National Water Commission

The Glenelg River water management area is located within the South East Coast Drainage Division, in western Victoria. Southern Rural Water is the licensing authority and manages both surface and groundwater diversions across the entire water management area except for the Glenelg River above the bridge on Casterton-Harrow Road, which is managed by Grampians Wimmera Mallee Water.

Grampians Wimmera Mallee Water also manages the Wimmera-Mallee water supply system which includes Rocklands and Moora Moora Reservoirs and several other small diversions weirs in the upper Glenelg and Wannon Rivers. Wannon Water supplies water to the majority of towns in the water management area, with the exception of Harrow which is supplied by Grampians Wimmera Mallee Water. The Glenelg-Hopkins Catchment Management Authority is responsible for waterway management in the Glenelg River water management area.

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



Figure 1 Glenelg River water management area locality map

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Stage 1 urban water restrictions were in place for Balmoral throughout the 2004-05 period and Stage 2 restrictions continued in Harrow. Between February and July 2005, irrigation bans were in place for Grange Burn Creek (except for May), and the Wannon and Glenelg Rivers.

Rainfall conditions were slightly below the long term average (Figure 3 and Figure 4), as was annual streamflow (DSE, 2006). Figure  shows a representative hydrograph from the Glenelg WSPA. The hydrograph shows steadily declining groundwater levels between 1975 and 1999. Over the past 5 years, groundwater levels have been gradually increasing.

Table 1 Summary of Glenelg River water management area contextual information

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




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




Figure 4 Representative bore hydrograph for the Glenelg 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 Glenelg Basin are shown in Table 2.

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

 Figure 5 Water balance summary diagram for Glenelg River water management

Outcomes from the water cycle report

The following information becomes apparent from Table 2.

• There was a large decline in the overall volume of water stored (56%), despite rainfall conditions and streamflow being close to the long term average.
• The error from unaccounted for groundwater in the water balance was 86%, due to a large volume of unaccounted for groundwater outflows.
• There were no estimates available for the volume of baseflow in the catchment (i.e. the volume of groundwater discharged to surface water features). This may account for the large error in the groundwater balance
• It is understood that evapotranspiration from groundwater is a dominant process in this water management area. This was not reflected in the numbers in the water balance.
• Self-extracted groundwater usage in the Glenelg and Condah WSPAs was metered. Self-extracted groundwater extractions outside these areas were un-metered and estimates contained in the water balance contain a large degree of uncertainty.
• 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 Glenelg River the volume was 9,500 ML.
• The storage capacity of farm dams in the catchment was estimated to be 77,000 ML (DSE, 2006). Information on start and end of season storage volumes was not available, however it was estimated that 80,100 ML was harvested and 55,500ML used in the 2004-05 season from small catchment dams.
• As outlined in the Victorian State Water Report 2004/05 (DSE, 2006), 2004-05 was the first year of operation of the Bulk Entitlement orders for the Wimmera Mallee system. A Flora and Fauna Bulk entitlement order for the Glenelg and Wimmera Rivers is one of five orders for the region.
• Consistent with the Bulk Entitlement conversion orders, a total of 11,987 ML was allocated to the Glenelg and Wimmera Rivers during the 2004-05 flow season (1 November 2004 – 30th October 2005). In addition, 3,300 ML was allocated to the Glenelg River as a compensation flow to contribute in achieving environmental objectives. The Inter Catchment Advisory Group (ICAG) met to determine the split of environmental allocation between catchments. As a result of these negotiations, and based on recommendations and priorities identified by the Stressed Rivers report, the Glenelg River received 4,900 ML (including the compensation flow) for implementation of a summer baseflow.
• The environment’s share of total flow in 2004-05 was 69,400 ML, which was about 39% of the streamflow in the basin. This amount consists of environmental flow releases and all other water flowing in the basin which was not taken out of the streams for consumptive uses.
• Evapotranspiration from groundwater and surface water and interaquifer flow are understood to be significant in the Glenelg. This is not reflected in the water balance.
• 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

Download 2004-05 water cycle report: