The O’Shannassy Aqueduct began life as a feat of early-twentieth-century engineering: an open concrete channel carrying Melbourne’s drinking water by gravity from a diversion weir on the O’Shannassy River. Designed and begun in 1911 and completed in October 1914, it is commonly named after Sir John O’Shannassy, three-times Premier of Victoria, and was built largely by Italian migrant labourers, relying on altitude alone to feed water toward the Surrey Hills Reservoir that served Melbourne’s growing eastern suburbs. A complementary dam and reservoir followed in 1928. The open aqueduct was closed in December 1996 and formally decommissioned in 1997, replaced by underground pipes, before being transferred to Parks Victoria for inclusion in the Yarra Ranges National Park.
Today the aqueduct’s old maintenance track is the O’Shannassy Aqueduct Trail, a roughly 30-to-34-kilometre walking and bike-riding route through the southern slopes of the Yarra Ranges National Park, running between East Warburton and the Don Valley / Woori Yallock area. Because it follows the line of the former water race, the grade is gentle the whole way, winding through tall mountain ash forest and fern gullies and offering valley views as it runs higher than, and roughly parallel to, the Lilydale-to-Warburton Rail Trail. The even gradient makes it welcoming for all fitness levels, and it can just as easily be tackled in shorter sections as end to end.
There is no single street address or staffed entrance: the trail is long and linear with several access points. Commonly used trailheads include the Dee Road carpark at Millgrove, the Yuonga Road carpark, and the O’Shannassy Weir at the East Warburton end; the easiest, flattest section runs between Dee Road, Millgrove and Yuonga Road, Warburton. Facilities along the route are sparse, so plan ahead; the nearest toilets are at Thomas Avenue in Warburton at the eastern end and at the Millgrove Rail Trail Reserve. The trail is open during daylight hours, year-round, with free public access and no gates or ticketing.
From time to time Parks Victoria applies temporary operational closures, including night-time restrictions and scheduled deer-control programs, so it is worth checking the Parks Victoria website for current alerts before you set out. With its quiet forest setting, easy gradient and rich water-supply heritage, the O’Shannassy Aqueduct Trail rewards a half-day ramble or a full-day ride within easy reach of Warburton.