Canberra: Supporting information
- Wet conditions in 2020–21 contributed to above-average annual runoff across the region.
- End-of-year storage was 100% full compared to 56% full the previous year.
- 60% of the allocated water was taken in 2020–21, primarily for residential use.
For further information on the region's water accounting statements scroll down this page or click on the links below:
Water assets
- Water asset volumes in the region at 30 June 2021 were 332 GL, about 84% of which is water held in storages. The remaining amount is water held in lakes, rivers, and the urban distribution pipe network.
Figure S1 Total storage volume in the region at 30 June 2021
compared with the previous 11 years
- Storage volumes increased from 56% full at 30 June 2020 to 100% full at 30 June 2021.
- In 2013 the Cotter Reservoir was enlarged, increasing the region's total storage capacity to better deal with water demand during periods of drought (see 2013 Account).
- Due to extraordinary rainfall and flooding in March 2012, the Cotter dam spilled as the dam was not fully constructed. However, in July 2016, the newly constructed dam spilled for the first time.
- The end-of-year storage volume at 30 June 2021 was the highest compared with the previous 11 years.
Figure S2 Percentage-full volume on
30 June 2021 for each storage and total daily storage volume from 2013–2021 (inset)
- Very high rainfall in August and October 2020 resulted in a large rise in storage levels across the region during a 3-month period between mid-August and mid-November 2020.
- Storage levels reached 100% full in mid-November 2020. Storage levels remained near capacity for the remainder of the 2020–21 year due to wet conditions throughout the first half of 2021.
- The storage volume in Googong Reservoir returned to 100% of capacity at 30 June 2021 for the first time since 2017. The reservoir had remained full, or near full, since the end of the Millennium Drought in 2010; however, from the start of 2017 to mid-2020, storage volumes had dropped by more than 50%.
- More detailed information on the individual storages within the region is available on the Bureau of Meteorology's Water Storage website.
Water liabilities
- Water liabilities in the Canberra region refer to the volume of allocation remaining on licence entitlements at the end of the 2020–21 year.
| Description | Individual users (ML) | Urban system (ML) | |
| Opening balance at 1 July 2020 | 0 | 0 | |
| add | Allocation | 8,341 | 71,060 |
| less | Allocated diversion | 933 | 49,319 |
| less | Adjustment and forfeiture | 7,408 | 21,741 |
| Closing balance at 30 June 2021 | 0 | 0 | |
| Description | Individual users (ML) | |
| Opening balance at 1 July 2020 | 0 | |
| add | Allocated | 4,698 |
| less | Allocation extraction | 549 |
| less | Adjustment and forfeiture | 4,149 |
| Closing balance at 30 June 2021 | 0 | |
- The water supply licences for the region have a water management year that ends on 30 June. The portion of water allocation that has not been abstracted at the end of the water year is either forfeited or is carried over into the next water year.
- For individual users and the urban licence entitlement the unused portion of the allocation is assumed to be forfeited and the allocation remaining at the end of the year was 0 ML.
- A more detailed description of water allocations in the Canberra region is given in the Water use section below.
Water flows
Figure S3 Water inflows and outflows for the region's water stores and systems during the 2020–21 year
- Total surface water flows into the region's storages was 997 GL. The key items contributing to surface water inflows were runoff and inflow from outside region, which made up 48 and 45%, respectively of the total surface water inflows.
- For the first time in four years, runoff was above average (based on modelled data from 1971–2021) due to high rainfall across the region.
- A key item contributing to surface water outflows from the region's storages was river outflow, which made up 84% of the total surface water outflows. River outflow was well above average due to the wet conditions and high runoff across the region.
- Water taken from surface water and groundwater resources for consumptive use was 52 GL, around 13% of the total outflow (see Water use section below).
Water availability
Figure S4 Annual surface water available in the Canberra region,
2011–12 to 2020–21
- Physical surface water availability is calculated as the sum of storage at the start of the year (see Water assets) and estimated inflows into storages and rivers during the year (see Figure S3).
- Surface water availability in the Canberra region in 2020–21 was above average for the first time in five years.
- As physical water availability is much higher than the region's water needs, water allocations vary little between years.
- Water taken during the year is influenced by the physical water availability. Typically, water taken from surface water resources is higher when water availability is low. This is discussed in more detail in the Water use section below.
Water use
Figure S5 Water taken for consumptive use in the Canberra region in
2020–21
- Total surface water diverted in the region was 50,747 ML.
- 97% of the total diversion was for the urban system while 3% was supplied to individual users under allocated diversions and statutory rights.
- Total groundwater extracted in the region was 983 ML.
- All of the groundwater extractions were for individual users; 56% of the total were allocated extractions while 44% was made under a statutory right.
Figure S6 Surface water allocations and diversions in the Canberra region
for the years ending 30 June, from 2012–2021
- In 2020–21, total surface water allocation was 79 GL, mostly for urban system supply. 89% of the allocated surface water was taken.
- Allocated diversion to the urban system was almost 11% less than last year. The recent trend of decreasing urban water supply reflects the wet conditions across the region over the last year, which has resulted in a decreased water demand from customers.
Figure S7 Groundwater allocations and extractions in the
Canberra region for the years ending 30 June, from 2012–2021
- Total groundwater allocation was 5 GL, all for private and commercial use. 12% of the allocated groundwater was taken.
- Allocated extractions for individual users were half to the previous year.
Urban system supply
Figure S8 Water sources used in Canberra's urban supply system during the
2020–21 year compared with the previous ten years
- Total inflow to the urban water supply system was 49 GL, almost 11% less than the previous year.
- Surface water diversions from the region's storages make up 100% of the urban supply.
Water restrictions
- Icon Water introduced permanent water conservation measures for potable water use in November 2010, which govern how water can be used on gardens and lawns and for pool filling, car washing, and cleaning.
- For more information, refer to the Bureau of Meteorology's Water Restrictions website.
Water market activity
- The volume of water allocation and entitlement traded in the region is small, typically representing less than 1% of the total water allocation.
- For more information on water markets in the region, see the Water Markets Dashboard.
Cultural and environmental water
Cultural benefit
- Cultural water values within the region are closely aligned with environmental water outcomes. In cases where complementary outcomes can be achieved, environmental water, delivered for environmental purposes, then also meet the cultural water requirements.
- More information on cultural water requirements are provided in the Cultural water management section in the 'Region description'.
Environmental benefit
Environmental water provisions
- Environmental water provisions are defined for aquatic ecosystem categories and specific river reaches in Chapter 5 of the 2013 Environmental Flow Guidelines.
- Environmental water requirements for one of these river reaches, on the Cotter River below Corin Dam, are presented below.
Figure S9 Example environmental water provisions for the Cotter River below
Corin Dam
- The required environmental flows are maintained through a combination of strategic water releases or spills from storages, as well as by restricting the volume of water that can be diverted from a catchment.
- The baseflow requirement is specified on a monthly basis, with fortnightly variations in the rate of release preferred compared to constant discharge for the month.
- Drawdown limits for impoundments, and protection of larger, less frequent 'channel maintenance' flows are also a part of the environmental water provisions, but are not shown on the figure above.
Environmental water outcomes
Figure S10 Flow in the Cotter River compared with the required flow regime
during the 2020–21 year
- In 2020–21, streamflow in the Cotter River below Corin Dam generally exceeded all environmental requirements.