National Water Commission

A more detailed introduction and information about water resources, water balance and water use in the Australian Capital Territory water management area is provided in the report for the Australian Capital Territory (Capital City).

Management indicator data for the Australian Capital Territory groundwater management unit (GMU) is provided via the 'Management Indicators GMU' tab above, and for the Australian Capital Territory surface water management area (SWMA) via the link in the list below.

Rainfall for 2004-05 was 649 mm, which is about 90% of the long term average. Rainfall is unevenly distributed in the ACT with the mountainous southern and western portion receiving about twice as much rainfall as the north of the Territory. Despite the rainfall being only slightly below average, low rainfall in the two preceeding years (Figure 2) meant that streamflow was significantly lower than normal at 30% of the long term average (Figure 4 and Figure 5). Due to a lack of monitoring (since rectifed) there is no information about groundwater trends in the ACT.

As a result of the low river flows and the bushfires in 2003, permanent water restrictions were in place during 2004-05 in the ACT. Consequently, the volume of water used in the ACT dropped to ~640 L/person/day compared to ~1200 L/person/day in 2000 01 (Figure 6).

Table 1 Summary of the Australian Capital Territory contextual information

Figure 2 Annual rainfall for the Australian Capital Territory (modified from BOM, 2006)




Figure 3 Monthly rainfall and evaporation for the Australian Capital Territory (modified from BOM, 2006 & Climate Atlas)




Figure 4 Representative streamflow hydrograph for the Australian Capital Territory at Murrumbidgee Halls Crossing (gauge 410777), located after the Murrumbidgee River leaves the ACT




Figure 5 Representative streamflow hydrograph for the Australian Capital Territory at Murrumbidgee Lobbs Hole (gauge 410761), located before the Murrumbidgee River enters the ACT




Figure 6 Total water supplied by ACTEW Corporation to ACT and Queanbeyan compared to population from 1999 2000 – 2004 05 (source: WSAA, 2005)

The total volumes of water available and supplied from water resources in the Australian Capital Territory are shown in Table 2.

In 2004-05 surface water runoff and groundwater recharge was well below average.

Table 2 Summary of water balance in the Australian Capital Territory, 2004-05

Figure 7 Water balance summary diagram for the Australian Capital Territory, 2004-05

Outcomes from the water cycle report

The following information becomes apparent from Table 2.

• As the ACT includes a capital city, Canberra, water use was primarily for urban and landscaping use.
• The recharge, runoff and outflow estimates dominated the water balance representing more than 71% of the overall balance. The Water 2010 estimates for runoff were accepted, but probably had an error of ±50% (Category C).
• Groundwater/surface water interaction was completely estimated and was set to be the same as the volume of groundwater recharge.
• None of the groundwater systems in the ACT were well understood.
• Water use was almost wholly from surface water.
• Water was generally supplied by ACTEW, although the National Capital Authority also took water from Lake Burley Griffin.
• In 2004-05 the environments’ share of the total flow in Australian Capital Territory was 60%.
• 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
• Farm dams
• Self extracted water
• River channels storage volumes
• Seepage from streams to groundwater
• Groundwater use
• Groundwater discharge to ET

Summary of data availability and reliability

Because of the small size of the WMA, the data for this water balance is generally good, except for the groundwater resource, which is poorly understood. The data for this water balance was predominantly category Aand D. The overall reliability index for the area was ±74% with a total water balance error of 2% (See Table 3).

Table 3 Summary of Australian Capital Territory data reliability