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 December, most of Victoria received average rainfall, though some areas in the south and northwest received below to very much below average rainfall. Areas of above average rainfall were recorded in the Wimmera, alpine northeast and Goulburn regions. Storms in late December resulted in some of the highest rain rates ever recorded in Victoria. Mount Hotham recorded the highest rainfall total, receiving 290.2 mm of rain during December. Six sites recorded the highest December daily rainfall on record, with Mount Hotham breaking its previous daily record by almost 50%. Across the state, rainfall was 18% below average.
Moderate to high stream flows were recorded in the southeast, northeast and north central part of the state during December, following heavy, scattered rainfall events that occurred at the end of the month. Six sites across the state recorded flows of over 100% of the long term average. The largest of these were Moe River at Darnum, Deep Creek at Bulla and Rose River at Matong North, all of which recorded flows above 380% of the long term average. The highest average flows in the state for December were recorded at Hollands Creek at Kelfeera, at 1241% of the long term average.
The northwest of the state continues to remain dry.
The total volume of water held in Victoria's major storages
decreased by -0.6% during December, ending the month at 81.8% capacity. Storage
volumes rose in two of the 16 monitored basins, with increases in storage
volume ranging from 1.1% in the Murray system, and 7.5% in the Ovens system. Storage volumes
decreased in 13 basins, with decreases ranging from -0.3% in the Maribyrnong
-10.7% in the Thomson/Macalister system.
Victoria's regional storage levels decreased by -0.8% to 83.6% of capacity during December. Melbourne's storage levels decreased by -1.3% to 71.4% of capacity over the same period. Melbourne's storages are 2.6% higher and regional storages are 38.9% higher than at the same time last year.
At the end of the December quarter, the short term (<5 years) groundwater level trends were categorised as declining for six of the 16 Water Supply Protection Areas (WSPAs). Groundwater levels are categorised as stable over the short term in 10 WSPAs. Over the long term (>10 years), groundwater level trends for 12 WSPAs are categorised as stable, one as declining and three as rising.
Of the 40 GMAs in Victoria, groundwater levels were categorised in the short term as stable in 26 areas and declining in seven areas; one is categorised as rising in the short term. There continued to be 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 December. All Victorian towns are subject to Permanent Water Saving Rules. This time last year there were no towns subject to water restrictions.
Allocations were increased during December for the Werribee/Bacchus Marsh District, with a 5% increase in low-reliability water share allocation. All other systems remained unchanged with seasonal determinations at 100% high-reliability water share and four systems with seasonal determinations against low-reliability water share: Broken, Bullarook, Campaspe and Werribee/Bacchus Marsh District.
Restrictions on diversions from unregulated streams
At the end of December 2016, across Victoria, there were 34 unregulated streams subject to diversion restrictions, compared to seven at the end of November. This time last year, there were 124 waterways subject to restrictions.
Seasonal climate outlook
The Bureau of Meteorology (BoM) released its January to March rainfall outlook on 15 December 2016. The outlook for January to March 2017 has changed from the November 2016 to January 2017 predictions, and now indicates a roughly equal chance of a wetter or drier summer for western Victoria, while eastern Victoria is predicted to be drier with a 35-45% chance of exceeding median rainfall in central Victoria and Gippsland.The BoM released its latest ENSO Wrap-Up on 20 December 2016. It announced that the tropical Pacific Ocean continues to remain in a neutral El Niño–Southern Oscillation (ENSO) state. Over the first two weeks of December, sea surface temperatures in the central tropical Pacifica Ocean cooled slightly, however ocean temperatures remained well within the neutral range. Most models indicate the central Pacific Ocean will slowly warm in the coming months, though neutral conditions are likely to persist. One model suggests that La Niña thresholds may be briefly exceeded. When ENSO is neutral, there is less of a tendency for Australia's climate to be very much wetter or drier than usual. The Indian Ocean Dipole has little influence on Australian climate through December to April.