The largest-ever order of water from Victoria’s Desalination Plant has begun to flow into Melbourne’s storages.

Minister for Water Lisa Neville says the 125 GL order has reached Cardinia Reservoir, to be delivered progressively over the next year.

The additional water will contribute 6.9 per cent to Melbourne’s storages - which would be a further 4.2 per cent lower today without the desalinated water delivered over recent years.

Even with recent rainfall, Melbourne’s water storage levels currently sit at 49.8 per cent, 8.3 per cent lower than same time in 2018 and close to their lowest level since 2011, after the Millennium Drought severely impacted water storages.

These low levels are a result of below average inflows into Melbourne storages in 18 out of the past 20 years, combined with higher than normal temperatures and huge population growth of 1.4 million in Melbourne since 2001.

The Bureau of Meteorology’s latest three-month seasonal climate outlook predicts the above average autumn temperatures and below average rainfall are set to continue.

Given Melbourne’s water demand has outstripped supply in recent years, authorities say the desalinated water order is crucial to providing water certainty.

Metropolitan Melbourne customers will pay for the desalination order. This year’s order is expected to add an average of around $10 per household for the year.