Perth
Resources and Systems

Surface water

Purpose of note

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.

Background

A description of the Perth region's surface water resources is provided in the Contextual information.

Water in store

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


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

 

Volume at 30 June 2011

(ML)

Volume at 30 June 2010

(ML)

 

 

 

1 Surface water

 

 

1.1 Storages

160,173

253,878

1.2 Unregulated river

1.3 Regulated river

1.4 Lakes and wetlands

Total

160,173

253,878

 

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 rivers and lakes is relatively small compared to the volume held in storages.

The location of each storage within the Perth region, and the volume of water in each storage (including dead storage) as a percentage of total storage capacity at the end of the 2010–11 year, is shown in Figure 1.



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


The water volume in almost all the storages within the Perth region at the end of the 2010–11 year is less than that at the start (1 July 2010) (see 1.1 Storages). Except for two storages (Mundaring and Serpentine Pipehead), storage volume within the Perth region was less than 50% of capacity on 30 June 2011 (Figure 1).

The large decrease in surface water storage during the 2010–11 year is primarily attributed to the record low inflows into the storages during the year (see Water Corporation website). Inflow into the storages during the 2010–11 year was below 20,000 ML, much less than the inflow recorded during the 2009–10 year of approximately 163,000 ML. The record low inflow reflects the below-average rainfall conditions observed throughout the region (see Climate overview).

Water flows

Surface water inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the surface water store in the Perth 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. The numbers on the diagram refer to the line item numbers in Table 2.


Figure 2. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the surface water store within the Perth 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.
Figure 2. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the surface water store within the Perth 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 2. Volume of inflows and outflows for the surface water store during the 2010–11 year. Line items in italics indicate between-store flows. These flows are not presented in the statements as they occur within the region.

 

Volume

(ML)

 

 

9 Surface water inflows

 

9.1 Precipitation on surface water

15,637

9.2 River inflow to region

9.3 Groundwater discharge

90,064

9.4 Runoff to surface water

125,396

9.5 Point return from irrigation scheme

9.6 Overbank flood return to river channel

9.7 Delivery of water from outside region

3,215

9.9 Discharge from urban water system

72,278

9.19 Other surface water increases

0

Total 9 Surface water inflows

306,590

 

 

17 Surface water outflows

 

17.1 Evaporation from surface water

40,330

17.2 River outflow from the region

117,192

17.3 Leakage to groundwater

0

17.4 Leakage to landscape

90

17.5 Overbank flood spilling

17.11 Surface water allocation diversion

42,640

17.12 Surface water allocation diversion - urban water system

115,629

17.13 Surface water allocation diversion - irrigation scheme

32,952

17.14 Surface water transfer under inter-region commitment

25,851

Total 17 Surface water outflows

374,684

 

 

Balancing item – surface water store

25,611

 

 

Change in surface water storage

(93,705)

 

 

Opening surface water storage

253,878

Closing surface water storage

160,173

 


Details of the inter-region transfers of water into and out of the region are given in the specific line item note (9.7 and 17.14, respectively).


Allocation diversions

Most of the allocation diversion from surface water is to the urban water system (line item 17.12), which accounts for approximately 53% of the total allocation diversion.

Figure 3 shows that allocation diversions from storages during the 2010–11 year to the urban water system and the irrigation scheme have decreased from last year. Allocation diversions for private use and inter-region supply are similar to the 2009–10 year. (Details on water abstraction for private use are provided in line item 17.11.)


Figure 3. Graph of allocation diversions from storages within the Perth region during the 2010–11 year and the 2009–10 comparison year. Line item numbers are given in brackets.
Figure 3. Graph of allocation diversions from storages within the Perth region during the 2010–11 year and the 2009–10 comparison year. Line item numbers are given in brackets.


These allocation diversions are all associated with a water access entitlement. 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. This was also the case for the inter-region agreement, under which water was transferred out of the region.

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.


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. 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 year

 

Account

Volume (ML)

 

Opening balance (30 June 2010)

253,878

add

Total 9 Surface water inflows (see Table 2)

306,590

minus

Total 17 Surface water outflows (see Table 2)

374,684

minus

Closing balance (30 June 2011)

160,173

 

Balancing item – surface water store

25,611

 

The calculation of the water balance on the surface water store yielded a balancing item of 25,611 ML. This is approximately 16% of the total surface water store volume at the end of the 2010–11 year and less than 10% of the total surface water inflows during the 2010–11 year.

It is likely that the balancing item is primarily attributed to errors associated with the runoff (a large source of surface water increase, line item 9.4) and river outflow from the region (a large source of surface water decrease, line item 17.2). The runoff volume is derived from a rainfall–runoff model and it is reasonable to expect a 10–20% uncertainty around the estimated runoff volume (+/– 25,000 ML). The river 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% (+/– 23,000 ML).


Storage inflows and outflows

In this section, water flow into and out of surface water storages used for urban water supply are presented. All but four of the 15 storages within the Perth region are used for urban water supply to the Perth metropolitan area (see Table P2).

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 because they represent only a subset of the total surface water store.


Table 4. Volume of inflows and outflows for urban water supply storages during the 2010–11 year

 

Volume

(ML)

 

 

Opening storage

218,064

 

 

41 Storage inflows

 

41.1 Precipitation on storages

12,903

41.2 Groundwater discharge into storages

0

41.3 Runoff into storages

19,260

41.4 Transfer of water into storages

72,064

Total 41 Storage inflows

104,227

 

 

42 Storage outflows

 

42.1 Evaporation from storages

34,082

42.2 Groundwater recharge from storages

0

42.3 Leakage from storages

90

42.4 Spillage from storages

0

42.5 Releases from storages

1,153

42.6 Diversions from storages

141,017

Total 42 Storage outflows

176,342

 

 

Closing storage

145,949

 

 

Net change in volume

(72,115)

 

The runoff into storages line item refers to inflows into a storage via river flow or direct landscape runoff. The inflow into each storage is calculated using a water balance approach, based on all the other measured or estimated volumes in Table 4, as described in 41.3 Runoff into storages.

 

Groundwater

Purpose of note

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

Background

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

Water in store and groundwater asset

The aquifers in the Perth region are described in the Contextual information. While good information exists on water movement to and from the aquifers (see following section on Water flows), no value is available for the volume of water stored in the aquifers. No value could be estimated for the volume of the groundwater asset either, indicated by dashes ('–') in Table 5. The Department of Water is currently working on a method to calculate the storage volume of water in the aquifers necessary to maintain and protect groundwater-dependent ecosystems and intends to use those values to estimate groundwater asset in the future.

A more detailed explanation is provided in line item notes 2.1 and 2.2.


Table 5. Groundwater store volume at the start and end of the 2010–11 year

 

Volume at 30 June 2011

(ML)

Volume at 30 June 2010

(ML)

 

 

 

2 Groundwater

 

 

2.1 Water table aquifer

2.2 Underlying aquifers

Total

 

Water flows

A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Perth region is provided in Figure 4. The inflow and outflow volumes for the groundwater store during the 2010–11 year are given in Table 6. The numbers on the diagram refer to the line item numbers in Table 6.


Figure 4. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the groundwater store within the Perth 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.
Figure 4. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the groundwater store within the Perth 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 groundwater store during the 2010-11 year. Line items in italics indicate between-store flows. These flows are not presented in the statements as they occur within the region.

 

Volume

(ML)

 

 

10 Groundwater inflows

 

10.1 Groundwater inflow from outside region

52,412

10.2 Groundwater inflow from outside region at coast

0

10.3 Recharge from landscape

966,393

10.4 Recharge from surface water

0

10.6 Leakage from urban water system

18,901

10.7 Leakage from irrigation scheme

2,274

10.9 Managed aquifer recharge - urban water system

680

10.10 Urban water discharge to groundwater

1,504

Total 10 Groundwater inflows

1,042,164

 

 

18 Groundwater outflows

 

18.1 Groundwater outflow to outside region

31,602

18.2 Groundwater outflow to outside region at coast

264,790

18.3 Discharge to landscape

570,020

18.4 Discharge to surface water

90,064

18.8 Non-allocated extractions to users

67,347

18.11 Groundwater allocation extraction

287,044

18.12 Groundwater allocation diversion - urban water system

165,269

18.13 Groundwater allocation diversion - irrigation scheme

0

Total 18 Groundwater outflows

1,476,136

 

 

Balancing item – groundwater store

(433,972)

 

 

Change in groundwater storage

 

 

Opening groundwater storage

Closing groundwater storage

 

Allocations and extractions

Most of the extractions from the groundwater store are for licensed private use (line item 18.11), which accounts for approximately 55% of the total groundwater extraction. Almost 75% of the private water extractions are for agriculture and parks, gardens and recreational use (see line item note 18.11).

Figure 5 shows that allocation extractions from aquifers during the 2010–11 year to the urban water system have increased from last year. Estimations of private use and non-allocated extractions are similar to the 2009–10 year. Non-allocated water use refers to unlicensed domestic bores within the Perth region (see line item 18.8).



Figure 5. Graph of extractions from aquifers within the Perth region during the 2010–11 year and the 2009–10 comparison year. Line item numbers are given in brackets.
Figure 5. Graph of extractions from aquifers within the Perth region during the 2010–11 year and the 2009–10 comparison year. Line item numbers are given in brackets.


The allocation extractions are all associated with a water access entitlement. When an allocation is announced, an obligation (water liability) is created on the groundwater 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 'Groundwater rights' table.


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.

The balancing item is calculated according to Table 7.


Table 7. Balancing item for the groundwater store for the 2010–11 year

 

Account

Volume (ML)

 

Opening balance (30 June 2010)

add

Total 10 Groundwater inflows (see Table 6)

1,042,164

minus

Total 18 Groundwater outflows (see Table 6)

1,476,136

minus

Closing balance (30 June 2011)

 

Balancing item – groundwater store

(433,972)


The calculation of the water balance on the groundwater store yielded a balance of –433,972 ML, approximately 42% of the total groundwater inflows during the 2010–11 year.

Because the volume of water in the groundwater stores within the Perth region could not be quantified, the volume disclosed in the balancing item (–433,972 ML) represents the net change in groundwater store throughout the 2010–11 year.

During the 2010–11 year, total groundwater outflow was about 375,000 ML less than the 2009–10 year. However, total groundwater inflows were much less than the 2009–10 year; in particular, recharge from landscape (line item 10.3) was approximately 810,000 ML less than that reported during the 2009–10 year. This large decrease in recharge reflects the below-average rainfall conditions observed throughout the region during the 2010–11 year (see Climate overview).

Therefore, the balancing item value, which represents a net change in groundwater storage during the 2010–11 year, is mainly due to a low recharge from the landscape during the year.

 

Urban system

a. System's interactions with the region

Purpose of the note

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

The urban water system within the Perth region is discussed in the Contextual information. For more information on the system, refer to the Water Corporation website.

Water instore

Table 1 shows that the volume of water in the urban water system changed little during the 2010–11 year in the Perth region.

 

Table 8. Urban water system store volume at the start and end of the 2010–11 year

 

Volume at 30 June 2011

(ML)

Volume at 30 June 2010

(ML)

 

 

 

3 Urban water system

 

 

3.1 Urban water supply system

7,003

6,942

3.2 Wastewater collection system

Total 3 Urban water system

7,003

6,942

 

The volume of water within the urban wastewater system cannot be quantified due to a lack of available data. However, given that this system is smaller than the urban water supply system, the volume of water within this system is likely to be relatively small.

Water flows

A schematic diagram representing all the inflows and outflows associated with the urban water system in the Perth region is provided in Figure 6. The inflow and outflow volumes for the urban water system during the 2010–11 year are given in Table 9. The numbers on the diagram refer to the line item numbers in Table 9.


Figure 6. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the urban water system within the Perth 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.
Figure 6. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the urban water system within the Perth 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 9. Volume of inflows and outflows for the urban water system during the 2010–11 year. Line items in italics indicate between-store flows. These flows are not presented in the statements as they occur within the region.

 

Volume

(ML)

 

 

11 Urban water system inflows

 

11.4 Wastewater collected

127,920

11.6 Delivery of desalinated water

52,010

11.7 Stormwater ingress

11.12 Allocation diversion of surface water to urban system

115,629

11.13 Allocation extraction of groundwater to urban system

165,269

Total 11 Urban system inflows

460,828

 

 

19 Urban water system outflows

 

19.3 Leakage to groundwater

18,901

19.4 Delivery to urban water system users

238,273

19.5 Urban water discharge to surface water

72,278

19.7 Wastewater discharge outside of region

117,078

19.8 Other wastewater discharge

4,787

19.9 Managed aquifer recharge

680

19.10 Urban water discharge to groundwater

1,504

19.20 Other urban water decreases

7,234

Total 19 Urban water system outflows

460,735

 

 

Balancing item – urban water system

32

 

 

Change in urban water system storage

61

 

 

Opening urban water system storage

6,942

Closing urban water system storage

7,003

 


Water sources, allocations and diversions

There are three main sources of water for the urban water supply system:

  • surface water
  • groundwater
  • desalinated water

Figure 7 shows that most of the water was obtained from groundwater during the 2010–11 year. The previous year, most of the urban supply water was sourced from surface water. Lower than average rainfall during the 2009–10 year (see the 2010 Account) resulted in lower storage levels across the region compared with previous years. As a consequence, less surface water was available for urban water supply during the 2010–11 year.



Figure 7. Sources of water for the Perth region's urban water supply system. Line item numbers are given in brackets.
Figure 7. Sources of water for the Perth region's urban water supply system. Line item numbers are given in brackets.


Desalinated water made up 16% of the urban supply water during the 2010–11 year, similar to the comparison year.


Discharge from the urban wastewater collection system

Most of the treated wastewater from the urban wastewater collection system is discharged into the sea (line item 19.7). Treated wastewater is also discharged into the groundwater store via injection wells (see line item 19.9) and via infiltration ponds (see line item 19.10). During the 2010–11 year, the total volume of aquifer recharge was equivalent to approximately 2% of the total treated wastewater discharged from treatment plants within the region.


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. 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.

The balancing item is calculated according to Table 10.


Table 10. Balancing item for the urban water system for the 2010–11 year

 

Account

Volume (ML)

 

Opening balance (30 June 2010)

6,942

add

Total 11 Urban water system inflows (see Table 9)

460,828

minus

Total 19 Urban water system outflows (see Table 9)

460,735

minus

Closing balance (30 June 2011)

7,003

 

Balancing item – urban water system

32

 


Urban water restrictions

During the 2010–11 year, urban water system users and garden bore users were on a sprinkler roster.

Whilst on the sprinkler roster, urban water users in the Perth region can use their sprinklers two days per week. The sprinkler days are determined by the last digit of the user's street number and sprinklers must be used before 9am and after 6pm.


b. Sub-systems analysis

Purpose of the note

This note complements the System's interactions with the region note. It gives the following additional information:

  • split of the urban water flows according to the sub-systems they affect by water type, source and quality
  • flows between sub-systems, which are not reported in the System's interactions with the region note as they occur within the urban water system itself
  • split of the total urban water use into several components.
Urban water system

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
  • the recycled water system.

The main urban water users are residential, commercial, industrial and municipal consumers.

The urban water supply system receives water from various sources, including surface water, groundwater and marine desalinated water. It treats and distributes water to urban water users. Part of the water is used outdoors (e.g. garden use) while the rest is collected into the wastewater collection system. Wastewater is treated and then discharged to surface water, groundwater, the sea or the landscape, or delivered into the recycled water system. The recycled water system, in turn, distributes treated water to users.

Tables 11 to 13 show the balance of each sub-system, including its inflows, outflows, balancing item and % error of the balancing item compared to the total of the inflows. The balancing items are calculated as the difference between the inflows and 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 14 shows a breakdown of the total urban water use per use sector and type of water (potable and recycled).

Some volumes in Tables 11 to 14 refer to line items that are reported in the water accounting statements and/or 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
  • 'Not applicable': meaning that there is no correspondence to a line item

Supporting information and quantifications approaches for each volume shown in Tables 11 to 14 can be accessed via links on the line item numbers.


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

 

Volume (ML)

Line item

Inflow component:

 

 

Surface water diverted

115,629

11.12

Groundwater extracted

165,269

11.13

Desalinated water produced

52,010

11.6

Total inflow

              332,908

 

 

 

 

Outflow component:

 

 

Non-potable water flow back to storage

72,016

Part of 19.5

Non-potable water supplied to environment (riparian releases)

2,582

Refer to Environmental benefit note

Operation losses

1,136

Not applicable

Water lost due to leakage

18,901

19.3

Potable water supplied to water users

238,273

19.4

Total outflow

332,908

 

 

 

 

Balance (inflows less outflows)

0

 

 

Table 12. Balance of the wastewater collection system for the 2010–11 year

 

Volume (ML)

Line item

Inflow component:

 

 

Wastewater collected within the region

              127,920

11.4

Recycled water used in-process

2,880

Part of 19.20

Ingress of stormwater and groundwater

11.7

Total inflow

130,800

 

 

 

 

Outflow component:

 

 

Wastewater (treated) discharged to rivers

 263

Part of 19.5

Wastewater (treated) discharged to infiltration lagoons

 4,787

19.8

Wastewater (treated) discharged to sea

117,078

19.7

Wastewater (treated) used in-process

2,880

Part of 19.20

Wastewater (treated) supplied to recycled water system

6,538

See Table 13

Total outflow

                   131,546

 

 

 

 

Balancing item (inflows less outflows)

(746)

 

Error

0.6%

 

 

Table 13. Balance of the recycled water system for the 2010–11 year

 

Volume (ML)

Line item

Inflow component:

 

 

Inflow from wastewater collection system

6,538

See Outflow

Total inflow

6,538

 

 

 

 

Outflow component:

 

 

Recycled water used for on-site irrigation

104

Part of 19.20

Recycled water supplied to users

3,935

Part of 19.20

Recycled water used for irrigation

315

Part of 19.20

Recycled water used to supplement aquifers

2,184

19.9 + 19.10

Total outflow

6,538

 

 

 

 

Balancing item (inflows less outflows)

0

 

 

Table 14. Urban water consumption for the 2010–11 year

 

Potable

Recycled

Total

 

Volume (ML)

Line item

Volume (ML)

Line item

 

Residential

183,441

Part of 19.4

0

 

183,441

Commercial, industrial and municipal uses

31,593

Part of 19.4

3,935

Part of 19.20

35,528

Other uses:

 

 

 

 

 

Agricultural/individual irrigation

0

Not applicable

315

Part of 19.20

315

Managed aquifer recharge

0

Not applicable

680

19.9

680

To infiltration basin to supplement groundwater

0

Not applicable

1,504

19.10

1,504

Other

16,486

Part of 19.4

0

 

16,486

Sub-total – other uses

16,486

 

2,499

 

18,985

 

 

 

 

 

 

Total volume supplied (including non-revenue)

231,520

 

6,434

 

237,954


The total volume of water supplied to users of 237,954 ML (Table 14) is only slightly different to that presented in the water accounting statements of 238,273 ML (see line item 19.4) and in Table 11. This small difference is likely to reflect small errors in measurement and missing data.

Figure 8 represents the inflows and outflows reported in Tables 11 to 14 that occur between and within urban sub-systems and between urban systems and urban users. Flows that occur in the urban water system but could not be quantified are faded out.


Figure 8. Schematic diagram of water inflows and outflows for the urban sub-systems. Flow volumes and the corresponding line item numbers are provided next to the arrows and are shown in [ ] or with reference to the appropriate table number. Faded out arrows indicate water flows that could not be quantified.
Figure 8. Schematic diagram of water inflows and outflows for the urban sub-systems. Flow volumes and the corresponding line item numbers are provided next to the arrows and are shown in [ ] or with reference to the appropriate table number. Faded out arrows indicate water flows that could not be quantified.


There are four unquantified inflow and outflow components in Figure 8. Insufficient data were 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. That is, 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 such as that which 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, park and sports field watering, car washing and paved surface cleaning.

The unquantified line item [11.7] indicates groundwater or stormwater ingress into the stormwater system.


Irrigation schemes

Purpose of the note

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

Background

The irrigation scheme within the Perth region is discussed in the Contextual information. For more information on the irrigation scheme, refer to the Harvey Water website.

Water in store

The volume of water in the irrigation scheme is 370 ML (see line item 4.1). This volume did not change during the 2010–11 year.

Water flows

A schematic diagram representing all the inflows and outflows associated with the irrigation scheme in the Perth region is provided in Figure 9. The inflow and outflow volumes for the irrigation scheme during the 2010–11 year are given in Table 15. The numbers on the diagram refer to the line item numbers in Table 15.


Figure 9. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the irrigation scheme within the Perth region. Solid arrows indicate water transfers; waved arrows indicate leakage. Line item numbers are provided next to the flows.
Figure 9. Schematic diagram of water inflows (blue arrows) and outflows (red arrows) for the irrigation scheme within the Perth region. Solid arrows indicate water transfers; waved arrows indicate leakage. Line item numbers are provided next to the flows.

 

Table 15. Volume of inflows and outflows for the irrigation scheme during the 2010–11 year. Line items in italics indicate between-store flows. These flows are not presented in the statements as they occur within the region.

 

Volume

(ML)

 

 

12 Irrigation scheme inflows

 

12.5 Delivery of water from outside region

0

12.9 Allocation diversion of surface water to irrigation scheme

32,952

12.10 Allocation extraction of groundwater to irrigation scheme

0

Total 12 Irrigation scheme inflows

32,952

 

 

20 Irrigation scheme outflows

 

20.3 Leakage to groundwater

2,274

20.4 Application of water for irrigation

30,678

20.5 Return of water to surface water

20.15 Other irrigation scheme decreases

0

Total 20 Irrigation scheme outflows

32,952

 

 

Balancing item – irrigation scheme

0

 

 

Change in irrigation scheme storage

0

 

 

Opening irrigation scheme storage

370

Closing irrigation scheme storage

370

 

Balancing item

This volume represents the difference between the measured opening and closing balances of the irrigation scheme, after physical inflows and outflows have been applied.

The balancing item of zero is calculated according to Table 16.


Table 16. Balancing item for the irrigation scheme for the 2010–11 year

 

Account

Volume (ML)

 

Opening balance (30 June 2010)

370

add

Total 12 Irrigation scheme inflows (see Table 15)

32,952

minus

Total 20 Irrigation scheme outflows (see Table 15)

32,952

minus

Closing balance (30 June 2011)

370

 

Balancing item – irrigation scheme

0