Canberra
Supporting information
Introduction
The following set of notes provides consolidated reports for each of the water stores and systems within the Canberra region during the 2013–14 year. The water stores and systems included in the region are shown in Figure 1.
For a more detailed description of the region, please refer to the General description section of the 'Contextual information'.
Figure 1 Water stores and systems within the Canberra region
Information on all water flows to and from each water store and system are presented in this note, including between-store flows and transfers that are not presented in the water accounting statements. The between-store flows and transfers that occur in the region are presented in Figure 2.
Figure 2 Between-store flows that occur within the Canberra region
The between-store flows and transfers (Figure 2), which are eliminated from the region's water accounting statements, are shown in italics throughout the following set of notes. The allocation announcement, forfeiture and allocation remaining line items associated with each between-store abstraction (brown arrows in Figure 2) are also shown in italics in the following notes.
Surface water store
Surface water assets
The volume of the surface water assets includes water held in storages (219,448 ML), and three of the region's primary lakes (38,742 ML). The volume of water in rivers and some lakes and wetlands could not be quantified due to a lack of both available data and a suitable quantification approach.
Storages
There are four urban water supply storages within the Canberra region: Bendora, Corin, Cotter and Googong reservoirs. The Googong Reservoir is the largest reservoir in the region with a total storage capacity of 121,084 ML. The location of each storage within the Canberra region and the volume of water in each storage (including dead storage) as a percentage of total storage capacity at the end of the 2013–14 year is shown in Figure 3.
Figure 3 Percentage-full volume for each storage in Canberra region on 30 June 2014
Total volume of water within each storage at 30 June 2014, and at the end of the previous three years (2013, 2012 and 2011) is given in Figure 4.
Figure 4 Total volume of water in each storage at 30 June 2011, 2012, 2013 and 2014
At the end of the 2013–14 year, Googong Reservoir was 100% full, which is similar to the previous few years (Figure 4).
During the 2012–13 year, the capacity of the Cotter Reservoir was increased (from 3,856 ML to 79,375 ML) to improve water supply security and reduce the risk of water restrictions in the region. During the 2013–14 year the reservoir continued to fill to its new capacity; the volume of water in the reservoir increased from 12% to 57% capacity during the year.
The water volume in the remaining two storages (Bendora and Corin reservoirs) marginally increased during the year. The overall increase in storage during the 2013–14 year can be attributed to the slightly above average rainfall experienced across the region (see Climate overview) as well as the significant flows that occurred in the primary river systems during September 2013 (see Water overview).
Lakes and wetlands
There are three lakes within the Canberra region: Lake Burley Griffen, Lake Ginninderra and Lake Tuggeranong. The lakes are primarily used for recreation, conservation and aesthetic purposes, and are not formally associated with the urban water supply system; however, water can be abstracted or released to maintain environmental flows and for small-scale irrigation.
The location of each lake within the region and the volume of water in each lake as a percentage of total capacity at the end of the 2013–14 year is shown in Figure 5.
Figure 5 Percentage full and storage capacity on 30 June 2014 for each major lake
All three lakes were either at, or very near, 100% capacity on 30 June 2014. Total volume of water within each lake at 30 June 2014, and at the end of the previous three years (2013, 2012 and 2011), is given in Figure 6.
Figure 6 Total volume of water in each lake at 30 June 2011, 2012, 2013 and 2014
Surface water liabilities
Surface water liabilities in the Canberra region refer to the volume of surface water allocation remaining on licence entitlements at the end of the 2013–14 year for:
- individual users (0 ML)
- urban water system (0 ML).
The water supply licences for the region have a water management year that ends on 30 June. The unused component of the annual allocation for these licence entitlements is forfeited at the end of the year; therefore, the allocation remaining is zero (tables 1 and 2).
| Account: urban water system | Volume (ML) |
| Opening balance at 1 July 2013 | 0 |
| Surface water allocation announcements | 71,000 |
| Entitled diversion of allocated surface water to urban water system | (48,695) |
| Adjustment and forfeiture of surface water allocation | (22,305) |
| Closing balance at 30 June 2014 | 0 |
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 7.
Figure 7 Schematic diagram of the water inflows and outflows for the surface water store within the Canberra region
Surface water inflows
The largest natural water inflow is runoff to surface water (391,658 ML). The volume of runoff during the 2013–14 year is approximately 15% less than that during the previous year, which primarily reflects the decline in flow conditions in the rivers compared to the higher flows experienced during the 2012–13 year (see Water overview). It should also be noted that a portion of the runoff into surface water is reduced due to runoff harvesting by off-channel storages (e.g., farm dams) in the region (see Off-channel storages note).
The remaining two natural surface water inflows are precipitation on surface water (13,650 ML) and river inflow into the region (205,263 ML). The volume of precipitation represents rainfall that fell on the major storages and lakes within the region; river inflow into the region represents flow from upstream Murrumbidgee River into the region.
The discharge from the urban water system (32,588 ML) is comprised of two components:
- internal water transfers (37 ML): treated water from Mount Stromlo Water Treatment Plant transferred into Googong Reservoir via the ACTEW Water water reticulation network.
- wastewater discharge to rivers (32,551 ML): treated wastewater from sewage treatment plants discharged into rivers within the region.
Groundwater discharge (– ML) was not recognised due to a lack of available data and a suitable quantification approach.
Surface water outflows
The largest natural water outflow is the river outflow from the region (468,263 ML), which refers to the annual volume of flow to outside the region boundary via the Murrumbidgee River during the 2013–14 year. This outflow is slightly less than that during the previous year, which primarily reflects the decline in flow conditions in the river compared to the higher flows experienced during the 2012–13 year (see Water overview).
Evaporation from surface water during the 2013–14 year was 18,433 ML, which represents evaporation from the major storages and lakes within the region. Total evaporation during the 2013–14 year is slightly lower than that during the previous year, which may be attributed to the increased rainfall (and hence cloud cover) that occurred during the year (see Climate overview).
Groundwater recharge (– ML) was not recognised due to a lack of available data and a suitable quantification approach. The volume of river and floodplain losses could also not be quantified accurately due to a lack of available data; however, given the region is a largely bedrock system, these losses are not considered to be relatively large and its omission will not have a material impact on the water balance of the surface water store.
Water diversions from the surface water store, both allocated and non-allocated, are described in Surface water diversions below.
Surface water diversions
Entitled diversion of allocated surface water to the urban water system (48,695 ML) during the 2013–14 year accounts for more than 97% of the total diversion in the Canberra region. The volume represents the water diverted from storages to the region's urban water supply system. The volume of water diverted from each storage to the urban water system is shown in Figure 8.
Figure 8 Surface water allocations and diversions for the urban water system during the 2013–14 year
Non-allocated surface water diversions are the diversions of unregulated flows under multi-use licences for nonpotable water within the Canberra region. Non-allocated diversions in the region during the 2013–14 year relate to licences for:
- individual users (1,156 ML)
- urban water system (37 ML).
Entitled diversion of allocated surface water to individual users and diversions for other statutory rights could not be quantified accurately due to a lack of available data. Surface water diversions for other statutory rights are described in more detail in the Surface water rights note.
Surface water forfeitures
The portion of surface 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. According to the Water Sharing Plan for the Murrumbidgee Unregulated and Alluvial Water Sources, carry-over of unused surface water allocation is allowed for licence holders; however, due to limited data availability the carry-over volume could not be quantified. Therefore, for the purposes of the 2014 Account, it is assumed the entire unused portion of the allocation is forfeited.
Water forfeitures in the Canberra region during the 2013–14 year relate to licence entitlements for:
- individual users (1,832 ML)
- urban water system (22,305 ML).
Surface water allocation announcements
Surface water allocation announcements in the Canberra region during the 2013–14 year refer to surface water supply to:
- individual users (1,832 ML)
- urban water system (71,000 ML).
The surface water allocation for individual users is based on information available in the Water Sharing Plan for the Murrumbidgee Unregulated and Alluvial Water Sources. Entitlements referred to as share component under New South Wales (NSW) legislation are specified on water licences as unit share and the allocation announcement is based on share component.
The water supply licences for individual users are divided into licence entitlement categories. Figure 9 shows the annual allocation announcement for each licence category for the 2013–14 year.
Figure 9 Surface water allocation announcements to individual users for each licence category for the 2013–14 year
The surface water allocation announcements for the urban water system (71,000 ML) relate to licences to divert water from storages to the Canberra region's urban water supply system. This annual allocation is not sub-divided into separate allocations for each of the storages (as shown in Figure 8 above).
A more detailed description of surface water allocations and associated water rights in the Canberra region is given in the Surface water rights note.
Surface water balancing item
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 (Table 3). 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.
| Account: surface water store | Volume (ML) |
| Opening balance (at 1 July 2013) | 215,921 |
| Total surface water inflows | 643,159 |
| Total surface water outflows | (536,584) |
| Closing balance (at 30 June 2014) | 258,190 |
| Balancing item | 64,306 |
The calculation of the water balance on the surface water store yielded a balancing item of 64,306 ML. This is approximately 25% of the total surface water store volume at the end of the 2013–14 year and approximately 10% of the total surface water inflows during the 2013–14 year.
It is likely that the balancing item is primarily attributed to uncertainties associated with the runoff (a large source of surface water increase). The runoff volume was derived from a rainfall–runoff model and it is reasonable to expect a 10–20% uncertainty around the estimated runoff volume (+/– 90,000 ML).
Groundwater store
Groundwater assets
The aquifers in the Canberra region are described in the Groundwater section of the 'Contextual information'. Given the majority of groundwater within the region is stored in fractured rock aquifers that are difficult to measure and monitor, the volume of water stored in the aquifers cannot be quantified, as indicated by dashes ('–') in the water accounting statements.
Groundwater liabilities
Groundwater liabilities in the Canberra region refer to the volume of groundwater allocation remaining on licence entitlements for individual users (0 ML). There are no groundwater licence entitlements for the urban water system.
The water supply licences for the region have a water management year that ends on 30 June. The unused component of the annual allocation for these licence entitlements is forfeited at the end of the year; therefore, the allocation remaining is zero (Table 4).
Groundwater inflows and outflows
A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Canberra region is provided in Figure 10.
Figure 10 Water inflows and outflows for the groundwater store within the Canberra region during the 2013–14 year
The only inflow to the groundwater store in the Canberra region that can be quantified is the leakage from the urban water system (2,081 ML). The only outflows from the groundwater store that can be quantified are the groundwater extractions (see Groundwater extractions below).
Natural groundwater movement across the region boundary as well as surface water-groundwater interactions are considered to occur within the region; however, these flows could not be quantified, as indicated by dashes ('–') in Figure 10.
Groundwater extractions
Entitled extraction of non-allocated groundwater to users was 459 ML during the 2013–14 year; groundwater extractions for other statutory rights was 435 ML. Statutory rights in the Canberra region refer to stock and domestic basic rights.
Entitled extraction of allocated groundwater to individual users (– ML) could not be quantified due to a lack of available data.
Groundwater forfeitures
The portion of groundwater allocation that has not been abstracted at the end of the water year is either forfeited or is carry-over into the next water year. According to the Water Sharing Plan for the Murrumbidgee Unregulated and Alluvial Water Sources, carry-over of unused groundwater allocation is allowed for licence holders; however, due to limited data availability the carry-over volume could not be quantified. Therefore, for the purposes of the 2014 Account, it is assumed the entire unused portion of the allocation is forfeited.
Water forfeitures in the Canberra region during the 2013–14 year relate to licence entitlements for individual users (851 ML).
Groundwater allocation announcements
Groundwater allocation announcements in the Canberra region during the 2013–14 year refer to groundwater supply to individual users (851 ML). There are no groundwater allocations for the urban water system.
The groundwater allocation for individual users is based on information available in the Water Sharing Plan for the Murrumbidgee Unregulated and Alluvial Water Sources. Entitlements referred to as share component under NSW legislation are specified on water licenses as unit share and the allocation announcement is based on share component.
A more detailed description of groundwater allocations and associated water rights in the Canberra region is given in the Groundwater rights note.
Groundwater balancing item
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. Given the volume of water in the aquifers and the natural groundwater movement in the region cannot be quantified, the balancing item is simply the difference between the leakage from the urban water system (2,081 ML) and the total volume of groundwater extraction (894 ML), as shown in Table 5.
| Account: groundwater store | Volume (ML) |
| Opening balance at 1 July 2013 | – |
| Total groundwater inflows | 2,081 |
| Total groundwater outflows | (894) |
| Closing balance at 30 June 2014 | – |
| Balancing item | 1,187 |
Urban water system
Urban water assets
The Canberra region’s urban water system comprises three subcomponents:
- urban water supply system (898 ML)
- wastewater system (– ML)
- recycled water system (2 ML).
The volume of water in the urban water supply system and recycled water system change little from year to year and comprises water in the distribution pipe network and service reservoirs.
Canberra region's urban water supply system is operated by:
- ACTEW Water
- Queanbeyan City Council (QCC)
Within ACTEW's water supply system there are 47 service reservoirs and approximately 3,140 km of pipes. QCC's water supply system is much smaller than ACTEW's; it contains 13 service reservoirs and approximately 283 km of pipes.
The recycled water system consists of approximately 18 km of pipes and two tanks: the Lower Russell tank and the Lower Molonglo Water Quality Control Centre nonpotable water tank. The volume of water within the wastewater system could not be quantified due to a lack of available data; however, given that this system is much smaller than the urban water supply system, the volume of water within this system is likely to be relatively small.
Urban water claims
The urban claim on surface water (0 ML) is equivalent to the volume of surface water allocation remaining for urban water supply licence entitlements at the end of the 2013–14 year. The allocation remaining for these licence entitlements is provided in Table 6. There are no groundwater licence entitlements for the urban water system.
| Account: urban claim on surface water | Volume (ML) |
| Opening balance at 1 July 2013 | 0 |
| Increase of urban claim on surface water | 71,000 |
| Entitled extraction of allocated surface water to urban water system | (48,695) |
| Adjustment and forfeiture of urban claim on surface water | (22,305) |
| Closing balance at 30 June 2014 | 0 |
Urban water system inflows and outflows
A schematic diagram representing all the inflows and outflows associated with the urban water system in the Canberra region is provided in Figure 11.
Figure 11 Water inflows and outflows for the urban water system within the Canberra region during the 2013–14 year
Urban water supply system inflows
The only source of water for the Canberra region's urban water supply system is surface water, which is comprised of:
- allocated surface water (48,695 ML)
- non-allocated surface water (37 ML).
The total volume of surface water diverted to the urban water system during the 2013–14 year (48,732 ML) is a slight increase from the previous year (47,904 ML).
The volume of allocated surface water diverted from each storage to the urban water system during the 2013–14 year is given in Figure 8.
Wastewater system inflows
Total wastewater collected during the 2013–14 year was 36,682 ML, a marginal increase from the previous year. The volume of wastewater treated at each treatment plant is given in Figure 12.
Figure 12 Wastewater treated and outflow from each wastewater treatment plant (source data)
It should be noted that a portion of the wastewater collected at the Fyshwick treatment plant (541 ML) is transferred to Lower Mologolo for treatment. Consequently, the volume of inflow to Lower Mologolo (32,055 ML) comprises wastewater collected from users (31,514 ML) and wastewater that's internally transferred from Fyshwick (541 ML).
Urban water supply system outflows
The largest water outflow from the Canberra region's urban water system is the delivery of water to consumers. During the 2013–14 year, the total delivery of water to consumers was 45,690 ML, of which 45,489 ML came from the urban water supply system (Figure 11). The remaining 201 ML came from the recycled water system (see Wastewater and recycled water system outflows).
A small portion of water is discharged from the urban water supply system to surface water storages (37 ML). This discharge refers to treated water from Mount Stromlo Water Treatment Plant transferred into Googong Reservoir via the ACTEW Water water reticulation network.
Losses from the system include urban water system leakage to groundwater (2,081 ML), which was approximately 25% less than the previous year. Other losses from the system (1,462 ML) include operational losses and all other non-revenue water from the urban water supply system, such as consumer meter inaccuracies and unauthorised consumption.
Wastewater and recycled water system outflows
A major water outflow from the Canberra region's urban water system is the discharge from the urban water system (32,588 ML). The majority of this discharge is from the wastewater system where treated wastewater is discharged into the rivers (32,551 ML). The remaining 37 ML came from the urban water supply system (see Urban water supply system outflows).
A portion of wastewater is further treated in the recycled water system (4,568 ML). The majority of the recycled water is recirculated within the wastewater system (4,367 ML); the remainder is supplied to users (201 ML), which includes onsite use (101 ML) and delivery for urban consumption (100 ML). Less than 1% of the total wastewater inflow to the system is recyled and delivered to users.
Evaporation from the wastewater system during the 2013–14 year (3,930 ML) is relatively unchanged from the previous year.
Total wastewater outflows from the Canberra region's wastewater and recycled water system is given in Figure 13. Outflows from each treatment plant are given in Figure 12.
Figure 13 Wastewater outflows from Canberra's wastewater and recycled water systems during the 2013–14 year
Decrease of urban water claims
The portion of the urban water claim that has not been abstracted at the end of the water year is forfeited, that is, there is no carry-over of entitlements into the next water year. The adjustment and forfeiture of the urban claim on surface water in the Canberra region during the 2013–14 year was 22,305 ML.
Increase of urban water claims
Increase of water claims for the urban water system refers to allocation announcements for water abstraction made during the year. The increase of urban claim on surface water in the Canberra region during the 2013–14 year was 71,000 ML.
Urban water system balancing item
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 (Table 8). 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.
| Account: urban water system | Volume (ML) |
| Opening balance at 1 July 2013 | 955 |
| Total urban water system inflows | 85,414 |
| Total urban water system outflows | (85,751) |
| Closing balance at 30 June 2014 | 900 |
| Balancing item | (282) |
The calculation of the water balance on the urban water system yielded a balancing item is –282 ML. This is more than 30% of the total urban water system store volume at the end of the 2013–14 year and less than 0.5% of of the total urban water system inflows during the year.
Unaccounted-for difference
The volume recognised in the water accounting statements (65,211 ML) represents the total unaccounted-for difference for the Canberra region for the 2013–14 year.
The unaccounted-for difference is the volume necessary to reconcile the opening water storage and closing water storage with the total water inflows and total water outflows reported in the water accounting statements (Table 9).
| Account: water storage | Volume (ML) |
| Opening balance at 1 July 2013 | 216,876 |
| Total water inflows | 647,253 |
| Total water outflows | (539,828) |
| Closing balance at 30 June 2014 | 259,090 |
| Unaccounted-for difference | 65,211 |
The unaccounted–for difference can also be calculated by summing the volumes necessary to reconcile (balance) the opening and closing storage with the water inflows and outflows of each of the separate water stores of the region, as shown in Table 10.
| Balancing item | Volume (ML) |
| surface water store | 64,306 |
| groundwater store | 1,187 |
| urban water system | (282) |
| Unaccounted-for difference | 65,211 |
Table 10 shows that the unaccounted-for difference volume is primarily explained by the balancing item of the surface water store. The surface water balancing item is largely attributed to uncertainty associated with runoff to surface water (see Surface water note).
Off-channel storages
Off-channel storages refer to farm dams or other landscape catchment storages used to harvest runoff, floodwater or collected rainwater. 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 General description in 'Contextual information').
This note provides additional information about water that has been harvested from the landscape into off-channel water storages and, therefore, did not contribute to groundwater recharge or runoff into surface water.
Off-channel water store
The volume of water held in off-channel water storages decreased marginally by approximately 2% from 7,389 ML to 7,229 ML during the 2013–14 year.
Off-channel water inflows and outflows
A schematic diagram representing all the inflows and outflows associated with the off-channel water store in the Canberra region is provided in Figure 14.
Figure 14 Water inflows and outflows for the off-channel water store within the Canberra region during the 2013–14 year
The volumes presented in Figure 14 only relate to off-channel water storages that are filled primarily by rainfall-runoff capture. Off-channel water storages in the region that are filled by groundwater extractions, surface water diversions or recycled water transfers are not included here as these inflows cannot be quantified due to a lack of available data; however, these volumes are considered to be relatively small as these types of off-channel water storages make up only a small portion of the total number of off-channel storages in the Canberra region.
The total volume of runoff harvested by off-channel storages during the 2013–14 year was 5,617 ML. Given the total runoff into surface water during the year was 391,658 ML (see Surface water note), it can be assumed that runoff harvesting reduced streamflow in the Canberra region by less than 2%.
Balancing item
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 (Table 11).
| Account: off-channel water store | Volume (ML) |
| Opening balance at 1 July 2013 | 7,389 |
| Total off-channel water inflows | 10,131 |
| Total off-channel water outflows | (10,282) |
| Closing balance at 30 June 2014 | (7,229) |
| Balancing item | 9 |
The calculation of the water balance on the off-channel water storages yielded a balance of 9 ML. This is about 0.1% of the total off-channel water storage volume at the end of the 2013–14 year.