National Water Commission

The Wimmera River water management area is located within the Murray-Darling Basin, and includes the Wimmera, Avon and Richardson River catchments. The Wimmera River flows from the north side of the Great Dividing Range near Elmhurst, and from the Grampians Ranges, to Lake Hindmarsh. During wet periods, Lake Hindmarsh overflows through Outlet Creek, into Lake Albacutya and onto a series of smaller lakes and the Wirrengern Plain in the Mallee. The Avon and Richardson Rivers flow into and terminate in Lake Buloke.

Grampians Wimmera Mallee Water is the licensing authority and manages both surface and groundwater diversions. They are responsible for the Wimmera-Mallee water supply system which delivers water to urban centres and farms in a large part of the water management area. Central Highlands Water supplies the towns of Landsborough and Navarre. The Wimmera Catchment Management Authority is responsible for waterway management in the Wimmera River catchment, while the North Central Catchment Management Authority is responsible for the Avon and Richardson River catchments.

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



Figure 1 Wimmera River water management area locality map

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As outlined in the Victorian State Water Report 2004/05 (DSE, 2006), urban water restrictions across the Wimmera Water Management area for 2004-05 included:

• Stage 3 restrictions continued (from November 2002) at Berriwillock, Beulah, Charlton, Culgoa, Dooen, Hopetoun, Marnoo, Nullawil, Rainbow, Tarranyurk, Warracknabeal, Watchem and Wycheproof.
• Stage 3 restrictions continued (from February 2003) at Ararat, Birchip, Donald, Glenorchy, Great Western, Halls Gap, Horsham, Jeparit, Minyip, Murtoa, Noradjuha, Pimpinio, Pomonal, St Arnaud, Stawell and Reids (Taits) Lane
• Stage 3 restrictions continued (from November 2003) at Antwerp, Brim, Lascelles, Rupanyup, Woomelang, and Yaapeet.
• Restrictions were increased to Stage 4 (of a five stage system) at Natimuk, Clear Lake, Jung and Dimboola in October 2005.
• Stage 3 restrictions were lifted at Lalbert in January 2005 as a result of the source for the town water supply being changed to the Murray River via the Cannie ridge pipeline system.

In terms of non-urban water restrictions, the 2004-05 summer domestic and stock channel run was limited to the filling of one dam per 250 ha, while the 2005 winter channel run filled only one dam for every 400 ha. Supply-by agreement customers’ allocation for 2004-05 was also low at 40%, while the seasonal allocation to irrigators in the Wimmera basin was approximately 8% of entitlement.
Rainfall in 2005-05 in the Wimmera River water management area was close to the long term annual average (Figure 2 and Table 1). Annual streamflow was much lower than the long term average (Figure 4).

Table 1 Summary of Wimmera River water management area contextual information

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




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




Figure 4 Streamflow hydrograph for the Wimmera River water management area for the Wimmera River at Glenorchy Weir Tail Gauge (gauge 415201)

Summary of the total water resources in the basin

The total volumes of water available and supplied from water resources in the Wimmera basin are shown in Table 2.

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

Figure 6 Water balance summary for Wimmera River water management area

Outcomes from the water cycle report

The following information becomes apparent from Table 2.

• There was a significant decline in the volume of water stored (27%), as streamflows were well below long term averages.
• The unaccounted for errors were relatively large due to significant volumes of unaccounted for groundwater outflows and surface water inflows (errors of 100% and 51% respectively). The error in the groundwater balance is likely to be due to no information being available on baseflow.
• Data accuracy for the groundwater usage estimates was low. For instance, groundwater recharge in the Wimmera River water management area is understood to be quite low, however the BRS Water 2010 estimate of deep drainage of 359,988 ML is quite high.
• Water use was predominantly from surface water resources.
• In May 2004, a Bulk Entitlement of 32,240 ML was granted to the Minister for Environment for the Wimmera and Glenelg rivers. This is the environment’s share of water savings from the Northern Mallee Pipeline Scheme which was completed in 2003. While annual allocations to the environment were made as the pipelining progressed, the first formal allocations under the Bulk Entitlement came into force on 1st November 2004. A total of 11,987 ML was allocated to the Glenelg and Wimmera Rivers during the 2004-05 flow season (1st November 2004 – 30th October 2005). The Inter Catchment Advisory Group (ICAG) met to determine the split of environmental allocation between catchments. As a result of these negotiations, the Wimmera River received 5,954 ML in 2004-05, whilst 4,433 ML was carried over in storage for future use.
• In 2004-05 the environments’ share of the total flow in the Wimmera Basin was 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 the Wimmera River the volume was 7,200 ML.
• Information on start and end of season storage volumes was not available, however it was estimated that 22,900 ML was harvested and 14,400 ML used in the 2004-05 season from small catchment dams.
• There was a decline in water availability, largely due to inflows for the period being 23% of the long term average of 316,400 ML (DSE, 2006).
• 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: