The Monthly Water Report provides a statewide monthly summary of the status of water resources and water supplies. Each month's report is published online towards the end of the following month. It is based on data provided by the State’s 20 urban and rural water corporations.

Rainfall

For the first May in a number of years, much of Victoria experienced a typical autumn break. Rainfall totals for May were above average for most of the State, with the exception of east Gippsland and Melbourne, which recorded falls well below average. Rainfall totals in the range of 100-200mm were recorded in the West Coast and parts of the Great Dividing Range. The Wimmera, Mallee, Western Plains, West Central, Lower North East and West Gippsland districts received up to 100mm.

Melbourne received 39.2mm of rain during the month, which is well below the average May rainfall of 67.8mm. Melbourne’s catchments fared better however, receiving on average a total of 104mm. May was the warmest on record in Victoria, with a mean maximum temperature 2.03oC above the long-term average.

Streamflows

The widespread distribution of heavy rainfall in May resulted in a dramatic improvement in streamflow patterns, particularly in southwest and east Victoria. At the end of May, 10 out of the 28 representative stations recorded flows below 10% of the long-term average. Of these, 5 stations recorded no flow conditions, compared with 10 in April. In contrast, six stations recorded flows exceeding 100% of the long-term average for May.

Storage Levels

Volumes in the major storages in Victoria increased by 1.1% in May. Melbourne Water's storages reduced by 1.2%, to finish the month at 28.8% of capacity (20.4% lower than at the same time last year). Rural Water Authority storages increased by 1.5%, to finish the month at 10.6% of capacity (19.4% lower than at the same time last year). Storages in the Glenelg-Wimmera Basin rose to 4.6% of capacity compared with 6.5% at the same time last year; Lake Eildon rose to be at 6.5% of capacity compared with 21.7% at the same time last year; and Rosslynne Reservoir decreased to 4.0% of capacity compared with 7.3% at the same time last year.

Urban Water Restrictions

A number of changes to towns on restrictions took effect during May 2007. Restrictions were relaxed at Corryong, Cudgewa, Meerijig, Sawmill Settlement, Mansfield, Woods Point, Omeo and Swifts Creek. Restrictions were increased for towns supplied from the Murray, Amphitheatre, Avoca, Aireys Inlet and Fairhaven. The total number of towns subject to water restrictions as at 31 May 2007 was 468. Twenty-nine towns were on Stage 1, 100 on Stage 2, 69 on Stage 3, 18 on Stage 3a and 252 on Stage 4 restrictions.

Irrigation Allocations

The irrigation season for Goulburn-Murray Water’s gravity irrigation system customers closed on 30 April 2007. Goulburn-Murray Water released its latest outlook for the 2007/08 irrigation season on 15 May. The outlook for the 2 July start of season indicates that average conditions (5 chances in 10) will not provide enough water for an allocation in any system. Wet conditions (9 chances in 10) would provide enough water for an allocation in the Murray and Campaspe systems of 50% and 58% respectively. The Goulburn system cannot expect an opening allocation even under wet conditions.

In the south-west of the State, allocations remain at 10% for the Bacchus Marsh and Werribee Irrigation Districts. Levels in the Deutgam Groundwater Management Area are low, and to protect the resource from seawater intrusion, allocations for the 2006/2007 season are at 25% of licensed volume. Rosslynne Reservoir is at 4.0% of capacity and the allocation for Southern Rural Water diverters remains at 5%.

Restrictions on Diversions

In the south-east of the State, on the Latrobe system, Blue Rock Lake is at 49.8% of capacity. SRW licence holders downstream are permitted to take up to their licence volume, but availability is likely to be limited by low unregulated river flows. Lake Glenmaggie, which supplies the Thomson-Macalister Irrigation District, increased to 13% of capacity during May. On 4 May, Southern Rural Water approved an increase of 5% in allocation for Licensed Diverters on the Thomson and Macalister Rivers and Rainbow Creek. This increase was due to increased inflows into Lake Glenmaggie. The total allocation for all MID diverters is now at 60% of Licensed Volume, Water Right and Domestic and Stock.

Seasonal Climate Outlook

The Seasonal Outlook released by the Bureau of Meteorology on 22 May 2007 reports that the chance of exceeding median rainfall for the June to August (winter) period is between 40-45%. The chances for a warmer than average season is between 50-60% across Victoria. If, as computer models predict, the Pacific cools to such an extent that a La Niña forms during the coming months, subsequent climate outlooks are likely to indicate increased chances of above average rainfall over the eastern half of Australia.