Roxburgh Hydro Dam

About

Built in 1949, the Roxburgh Dam is still impressive, especially when in flood or cleaning out silt. Located only 9 km from Roxburgh town, you can get there from either side of the Clutha River and drive, walk or bike right over it. You’ll find lookout points on either side, on the left is a car park and toilets with a little park where you can walk right up to the dam face. On the other side is an excellent picnic spot with great views of the dam as well. The Roxburgh Gorge and Clutha Gold cycling and walking tracks end and begin here.

Facts about the Roxburgh Hydro Dam

• • • The first hydroelectric project to be constructed in the South Island of New Zealand.
    • The height of the dam is 76 m.
    • The initial completion date was July 1955, and was officially opened on 3 November 1956 by National Politician, Sir William Stanley Goosman.
    • Commissioned during the period 1956 -1962.
    • Materials and equipment required to build the dam were transported by rail to Roxburgh.  As the Roxburgh railway station was located at Hercule’s Flat this meant that everything had to be transported the rest of the way by road.
    • A total of 1,300,000 cu yd (993,921 m3) of concrete was used in the construction of the dam and spillway.
    • Cement used in the project was mostly sourced from the Milburn Lime and Cement Company in Dunedin.
    • A total of 3,500 drawings were produced for the construction of the Roxburgh Dam.
    • The New Zealand Government made an initial expected cost of building the Roxburgh Dam at £17,000,000 (approximately $1.4 billion today).  However the final total cost of the project was £24,102, 800 (approximately $2 billion today).

Interestingly, very little gold was found during the construction of the dam. Disappointing for the Government as they had purchased a miners permit and employed a couple of miners. Contact Energy took over ownership of the Roxburgh Dam in 1996 from the Electricity Corporation of New Zealand.

Sediment flushing at Roxburgh Dam

Following three “one-in-one-hundred-year” floods, which inundated Lower Alexandra in 1994, 1995 and 1999, it was found the sediment build-up in Lake Roxburgh caused the water level to rise during such events. When a barrier (dam) is placed across a river and a lake is formed, the current is reduced so the sediment falls to the bottom. As the sediment level on the bottom increases, the volume is reduced. For any given river flow, the water level will be higher. This occurred in the Roxburgh Gorge, causing Alexandra to flood.

During the re-consenting process for the operation of the dams, the council introduced a condition called “flushing”. When the river flows are high, the lake level at Roxburgh is lowered. This makes it more like a river, thus increasing the velocity and “flushing” the sediment past the dam.

In Dec 2019 further upstream in Wanaka and Queenstown, due to heavy rain, water flows were massive. Spillways were opened and Lake Roxburgh dropped by at least 6m to cope with rising river levels. By reducing the lake level, combined with fast flows, it creates a steeper gradient from Alexandra to the Roxburgh dam and sediment is flushed further up Lake Roxburgh and beyond. It’s an impress sight to see the flood gates open.

Videos on the Roxburgh Hydro Dam

Watch the video from The Encyclopedia of New Zealand

• • • Building the Roxburgh Dam 1
    • Building the Roxburgh Dam 2 & 3

Building the Roxburgh Dam from the Otago Daily Times

Flood gates open & sediment flushing in Dec 2019 at Roxburgh Dam