Sydney
Resources and Systems

The purpose of this note is to provide a consolidated report on the surface water store within the region during the 2010–11 year. Information on all water flows to and from the surface water store are presented here, including between store flows and transfers that are not presented in the water accounting statements.

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).

There are three main river systems within the Sydney region being the Hawkesbury–Nepean River catchment, the Shoalhaven River catchment and the Upper Nepean catchment which includes the metropolitan Sydney rivers.The flows from a number of main rivers in the region are heavily controlled by dams and numerous major weirs, particularly for urban water supply. Further information on the urban supply storages, including current levels and volumes, is given on the Bureau of Meteorology's water storage website.  Land use within the region varies between industrial, environmental, agricultural and urban areas.

Further details of these storages, including location, capacity and their management has been reported in the Contextual information under Surface water.

 

Table 1 shows that the total surface water store increased during the 2010–11 year in the Sydney region.

 

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

		30 Jun 11	1 Jul 10
		ML	ML
1 Surface water
	1.1 Storages	2,239,105	1,708,184
	1.2 Unregulated river	2,205	1,465
	1.4 Lakes and wetlands	–	–
Total		2,241,310	1,709,649

 

Of the physical water assets that could be quantified, there was the equivalent of 2,241,310 ML of water in storages in the Sydney region at 30 June 2011, which is an increase of 531,661 ML from 30 June 2010.

The volume reported for storages includes dead storage. The volume of water in rivers and lakes and wetlands could not be quantified due to a lack of available data. However, it is considered that the volume of water held in the channels and lakes is 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 within each storage, including dead storage, is shown in Figure 1. The storage at the end of the 2010–11 year is shown as a percentage of total capacity (% full). 

Figure 1. Location map of the storages within the Sydney region. The volume on 30 June 2011 for each storage is also shown (%)

The water volume in almost all the storages within the Sydney region at the end of the 2010–11 year was more than at the start (1 July 2010) (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 2010-11 year. Inflow into the storages during this period was approximately 2,032,808 ML (see 41.3 Runoff into storages). This was more than the 2009–10 year inflow volume of around 709,000 ML. 

A schematic diagram representing all the inflows and outflows associated with the surface water store in the Sydney region is provided in Figure 2. The inflow and outflow volumes for the surface water store during the 2010–11 year are given in Table 2.

Figure 2.Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the surface water store within the Sydney region during the 2010–11 year. Solid arrows indicate water transfers; dotted arrows indicate natural water movement; waved arrows indicate leakage. Line item numbers are provided next to the flows. 

Table 2. Volume of inflows and outflows for the surface water store during the 2010-11 reporting period. Line items in italic represent between store flows. These flows are not presented in the water accounting statements as they occur within the region.

			Volume
			ML
9 Surface water increases
		9.1 Precipitation on surface water	112,395
		9.3 Groundwater discharge	–
		9.4 Runoff to surface water	4,173,310
		9.6 Overbank flood return to river channel	–
		9.9 Discharge from urban water system	64,591
		9.10 Direct discharge by user	4,885
		9.11 Delivery of water under inter-region agreement	224
Total 9 Surface water increases			4,355,405
17 Surface water decreases
	17.1 Evaporation from surface water		114,894
	17.2 River outflow from the region		3,039,529
	17.3 Groundwater recharge		–
	17.5 Overbank flood spilling		–
	17.6 Diversions: other statutory rights		32,555
	17.11 Surface water allocation diversion		23,797
	17.12 Surface water allocation diversion - urban system		438,169
	17.16 Other delivery of allocated surface water		7,532
Total 17 Surface water decreases			3,656,476
Balancing item – surface water store			167,268
Change in water storage			531,661
Opening water storage			1,709,649
Closing water storage			2,241,310

Details of the each of the storage increases and decreases are given in the specific line item notes.

Most of the diversions from surface water are diversions to the urban water system (17.12 Surface water allocation diversion – urban system), which accounts for approximately 87% of the total allocation diversion.

Figure 3 shows that diversions from storages during 2010–11 for urban supply and private use decreased from 2009–10. Other statutory rights are assumed to be the same and Sydney Catchment Authority's release of banked environmental flow (line item 17.11) was increased from 2009–10.

Figure 3. Graph of allocation diversions from storages within the Sydney region during the 2010–11 year and 2009–10 comparison

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 were not diverted by the end of the year was forfeited.

The entitlement, allocation announcement and forfeiture for each of these water rights during the 2010–11 year are provided in 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 3.

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

Calculation	Account	Volume (ML)
	Opening balance (30 June 2010)	1,709,649
add	Total 9 Surface water increases	4,355,405
less	Total 17 Surface water decreases	3,656,476
less	Closing balance (30 June 2011)	2,241,310
	Balancing item – surface water store	167,268

The calculation of the water balance on the surface water store yielded a balancing item 167,268 ML.

It is likely that errors in the balancing item is 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 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%.

In this section, water flow into and out of surface water storages used for urban water supply are presented. All  storages within the Sydney region are used for urban water supply (see Figure 1 for their location).

The inflows and outflows into and out of these urban water supply storages are shown in Table 4. These volumes are different from the flows reported in the water accounting statements and in Table 2 above because they represent only a subset of the total surface water store.

Table 4. Volume of inflows and outflows for storages in the Sydney region during the 2010-11 year

		Volume (ML)
Opening storage		1,708,184
41 Storage inflows
	41.1 Precipitation on storages	101,704
	41.3 Runoff into storages	2,032,808
	41.4 Transfer of water into storages	115,235
Total 41 Storage inflows		2,249,747
42 Storage outflows
	42.1 Evaporation from storages	101,062
	42.4 Spillage from storages	576,421
	42.5 Releases from storages	939,755
Total 42 Storage outflows		1,617,238
Balancing item – storages		101,588
Closing storage		2,239,105
Net change in volume		632,509

This volume represents the difference between the measured opening and closing balances of the storages, 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.

Table 5. Balancing item for storages in the Sydney region during the 2010–11 year

Calculation	Account	Volume (ML)
	Opening balance (30 June 2010)	1,708,184
add	Total 41 Storage inflows	2,249,747
less	Total 42 Storage outflows	1,617,238
less	Closing balance (30 June 2011)	2,239,105
	Balancing item – storages	101,588

The calculation of the water balance on the surface water store yielded a balancing item 101,588 ML.

It is likely that errors in the balancing item is primarily attributed to errors associated with 41.3 Rainfall runoff. The rainfall runoff volume is derived from several sources of data a rainfall–runoff model and it is reasonable to expect a 10–20% uncertainty around the estimated runoff volume.

The purpose of this note is to provide a consolidated report on the urban water system within the region during the 2010–11 year. Information on all water flows to and from the urban water system are presented here, including between store flows and transfers that are not presented in the Water accounting statements.

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

The extent of the urban water supply and collection systems within the Sydney region can be seen in Figure P4 under Surface Water.

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 line item 1.1 Storages, part of the surface water store. Water stored in pipes, tanks and channels could not be quantified in a way that is complete, neutral and free from material error. On 30 June 2011 there was a claim remaining of 216 ML (see line item 3.4 Urban inter-region claim on water) on behalf of the urban water system, over water outside the region's boundary.

A schematic diagram representing all the inflows and outflows associated with the urban water system in the Sydney region is provided Figure 4. The inflow and outflow volumes for the urban water system during 2010–11 are given in the table below.



Figure 4. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the urban water system within the Sydney region. Solid arrows indicate water transfers; dotted arrows indicate natural water movement; waved arrows indicate leakage. Line item numbers are provided next to the flows.

Table 6. Volume of inflows and outflows for the urban water system during the 2010–11 year. Line items in italic indicate between-store flows. These flows are not presented in the water accounting statements

			Volume
			ML
11 Urban system increases
		11.4 Wastewater collected	513,998
		11.6 Delivery of desalinated water to urban water system	77,102
		11.7 Stormwater ingress	841
		11.9 Delivery of water to urban system under inter-region agreement	5,183
		11.12 Allocation diversion of surface water to urban system	438,169
		11.14 Other delivery of water to urban system	21,308
		11.21 Other urban water increases	5,768
TOTAL 11 Urban system increases			1,062,369
19 Urban system decreases
	19.2 Leakage to landscape		39,206
	19.3 Leakage to groundwater		–
	19.4 Delivery to urban water system users		474,594
	19.5 Urban water discharge to surface water		64,591
	19.7 Wastewater discharge outside of region		428,215
	19.20 Other urban water outflows		4,936
TOTAL 19 Urban system decreases			1,011,542
Balancing item – urban water system store			50,827
Change in water storage			0
Opening water storage			0
Closing water storage			0

 

In the Sydney region, the NoW 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.

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 rights, entitlements, allocations and restrictions.

The Sydney Catchment Authority (SCA) holds a large portion of the urban water entitlements for the Sydney region. SCA'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 SCA. Each of SCA's customers filter and treat the water and distribute it within their respective areas. Surface water allocation announcements to the urban system for the 2011 Account are reported in line item 11.18, with the associated diversions in line item 11.12.

Delta Electricity also holds a corporate licence to abstract water from the Coxs River water source for power generation purposes. More information on Delta Electricity's entitlements can be found under Delta Electricity on the NoW website.  Details of Delta Electricity's allocation volume in the 2010–11 year can be found in line item 11.20 Increase of other urban claims on water and the diversions under this allocation is reported in line item 11.14 Other delivery of water to urban system.

Delta Electricity and Lithgow City Council also source water for the urban water system through the Fish River Water Supply Scheme (FRWSS). As the water sources for this scheme are located outside the Sydney region, the allocations and diversions to the urban system are considered to be inter-region transfers. More details on the FRWSS can be found in Contextual information under Surface water. Deliveries and inter-region claims to the Sydney region through the FRWSS have been reported in line item 11.15 Increase of urban inter-region claim on water and line item 11.9 Delivery of water to urban system under inter-region agreement.

Sydney Water Corporation operates Kurnell Desalination Plant to supply Sydney with up to 30% of its water supply needs if necessary. In the 2010-11 year the plant supplied the Sydney region with 77,102 ML of water, which was quite a bit more than the 19,952 ML provided in 2009-10 (see line item 11.6 Delivery of desalinated water). For further details of Kurnell Desalination Plant, see Sydney Water Corporation's website.

Figure 6 summarises the volumes received by the urban water supply system from various sources. 

Figure 5. Graph of sources of water for the Sydney region's urban water supply system

Figure 5 shows that the majority of urban supply water in the Sydney region is sourced from its vast network of surface water storages (line item 11.12, 11.14 and 11.15), with around 14% of water supplied by Kurnell Desalination Plant.

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 474,863 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 6. Graph of wastewater discharged from the urban water system in the Sydney region

Figure 6 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 unaccounted-for difference 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 7. Balancing item for the urban water system for the 2010–11 reporting period

Calculation	Account	Volume (ML)
	Opening balance (30 June 2010)	0
add	Total 11 Urban system increases	1,062,369
less	Total 19 Urban system decreases	1,011,542
less	Closing balance (30 June 2011)	0
	Balancing item	50,827

 

Some of the arrangements under which water is sourced for the urban water system may create a claim on water (non-physical water asset) on behalf of the urban water system. As it is considered a claim/diversion that occurs within the reporting entity it does not appear in the Water accounting statements. The claim on surface water for the urban water system and its associated transfers is recognised in the following line items;

• 11.18 Increase of urban claim on surface water represents the allocation announced on the surface water resource on behalf of the urban water system during the 2010–11 year
• 11.12 Allocation diversion of surface water to urban system represents the diversion made under this claim
• 19.17 Decrease of urban claim on surface water represents the remaining volume of allocated water that was not diverted during 2010–11. For the purposes of the National Water Account, this volume was forfeited at the end of the 2010–11 year.
  

The urban water system is made up of three sub-systems which serve the urban water users: the urban water supply system, the wastewater collection system and the recycled water system. The main urban water users are residential, commercial, industrial and municipal consumers.

This note complements the Systems interactions with the region note. It gives the following additional information:

• split of the urban water flows according to the sub-systems they affect
• flows between sub-systems, which are not reported in the Systems interactions with the regionnote as they occur within the whole urban water system
• split of the total urban water use into several components.

In the Sydney region, the urban water supply system collects water from various sources including surface water, marine desalinated water and transfers-in across the region's geographical boundaries. It treats and distributes water to urban water users. Wastewater is treated and then discharged to surface water, the sea or the landscape, or delivered into the recycled water system. The recycled water system, in turn, distributes treated water to users.

Tables 6 to 8 show the balance of each sub-system including, including its inflows, outflows, balancing item and percentage error of the balancing item compared to the total of the inflows. The balancing items are calculated as the difference between the inflows less the outflows, considering that the changes in storage are not material. The values of the balancing items reflect measurement and data handling errors and/or missing data.

Table 9 shows a breakdown of the total urban water use per use sectors and type of water (potable, non-potable and recycled).

For each row in the Tables 8 to 11, correspondence is given to the line items that are reported in the Water accounting statements and the System's interactions with the region note. The correspondence can either be:

• 'Line item A': meaning a one to one correspondence of the volume in the table with the line item A
• 'Part of: line item A': meaning that the volume in the table is a part of the line item A
• 'Line item A + line item B': meaning that the volume in the table is the sum of line items A and B
• 'Part of: line item A + line item B': meaning that the volume in the table is the sum of a part of line items A and a part of line item B
• 'Not applicable': in the case when there is no correspondence to a line item.

When a volume in a table is given as '0' it means that the value has been evaluated as nil for the 2010–11 year. When the volume in a table is given as dash ('–'), it means that the volumes could not be quantified for the 2010–11 year.

Supporting information and quantification approaches for each volume shown in the tables 8 to 11 can be accessed via links on the line item numbers. In the cases when there is no corresponding line item, the supporting information and quantification approaches are given at the end of the note. 

Table 8. Balance of the regional urban water supply system for the 2010–11 year

	Volume (ML)	Line item
Inflow component:
Surface water diverted	443,937	11.12 + 11.21
Desalinated water produced	77,102
Total inflow	521,039
Outflow component:
Water lost due to leakage	39,206	19.2
Potable water supplied to users	474,594	19.4
Total outflow	513,800
Balance (inflows less outflows)	7,2391
Error	1%

¹Error can be due to meter errors, data handling errors and/or estimation.

Table 9. Balance of the regional wastewater collection system for the 2010–11 year

	Volume (ML)	Line item
Inflow component:
Wastewater collected within the region	513,998	11.4
Wastewater collected from outside the region	5,399	11.9
Ingress of stormwater and groundwater	841	11.7
Total inflow	520,238
Outflow component:
Wastewater (treated) discharged to surface water	62,291	Part 19.5(SWC, WSC and SCC only)
Wastewater (treated) discharged to landscape	213	Part of 19.7
Wastewater (treated) discharged to sea	428,000	Part of 19.7
Wastewater delivered outside the region	0
Wastewater (treated) supplied as recycled water	32,148
Total outflow	514,722
Balance (inflows less outflows)	5,5161
Error	1%

¹Error can be due to meter errors, data handling errors and/or estimation.

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

	Volume (ML)
Inflow component:
Recycled water imported	0
Total produced ar WWTP and sewermining	32,148
Total inflow	32,148
Outflow component:
Recycled water exported	0
Recycled water supplied to residential, commercial and municipal users	10,148
Recycled water use other than residential, commercial municipal and industrial users	21,189
Recycled water supplied for agricultural/individual irrigation	810
Total outflow	32,147
Balance (inflows less outflows)	11
Error	0%

¹Error can be due to meter errors, data handling errors and/or estimation.

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

	Potable		Nonpotable		Recycled
	Volume (ML)	Line Item	Volume (ML)	Line Item	Volume (ML)	Line Item	Total
Residential	330,608	Part of 19.4	5	Part of 19.4	2,250		10,148
Commercial, industrial and municipal uses	110,632	Part of 19.4	2,412	Part of 19.4	7,898		113,044
Agricultural/individual irrigation	0		0		810		0
Other uses	30,937	Part of 19.4	0		21,189		63,084
Total	472,177		2,417		32,147		516,889

Figure 7 graphically represents the inflows and outflows reported in Tables 8 to 11 that occur between and within urban sub-systems and between urban systems and urban users. Flows that do occur in the urban water system but could not be quantified have been faded-out.

Figure 7.Schematic diagram of water inflows and outflows for the urban sub-systems. Flow volumes and the corresponding line item numbers [] or table number where the value is reported, are provided next to the arrows. Faded-out arrows indicate water flows that could not be quantified.

Figure 7 shows three unquantified inflows and outflow components of Urban water consumption. There were insufficient data available to quantify these volumes however they are important components of the urban water balance.

Individually abstracted water includes water abstracted from surface water, groundwater or rainwater by individual users, i.e. water diverted from a stream, pumped from a domestic garden bore or sourced from a rainwater harvesting system.

The unquantified stormwater component represents stormwater that is claimed and then used by urban water consumers, as is the case for stormwater that is collected, treated and used in municipal stormwater schemes or projects.

The outflow of water to landscape/outdoor represents the unquantified volume of water that urban users apply or discharge to the landscape. This includes garden and park watering, sports field watering, car washing, paved surface cleaning, etc.

                     

 

The following notes are provided for the volumes in the Tables 4 to 7 and Figure 3 that do not correspond to any line item in the water accounting statements or the System's interactions with the region note.

 32,148 ML.

Data source

Derived from measured data used in Water Conservation & Recycling Implementation Report.

Providing agency

Sydney Water Corporation, Wingecarribee Shire Council, Shoalhaven City Council.

Method
This item represents the total metered volume of recycled water produced at the above mentioned three water utilities' wastewater treatment and recycling plants. The total volume includes 31,125 ML for Sydney Water Corporation, 942 ML for Shoalhaven City Council and 81 ML for Wingecarribee Shire Council.

Volume of recycled water produced by Sydney Water Corporation

Water Recycling Plant	Recycled water Volume (ML)
Bombo	48
Castle Hill	63
Gerroa	13
Glenfield	0
Liverpool	163
Picton	334
Penrith	11
Quakers Hill	435
Richmond	185
Rouse Hill	2,250
St Mary's	18,476
West Camden	2,059
Wollongong	7,088
Total	31,125

 

Volume of recycled water produced by other organisations

Water recycling plant	Recycled water volume (ML)
Shoalhaven City Council	942
Wingecarribee Shire Council	81

Uncertainty

Estimated in the range +/– 5%.

Assumptions, approximations and caveats/limitations

Total volume of recycled water produced from sewage is assumed to be equal to the volume of recycled water supplied for use.