Yan Yean Reservoir

Yan Yean Reservoir
The Yan Yean Reservoir with Whittlesea in the foreground
Coordinates	37°33′S 145°08′E / 37.550°S 145.133°E / -37.550; 145.133Coordinates: 37°33′S 145°08′E / 37.550°S 145.133°E / -37.550; 145.133
Type	reservoir
Primary inflows	Toorourrong Reservoir via aqueduct (off stream storage)
Primary outflows	Plenty River
Basin countries	Australia
Water volume	30 mio m³ (30,000 ML)

Yan Yean Reservoir is the oldest water supply for the city of Melbourne, Australia. At the time of its completion in 1857 it was the largest artificial reservoir in the world. It is 30 kilometres (19 mi) north of the city and is built on the Plenty River, a tributary of the Yarra River. An embankment 9.5 metres (31 ft) high holds back 30,000 megalitres (1,100×10^⁶ cu ft) of water. As of April 21, 2016 the reservoir sits at 78.8% of capacity.

The reservoir is managed by Melbourne Water as part of the water supply system for Melbourne.

Work commenced on 20 December 1853 when Governor Charles La Trobe turned the first sod. Construction took place at the height of the gold rush employing a tent city of 1000 workers returning from the goldfields. The reservoir took four years to construct at a cost of £750,000. Other sources estimate the cost of the project to be £1,017,087.

The reservoir was designed by James Blackburn, an English Civil Engineer and former London sanitary inspector who was transported to Tasmania as a convict following charges of embezzlement. After being pardoned he came to Melbourne in 1849.

The water was originally supplied by the Plenty River however the water quality was poor due to stock crossings and pollution from rural towns. The problem was solved by bypassing the Plenty River and diverting water from Wallaby Creek and Silver Creek, both originating in the Great Dividing Range feeding the Goulburn River. This mountain water was captured in the Toorourrong Reservoir system, constructed in 1883–1885, and supplies water to Yan Yean via an aqueduct to this day.

At the time of its completion in 1857 it was the largest artificial reservoir in the world. Photographer Fred Kruger was commissioned by the government to provide images of the extensive works for display at the Colonial and Indian Exhibition of 1886.