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.
In September, most of Victoria received very much above average rainfall, with areas in the north and west receiving highest on record rainfall. Victoria, as a whole, experienced the second-wettest September on record, though parts of West Gippsland received average or below average rainfall. The state's highest daily rainfall total was recorded at Mount William in the Grampians at 78.6 mm; 25 sites across the state received highest on record September daily rainfall totals. Statewide, the rainfall total was 94% above the September average.
High to extremely high streamflows were recorded throughout most of the state during September due to sustained high rainfall across the state. All 28 representative stations recorded flows in September, with 19 sites across the state recording flows greater than 100% of the long term average. The highest average flows in the state for September were recorded at Hollands Creek at Kelfeera, Sunday Creek at Tallarook and Wimmera River at Eversley with flows above 1400% of the long term average.
Small sections along the south west and central coast of the state continue to remain dry.
The total volume of water held in Victoria's major storages increased by 8.6% during September, ending the month at 70.1% capacity. Storage volumes rose in all of the 16 monitored basins, with increases in storage ranging from 1.8% in the Latrobe System to 60.6% in the Loddon system. Two of the three monitored reservoirs in the Latrobe system have remained at 100% capacity since August.
Victoria's regional storages increased by 9.7% to 70.4% of capacity during September 2016. Melbourne's storage levels increased by 2.1% to 68.3% of capacity over the same period. Melbourne's storages are 6.2% lower and regional storages are 14% higher than at the same time last year.
At the end of the September quarter, the short term (<5 years) groundwater level trends were categorised as declining for 10 of the 16 Water Supply Protection Areas (WSPAs). Groundwater levels are categorised as stable over the short term in three WSPAs and rising for one.
Of the 40 Ground Management Areas (GMAs) in Victoria, groundwater levels are categorised in the short term as stable in 20 areas and declining in 14 areas; none are categorised as rising in the short term. There is insufficient information (through lack of state observation bores) to determine a trend in six areas.
Restrictions on urban water supplies
There were no towns on water restrictions at the end of September. All Victorian towns are subject to Permanent Water Saving Rules.
Allocations were increased for all systems during September, except the Bullarook and Coliban Rural systems, which were already at 100% allocation at the end of August 2016, and the Macalister Irrigation District (MID). In July 2016 the MID received 100% against high-reliability water shares (HRWS) and no further allocation will be made until after the end of the spill period on 15 December 2016. At the end of September there were three systems with seasonal determinations against low-reliability water shares (LRWS): the Broken System, Bullarook System and Werribee/Bacchus Marsh District.
Restrictions on diversions from unregulated streams
At the end of September 2016, across Victoria, there were no unregulated streams and lakes subject to diversion restrictions, compared to five at the end of August 2016. This time last year there were 35 waterways subject to restrictions.
Seasonal climate outlook
The Bureau of Meteorology (BoM) released its October to December 2016 rainfall outlook on 29 September 2016. The outlook shows an increased chance of exceeding median rainfall, now predicting a 70-80% chance of a wetter end to the year for most of the state. Areas in southern Victoria are the most likely to have above median rainfall, with a greater than 80% chance. The next update is expected on 27 October 2016.
The BoM released its latest ENSO Wrap-Up on 27 September 2016. It announced that the tropical Pacific Ocean remains in a neutral El Niño–Southern Oscillation (ENSO) state, though a late La Niña remains possible. A persistent and strong negative Indian Ocean Dipole (IOD) phase, combined with La Niña-like warm seas around northern Australia, are increasing the likelihood of wet conditions over Australia. Most international models indicate the Pacific Ocean is likely to remain at ENSO neutral levels through to the end of 2016 and indicate the IOD will return to neutral levels by the end of spring.
Over the last two weeks of September the Southern Oscillation Index exceeded La Niña thresholds. Since August there have been some indications of atmospheric coupling around the Date Line, which is typical of La Niña. As a result, the Bureau's ENSO Outlook remains at La Niña WATCH, which means there is a 50% likelihood of La Niña developing towards the end of 2016. As at the end of September 2016, the next ENSO update is expected on 11 October 2016.