National Water Commission

The Murrumbidgee River is located within the Murray-Darling Drainage Division in southern New South Wales. Although the complete Murrumbidgee River catchment includes the regulated and unregulated areas within New South Wales and covers the entire Australian Capital Territory, only the regulated area was assessed for the water balance.

The Murrumbidgee River is a major tributary of the Murray River. It has several tributaries, including the Yass River, Tumut River, Kyeamba Creek, Hillas Creek, Tarcutta Creek and Jugiong Creek.

Intensive irrigation occurs within the Murrumbidgee River – Regulated WMA, including the Murrumbidgee Irrigation Area and Coleambally Irrigation Area. There are two primary water storages in the area (Blowering and Burrinjuck Dams) and a further 6 major storages (above 1,000 ML in capacity). Major towns in the area include Wagga Wagga, Tumut, Narrandera, Leeton, Griffith, Hay, Balranald and Coleambally.

The Department of Natural Resources (DNR) is the licensing authority and manages both surface and groundwater diversions for urban, commercial/industrial, irrigation and environmental purposes. The Murrumbidgee CMA is responsible for managing the native vegetation, soil and other natural resources in the catchment in conjunction with the local community, local government, industry and State Government. State Water manages the major water supply storages in New South Wales and supplies bulk water to the irrigation authorities, town water supply authorities, mines, electricity generators and other industry by releasing water from its dams into rivers to be accessed by downstream water users. State Water also delivers water for private irrigators and stock and domestic users and is responsible for delivering environmental flows, in accordance with rules as set out in NSW Water Sharing Plans, on regulated rivers in the state. Local councils treat the bulk water and deliver it to urban users in the major towns within the catchment (e.g. Riverina Water County Council supplies Wagga Wagga and the surrounding region). Local councils also manage the wastewater collection and treatment network (e.g. Wagga Wagga City Council for Wagga Wagga and the surrounding area). Both surface and groundwater resources are used for town water supplies in the Murrumbidgee River – Regulated WMA. 



Figure 1 Murrumbidgee River - Regulated water management area locality map

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No obligatory restrictions were in place for 2004-05 urban areas within the Murrumbidgee River – Regulated WMA, however the community was encouraged to comply with voluntary restrictions. State Water storage levels were amongst the lowest in history in 2004-05, and the rice crop was the smallest on record due to the drought (State Water, 2006).

Rainfall across the Murrumbidgee River - Regulated WMA was about average in 2004-05, at around 94% of long term average rainfall and the 10 year average was 95% of the long term average (see Figure 2 and Figure 3).

The reduced water level in the deeper aquifer zones is falling due to groundwater pumping in Murrumbidgee catchment (shown in Figure 4); however these are within the range predicted by the regional groundwater flow model. The model predicts the pressure decline will continue for another decade before a new equilibrium (i.e. stable pressure levels) is reached.

Table 1 Summary of the Murrumbidgee River - Regulated water management area contextual information

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




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




Figure 4 Modelled pre development streamflow hydrograph for the Murrumbidgee River - Regulated water management area for the Murrumbidgee River at Burrinjuck Dam (site 410131)




Figure 5 Representative bore hydrograph for the Murrumbidgee River - Regulated water management area (Bore name: Coleambally Creek)

Summary of the total water resources in the basin

The total volumes of water available and supplied from water resources in the Murrumbidgee River – Regulated WMA are shown in Table 2.

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

Figure 6 Water balance summary diagram for the Murrumbidgee River - Regulated water management area

Outcomes from the water cycle report

The following information becomes apparent from Table 21.

• The water balance was completed for the regulated area of the Murrumbidgee catchment. There was a large amount of data available, including detailed modelling, for the regulated area, and hence the data quality for this water balance was relatively high. However, the balance may be misleading without considering the entire hydrological catchment (i.e. the combined regulated and unregulated areas). This is an opportunity for improvement in future assessments.
• The error in the water balance was 0%. This was due to the unaccounted for flows being incorporated with other items in the water balance. For surface water the balancing item was ‘Other losses’, the groundwater balancing item was the closing storage volume. Other jurisdictions reported unaccounted flows as an error term.
• About 80% of water used in the regulated area was sourced from surface water in 2004-05, with the remainder from groundwater sources.
• The vast majority of water used within the regulated area was for irrigation or other agricultural uses as there are few urban areas. Rice is the predominant irrigated crop in the WMA.
• The interaction between surface water and groundwater (predominantly seepage from streams to groundwater) was 194,000ML in 2004-05, or 10% of the total captured rainfall (sum of runoff and recharge).
• There was about 15% more surface water available in storage at the end of 2004-05 than at the start, including the water stored in river channels. The major surface water storages had a 13% increase in volume over the year, in real terms the storages started at 19% of capacity in July 2004 and finished at 21% of capacity in June 2005.
• The water balance was dominated by rainfall, inflows, surface water diversions and groundwater extractions.
• The volume of groundwater stored was estimated by DNR by calculating the volume in the aquifer(s) to a depth of 20m below the ground surface (assuming a saturated thickness, estimating the water table drawdown depth from bore levels, and using the area and aquifer porosity). For the Murrumbidgee River – Regulated area, the volume of groundwater at the end of the year was determined from the volume at the start of the year plus any unaccounted for groundwater errors (i.e. it has been used as the balancing item).
• Data could not be obtained for the following items in the water balance:
• Minor catchment dams (may be a large part of the water balance).
• Soil - unsaturated zone storage volumes
• Urban treated effluent (returns to the river)

Download 2004-05 water cycle report: