May 2018

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 Fortnightly Water Report on the Water Register website.

Rainfall

Several areas in the north of Victoria observed drier than average conditions in May; elsewhere rainfall was close to average, with parts of the West Coast, Western Plains, South and East Gippsland Districts recording above average rainfall. Total monthly rainfall was 10.1% below the long-term May mean of 64.8 mm.

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Streamflows

At the end of May, one site in the South East of the State experienced high streamflows above 100% of the long-term average for the month (Moe River at Darnum, at 101% of the long-term average). Moderate streamflows were recorded in the North East and southern parts of the state (Tallangatta Creek at McCallums, Glenelg River at Sandford, Merri River at Woodford and Yarra River at Millgrove). These sites recorded 99%, 98%, 92% and 73% of the May long term streamflow average respectively.

At the end of the month, flows at 13 of the 28 representative stations recorded less than 10% of the long-term average for May. Seven sites across the State were dry at the end of May. A further six sites across the state (Genoa River at The Gorge, Deep Creek at Bulla D/S Emu Creek, Woady Yalloak River at Cressy, Rose River at Matong North, Sunday Creek at Tallarook and Wimmera River at Eversley) recorded low streamflows under 10% of the May long term average.

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Storage levels

The total volume of water held in Victoria's major storages increased by 0.1% during May, ending the month at 56.3% capacity. Decreases were recorded in 13 monitored systems, with the Thomson/Macalister and Broken systems recording the largest percentage falls of 6.2 and 4.3% respectively.

There was a 1.6% increase in the storage volumes in the Victorian Murray system. However, it should be noted that Victorian Murray shares for the end of May 2018 have not yet been agreed by the intergovernmental Water Liaison Working Group, owing to end of year water accounting by the Murray-Darling Basin Authority. The end of month storage volumes provided for Dartmouth Dam, Hume Dam, Lake Victoria and Menindee Lakes should therefore be considered interim.

Victoria’s regional storage levels increased by 0.4% to 56% of capacity during May. Melbourne’s storage levels decreased by 1.2% to 58.5% of capacity over the same period. Victoria’s major storages were 10.6% lower than at the same time last year.

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Groundwater

Groundwater is reported quarterly. The next update will be in June 2018.

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Urban water restrictions

South Gippsland Water announced that Stage 3 restrictions for Korumburra from midnight 3 May 2018.  All other towns are subject to Permanent Water Savings Rules.

This time last year, South Gippsland Water placed Korumburra on Stage 1 restrictions. All other Victorian towns were subject to Permanent Water Saving Rules.

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Irrigation allocations

Seasonal determinations in all GMW systems remained at 100% High Reliability Water Share (HRWS) from the previous monthly report. There was no change to Low Reliability Water Share (LRWS) in the GMW system from the previous monthly report. The next seasonal determination will be made on 2 July.

As at 22 May, the HRWS seasonal determination for the Werribee/ Bacchus Marsh Irrigation Districts stands at 45%, and the Macalister Irrigation District stands at 100% HRWS and 20% Low Reliability Water Shares.  The next announcement will be made 5 June 2018.

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Restrictions on diversions 

At the end of May, there were 77 unregulated streams subject to diversion restrictions across Victoria, 10 less than reported at the end of April. This time last year, there were 63 waterways subject to restrictions.

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Seasonal climate outlook

The Bureau of Meteorology (BoM) released its latest ENSO Wrap-Up on 22 May 2018. The El Niño–Southern Oscillation (ENSO) Outlook remains neutral —neither El Niño nor La Niña. Climate models favour ongoing neutral conditions for the southern hemisphere winter, despite continued warming of the tropical Pacific Ocean.

Models suggest further warming of the tropical Pacific Ocean is possible over the coming months, with two of eight models indicating an El Niño could develop after the southern winter. However other models fall well short of El Niño thresholds, resulting in a broad range of possible scenarios for spring.

BoM released its latest June to August 2018 climate outlook on 31 May 2018. The outlook indicates below drier than average rainfall is likely for the southeast mainland of Australia.

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Water for the environment

Environmental use is reported quarterly, with the next update due June 2018.