Monthly Water Report
Monthly Water Report
The Monthly Water Report provides a summary of the status of Victoria's water resources and water supplies at the end of the reporting month. It is based on validated water resource information provided by Victoria's 19 Urban and Rural Water Corporations and the Bureau of Meteorology. Each month's report is published online the following month. For detailed, specific and up-to-date information, please contact the relevant Water Corporation or the Bureau of Meteorology. Links to these organisations are located within the Monthly Water Report.
For a weekly snapshot you can now download the Department's Weekly Water Report on the Water Register website.
In May, rainfall was above average across most of Victoria. East and Central Gippsland generally experienced average rainfall, with small areas receiving below average rainfall. The northern Melbourne region also received average rainfall. The Otway coast, the middle and upper Murray, Westernport, Wilson's Promontory, and the North East all received very much above average rainfall while the Mallee, Wimmera, and parts south Gippsland, the south west coast and central Murray region all received above average rainfall. The wettest station in the state was Mt Hotham, where a total of 424 mm of rainfall was recorded during the month. Nine stations had record high May rainfall: Barnawartha, Mt Buller, Edi Upper, Yarrawonga, Hunters Hill, Mt Hotham, Stawell Aerodrome, Lima East and Shepparton Airport. Statewide, the rainfall total was 32.5% above the May average, and it was the wettest May since 1995.
The above average rainfall in western Victoria was not reflected in streamflows during May, with central and western parts of the state continuing the low streamflow trend that has persisted throughout 2015 and into 2016. The south west coast was an exception to this. Streamflow was low to moderate in east and south Gippsland.
At the end of May, the highest streamflows were recorded across eastern Victoria, with the Macalister River at Glencairn, the Snowy Creek at Granite Flat and the Rose River at Matong North all recording flows over 100% of the long term average. A further three stations recorded flows between 80% and 100% of the long term average.
At the end of the month, flows at 10 of the 28 representative stations were less than 10% of the long term average for May, with no flows (i.e. the rivers were dry) at four of these stations. Of the 24 representative stations that were flowing, 23 recorded higher flows than the May historic minimum.
The total volume of water held in Victoria's major storages increased by 1.9% during May, ending the month at 36.7% of capacity. Slight decreases in storage (less than 1.5% change) in 10 of the 16 monitored basins were outweighed by an increase in the Murray, Ovens, Goulburn and Glenelg/Wimmera systems.
Victoria's regional storages increased by 2.4% to 33.0% of capacity during May 2016. Melbourne's storage levels decreased by 1.2% to 58.7% of capacity over the same period. Melbourne's storages are 10.3% lower and the regional storages are 18.6% lower than at the same time last year.
Restrictions on urban water supplies
On 1 May, Barwon Water raised the level of restrictions on its Lorne, Colac and Apollo Bay systems to Stage 3. Later in the month, the restrictions on Lorne were removed as above average rain caused storage levels to recover. The urban water restrictions that were applied during March by South Gippsland Water and Grampians Wimmera Mallee Water remained unchanged during May. At the end of May, 23 towns were on restrictions.
Out of the 23 towns affected by restrictions at the end of May, nine were on Stage 2 restrictions and 14 were on Stage 3 restrictions.
The groundwater section of the Monthly Water Report is updated on a quarterly basis. For the last update go to the March 2016 report.
During May, the allocation status in all systems remained the same.
Restrictions on diversions from unregulated streams
At the end of May 2016, there were 123 unregulated streams and lakes subject to diversion restrictions, compared to 150 at the end of April. This time last year, there were 87 waterways subject to restrictions.
Seasonal climate outlook
BoM released its June to August 2016 rainfall outlook on 26 May 2016. The outlook has improved, with most areas having an increased chance of above median rainfall. It suggests northern Victoria is the most likely to have above median rainfall, with a 65-80% chance. The southern Wimmera, Yarra Ranges and Central Gippsland regions are predicted to have a roughly 50 to 60% chance of exceeding median rainfall, while the south west coastal areas, and South Gippsland coast, have a roughly equal chance (45-55%). While above average July to August rainfall forecast for parts of Victoria will be welcome, particularly in areas suffering from mid to long-term rainfall deficiencies, recovery is likely to require a significant period of above average rainfall. The next update is expected on 30 June 2016.
BoM released its latest ENSO Wrap-Up on 24 May 2016. The 2015–16 El Niño has now ended, with sea surface temperatures across the tropical Pacific Ocean cooling to neutral levels. In the atmosphere, indicators such as the trade winds, cloudiness near the Date Line, and the Southern Oscillation Index have also returned to neutral levels. International climate models indicate the tropical Pacific Ocean will continue to cool, with six of eight models suggesting La Niña is likely to form during the austral winter (June–August). However, individual model outlooks show a large spread between neutral and La Niña scenarios.
Based on recent changes in the tropical Pacific Ocean and atmosphere, combined with current climate model outlooks, the ENSO Outlook remains at La Niña watch suggesting the likelihood of a La Niña forming in the second half of 2016 is around 50%. The next ENSO update is expected on 7 June 2016.