Sydney
Water resources and systems

The following set of notes provides consolidated reports for each of the water stores and systems within the Sydney region during the 2011–12 year. The water stores and systems included in the region are shown in Figure 1.

For more information about the region, please refer to the General description section of the Contextual information.


Figure 1  Schematic diagram of the water stores and systems within the Sydney 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.

The numbers on the diagram refer to the line item numbers in the water store notes. For each between store flow, there are two line item numbers– one refers to flow out of a water store and the other refers to flow into a water store.

Figure 2  Schematic diagram of between store flows that occur within the Sydney region- line item numbers are provided next to the flows

Surface water is the main water source in the Sydney region. Surface water resources within the region have been developed to meet the water needs of Sydney. Storage capacity in the Sydney region is one of the largest in the world per head of population (source: NSW Office of Water 2010a). Further information on the urban supply storages, including current levels and volumes, is given on the Bureau's water storage website. 

Further details about these storages, including location, capacity and their management is available in the Surface water section of Contextual information.

 

The Statement of Water Assets and Water Liabilities shows that the total surface water store increased during the 2011–12 year in the Sydney region.

 

Table 1  Statement of Water Assets and Water Liabilities for the surface water store

Water assets	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)
1 Surface water
1.1 Storages	2,776,537	2,239,105
1.2 Unregulated river	3,985	2,205
1.3 Regulated river	–	–
1.4 Lakes and wetlands	–	–
1.5 Inter-region claim on water	2,723	371
Total surface water assets	2,783,245	2,241,681
Water liabilities
5 Surface water liability
5.1 Surface water allocation remaining	0	0
5.2 Surface water allocation remaining - urban water system	0	0
5.6 Other surface water liability	0	5,363
Total surface water liabilities	0	5,363
Opening net water assets	2,236,318	1,699,854
Change in net water assets	546,927	536,464
Closing net water assets	2,783,245	2,236,318

The volume reported for storages includes dead storage. The volume of water in rivers and lakes and wetlands is not quantified due to a lack of available data, however, the volume of water held in the channels and lakes is considered relatively small in comparison to the volume held in storages.

The location of each major storage within the Sydney region and the volume of water in each storage (including dead storage) are shown as a percentage of total storage capacity at the end of the 2011–12 year (Figure 3). 

Figure 3  Location map of storages in the Sydney region and their volume (%) as at 30 June 2012

The water volume in almost all the storages within the Sydney region at the end of the 2011–12 year was more than at the start, on 1 July 2011. (see line item 1.1 Storages). Several of the storages were at full or close to full capacity at the end of the reporting period.

The Sydney region experienced average to above average rainfall in the area during the 2011–12 year. Inflow into the storages during this period was approximately 3,831,161 ML (see 9.4 Runoff to surface water ). This was more than the 2010–11 year inflow volume of approximately 1,972,808 ML. 

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the surface water store are provided in Table 2 and Table 3, respectively.

Table 2  Statement of Changes in Water Assets and Water Liabilities for the surface water store

Water asset increases	2011–12 volume (ML)	2010–11 volume (ML)
9 Surface water increases
9.1 Precipitation on surface water	164,426	112,395
9.4 Runoff to surface water	8,252,376	4,173,310
9.9 Discharge from urban water system	92,868	64,591
9.10 Direct discharge by user	4,693	4,885
9.15 Increase of inter-region surface water claim on water	13,612	13,612
Total surface water increases	8,527,975	4,368,793
Water liability decreases
13 Surface water liability decreases
13.1 Adjustment and forfeiture of surface water allocation	125,455	118,465
13.2 Adjustment and forfeiture of surface water allocation–urban water system	597,366	599,518
13.6 Other surface water liability decreases	5,363	0
Total surface water liability decreases	728,184	717,983
Water asset decreases
17  Surface water decreases
17.1 Evaporation from surface water	120,977	114,894
17.2 River outflow from the region	7,132,288	3,039,529
17.6 Surface water diversions–other statutory rights	32,529	32,555
17.17 Decrease of inter-region surface water claim on water	7,077	7,834
Total surface water decreases	7,292,871	3,194,812
Water liability increases
21 Surface water liability increases
21.1 Surface water allocation announcements	157,620	157,802
21.2 Surface water allocation announcements–urban system	1,038,355	1,043,455
21.6 Other surface water liability increases	0	3,100
Total surface water liability increases	1,195,975	1,204,357
Balancing item–surface water	220,386	151,143
Change in net water assets	546,927	536,464

Table 3  Statement of Water Flows for the surface water store

Water inflows	2011–12 volume (ML)	2010–11 volume (ML)
9 Surface water inflows
9.1 Precipitation on surface water	164,426	112,395
9.4 Runoff to surface water	8,252,376	4,173,310
9.9 Discharge from urban water system	92,868	64,591
9.10 Direct discharge by user	4,693	4,885
9.11 Delivery of water under inter-region agreement to surface water	4,183	5,407
Total surface water inflows	8,518,546	4,360,588
Water outflows
17 Surface water outflows
17.1 Evaporation from surface water	120,977	114,894
17.2 River outflow from the region	7,132,288	3,039,529
17.6 Surface water diversions–other statutory rights	32,529	32,555
17.11 Entitled diversion of allocated surface water to users	32,165	39,337
17.12 Entitled diversion of allocated surface water to urban water system	440,989	443,937
17.16 Other delivery of allocated surface water	0	7,532
Total surface water outflows	7,758,948	3,677,784
Balancing item–surface water	220,386	151,143
Opening water storage	2,241,310	1,709,649
add/(less): Change in water storage	539,212	531,661
Closing water storage	2,780,522	2,241,310

A schematic diagram representing all the inflows and outflows associated with the surface water store in the Sydney region is provided in Figure 4. The inflow and outflow volumes for the surface water store during the 2011–12 year are given in Table 3.

Figure 4  Schematic diagram of water inflows and outflows for the surface water store within the Sydney region during the 2011–12 year; line item numbers are provided next to the flows

Most of the diversions from surface water are diversions to the urban water system (17.12 Surface water allocation diversion–urban water system), which accounts for approximately 92% of the total allocation diversion.

Figure 5 shows diversions from storages during 2011–12 for urban supply and private use was very similar to the diversions made in 2010–11. The Sydney Catchment Authority did not make any releases from banked environmental flow (line item 17.16) under the direction of NSW State Water. The bank of environmental water was deleted at the end of the 2011–12 year as a result of spills from storages.

Figure 5  Graph of allocation diversions from storages within the Sydney region during the 2011–12 year compared to 2010–11; line item numbers are given in brackets

The allocation diversions (line item 17.6, 17.11 and 17.12) are all associated with a water access entitlement or water right. When an allocation is announced, a present obligation (water liability) is created on the surface water to deliver water to the users. As there is no carry-over provision in the region, the portion of the announced allocations that was not diverted by the end of the year was forfeited.

The entitlement, allocation announcement and forfeiture for each of these water rights during the 2011–12 year are provided in Table 2 and the Water rights, entitlements, allocations and restrictions note in the Surface water rights table.

This 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 4.

Table 4  Balancing item for the surface water store for the 2011–12 year

Calculation	Account	Volume (ML)
	Opening balance (30 June 2011)	2,241,310
add	Total surface water inflow (see Table 3)	8,518,546
less	Total surface water outflow (see Table 3)	7,758,948
less	Closing balance (30 June 2012)	2,780,522
	Balancing item – surface water store	220,386

The calculation of the water balance on the surface water store yielded a balancing item of 220,386 ML. This is approximately 7.5% of the total surface water store at the end of the 2011–12 year.

It is likely that errors in the balancing item are primarily attributed to errors associated with the rainfall runoff (a large source of surface water increase in line item 9.4) and outflow to outside region (a large source of surface water decrease, line item 17.2). The rainfall runoff volume is derived from a rainfall-runoff model and it is reasonable to expect a 10–20% uncertainty (approximately 1,500,00 ML–3,000,000 ML) around the estimated runoff volume. The surface water outflow to sea is based on measured flow data collected at the most downstream station along a river. There is no adjustment made for the contributing area below the gauging station. As such, outflow to sea is likely to be underestimated by 10–20%.

A description of the Sydney region's groundwater resources are provided in the Contextual information.

Whilst there is information that exists for the groundwater rights and entitlements for the region, there is no quantifiable value available for the groundwater asset or the extraction of water from the groundwater asset. More information is available in the supporting information of line item 2.1.

The Statement of Water Assets and Water Liabilities for the groundwater store is shown in Table 5.

Table 5  Statement of Water Assets and Water Liabilities for the groundwater store

Water assets	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)
2 Groundwater
2.1 Water table aquifer	-	-
Total groundwater assets	-	-
Water liabilities
6 Groundwater liability
6.1 Groundwater allocation remaining	0	0
6.2 Groundwater allocation remaining–urban water system	0	0
Total groundwater liabilities	0	0
Opening net water assets	0	0
Change in net water assets	0	0
Closing net water assets	0	0

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the groundwater store are provided in Tables 6 and 7, respectively.

Table 6  Statement of Changes in Water Assets and Water Liabilities for the groundwater store

Water asset increases	2011–12 volume (ML)	2010–11 volume (ML)
10 Groundwater increases
10.1 Groundwater inflow from outside region	-	-
10.2 Groundwater inflow from outside region at coast	–	–
10.3 Recharge from landscape	–	–
Total groundwater increases	–	–
Water liability decreases
14 Groundwater liability decreases
14.1 Adjustment and forfeiture of groundwater allocation	62,204	–
14.2 Adjustment and forfeiture of groundwater allocation–urban water system	140	–
Total groundwater liability decreases	62,344	–
Water asset decreases
18 Groundwater decreases
18.1 Groundwater outflow to outside region	–	–
18.2 Groundwater outflow to outside region at coast	–	–
18.3 Discharge to landscape	–	–
18.7 Groundwater extractions - other statutory rights	19,652	–
Total groundwater decreases	19,652	–
Water liability increases
22 Groundwater liability increases
22.1 Groundwater allocation announcements	62,204	–
22.2 Groundwater allocation announcements - urban system	140	–
Total groundwater liability increases	62,344	–
Balancing item–groundwater	(19,652)	0
Change in net water assets	0	0

Table 7  Statement of Water Flows for the groundwater store

Water inflows	2011–12 volume (ML)	2010–11 volume (ML)
10 Groundwater inflows
10.1 Groundwater inflow from outside region	–	–
10.2 Groundwater inflow from outside region at coast	–	–
10.3 Recharge from landscape	–	–
Total groundwater inflows	–	–
Water outflows
18 Groundwater outflows
18.1 Groundwater outflow to outside region	–	–
18.2 Groundwater outflow to outside region at coast	–	–
18.3 Discharge to landscape	–	–
18.7 Groundwater extractions - other statutory rights	19,652	–
Total groundwater outflows	19,652	0
Balancing item–groundwater	(19,652)	0
Opening water storage	0	0
add/(less): Change in water storage	0	0
Closing water storage	0	0

A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Sydney region is provided in Figure 6. The inflow and outflow volumes for the groundwater store during the 2011–12 year are given in Table 7. The numbers on the diagram refer to the line item numbers in Table 7.

Figure 6  Schematic diagram of water inflows and outflows for the groundwater store within the Sydney region during the 2011–12 year; line item numbers are provided in brackets

All changes to the groundwater store reported in the water accounting statements are related to the entitlements and basic rights on the groundwater stores. There was a total of 81,996 ML water rights on the groundwater store of the Sydney region. Approximately 75% of the total water rights are categorised as other lumped entitlement (see line item 22.1 Groundwater allocation announcements) with only 140 ML allocated to the urban water system for local water utilities.

As there is no quantifiable method for groundwater use, the extraction associated with the rights is not recorded in the water accounting statements.

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.

The balancing item is calculated in Table 8.

Table 8. Balancing item for the surface water store for the 2011–12 year

Calculation	Account	Volume (ML)
	Opening balance (30 June 2011)	0
add	Total groundwater inflows (see Table 7)	0
less	Total groundwater outflows (see Table 7)	19,652
less	Closing balance (30 June 2012)	0
	Balancing item–groundwater	(19,652)

The calculation of the water balance on the groundwater store yielded a balance of -19,652 ML. As the total groundwater asset and total groundwater increases cannot be quantified the balancing item is equal to the total groundwater store decreases.

Background information on the urban water system within the Sydney region is available in Surface Water and Organisations responsible for water management sections in Contextual information.

The Statement of Water Assets and Water Liabilities for the urban water system is provided in Table 9. As most of the water in Sydney's urban system is derived from surface water sources, the majority of the water used within the urban water system is stored in the surface water storages listed in line item 1.1 Storages, which forms part of the surface water store. The volume of water water in pipes, tanks and channels could not be quantified; however, this is not considered to present a material error as this volume is relatively small.

Table 9  Statement of Water Assets and Water Liabilities for the urban water system

Water assets	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)
3 Urban water system
3.1 Urban water supply system	–	–
3.2 Wastewater system	–	–
3.3 Recycled water system	–	–
Total urban water system assets	–	–
Opening net water assets	–	–
Change in net water assets	–	–
Closing net water assets	–	–

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the urban water store are provided in Tables 10 and 11, respectively.

Table 10  Statement of Changes in Water Assets and Water Liabilities for the urban water system

Water asset increases	2011–12 volume (ML)	2010–11 volume (ML)
11 Urban water system increases
11.4 Wastewater collected	601,502	513,998
11.6 Delivery of desalinated water to urban water system	61,290	77,102
11.7 Stormwater ingress	1,717	841
11.18 Increase of urban claim on surface water	1,038,355	1,043,455
11.19 Increase of urban claim on groundwater	140	0
Total urban water system increases	1,703,004	1,635,396
Water asset decreases
19 Urban water system decreases
19.2 Leakage to landscape	42,987	39,206
19.4 Delivery to urban water system users	489,557	506,242
19.5 Discharge from urban water system to surface water	92,868	64,591
19.7 Wastewater discharge outside of region	472,073	431,504
19.17 Adjustment and forfeiture of urban claim on surface water	597,366	599,518
19.18 Adjustment and forfeiture of urban claim on groundwater	140	0
19.20 Other urban water decreases	447	4,936
Total urban water system decreases	1,695,438	1,645,997
Balancing item–urban water system	7,566	(10,601)
Change in net water assets	0	0

Table 11  Statement of Water Flows for the urban water system

Water inflows	2011–12 volume (ML)	2010–11 volume (ML)
11 Urban water system inflows
11.4 Wastewater collected	601,502	513,998
11.6 Delivery of desalinated water to urban water system	61,290	77,102
11.7 Stormwater ingress	1,717	841
11.12 Entitled diversion of allocated surface water to urban water system	440,989	443,937
Total urban water system inflows	1,105,498	1,035,878
Water outflows
19 Urban water system outflows
19.2 Leakage to landscape	42,987	39,206
19.4 Delivery to urban water system users	489,557	506,242
19.5 Discharge from urban water system to surface water	92,868	64,591
19.7 Wastewater discharge outside of region	472,073	431,504
19.20 Other urban water decreases	447	4,936
Total urban water system outflows	1,097,932	1,046,479
Balancing item–urban water system	7,566	(10,601)
Opening water storage	0	0
add/(less): Change in water storage	0	0
Closing water storage	0	0

A schematic diagram representing all the inflows and outflows associated with the urban water system in the Sydney region is provided Figure 7. The inflow and outflow volumes for the urban water system during the 2011–12 year are given in Table 11. The numbers on the diagram refer to the line item numbers in Table 11.

Figure 7  Schematic diagram of water inflows and outflows for the urban water system within the Sydney region during the 2011–12 year; line item numbers are provided in brackets.

Urban water supply is mainly sourced from surface water storages (see line item 11.18). The NSW Office of Water issues corporate licences to major water utilities, which entitles them to take and use water from authorised sources subject to a set of conditions. Details of corporate licences and approvals can be found under major utilities on the NSW Office of Water website.

The Sydney Catchment Authority holds a large portion of the urban water entitlements for the Sydney region. Sydney Catchment Authroity's main role within the region is to manage and protect Sydney's drinking water catchments and infrastructure and supply bulk water to its customers. In the Sydney region, these customers include Sydney Water Corporation, Wingecarribee Shire Council and Shoalhaven City Council. Since 2012, Goulburn Mulwaree Council has become a customer of the Sydney Catchment Authority. Each customer filters and treats the water and distributes it within their respective areas.

The Sydney Water Corporation operates the Kurnell Desalination Plant to supply Sydney with up to 30% of its water supply needs if necessary (see line item 11.6 Delivery of desalinated water). For further details of Kurnell Desalination Plant, see Sydney Water Corporation's website.

Additional information on the types of entitlements used to provide the urban water supply system with water can be found in the region notes  Water access and use section.

Figure 8 summarises the volumes received by the urban water supply system from various sources. 

Figure 8  Graph of sources of water for the Sydney region's urban water supply system

 
Figure 8 shows that the majority of urban supply water in the Sydney region is sourced from its vast network of surface water storages with around 14% of water supplied by Kurnell Desalination Plant (line item 11.12 and 11.6).

Wastewater collected in the Sydney region was either treated and discharged to receiving environments either inside or outside the region, or treated and provided to recycled water customers inside the region. A total of 453,978 ML was provided to customers as potable water through Shoalhaven City Council, Sydney Water Corporation and Wingecarribee Shire Council (see line item 19.4).

Figure 9  Graph of wastewater discharged from the urban water system in the Sydney region

Figure 9 shows that the majority of wastewater is discharged to the surface water either in or out of the region. 

There are several factors that may have led to the balancing item in the urban system of the Sydney region. These are:

• uncertainty in estimating leakage both to landscape and to groundwater
• error in measurement equipment or meter accuracy could have affected inflow/outflow volumes.

 

Table 12  Balancing item for the urban water system for the 2011–12 year

Calculation	Account	Volume (ML)
	Opening balance (30 June 2010)	0
add	Total urban system inflows (see Table 11)	1,105,498
less	Total urban system outflows (see Table 11)	1,097,932
less	Closing balance (30 June 2011)	0
	Balancing item	7,566

The calculation of the water balance on the urban water system yielded a balance item of 7,566 ML. This is approximately 0.7% of the total urban water system inflows during the 2011–12 year.