1996 - Decommissioning

In the 1960's, with the increase of residential development around the aqueduct - in the Mt Evelyn area in particular - and with the increased pollution or contamination risks from an open aqueduct, parts of the Mt Evelyn section of the Aqueduct were closed and replaced by underground pipelines (the entire Mt Evelyn section of the aqueduct was finally decommissioned in February 1972).  Much of the original open Mt Evelyn channel was filled in during the 1970's but portions of it still remain.
 
By 1968 the MMBW had developed an ambitious plan to meets Melbourne's future water needs and over the next decade a number of major new storages were built; including Greenvale, Cardinia, Thompson and Sugarloaf. 

Whilst the water coming from the O'Shannassy watershed was, and still is, vitally important to Melbourne, the ageing aqueduct was nearing the end of its days. A number of major landslips had caused severe damage to the aqueduct over a period of years (the main ones being at the Dee Road slip and Marysville slip, near Warburton)  and whilst they had been repaired, the repairs were now failing.  In addition, the cement channel which had for so long stood the test of time was beginning to deteriorate and break up - damage from wild deer, wombats, tree roots, falling trees and water seepage were taking their toll. 

On an increasing number of occasions, there were major breaches in the channel causing millions of litres of water to come rushing down the moutainside like a tidal wave, carrying everything in its path. Considerable damage to property and homes was caused and whilst, fortunately, no lives were lost, this could easily have been the case. 

As the risks increased and the cost of repairs escalated, landowners near the aqueduct began to lobby for its closure and with so many alternatives available (piping the entire aqueduct underground was the preferred option) the long term future of the aqueduct was being seriously questioned. In particular, the very costly and labour-intensive nature of the aqueduct's operation, with its extensive "army" of caretakers all performing management of the aqueduct system manually, was in doubt.

After 100 years of service to the people of Melbourne, the MMBW merged with a number of smaller urban water authorities in 1991 to form a new organisation called Melbourne Water. The new organisation brought a fresh, new, more modern approach (they were able to break away from the 100 year old traditions and historical attachments of the Board) and the end of the open aqueduct was clearly on the cards.  Increasingly, caretakers were laid off and old infrastructure was replaced with new, more automated versions. 

In January 1996 Melbourne Water announced that the aqueduct would be closed in December of that year. Poor water quality and increasing safety concerns were cited as reasons for the closure. Eventually, the open aqueduct was closed in its entirety in December 1996, being replaced by large undergound pipes to carry the water from O'Shannassy to Silvan, via a more direct route.  The O'Shannassy aqueduct had served Melbourne well for 82 years.

The aqueduct channel remained in a closed catchment, protected by Melbourne Water, and the walkway beside the aqueduct became a popular (and beautiful) walking and cycling trail for locals (and a popular access trail for illegal deer shooters at night).
 
As the years progressed, with little maintenance of the remnants of the once-great aqueduct and related infrastructure, the aqueduct fell increasingly into disrepair and today relatively little of of earlier appearance or purpose is generally understood or appreciated. Many of the buildings and infrastructure has been removed or disappeared and much of the open channel has now been consumed and overtaken by the bush. The former caretakers have long since retired or passed on. Only the track beside the aqueduct remains in good condition.