Melbourne Water reports that following below average rainfall this winter, water storage is below the desired level.
Melbourne’s water storages have risen by just 2.3 per cent, or 41 billion litres, over winter following rainfall 12.9 per cent below the 30-year average, and runoff into storages 35 per cent below average.
As of 31 August 2017, Melbourne’s water storages were at 65.4 per cent capacity (1,185 billion litres), compared with 63.1 per cent (1,144 billion litres) on 31 May 2017.
By comparison, the average winter increase for Melbourne’s storages over the past five years was 137.3 billion litres (6.8 per cent).
Average rainfall over the four major catchments (Thomson, Upper Yarra, O’Shannassy and Maroondah) this winter was 289.9mm, or 12.9 per cent below the 30-year average.
Generally, drier than average conditions, particularly during June and July 2017, contributed to a reduction in the amount of runoff that entered the reservoirs. Streamflow into the reservoirs in winter 2017 was only 117.7 billion litres, compared with 190.6 billion litres in winter 2016.
Melbourne’s water use was also slightly higher this winter compared with the same time in 2016.
Average total daily water consumption for Melbourne’s homes, businesses and industry was 1,083 million litres of water a day, compared to 1,048 million litres a day in winter 2016.
Melbourne Water General Manager of Integrated Planning, Chris Williams, said the winter filling season had not provided the usual large increase in storage volume.
“We have had a drier than average winter, particularly June and July, and this has impacted on our storage levels,” Mr Williams said.
“At August 31 storages were slightly below where they were at the time last year. Without the water that has been supplied by the Victorian Desalination Plant in 2017, storage levels would have been about be around 3.4 per cent lower still.
“We would prefer a larger buffer in the event of severe drought of 10 years or more”.
Storages typically increase significantly in winter and spring, which is the traditional storage filling season in Victoria.
The Bureau of Meteorology’s latest three-month seasonal climate outlook suggests near equal chances of a wetter or drier Spring across Melbourne and its four major catchments.