Canberra
Resources and Systems

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.

Table 1. Surface water store volume at the start and end of the 2010–11 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.

Table 2. Volumes of inflows and outflows from the surface water store during the 2010–11 year.

	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

Table notes:

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.

Table 3. Balancing item for the surface water store for the 2010–11 year

	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.

 

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.

Table 4. Volumes of inflows and outflows for the groundwater store during the 2010–11 year. Line items in italics indicate between–store flows. These flows are not presented in the Water accounting statements as they occur within the region.

	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.

Table 5. Balancing item for the groundwater store in the 2010–11 year

	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

 

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.

Table 6. Urban water system store volume at the start and end of the 2010–11 year

	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.

Table 7. Volume of inflows and outflows for the urban water system during the 2010–11 year

	Volume (ML)
11 Urban water system inflows
11.4 Wastewater collected	33,281
11.7 Stormwater ingress	6,176
11.12 Allocation diversion of surface water to urban system	40,944
Total 11 Urban system inflows	80,401
19 Urban water system outflows
19.1 Evaporation from urban water	4,353
19.2 Leakage to landscape	–
19.3 Leakage to groundwater	3,099
19.4 Delivery to urban water system users	37,015
19.5 Urban water discharge to surface water	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.

Table 8. Balancing item for the urban water system for the 2010–11 year

	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.

Table 9. Balance of the regional urban water supply system for the 2010–11 year

Inflow component	Volume (ML)	Line Item		Outflow component	Volume (ML)	Line item
Surface water taken	40,944	11.12		Potable water supplied to water users	36,809	Potable component of 19.4
Groundwater taken	–			Water lost due to leakage	3,099	19.3
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.

Table 10. Balance of the regional wastewater collection system for the 2010–11 year

Inflow component	Volume (ML)	Line Item		Outflow component	Volume (ML)	Line Item
Wastewater collected within the entity	33,281	11.4		Wastewater (treated) discharged to surface water	34,897	Wastewater component of 19.5
Ingress of stormwater and groundwater	6,176	11.7		Overflow to stormwater and groundwater	–
Wastewater treatment plant and sewer mining inflow	39,457			Wastewater treatment process losses	4,353	19.1
				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.  

 

Table 11. Regional urban water consumption for the 2010–11 year

	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.

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

Table 12. Inflows and outflows for the off–channel water store in the Canberra region during the 2010–11 year

	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.

Table 13. Balancing item – off–channel water store for the 2010–11 year

	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.