water paddlers to kayak this section before the dam is completed down stream as it raise the level of the lake drowning the section. Below the dam are also kayaking opportunities. Located near the top picnic area the 'Cotter Play Wave' is the only one in the area and creates playboating opportunities formed by a small weir, however again it requires high flows. From the play wave it is possible to paddle to the confluence of the Murrumbidgee River. Caution is advised as it is prone to strainers formed by trees, weirs and man made objects.

References

1. ^ Edited by H.L. White, ed (1954). Canberra: A Nation's Capital. Angus and Robertson, Sydney. 
2. ^ Wigmore, Lionel (1963). The Long View: Australia's National Capital. Melbourne, Australia: F.W. Cheshire Pty Ltd. p. 178. 
3. ^ "Cotter Dam". Water: Catchment. ActewAGL. http://www.actewagl.com.au/water/catchment/cotter.aspx. Retrieved 2006-11-29. 
4. ^ "Cotter Dam Update". ACTEW Corporation. http://www.actew.com.au/Our%20Projects/Enlarged%20Cotter%20Dam.aspx. Retrieved 2011-01-08. 

External links

Media related to Cotter River at Wikimedia Commons

• ACTEW Corporation. Future Water Options
• Ecological effects of serial impoundment on the Cotter River, Australia
• High-resolution total stream power estimates for the Cotter River, Namadgi National Park, Australian Capital Territory
• State of the Environment Report 2003 Australian Capital Territory Indicator: water use

Coordinates: 35°19′S 148°57′E / 35.317°S 148.95°E / -35.317; 148.95