National Water Commission

The Moorabool River water management area is located within the South East Coast Drainage Division, west of Melbourne. The Moorabool River joins the Barwon River near Geelong, which flows into Bass Strait. Little River, also located in the Moorabool River water management area, flows into Port Phillip Bay.

Southern Rural Water is the licensing authority and manages both surface and groundwater diversions. Barwon Water supplies water to Geelong while Central Highlands Water supplies water to Ballarat and a number of smaller towns such as Bungaree and Wallace. The Corangamite Catchment Management Authority is responsible for waterway management in the Moorabool River water management area.

This chapter draws extensively on the State Water Report 2004/05 (DSE, 2006). 



Figure 1 Moorabool River water management area locality map

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As outlined in the Victorian State Water Report 2004/05 (DSE, 2006), Ballarat and surrounding towns supplied by the Ballarat system were on Stage 3 water restrictions between September 2003 and March 2005. For the remainder of 2004-05, Stage 2 restrictions were in place.

Stage 3 water restrictions were in place for licensed diverters on the Moorabool River in July 2004, followed by various levels of restriction from January 2005 to the end of the 2004-05 period. Restrictions ranged from an irrigation ban on winter fill, to a complete irrigation ban in January, April and May 2005.

There were several large rainfall events in 2004-05 which resulted in poor water quality in Lal Lal dam at She Oaks. The poor quality of releases prevented some extraction for urban water supply.

Rainfall conditions (Figure 2) in the Moorabool River water management area in 2004-05 were close to the long term annual average across most of the water management area. Annual streamflow (Figure 4), while higher than previous years at many gauges, was largely impacted by a one-in-20 year rain event that occurred in February 2005 (Figure 3). See Table 1 for a summary of contextual data.

The representative hydrograph from the Bungaree WSPA shown in Figure 5 illustrates seasonal fluctuations in groundwater levels, with the overall trend relatively stable.

Table 1 Summary of Moorabool River water management area contextual information

Figure 2 Annual rainfall for the Moorabool River water management area (modified from BOM, 2006)




Figure 3 Monthly rainfall and evaporation for the Moorabool River water management area (modified from BOM, 2006 & Climate Atlas)




Figure 4 Streamflow hydrograph for the Moorabool River water management area for Little River at Little River (gauge 232200)




Figure 5 Representative bore hydrograph for the Moorabool River water management area

Summary of the total water resources in the basin

The total volumes of water available and supplied from water resources in the Moorabool River water management area are shown in Table 2.

Table 2 Summary of water balance in the Moorabool River water management area, 2004-05

Figure 6 Water balance summary diagram for the Moorabool River water management area

Outcomes from the water cycle report

The following information becomes apparent from Table 2.

• There was a large increase in the overall volume of surface water stored (73%). This increase may be attributable to the higher than average rainfall and runoff. Despite this increase, storage volumes within large dams in the Moorabool River water management area (i.e. Korwinguboora Reservoir, Bostock Reservoir, Lal Lal Reservoir and Moorabool Reservoir) were at 34% of total capacity by June 2005.
• There were no estimates available for the volume of baseflow in the catchment (i.e. the volume of groundwater discharged to surface water features). There is concern that groundwater extraction from the Bungaree WSPA may be reducing streamflows in the Upper Moorabool catchment (DSE, 2006).
• Data accuracy for the groundwater usage estimates was low as much of it was self extracted and un-metered. This may also contribute to the large error term in the groundwater balance. For all the groundwater usage the total estimated licensed volume was used, this volume included metered and unmetered extractions.
• Licences on unregulated streams were not generally metered.
• Water use was predominantly from surface water resources.
• There were no effluent recycling plants within the water management area. There may be opportunities for significant water efficiency savings within this water management area.
• As outlined in the Victorian State Water Report 2004/05 (DSE, 2006), an estimate of in-stream losses to groundwater and evaporation was made using the Moorabool and Lower Barwon REALM models. The estimates calculated by the REALM models do not include losses occurring between the point of water diversion from the Moorabool basin and the point of use. Transmission losses in the East Moorabool system through leakage in the Bostock and Ballan channels are estimated to be 15-20%. In the West Moorabool system transmission losses are estimated to be 10%.
• There was a volume in the State Water Report 2004/05 for the combined in-stream infiltration of groundwater, flows to floodplain and evaporation.This volume could not be separated into the relevant components so was incuded in the system losses as one figure. For Moorabool River the volume was 4,400 ML.
• The storage capacity of farm dams in the catchment was estimated to be 28,900 ML (DSE, 2006). Information on start and end of season storage volumes was not available, however it was estimated that 29,400 ML was harvested and 22,200 ML used in the 2004-05 season from small catchment dams.
• The environment’s share of total water flow at the basin outlet was approximately 43,600 ML, which is about 50% of total inflows into the basin. This volume represents water flowing from the basin which was not taken out of waterways for consumptive use.
• Data could not be obtained for the following items in the water balance:
• Groundwater storage volumes (renewable and non-renewable)
• Soil - unsaturated zone storage volumes
• River channels storage volumes
• Baseflow
• Groundwater extraction from unincorporated groundwater management units
• Groundwater discharged to evapotranspiration

Download 2004-05 water cycle report: