National Water Account 2015

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Region overview

Contextual information

Physical information

Administration

Water rights

Climate and water overview

Water Accounting Statements

Water Assets and Water Liabilities

Changes in Water Assets and Water Liabilities

Water Flows

Notes

Accounting policies

Supporting information

Quantification approach

Reconciliations

Water resources & systems

Water access & use

Future outlook

References

Accountability statement

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 2014–15 year. The water stores and systems included in the region are shown in Figure N1.

For a more detailed description of the region, please refer to the General description section of the 'Contextual information'.

Figure N1 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 N2.

Figure N2 Between-store flows that occur within the Canberra region

The between-store flows and transfers (Figure N2), 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 items associated with each between-store abstraction (red arrows in Figure N2) are also shown in italics in the following notes.

Surface water store

The Canberra region's surface water store has four components:

• storages
• regulated rivers
• unregulated rivers
• lakes and wetlands.

A reconciliation of the surface water Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N2. Further details on assets, liabilities, and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical assets

Physical asset volumes, including water held in reservoirs, and lakes and wetlands, at 30 June 2015 were:

• storages—225,896 ML
• lakes and wetlands—39,223 ML (for three of the region's primary lakes).

The volume of water in regulated and unregulated rivers, and some lakes and wetlands, could not be quantified due to a lack of data and a suitable quantification approach.

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 2014–15 year is shown in Figure N3.

Figure N3 Percentage-full volume on 30 June 2015 for each storage

The overall storage volume within the Canberra region increased during the 2014–15 year from 78% to 80% capacity. This was mainly due to the increase of storage in Cotter reservoir from 45,170 ML to 67,069 ML during the year. Total volume of water within each storage at 30 June 2015 compared with the previous year and the 5-year mean is given in Figure N4.

Figure N4 Total volume of water in each storage at 30 June 2015 compared with the previous year and the 5-year mean 

At the end of the 2014–15 year, Googong Reservoir was 100% full, which is similar to the previous 4 years.

During the 2012–13 year, completion of the Cotter Dam enlargement increased the reservoir's capacity (from 3,856 ML to 79,374 ML), thereby improving water supply security and reducing the likelihood of water restrictions in the region. As Cotter Reservoir continued to fill during the 2014–15 year, its water storage increased from 57% to 84% of capacity.

In 2014–15, water volume in the Bendora Reservoir increased marginally while water volume in Corin Reservoir decreased from 61% to 38% of capacity because most water for urban consumption was taken from these two reservoirs. The overall increase in storage during the 2014–15 year can be attributed to the slightly above average rainfall experienced across the region (see Climate and water overview).

Lakes and wetlands

There are three lakes within the Canberra region: Lake Burley Griffin, 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 2014–15 year is shown in Figure N5.

Figure N5 Percentage-full volume on 30 June 2015 for each major lake

All three lakes were either at, or very near, 100% capacity on 30 June 2015. The total volume of water within each lake at 30 June 2015 compared with the previous year and the 5-year mean is given in Figure N6.

Figure N6 Total volume of water in each lake at 30 June 2015 compared with the previous year and the 5-year mean

Non-physical assets

There are no non-physical surface water assets in the region.

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 2014–15 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 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. The unused water volume is not allowed to carryover in the ACT portion of the region. According to the Water Sharing Plan for the Murrumbidgee Unregulated and Alluvial Water Sources, carryover of unused surface water allocation is allowed for licence holders for NSW portion of the region; however, due to limited data availability the carryover volume could not be quantified. Therefore, for the purposes of the 2015 Account, it is assumed the entire unused portion of the allocation is forfeited and the allocation remaining is zero (Tables N3 and N4).

Further information on all entitlements and allocation arrangements are detailed in the Surface water rights note.

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 N7.

Figure N7 Water inflows and outflows for Canberra's surface water store during the 2014–15 year

Surface water inflows

Total inflows to surface water were 815,068 ML and comprised the following:

• Precipitation—13,984 ML
• Runoff—407,874 ML
• Inter-region inflow—360,255 ML
• Discharge: wastewater system—32,955 ML
• Discharge: urban supply system—0 ML.

The largest natural water inflow is runoff to surface water (407,874 ML). The volume of runoff during the 2014–15 year was more than that during the previous year, which primarily reflects the increase in flow conditions in the rivers compared to the flows experienced during the 2013–14 year (see Climate and water overview). It should also be noted that a portion of the runoff into surface water is reduced due to runoff harvesting by farm dams in the region (see Farm dams).

Precipitation represents rainfall that fell on the major storages and lakes within the region. Inter-region inflow represents flows entering the Canberra region from the upstream reaches of the Murrumbidgee River. Discharge from urban supply system refers to the water transfer from Bendora and Cotter reservoirs and Murrumbidgee River to Googong reservoir to take advantage of storage capacity. Discharge from the wastewater system is the sum of treated wastewater outflows to rivers from treatment plants at Lower Molonglo Water Quality Control Centre (29,650 ML), Queanbeyan sewage treatment plant (3,293 ML) and Uriarra sewage treatment plant (12 ML).

Groundwater discharge (– ML) was not recognised due to a lack of available data and a suitable quantification approach.

Surface water outflows

Total outflows from surface water were 695,899 ML and comprised the following:

• Evaporation—30,679 ML
• Outflow—616,452 ML
• Allocated diversion: urban system—47,115 ML
• Non-allocated diversion: individual users—1,653 ML
• Non-allocated diversion: urban system—0 ML.

The largest natural water outflow is the river outflow from the region (616,452 ML), which refers to the annual volume of flow to outside the region boundary via the Murrumbidgee River during the 2014–15 year. This outflow was 32% higher than that during the previous year, which primarily reflects the increase in flow conditions in the river compared to the flows experienced during the 2013–14 year (see Climate and water overview).

Evaporation from surface water during the 2014–15 year was 30,679 ML, which represents evaporation from the major storages and lakes within the region. Total evaporation during the 2014–15 year was 66% higher than that during the previous year (see Climate and water overview).

Allocated diversion to urban system remains relatively unchanged and non-allocated diversion to individual users increased by 43% compared with the previous year. Non-allocated diversion to urban system refers to water transfer from Bendora and Cotter reservoirs and Murrumbidgee River to Googong reservoir.

Recharge: groundwater (– ML) and recharge to landscape (– ML) were not recognised due to a lack of available data and a suitable quantification approach.

Allocated diversions

Most of the allocated diversion in the Canberra region is for urban water system. Allocated diversion to the urban water system was 47,115 ML during the 2014–15 year, approximately 66% of the total allocation to the urban system (71,000 ML), which accounts for more than 97% of the total allocation in the Canberra region. The total allocation is not split up and defined for individual storages. Surface water diverted from the Bendora Reservoir was approximately 85% of total water diversion to urban water system. Cotter and Googong reservoirs contributed the remaining 15% of diversion. This water was diverted to the Mount Stromlo and Queanbeyan water treatment plants for the urban water supply system.

Water allocation to individual users in the Canberra region was 1,832 ML, less than 3% of total water allocation in the region. Allocated diversion to individual users could not be quantified due to a lack of available data.

Water diversions in the Canberra region are shown in Figure N8. The volume shown against reservoirs represents the water diverted to the region's urban water supply system.

 
Figure N8 Surface water allocations and diversions to the urban water system during the 2014–15 year

Non-allocated diversions

Non-allocated diversions are the diversions of unregulated flows under multi-use licences for nonpotable water within the Canberra region. Non-allocated diversions in the region was 1,653 ML during the 2014–15 year.

Diversions: statutory rights

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 balancing item

The surface water balance (Table N5) yielded a balance of 112,240 ML. This is approximately 14% of the total surface water inflows and 16% of the total surface water outflows during the 2014–15 year. The balancing item indicates that either the inflows are too high or the outflows are too low.

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 an uncertainty around the estimated runoff volume.

Groundwater store

The Canberra region's groundwater store has two components:

• water table aquifer
• underlying aquifer.

A reconciliation of the groundwater Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N6. Further details on assets, liabilities, and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical 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.

Non-physical assets

There are no non-physical groundwater assets in the region.

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 portion of groundwater 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, carryover of unused groundwater allocation is allowed for licence holders; however, due to limited data availability the carryover volume could not be quantified. Therefore, for the purposes of the 2015 Account, it is assumed the entire unused portion of the allocation is forfeited and the allocation remaining is zero (Table N7).

Further information on all entitlements and allocation arrangements are detailed in the Groundwater rights note.

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 N9.

Figure N9 Water inflows and outflows for Canberra's groundwater store during the 2014–15 year

The only inflow to the groundwater store in the Canberra region that can be quantified is the leakage from the urban water system (2,920 ML). The only outflows from the groundwater store that can be quantified are the groundwater extractions.

Natural groundwater movement across the region boundary, recharge from/discharge to landscape, and surface water-groundwater interactions are considered to occur within the region; however, these flows could not be quantified, as indicated by dashes ('–') in Figure N9.

 Allocated extractions

Allocated groundwater extractions to individual users (– ML) could not be quantified due to a lack of available data.

Non-allocated extractions

Non-allocated extraction of groundwater to individual users was 626 ML during the 2014–15 year.

Extractions: statutory rights

Groundwater extractions for other statutory rights was 435 ML. Statutory rights in the Canberra region refer to stock and domestic basic rights.

Groundwater balancing item

The groundwater balance (Table N8) yielded a balance of 1,859 ML. Given that the volume of water in 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 (2,920 ML) and the total volume of groundwater extraction (1,061 ML), as shown in Table N8.

Urban water system

The Canberra region's urban water system has three core components:

• water supply: raw water transfers, water treatment and potable water supply
• wastewater: collections, transfers and treatment
• recycled water supply.

A reconciliation of the urban water Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N9. Further details on assets, liabilities, and flows are provided in the following sections. 

Methods used to derive reported volumes can be found in the Quantification approach note. 

Assets and liabilities

Physical assets

Physical asset volumes, including water held in pipes, service reservoirs, storage tanks, and lagoons, at 30 June 2015 were:

• Water supply—964 ML
• Recycled water system—2 ML.

Canberra region's urban water supply system is operated by:

• Icon Water
• Queanbeyan City Council (QCC).

Within Icon Water'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 Icon Water's; it contains 13 service reservoirs and approximately 290 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 water supply system, the volume of water within this system is likely to be relatively small.

The volume of water in the water supply system and recycled water system changes little from year to year.

Non-physical assets

Non-physical assets represent the urban claim on surface water (0 ML), which is the volume of surface water allocation remaining for urban water supply licence entitlements at the end of the 2014–15 year. Details are provided in Table N10. There are no groundwater licence entitlements for the urban water system.

Increase in claims for the urban water system refers to allocation announcements for water abstraction made during the year. 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 carryover of entitlements into the next water year. 

Further information on all entitlements and allocation arrangements are detailed in the Surface water rights note.

Liabilities

There are no urban water liabilities in the Canberra region. 

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 N10.

Figure N10 Water inflows and outflows for the urban water system within the Canberra region during the 2014–15 year

A detailed breakdown of the inflows and outflows of the urban water system components are provided in the urban water balance diagram.

Water supply inflows

The only source of water for the Canberra region's urban water supply system is surface water. Inflows to the water supply system were relatively unchanged during 2014–15 compared with the previous year. Total inflows were 47,115 ML and were sourced from allocated surface water diversions.

The volume of allocated surface water diverted from each storage to the urban water system during the 2014–15 year is given in Figure N8.

Further information on supply system inflows is available in the Supply inflows table.

Wastewater and recycled water inflows

Total wastewater collected during the 2014–15 year was 37,285 ML, similar to the previous year volume of 36,682 ML. The volume of treated wastewater produced at each treatment plant is given in Figure N11. 

Figure N11 Wastewater treated and outflow from each wastewater treatment plant

Further to Figure N11, it should be noted that the total wastewater collected at Fyshwick Sewage Treatment Plant was 1,485 ML, and that 763 ML of treated effluent was transferred from Fyshwick wastewater treatment plant to Lower Molonglo for further treatment. A further 22ML of wastewater was transferred to Lower Molonglo from Googong township by Queanbeyan City Council. Consequently, the volume of inflow to Lower Molonglo (32,955 ML) was comprised of wastewater collected from users (32,170 ML) and wastewater that was internally transferred from Fyshwick wastewater treatment plant and Queanbeyan City Council (785 ML). 

Further information on wastewater and recycled water system inflows is available in the Wastewater flows table.

Water supply outflows

Total outflows from the water supply system were 47,019 ML and comprised the following:

• Supply system delivery: urban users—42,694 ML
• Leakage: groundwater—2,920 ML
• Other supply system decreases—1,405 ML.

A comparison of water supply outflows to the previous year is provided in Figure N12. A small decrease in consumption of potable water was evident. The majority of water supplied was for residential purposes.

Figure N12 Outflows from the water supply system

No water was discharged from the urban water supply system to surface water storages during the year, compared with the previous year's discharge of 37 ML. This discharge refers to treated water from Mount Stromlo Water Treatment Plant transferred into Googong Reservoir via the Icon Water water reticulation network.

Further information on supply system outflows is available in the Supply outflows table.

Wastewater and recycled water outflows

 Total outflows from the wastewater and recycled water systems were 37,286 ML and comprised the following:

• Recycled water delivery: urban users—128 ML
• Wastewater discharge: surface water—32,955 ML
• Evaporation—4,203 ML.

A comparison of wastewater and recycled water outflows to the previous year is provided in Figure N13. Outflows from each treatment plant are given in Figure N11.

Figure N13 Outflows from Canberra's wastewater and recycled water systems during the 2014–15 year

The majority (88%) of treated wastewater was disposed to surface water. The balance of the outflows from the wastewater system were recycled water delivery to urban users and evaporative losses during wastewater treatment processes.

Recirculation of treated wastewater and recycled water occurs in the system which may be subjected to additional treatment and/or re-use on site. The reported urban system outflows exclude any such recirculated volumes in the system.

Further information on wastewater and recycled water system outflows is available in the Wastewater flows table.

Urban water balancing item

The urban water balance (Table N11) yielded a balance item of 29 ML. This is less than 1% of the total urban water inflows during the year 2014–15 year. The misbalance can mainly be attributed to unaccounted volumes in the water supply system. The misbalance may be due to a number of factors, such as metering inaccuracies, unaccounted losses, and inaccuracies in the estimation of certain volumes.

Unaccounted-for difference

The volume recognised in the water accounting statements (274,079 ML) represents the total unaccounted-for difference for the Canberra region for the 2014–15 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. It is calculated according to Table N12.

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 N13.

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).