Sydney
Water resources and systems
Introduction
The following set of notes provides consolidated reports for each of the water stores and systems within the Sydney region during the 2012–13 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
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
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 region is one of the largest in the world per head of population (New South Wales 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 assets on 30 June 2013 remained similar to the surface water assets at 30 June 2012 in the Sydney region.
| Water assets | Volume at 30 June 2013 |
Volume at 30 June 2012 |
| 1 Surface water | ||
| 1.1 Storages | 2,813,222 | 2,776,537 |
| 1.2 Unregulated river | 25,162 | 3,985 |
| 1.3 Regulated river | – | – |
| 1.4 Lakes and wetlands | – | – |
| 1.5 Inter-region claim on water | 2,367 | 2,367 |
| Total surface water assets | 2,840,751 | 2,782,889 |
| 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 | 0 |
| Total surface water liabilities | 0 | 0 |
| Opening net water assets | 2,782,889 | 2,236,282 |
| Change in net water assets | 57,862 | 546,607 |
| Closing net water assets | 2,840,751 |
2,782,889 |
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 2012–13 year (Figure 3).
Figure 3 Location map of storages in the Sydney region; the percentage-full volume at 30 June 2013 for each storage is also shown and their volume
At the end of the 2012–13 year, the water volume in almost all the storages remained similar to that observed at 30 June 2012 (see 1.1 Storages). Several of the storages were at full or close to full capacity at the end of the reporting period. The volume reported as water held in rivers increased (see 1.2 Unregulated river) between 2012 (3,985 ML) and 2013 (25,162 ML). At the end of the reporting period the storages were at full, or close to full capacity and rainfall that fell in the June event was available as runoff in the downstream rivers.
Reported runoff and subsequent inflow into storages during this period was around 60% less than the previous year (see 9.4 Runoff to surface water ). The dry period experienced between July and December in the Sydney region resulted in less runoff in the earlier part of the reporting year, particularly in the Colo River. See the Water overview for further details of rainfall events experienced in the Sydney region.
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.
| Water asset increases | 2012–13 volume |
2011–12 volume |
| 9 Surface water increases | ||
| 9.1 Precipitation on surface water | 134,391 | 164,426 |
| 9.4 Runoff to surface water | 4,968,033 | 8,252,376 |
| 9.9 Discharge from urban water system | 68,523 | 92,868 |
| 9.10 Direct discharge by user | 4,860 | 4,693 |
| 9.15 Increase of inter-region surface water claim on water | 11,834 | 11,834 |
| Total surface water increases | 5,187,641 | 8,256,197 |
| Water liability decreases | ||
| 13 Surface water liability decreases | ||
| 13.1 Adjustment and forfeiture of surface water allocation | 122,416 | 254,054 |
| 13.2 Adjustment and forfeiture of surface water allocation–urban water system | 497,873 | 628,646 |
| 13.6 Other surface water liability decreases | 0 | 5,363 |
| Total surface water liability decreases | 620,289 | 888,063 |
| Water asset decreases | ||
| 17 Surface water decreases | ||
| 17.1 Evaporation from surface water | 141,766 | 120,977 |
| 17.2 River outflow from the region | 4,232,133 |
7,132,288 |
| 17.6 Surface water diversions–other statutory rights | 32,529 | 32,529 |
| 17.17 Decrease of inter-region surface water claim on water | 4,955 | 5,636 |
| Total surface water decreases | 4,411,383 |
7,291,430 |
| Water liability increases | ||
| 21 Surface water liability increases | ||
| 21.1 Surface water allocation announcements | 159,462 | 286,219 |
| 21.2 Surface water allocation announcements–urban system | 1,040,588 |
1,069,635 |
| 21.6 Other surface water liability increases | 0 | 0 |
| Total surface water liability increases | 1,200,050 | 1,355,854 |
| Balancing item–surface water |
138,635 | 220,369 |
| Change in net water assets | 57,862 |
546,607 |
| Water inflows | 2012–13 volume |
2011–12 volume |
| 9 Surface water inflows | ||
| 9.1 Precipitation on surface water | 134,391 | 164,426 |
| 9.4 Runoff to surface water | 4,968,033 | 8,252,376 |
| 9.9 Discharge from urban water system | 68,523 | 92,868 |
| 9.10 Direct discharge by user | 4,860 | 4,693 |
| 9.11 Delivery of water under interregion agreement | 6,879 | 4,166 |
| Total water inflows |
5,182,686 | 8,518,529 |
| Water outflows |
||
| 17 Surface water outflows |
||
| 17.1 Evaporation from surface water | 141,766 | 120,977 |
| 17.2 River outflow from the region | 4,232,133 |
7,132,288 |
| 17.6 Surface water diversions–other statutory rights | 32,529 | 32,529 |
| 17.11 Surface water allocation diversion | 37,046 |
32,165 |
| 17.12 Surface water allocation diversion – urban water system | 542,715 |
440,989 |
| 17.16 Other delivery of allocated surface water | 0 | 0 |
| Total water outflows |
4,986,189 |
7,758,948 |
| Balancing item–surface water |
138,635 |
220,369 |
| Opening water storage |
2,780,522 | 2,241,310 |
| Change in water storage |
57,862 |
539,212 |
| Closing water storage |
2,838,384 |
2,780,522 |
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 2012–13 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 2012–13 year; line item numbers are provided next to the flows
Allocations and diversions
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 88% of the total diversions. There is an increase of 101,726 ML of diversions from rivers and storages to the urban water system between 2011–12 and 2012–13. It is likely that this increase is directly attributed to there being no desalinated water delivered to the urban water system during 2012–13, and also a higher level of water use (see 19.4 Delivery to urban water system users) resulting in a higher reliance on the surface water store.
Figure 5 shows that diversions from storages during 2012–13 for urban supply and private use were higher in than the diversions made in 2011–12. The Sydney Catchment Authority did not make any releases from banked environmental flow during the 2012–13 year (line item 17.16 Other delivery of allocated surface water). Banked environmental water was deleted in the 2011–12 year and no further water was available for release due to spills from storages and the implementation of the Water Sharing Plan for the Greater Metropolitan Region Unregulated River Water Sources (New South Wales [NSW]). See Environmental Water in Water Access and Use for further information.
Figure 5 Graph of allocation diversions from storages within the Sydney region during the 2012–13 year compared to 2011–12; line item numbers are given in brackets
The allocation diversions (17.11 Surface water allocation diversion and 17.12 Surface water allocation diversion–urban water system) 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. There are carry-over rules as stated in the Water Sharing Plan for the Greater Metropolitan Region Unregulated River Water Sources; however, carry-over is not able to be quantified in the Sydney region National Water Account and therefore the portion of the announced allocations that are not diverted by the end of the year are forfeited in order to balance the statements.
The entitlement, allocation announcement, and forfeiture for each of these water rights during the 2012–13 year are provided in Table 2 and the Water rights, entitlements, allocations and restrictions note in the 'Surface water rights table'.
Balancing item
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.
Calculation |
Account |
Volume (ML) |
|
Opening balance (30 June 2012) |
2,780,522 |
add |
Total surface water inflow (see Table 3) |
5,182,686 |
less |
Total surface water outflow (see Table 3) |
4,986,189 |
less |
Closing balance (30 June 2013) |
2,838,384 |
|
Balancing item–surface water store |
138,635 |
The calculation of the water balance on the surface water store yielded a balancing item of 138,635 ML. This is approximately 5% of the total surface water store at the end of the 2012–13 year, and 2% of the surface water inflows.
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 seen in 9.4 Rainfall runoff) and outflow to outside region (a large source of surface water decrease seen in 17.2 River outflow from the region). The rainfall runoff volume is derived from a rainfall-runoff model and it is reasonable to expect a 10–20% uncertainty (approximately 1,500,000 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%.
Urban water system
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'. There are several differences with some of the line items between the 2012–13 year and the 2011–12 year. This is because Goulburn Mulwaree Council and Lithgow City Council are now considered to be part of the urban water system and as such the information received from both organisations has improved the amount of data available to be reported to the National Water Account. Several line items have been restructured as a result, and where applicable these have been restated in the individual line item note.
The Statement of Water Assets and Water Liabilities for the urban water system is provided in Table 5. 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.
| Water assets | Volume at 30 June 2013 |
Volume at 30 June 2012 |
| 3 Urban water system | ||
| 3.1 Urban water supply system | – | – |
| 3.2 Wastewater system | – | – |
| 3.3 Recycled water system | – | – |
| 3.4 Urban inter-region claim on water | 356 |
356 |
| 3.7 Urban claim on surface water | 0 |
0 |
| Total urban water system assets | 356 |
356 |
| Opening net water assets | 356 | 36 |
| Change in net water assets | 0 | 320 |
| Closing net water assets | 356 |
356 |
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 6 and 7, respectively.
A schematic diagram representing all the inflows and outflows associated with the urban water system in the Sydney region is provided Figure 6. The inflow and outflow volumes for the urban water system during the 2012–13 year are given in Table 11. The numbers on the diagram refer to the line item numbers in Table 10.
Figure 6 Schematic diagram of water inflows and outflows for the urban water system within the Sydney region during the 2012–13 year; line item numbers are provided in brackets
Water sources, allocations and diversions
Corporate licenses are issued by the New South Wales Office of Water issues 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 New South Wales Office of Water website.
The Sydney Catchment Authority holds a large portion of the urban water entitlements for the Sydney region (see 11.18 Increase of urban claim on surface water). Sydney Catchment Authority'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. 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.
The amount of water diverted from rivers was 542,715 ML (see 11.12 Allocation diversion of surface water to urban water system) and a further 596 ML was diverted from the Fish River Water Supply System by Lithgow City Council, equaling 543,311 ML of water supplied to the urban water system. This was higher than the 2011–12 year, where 440,989 ML was sourced from rivers and 17 ML was diverted from the Fish River Water Supply Scheme by Lithgow CIty Council. This increased reliance on surface water is mainly attributed to there being no desalinated water delivered to the urban water system from the Kurnell desalination plant (see 11.6 Delivery of desalinated water to urban water system) which provided 61,290 ML to Sydney Water Corporation in the previous year. There was also a slight increase in the delivery of water to users.
A total of 469,145 ML was provided to customers as potable water through urban utilities, and a further 3,396 ML was supplied as non-potable water for commercial, industrial and municipal use (see 19.4 Delivery to urban water users).
Figure 7 summarises the volume of water supplied to the urban water supply system from various sources.
Figure 7 Graph of water supplied to the urban water supply system in the Sydney region
Discharge from the urban wastewater collection system
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 470,978 ML was discharged from wastewater treatment plants either to surface water (68,523 ML see 19.5 Urban water discharge to surface water) or outside the region (402,455 ML, see 19.7 Wastewater discharge outside of region).
Figure 8 Graph of wastewater discharged from the urban water system in the Sydney region
Figure 8 shows that most of the wastewater discharged is to the sea out of the region, with some being discharged to rivers.
Balancing item
The balancing item volume represents the difference between the measured opening and closing balances of the urban water store, after physical inflows and outflows have been applied.
The balancing item is calculated according to Table 8.
Calculation |
Account |
Volume (ML) |
|
Opening balance (30 June 2012) |
0 |
add |
Total urban system inflows (see Table 11) |
1,052,209 |
less |
Total urban system outflows (see Table 11) |
1,046,484 |
less |
Closing balance (30 June 2013) |
0 |
|
Balancing item |
5,725 |
The calculation of the water balance on the urban water system yielded a balance item of 5,725 ML. This is approximately 0.5% of the total urban water system inflows during the 2012–13 year.
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.