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Upper Canal

For most of us, the modern world provides the convenience of a never-ending supply of clean and safe drinking water whenever we turn on a tap.

However, at the Australian Botanic Garden Mount Annan, the main water supply is principally derived from a very special water canal built in the 1880s, which is on the State Heritage Register.

WaterNSW's Upper Canal is a remarkable engineering feat, delivering water from four water supply dams to the south of the Garden (Cataract, Cordeaux, Nepean and Avon) to Prospect Reservoir in Sydney's West. Currently, 20 per cent of Sydney’s drinking water travels through the Garden on a 64km journey, dropping a mere 50m elevation in all but 10km of the canal’s length. We have sections of sandstone-lined open canal in the Garden, as well as a beautiful brick-constructed arched aqueduct hidden among an African olive forest, and a tunnel section under our eastern ridge line.

Sandstone-lined tunnel forming part of the Garden's canal system.The Garden’s irrigation infrastructure draws water from the canal opposite the Australian PlantBank and pumps it uphill some distance to the tank behind the Connections Garden, where it is pressurised and distributed in a ring main around the Garden.

Unfortunately the canal is often shut for essential maintenance, due to failures in the floor or walls of the canal, and our main water supply is cut off. We have a potable town water supply, but the size of the town water supply pipe is significantly smaller than the two canal water supply pipes. Running flat out, the town water supply can’t fill our header tank even when turned on and operating overnight. While our horticulturists endeavour to minimise water consumption, the header tank can be emptied in just a few hours and we then must wait another 24 hours for the tank to refill.

As a consequence of the canal system’s most recent maintenance, the Garden has been on water restrictions, rationing our water supply via a rostering system. With our strategic planning process kicking off at the beginning of 2017, the Garden’s water infrastructure and water security will be a key focus for investigation.