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Drought dominant in 2006-2007

Drought and its impacts are key themes of the 2006/07 Report. Victoria recorded lower than average rainfall for an eleventh consecutive year.

• Melbourne experienced its lowest ever rainfall in the year leading up to 15 May 2007.
• Storage levels in 17 of the 19 river basins with major storages finished the year lower than they began. In aggregate, Victoria’s major water storages held 2,438,000 ML less water as at 30 June 2007 compared with 30 June 2006 – a decline of 52 per cent.
• Increases in storage levels that normally occur during the winter-spring period did not occur in 2006/07, with aggregate storage levels declining every month until heavy rains late in the year resulted in a small increase.
• Basin inflows in 2006/07 were just 26 per cent of the long-term average, with the majority of basins recording less than 20 per cent of the long-term average streamflow. Only the Thomson and East Gippsland basins experienced an increase in streamflow compared to 2005/06.
• Inflows into the Murray basin were 3,253,000 ML lower in 2006/07 compared with 2005/06.
• The volume of water diverted for consumptive purposes fell by 24 per cent, or approximately 1,289,000 ML, due to more stringent urban water restrictions, lower seasonal allocations for irrigators and increased bans on diversions from unregulated streams.
• Groundwater use increased by 44 per cent as surface water supplies came under threat. The volume of groundwater used to augment urban supplies doubled compared to 2005/06.

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Securing water supplies - drought contingency measures

The drought prompted Government and water businesses to implement a range of contingency measures and response plans.

• The Minister for Water used his powers under the Water Act 1989 to qualify rights to water in a number of basins to secure essential water supplies to towns and rural communities at times of water shortage. Temporary qualifications were imposed on 28 occasions in 12 different basins during 2006/07.
• More than 220 emergency water supply points were in operation around Victoria where water shortages became critical. Municipal drought relief bores, urban surface water standpipes and surface extraction points including access to selected points on channels and streams were used and the emergency water supply network was expanded to meet the needs of users.
• Water restrictions affected nearly all Victorian urban customers throughout the State. At 1 July 2006, 192 towns were on some form of restriction, and by 30 June 2007 the number had increased to 457 with 214 towns experiencing the highest, Stage 4, restrictions.
• Seasonal allocations were significantly lower in 2006/07. The Murray, Broken and Thomson-Macalister districts were the only districts to receive more than 40 per cent allocation, with Campaspe, Loddon and Bacchus Marsh irrigators receiving zero allocation for the entire year.
• Supplementary water supplies were secured from a range of sources in response to critical need. Groundwater (sometimes sourced from emergency bores), greater use of recycled water to augment urban and rural supplies, carting water and infrastructure upgrades of pipelines, storages and treatment plants were all also used as a last resort to move water from one town to another.

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Rainfall

In 2006/07 Victoria experienced the eleventh successive year of below average rainfall. The majority of the State received between 60-80 per cent of its long-term average. Most of the Murray and Goulburn basins, home to the majority of irrigation in the State, received between 40-60 per cent of the long-term average.

Particularly low levels were experienced throughout most of the state between August – October 2006: southern regions received 40-60 per cent of their average rainfall and northern regions only 20-40 per cent.

The year leading up to 15 May 2007 was Melbourne’s driest 365-day period on record, receiving 316.4 mm of rain, less than half the average rainfall (the previous record of 318.0 mm was in 1967-68).

The rainfall in central and east Gippsland, which includes parts of the Latrobe, Thomson, Mitchell, Tambo and Snowy basins, was also well below average until 26 June, when between 140 and 250 millimetres fell in 72 hours, approximately a quarter of the average annual rainfall.

Victorian average rainfall

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Streamflows

The impact of low rainfall levels on streamflows was severe in 2006/07. At a statewide level, streamflow was just 26 per cent of the long-term average, a decline of more than half compared with the streamflow recorded in 2005/06.

Despite rainfall of between 60 per cent and 100 per cent of the long-term average across the majority of the State, streamflows were significantly lower than average. Only the Snowy and East Gippsland basins recorded streamflows of more than 50 per cent of the long-term average.

Many areas of the State experienced record low flows. Out of Victoria’s 29 river basins, 15 experienced inflows of less than 20 per cent of the long-term average, including the Murray basin where inflows declined by more than 3,273,000 ML.  When compared with 2005/06, streamflows in all but two basins were significantly reduced: Corangamite (84 per cent below previous year), Ovens (87 per cent), Broken (72 per cent), Kiewa (74 per cent), Murray (74 per cent), South Gippsland (70 per cent). Only the Thomson and East Gippsland basins recorded higher flow levels.

Streamflow July 1997 to June 2007 expressed as a percentage of long-term average flow

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Impact of bushfires

Bushfires in the summer of 2006/07 had a major influence on water availability and quality in many areas. Large parts of the Thomson, Macalister, Mitchell, Goulburn, Broken and Ovens catchments in eastern Victoria, and the Grampians in western Victoria were burnt.

Serious water quality concerns did not eventuate as contingency measures were implemented in different regions.

North of the divide, water corporations issued alerts to boil drinking water and cautioned their customers about the use of poor quality water.

South of the divide, there were acute water quality problems after the bushfires for Maffra and towns supplied by the Mitchell River, including Bairnsdale and Lakes Entrance.

The first significant rainfall events after the bushfires in the Macalister catchment resulted in extremely turbid water. Gippsland Water upgraded its water treatment plant to cope, and water was carted to the small settlements of Glenmaggie and Coongulla which are supplied directly from Lake Glenmaggie.

Post-bushfire rainfall events in the Mitchell River catchment resulted in extremely turbid water in the Mitchell River.  Fortunately, East Gippsland Water had enough water stored in its off-stream storages to give it time to implement emergency measures

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Storage levels

During 2006/07 storage levels fell from 4,709,800 ML (37 per cent of capacity) at the start of July 2006 to 2,271,500 ML (18  per cent of capacity) at the end of June 2007.

Rather than following the typical pattern of increased volumes in major rural reservoirs over the winter/spring filling period, peaking in October, storage levels in 2006/07 actually decreased during this period. They then continued to drop over the summer/autumn as water was released from the reservoirs, predominantly supplying irrigation demands.

At the end of June 2007 storages in the Wimmera, Glenelg, Maribyrnong, Campaspe, Loddon and Werribee basins were all less than 10 per cent full. Storages in the Ovens basin, however, were 80 per cent full due to greater inflows received in the latter part of the year.

Water stored in key regional cities' reservoirs at the end of October, 2000-2006

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Groundwater

Groundwater reserves became increasingly important as alternative water supply sources in many regions.

As a result of the declining availability of surface water, groundwater use increased significantly compared to 2005/06. The total estimated groundwater use across the State, including domestic and stock use, was approximately 526,100 ML, an increase of 44 per cent from the volume used in 2005/06 (366,300 ML).

Urban water businesses relied significantly more on groundwater to supplement surface water for urban supplies. Water businesses in aggregate used their 47,000 ML of licensed entitlements to extract 22,800 ML of groundwater for urban use. This is an 87 per cent increase on the 2005/06 groundwater extraction (12,200 ML).

Licensed groundwater entitlements totalled approximately 1,001,000 ML as at 30 June 2007.  In 2006/07, groundwater extractions (526,100 ML) were approximately 53 per cent of total licensed volume.

Water levels in some heavily used aquifers fell throughout 2006/07. This is attributable to reduced aquifer recharge during the drought while the demand for groundwater continued.

Only one restriction was applied to groundwater use in 2006/07, for the Deutgam WSPA in the Werribee basin.

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Water Consumption

Irrigation remains by far the highest category of water use in the State, comprising 74 per cent of all diversions. Metered urban water consumption fell as water restrictions and increased awareness of sustainable water use took effect. Total urban consumption by residential and non-residential users fell by eight per cent from 2005/06 with regional residential customers reducing their consumption by 13 per cent and regional non-residential consumption dropping by 11 per cent.

A number of Government water conservation schemes were effectively used to strengthen awareness of, and participation in, water conservation activities.

They include the Water Smart Gardens and Homes Rebate Scheme and the Stormwater and Urban Water Conservation Fund.

The Schools Water Efficiency Program was also supported by 307 schools achieving an average reduction in water use of around 14 per cent by the end of 2006/07.

Total diversions for consumptive purposes in Victoria, 2006-2007

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Recycled Water

The volume of water that was recycled by Victoria’s water businesses continued to grow in 2006/07, with a total of 95,500 ML of wastewater recycled for use external to treatment plants.

The total volume of water recycled across Victoria increased by 20 per cent in 2006/07 (an additional 15,600 ML) compared to 2005/06. This growth was predominately driven by increased availability from Melbourne Water’s two wastewater treatment plants – the Eastern Treatment Plant and the Western Treatment Plant.

Including the treatment plants operated by the Melbourne metropolitan retailers, the volume of water recycled in Melbourne was 64,650 ML, or 22 per cent of the water available for reuse. The percentage of recycled water is higher outside Melbourne where weather conditions, the availability of land and access to potential purchasers (i.e. agricultural producers) are more favourable.

The remainder of the state recycled 31 per cent, or 30,878 ML, of the wastewater available for reuse. Although the volume of recycled water used in regional Victoria fell from 2005/06 (33,105 ML), this was due to lower overall water consumption and therefore less wastewater entering the treatment plants.

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Water entitlement transfers

Water trading in response to dry conditions, and as a result of low seasonal allocations, occurred in many areas in 2006/07.  Some 450,000ML of water entitlements were traded on a permanent or a temporary basis.

As the drought continued, more irrigators decided to permanently sell their water entitlements. Approximately 70,000 ML of permanent water entitlements were traded in 2006/07, from more than 1,100 transactions. This included a net 14,570 ML transferred interstate, four times as much as 2005/06. The volume of permanent water traded increased by some 30,000ML from 40,000ML in 2005/06, an increase of 75 per cent.

Approximately 380,000 ML was exchanged on the temporary market via more than 23,000 transactions.

Temporary trades in the Murray irrigation districts, including the Murray, Kiewa and Ovens basins, more than doubled compared to 2005/06. Basins where seasonal allocations were significantly lower than 2005/06, including the Goulburn, Loddon, Campaspe, Thomson, Latrobe and Werribee basins, experienced lower volumes of temporary trades as there was limited water to sell.

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Restrictions on diversions from unregulated streams

Restrictions generally followed a typical pattern of severe restrictions during the summer and autumn months and lower restrictions over winter and spring. However, the magnitude of restrictions increased from previous years.

At March 2007, 217 unregulated streams were under restriction, with irrigation bans on the majority. In June 2007, 149 streams were still subject to some form of restriction.

Number of Victorian unregulated streams on restrictions

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Water for the Environment

Across the State, the proportion of total flow leaving the basins has increased slightly in recent years, from 60 per cent in 2005/06 to 67 per cent in 2006/07. However, in volumetric terms the amount of water leaving the basins reduced by 49 per cent from 9,231 GL in 2005/06 to 4,747 GL in 2006/07, reflecting substantially lower basin inflows.

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Basin Accounts

The basin accounts in part two of the Victorian Water Accounts provide a detailed report on water availability and use in each of Victoria’s 29 basins. They include a map of the basin, the current management arrangements for water resources and drought contingency measures. They also provide a summary of total water resources in each basin including surface water, groundwater, recycled water and water for the environment.

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