Canberra
Resources and Systems
Surface water
The purpose of this note is to provide a consolidated report on the surface water store within the region during the 2010–11 year. Information on all water flows to and from the surface water store are presented here, including between store flows and transfers that are not presented in the water accounting statements.
A description of the Canberra region's surface water resources is provided in the Contextual information under Physical information > Surface water.
Table 1 shows that the total surface water store in the Canberra region at the end of 2010–11 year increased relative to the end of the 2009–10 year.
30 June 11 (ML) | 30 June 10 (ML) | ||
1 Surface water | |||
1.1 Storages | 201,252 | 114,648 | |
1.2 Unregulated river | – |
– |
|
1.3 Regulated river | – | – | |
1.4 Lakes and wetlands | 38,500 | 38,500 | |
Total | 239,752 | 153,148 |
The volume of the surface water asset included water held in surface water storages within the Canberra region. The surface water asset excluded the water in river channels and some lakes and wetlands in the region due to the lack of both data and a suitable quantification approach.
There are four urban water supply storages within the Canberra region: Bendora Reservoir, Corin Reservoir, Cotter Reservoir and the Googong Reservoir. At the end of the 2010–11 year the volume of water in these storages increased considerably compared to at the end of the 2009–10 year (30 June 2010) (see line item 1.1 Storages). Overall, storage volume was approximately 98% at 30 June 2011 compared to approximately 56% at 30 June 2010.
The substantial increase in surface water storage during the 2010–11 year is attributed to the increased inflows into the storages, primarily driven by higher than average rainfall experienced throughout the period (see Climate statement).
The location of each storage within the Canberra region, and the volume of water, including dead storage, in each storage as a percentage of total storage capacity (per cent full) at the end of the 2010–11 year, is shown in Figure 1.

Figure 1. Location map of the storages within the Canberra region. The full volume on 30 June 2011 for each storage is also shown
Surface water inflows and outflows
A schematic diagram representing all the inflows and outflows associated with the surface water store in the Canberra region is provided in Figure 2. The inflow and outflow volumes for the surface water store during 2010–11 are given in Table 2. In addition to flows reported in the water accounting statements, Figure 2 and Table 2 also show flows between water stores that are part of the region.
Figure 2 is a schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the surface water store within the Canberra region during the 2010–11 year.

Figure 2. Schematic diagram of water inflows and outflows for the surface water store within the Canberra region during the 2010–11 year. Solid arrows indicate water transfers; dotted arrows indicate natural water movement; waved arrows indicate leakage. Line item numbers are provided next to the flows.
Volume (ML) | |
9 Surface water inflows | |
9.1 Precipitation on surface water | 19,787 |
9.2 Inflow from outside region | 279,762 |
9.3 Groundwater discharge | – |
9.4 Rainfall runoff | 1,179,859 |
9.6 Overbank flood return to river channel | - |
9.9 Discharge from urban water system | 39,262 |
Total 9 Surface water inflows | 1,518,670 |
17 Surface water outflows | |
17.1 Evaporation from surface water | 21,689 |
17.2 Outflow to outside region | 1,144,888 |
17.3 Groundwater recharge | – |
17.5 Overbank flood spilling | – |
17.6 Diversions: other statutory rights | – |
17.7 Non-allocated diversions to users | 1,188 |
17.12 Surface water allocation diversion - urban system | 40,944 |
Total 17 Surface water outflows | 1,208,709 |
Balancing item – surface water store | 223,357 |
Change in surface water storage | 86,604 |
Opening surface water storage | 153,148 |
Closing surface water storage | 239,752 |
Lines in italics indicate between–store flows, which are not presented in the water accounting statements as they occur within the region.
In the 2010–11 year the largest diversion made from the surface water system was for the public water supply (17.12 Surface water allocation diversion - urban system).
The balancing item volume represents the difference between the measured opening and closing balances of the surface water store, after physical inflows and outflows have been applied. This item is an indication of both the accuracy of the volumes reported and the degree to which the reported water flows represents a complete surface water store balance.
The balancing item is calculated according to Table 3.
|
Account |
Volume (ML) |
|
Opening balance (30 June 2010) |
153,148 |
add |
Total 9 Surface water inflows (see Table 2) |
1,518,670 |
less |
Total 17 Surface water outflows (see Table 2) |
1,208,709 |
less |
Closing balance (30 June 2011) |
239,752 |
|
Balancing item – surface water store |
223,357 |
The calculation of the water balance on the surface water store yielded a balance difference of 223,357 ML. This is approximately 15% of the total surface water inflows during the 2010–11 year.
Groundwater
The purpose of this note is to provide a consolidated report on the groundwater store within the region during the 2010–11 year. Information on all water flows to and from the groundwater store are presented here, including between-store flows and transfers that are not presented in the water accounting statements.
A description of the Canberra region's groundwater resources are provided in the Contextual information under Physical Information > Groundwater.
The aquifers in the Canberra region are described in Physical information > Groundwater. Given the majority of groundwater within the region is stored in fractured rock aquifers that are difficult to measure and monitor, no value was available for the volume of water stored in the aquifers. There is at present no value estimated for the volume of the groundwater asset either.
A more detailed explanation is provided in line item notes 2.1 and 2.2.
A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Canberra region is provided in Figure 3. The inflow and outflow volumes for the groundwater store during 2010–11 are given in Table 4. The numbers on the diagram refer to the line item numbers in Table 4.

Figure 3. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the groundwater store within the Canberra region during 2010–11. Solid arrows indicate water transfers; dotted arrows indicate natural water movement; waved arrows indicate leakage. Line item numbers are provided next to the flows.
Volume (ML) | |
10 Groundwater inflows | |
10.1 Groundwater inflow from outside region | – |
10.3 Recharge from landscape | – |
10.4 Recharge from surface water | – |
10.6 Leakage from urban system | 3,099 |
Total 10 Groundwater inflows | 3,099 |
18 Groundwater outflows | |
18.1 Groundwater outflow to outside region | – |
18.3 Discharge to landscape | – |
18.4 Discharge to surface water | – |
18.5 Discharge to off-channel water storage | – |
18.6 Infiltration to urban water system | – |
18.7 Extraction: other statutory rights | 435 |
18.8 Non-allocated extractions to users | 335 |
Total 18 Groundwater outflows | 770 |
Balancing item – groundwater store | 2,329 |
Change in groundwater storage | – |
Opening groundwater storage | – |
Closing groundwater storage | – |
The balancing item volume represents the difference between the measured opening and closing balances of the groundwater store, after physical inflows and outflows have been applied.
|
Account |
Volume (ML) |
|
Opening balance (30 June 2010) |
– |
add |
Total 10 Groundwater increases |
3,099 |
less |
Total 18 Groundwater decreases |
770 |
less |
Closing balance (30 June 2011) |
– |
|
Balancing item – groundwater store |
2,329 |
Urban system
Systems interactions with the region
The purpose of this note is to provide a consolidated report on the urban water system within the region during the 2010–11 year. Information on all water flows to and from the urban water system are presented here, including between store flows and transfers that are not presented in the water accounting statements.
Background information on the urban water system within the Canberra region is available in Other water resources and distribution systems in the Contextual information.
Table 6 shows that the volume of water in the urban water system changed little during the 2010–11 year in the Canberra region.
30 June 2011 (ML) |
30 June 2010 (ML) |
|
3 Urban water system | ||
3.1 Urban water supply system | 853 | 885 |
3.2 Wastewater collection system | – | – |
3.3 Recycled water supply system | 2 | 2 |
Total 3 Urban system | 855 | 887 |
The information in Table 6 does not include service water storages or the pipe network managed and owned by Queanbeyan City Council (QCC). The QCC water supply system is much smaller in size than the ACTEW system and it is expected that the volume stored within the QCC tanks and pipes would be much less than that reported for ACTEW's system.
Table 6 shows that for the urban system in the Canberra region, only the volume of water contained in the urban water supply system could be quantified. The volume only includes 47 tanks and the pipe network owned by ACTEW. This volume does not include any data from the Queanbeyan area as it was unavailable.
A schematic diagram representing all the inflows and outflows associated with the urban water system in the Canberra region is provided in Figure 4. The inflow and outflow volumes for the urban water system during 2010-11 are given in Table 7. In addition to flows reported in the water accounting statements, Figure 2 and Table 7, also show flows between water stores that are part of the region.

Figure 4. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) of the urban water system within the Canberra region. Solid arrows indicate water transfers; dotted arrows indicate natural water movement; waved arrows indicate leakage. Line item numbers are provided next to the flows.
|
Volume (ML) |
|
|
11 Urban water system inflows |
|
11.4 Wastewater collected | 33,281 |
11.7 Stormwater ingress | 6,176 |
40,944 |
|
Total 11 Urban system inflows |
80,401 |
|
|
19 Urban water system outflows |
|
4,353 |
|
– |
|
3,099 |
|
37,015 |
|
39,262 |
|
Total 19 Urban water system outflows |
83,729 |
|
|
Balancing item – urban water system |
(3,296) |
|
|
Change in urban water system storage |
(32) |
|
|
Opening urban water system storage |
887 |
Closing urban water system storage |
855 |
Table note:
Line item volumes in italics indicate between-store flows. These flows are not presented in the water according statements as they occur within the region.
ActewAGL holds a licence to deliver urban water to the Canberra region. The total annual urban water access entitlement to ActewAGL is 71,000 ML. More information on this entitlement is available in line item 21.2 Surface water allocation announcements - urban system.
The balancing item volume represents the difference between the measured opening and closing balances of the urban water system, after physical inflows and outflows have been applied. This item is an indication of both the accuracy of the volumes reported and the degree to which the reported water flows represents a complete urban water system store balance.
The balancing item is calculated according to Table 8.
|
Account |
Volume (ML) |
|
Opening balance (30 June 2010) |
887 |
add |
Total 11 Urban water system inflows (see Table 7) |
80,401 |
less |
Total 19 Urban water system outflows (see Table 7) |
83,729 |
less |
Closing balance (30 June 2011) |
855 |
|
Balancing item – urban water system |
(3,296) |
The urban water system is made up of three subsystems which serve the urban water users: the urban water supply system, the wastewater collection system and the recycled water system. The main urban water users are residential, commercial, industrial and municipal consumers.
This note complements the Systems interactions with the region note. It gives the following additional information:
- Split of the urban water flows according to the subsystems they affect
- Flows between subsystems, which are not reported in the Systems interactions with the region note as they occur within the whole urban water system
- Split of the total urban water use into several components.
The urban water supply system collects water from various sources including surface water, groundwater and transfers-in across the region's geographical boundaries. It treats and distributes water to urban water users. Part of the water is used outdoor (e.g. garden use) while the rest is collected into the wastewater collection system. Wastewater is treated and then discharged to surface water or delivered into the recycled water system. The recycled water system, in turn, distributes treated water to users.
Tables 9 to 11 show the balance of each subsystem, including its inflows, outflows, balancing item and percentage error of the balancing item compared to the total of the inflows. The balancing items are calculated as the difference between the inflows less the outflows, considering that the changes in storage are not material. The values of the balancing items reflect measurement and data handling errors and/or missing data.
Table 9 shows a breakdown of the total urban water use by use sectors and type of water (potable, non-potable and recycled).
For each row in Tables 9 and 10, correspondence is given on the line items that are reported in the Water accounting statements and the System's interactions with the region note. The correspondence can either be:
· 'Line item A' – meaning a one-to-one correspondence of the volume in the table with the line item A
· 'Part of: line item A' – meaning that the volume in the table is a part of the line item A
· 'Line item A + line item B' – meaning that the volume in the table is the sum of line items A and B
· 'Part of: line item A + line item B' – meaning that the volume in the table is the sum of a part of line items A and a part of line item B
· 'Not applicable' – in the case when there is no correspondence to a line item.
When a volume in a table is given as '0' it means that the value has been evaluated as nil for the 2010–11 year. When the volume in a table is given as dash ('–'), it means that the volumes could not be quantified for the 2010–11 year.
Supporting information and quantifications approaches for each volume shown in tables 4 to 6 can be accessed via links on the line item numbers. In the cases when there is no corresponding line item, the supporting information and quantification approaches are given at the end of the note.
Inflow component |
Volume (ML) |
Line Item |
|
Outflow component |
Volume (ML) |
Line item |
Surface water taken |
40,944 |
|
Potable water supplied to water users |
36,809 |
Potable component of 19.4 |
|
Groundwater taken |
– |
|
|
Water lost due to leakage |
3,099 |
|
|
|
|
|
|
|
|
Total Inflow |
40,944 |
|
|
Total outflow |
39,908 |
|
|
|
|
|
|
|
|
Balancing item (inflows less outflows) |
1,036 |
|
|
|
|
|
Error |
3% |
|
|
|
|
|
Balancing item is due to meter errors, data handling errors, estimation errors from databases and missing items.
Inflow component |
Volume (ML) |
Line Item |
|
Outflow component |
Volume (ML) |
Line Item |
Wastewater collected within the entity |
33,281 |
|
Wastewater (treated) discharged to surface water |
34,897 |
Wastewater component of 19.5 |
|
Ingress of stormwater and groundwater |
6,176 |
|
Overflow to stormwater and groundwater |
– |
|
|
Wastewater treatment plant and sewer mining inflow |
39,457 |
|
|
Wastewater treatment process losses |
4,353 |
|
|
|
|
|
Treated wastewater supplied as recycled water |
206 |
Part of 19.4 (see table 6) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Total inflow |
39,457 |
|
|
Total Outflow |
39,456 |
|
|
|
|
|
|
|
|
Balancing item (inflows less outflows) |
1 |
|
|
Recycled water used onsite in-process |
4,145 |
* See note following Figure 5 |
Error |
0% |
|
|
|
|
|
Balancing item is due to errors in rounding.
|
Potable |
Non-Potable |
Recycled |
Total |
Line item |
|||
|
Volume (ML) |
Line item |
Volume (ML) |
Line item |
Volume (ML) |
Line item |
||
Residential |
27,618 |
Part of 19.4 |
|
|
|
|
27,618 |
|
Commercial, industrial and municipal uses |
9,191 |
Part of 19.4 |
|
|
158 |
Part of 19.4 |
9,349 |
|
Other, including agriculture |
|
|
|
|
48 |
Part of 19.4 |
48 |
|
|
|
|
|
|
|
|
|
|
Total volume supplied |
36,809 |
|
0 |
|
206 |
|
37,015 |
19.4 |

Figure 5. Schematic diagram of the inflows and the outflows for the urban subsystem. Flow volumes and corresponding line item number or tables where the value is reported, are provided next to the arrows. Fade-out arrow indicate water flows that could not be quantified.
Figure 5 shows three unquantified inflow and outflow components of the urban water consumption subsystem. There were insufficient data available to quantify these volumes. However, they are important components of the urban water balance.
Individually abstracted water includes water abstracted from surface water, groundwater or rainwater by individual users (e.g. water diverted from a stream, pumped from a domestic garden bore or sourced from a rainwater harvesting system).
The unquantified stormwater component represents stormwater that is claimed and then used by urban water consumers, as is the case for stormwater that is collected, treated and used in municipal stormwater schemes or projects.
Off-channel storages
The purpose of this note is to report on water held in off-channel water storages within the Canberra region during the 2010–11 year. Where available, water flows to and from off-channel water storages are reported here. Water held in off-channel water storages is not reported in the water accounting statements because the statements report only on water resources yet to be shared. Water held in off-channel water storages is considered to be taken from the shared pool of water resources and, as such, is not included as part of the region's water assets (see Scope of the Canberra region in Contextual information under Physical information > General description).
This note provides additional information about the water assets and water liabilities recognised in the water accounting statements. This note reports on water that has been harvested from the landscape into off-channel water storages and thus did not contribute to groundwater recharge or runoff into surface water.
The volume of water held in off-channel water storages increased from 5,861 ML at the beginning of the 2010–11 year by almost 30% to 8,004 ML at the end of the 2010–11 year. This increase in off-channel water storage is attributed to the increased inflows into the storages during 2010–11, driven by above average rainfall experienced throughout the year (see Contextual information under Climate overview > Rainfall).
The volume of water held in off-channel water storages included only off-channel water storages filled primarily by rainfall-runoff capture. Volumes of water held in off-channel water storages filled by groundwater extractions, surface water diversions, or recycled water were excluded as these volumes could not be quantified due to a lack of available data. However, it is expected that this volume is not material as these types of off-channel water storages only make up a small proportion of off-channel water storage capacity within the Canberra region.
Off-channel water storage inflows and outflows
Volume (ML) | |
30 Off-channel water inflows | |
30.1 Precipitation on off-channel water store | 6,408 |
30.2 Groundwater discharge into off-channel water store | - |
30.3 Runoff harvesting into off-channel water store | 7,132 |
Total 30 Off-channel water inflows | 13,540 |
31 Off-channel water outflows | |
31.1 Evaporation from off-channel water storages | 6,497 |
31.2 Leakages from off-channel water storages | - |
31.3 Water use | 4,892 |
Total 31 Off-channel water outflows | 11,389 |
Balancing item – off-channel water store | 8 |
Change in off-channel water storage | 2,143 |
Opening off-channel water storage | 5,861 |
Closing off-channel water storage | 8,004 |
The majority of volumes reported for inflows and outflows to off-channel water storages were modelled (see individual item quantification approaches). Data was unavailable for inflows to off-channel water storages via surface water diversions and groundwater extractions. Thus, the only volumes reported for inflows to off-channel water storages were runoff harvesting and precipitation, both of which made a significant contribution to the overall inflow to off-channel water storages in 2010–11.
Evaporation from off-channel water storages was the most significant outflow from off-channel water storages and was substantially higher than the volume reported for water use.
This volume represents the volume necessary to reconcile the opening and closing balances of the off-channel water storage with the physical water inflows and outflows. The difference was calculated according to Table 13.
Account | Volume (ML) | |
Opening balance (30 June 2010) | 5,861 | |
add | Total 30 Off-channel water inflows (see Table 12) | 13,540 |
less | Total 31 Off-channel water outflows (see Table 12) | 11,389 |
less | Closing balance (30 June 2011) | 8,004 |
Balancing item – off-channel water store | 8 |
The calculation of the water balance on the off-channel water storages yielded a balance of 8ML. This is less than 1% of the total off-channel water storage volume at the end of the 2010–11 year and less than 1% of the total off-channel water storage inflows during the 2010–11 year.
Although a large balancing item was not observed for the off-channel water store, it should be noted that volumes reported were mainly derived from modelled data. The modelling process essentially constrains the data to achieve a water balance, hence removing any potential balancing difference.