Adelaide
Water resources and systems

Introduction

The following set of notes provides consolidated reports for each of the water stores and systems within the Adelaide 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 water stores and systems within the Adelaide region
Figure 1  Schematic diagram of water stores and systems within the Adelaide 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 Adelaide region; line item numbers are provided next to the flows
Figure 2  Schematic diagram of between store flows that occur within the Adelaide 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.

Surface water

Background

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

Water in store

The Statement of Water Assets and Water Liabilities for the surface water store (Table 1) shows that total surface water assets and net water assets decreased during the 2011–12 year in the Adelaide 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 97,182 136,915
1.2 Unregulated river 481 461
1.4 Lakes and wetlands
Total surface water assets 97,663 137,376
     
Water liabilities    
5 Surface water liability    
5.1 Surface water allocation remaining 377
Total surface water liabilities 377
     
Opening net water assets 137,376 93,753
Change in net water assets (40,090) 43,623
Closing net water assets 97,286 137,376


The surface water asset excluded water in river channels (1.2 Unregulated river) and lakes and wetlands (1.4 Lakes and wetlands) as these volumes could not be quantified in a way that was complete, neutral and free from material error, due to a lack of available data.

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


Figure 3  Location map of the storages within the Adelaide region; the % full volume on 30 June 2012 for each storage is also shown
Figure 3  Location map of the storages within the Adelaide region; the % full volume on 30 June 2012 for each storage is also shown

The surface water storage volume within the Adelaide region decreased by approximately 30% during the 2011–12 year (Table 1). With the exception of Myponga Reservoir and Hope Valley Reservoir, all storages recorded a decrease in storage volume and, at the end of the 2011–12 year, the volume of water held in storages as a proportion of total storage capacity was 49% across the Adelaide region.

The decrease in surface water storage volume during the year is attributed to the decreased inflows into the storages during the 2011–12 year, primarily driven by reduced runoff (see Table 2) and average rainfall conditions experienced throughout the 2011–12 year compared to the 2010–11 year (refer to the Rainfall section of the Contextual information).  Diversion of water from storages to the urban water system also increased in the 2011–12 year compared to the 2010–11 year (see Table 2).

Changes in water store

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

Table 2  Statement of 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 9,770 13,026
9.3 Groundwater discharge 72,148 72,148
9.4 Runoff to surface water 287,548 523,213
9.6 Overbank flood return to river channel

9.9 Discharge from urban water system 2,203 2,425
Total surface water increases 371,669 610,812
     
Water liability decreases    
13 Surface water liability decreases    
13.1 Adjustment and forfeiture of surface water allocation 1,919 2,163
Total surface water liability decreases 1,919 2,163
     
Water asset decreases    
17  Surface water decreases    
17.1 Evaporation from surface water 17,433 17,806
17.2 River outflow from the region 167,672 305,853
17.3 Leakage to groundwater
17.4 Leakage to landscape
17.5 Overbank flood spilling
17.6 Surface water diversions – other statutory rights 2,230 2,728
17.8 Entitled diversion of non-allocated surface water to urban water system 101,099 92,965
Total surface water decreases 288,434 419,352
     
Water liability increases    
21 Surface water liability increases    
21.1 Surface water allocation announcements 3,412 3,397
Total surface water liability increases 3,412 3,397
     
Balancing item—surface water 121,832 146,603
     
Change in net water assets (40,090) 43,623

Table 3 shows that inflows to the surface water store were significantly reduced in the 2011–12 year compared to the 2010–11 year, resulting in a 30% decrease in surface water storage. Besides reducing runoff (line item '9.4 Runoff to surface water'), the decrease of rainfall in the Adelaide region in the 2011–12 year compared to the 2010–11 year (refer to the Climate overview section of the 'Contextual information') resulted in decreasing river outflow to sea (line item '17.2 River outflow from the region'). Rainfall runoff provided the most significant contribution to surface water inflows. Outflows from the surface water store were mainly due to diversions to the urban water system and outflow from rivers to sea.


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 9,770 13,026
9.3 Groundwater discharge 72,148 72,148
9.4 Runoff to surface water 287,548 523,213
9.6 Overbank flood return to river channel

9.9 Discharge from urban water system 2,203 2,425
Total surface water inflows 371,669 610,812
     
Water outflows    
17 Surface water outflows    
17.1 Evaporation from surface water 17,433 17,806
17.2 River outflow from the region 167,672 305,853
17.3 Leakage to groundwater

17.4 Leakage to landscape

17.5 Overbank flood spilling

17.6 Surface water diversions – other statutory rights 2,230 2,728
17.8 Entitled diversion of non-allocated surface water to urban water system 101,099 92,965
17.11 Entitled diversion of allocated surface water to users 1,116 1,234
Total surface water outflows 289,550 420,586
     
Balancing item—surface water 121,830 146,603
     
Opening water storage 137,376 93,753
Add/(Less): Change in water storage (39,713) 43,623
Closing water storage 97,663 137,376


A schematic diagram representing all the inflows and outflows associated with the surface water store in the Adelaide region is provided in Figure 4. The numbers in brackets on the diagram refer to the line item numbers in Table 3.


Figure 4 Schematic diagram of water inflows and outflows for the surface water store within the Adelaide region during the 2011–12 year; line item numbers are provided in brackets
Figure 4 Schematic diagram of water inflows and outflows for the surface water store within the Adelaide region during the 2011–12 year; line item numbers are provided in brackets

Surface water diversions

The majority of surface water diversions in the Adelaide region during the 2011–12 year were for delivery of water to the urban water system (line item 17.8), accounting for almost 97% of all surface water diversions. The volume diverted in the 2011–12 year represents a modest increase (8%) compared to the 2010–11 year (Figure 5).

Collectively, allocation diversions from the surface water store (line item 17.11) and surface water diversions representing other statutory rights (line item 17.6) accounted for only a very small portion (3,346 ML: 3%) of surface water diversions in the Adelaide region during the 2011–12 year and were marginally less than during the 2010–11 year (3,962 ML: 4%).


Figure 5  Graph of diversions from the surface water store within the Adelaide region during the 2011–12 year and the 2010–11 comparison year
Figure 5  Graph of diversions from the surface water store within the Adelaide region during the 2011–12 year and the 2010–11 comparison year

Balancing item—surface water store

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 4.

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

Account Volume (ML)

Opening balance (30 June 2011) 137,376
add
Total surface water inflows (see Table 3) 371,669
less
Total surface water outflows (see Table 3) 289,550
less
Closing balance (30 June 2012) 97,663

Balancing item—surface water store 121,832

The calculation of the water balance on the surface water store yielded a balance of 121,832 ML. This is approximately 125% of the total surface water store volume at the end of the 2011–12 year and 33% of the total surface water inflows during the 2011–12 year.

The balancing item for the surface water store is due to a combination of line items that were wholly or partly not quantified, and due to errors and uncertainty associated with the quantification methods. Items that were not quantified include evaporation from rivers (except at certain weirs) and some surface water/groundwater interactions.

A large component of the balancing item is likely to be attributed to the quantification of rainfall-runoff (line item 9.4). There is uncertainty associated with the meteorological inputs into the model and the model structure, estimated to be in the range of 10–20% (up to +/– 60,000 ML). Similarly, quantification of river outflow to sea also contributes to the large balancing item for the surface water asset. 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% (up to 30,000 ML).

Groundwater

Background

A description of the Adelaide region's groundwater resources is provided in the Groundwater section of the Contextual information.

Water in store and groundwater asset

The value of the groundwater asset (90,858 ML) was the managed groundwater volume described in the relevant water allocation plans and the carryover balance of managed aquifer recharge credits. The groundwater asset could not be separated by water table aquifer and underlying aquifer volumes; therefore these items were reported as unquantified (–) and the groundwater asset was reported as a combined volume at line item 2.5 Other groundwater assets. The groundwater asset did not include the Northern Adelaide Plains, Central Adelaide Plains and Dry Creek prescribed wells areas.

The closing balance of the groundwater store was marginally higher than the opening balance in the 2011–12 year. Given that the groundwater asset is equivalent to the managed groundwater volume and the balance of recharged water credits, the volume reported is not expected to vary significantly among years. The managed groundwater volume is a planning volume that does not reflect temporal fluctuations of groundwater levels. Therefore, groundwater assets for the region are not responsive to groundwater storage changes resulting from water table fluctuations. As a result groundwater assets are constant except for the carryover balance of managed aquifer recharge credits.

The Statement of Water Assets and Water Liabilities for the groundwater store is shown in Table 5 (values in brackets are negatives).

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

2.2 Underlying aquifers

2.5 Other groundwater assets 90,858 89,653
Total groundwater assets 90,858 89,653
     
Water liabilities    
6 Groundwater liability    
6.1 Groundwater allocation remaining 6,641 4,948
Total groundwater liabilities 6,641 4,948
     
Opening net water assets 84,705 84,976
Change in net water assets (488) (271)
Closing net water assets 84,217 84,705
Changes in water store

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 (values in brackets are negatives).

Inflows to the groundwater store mainly comprised recharge from the landscape, which decreased in the 2011–12 year compared to the 2010–11 year, due to reduced rainfall in the region. Outflows from the groundwater store mainly comprised discharge to the landscape, which increased in the 2011–12 year compared to the 2010–11 year. 

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 38 36
10.2 Groundwater inflow from outside region at coast 1,938 2,051
10.3 Recharge from landscape 299,451 685,221
10.4 Recharge from surface water
10.5 Leakage from off-channel water storage 930 1,011
10.6 Leakage from urban water system 14,718 13,962
10.7 Leakage from irrigation scheme 33 62
10.8 Managed aquifer recharge – private user
5,455
Total groundwater increases 317,108 707,798
     
Water liability decreases    
14 Groundwater liability decreases    
14.1 Adjustment and forfeiture of groundwater allocation 24,851 24,445
Total groundwater liability decreases 24,851 24,445
     
Water asset decreases    
18 Groundwater decreases    
18.1 Groundwater outflow to outside region 405 390
18.2 Groundwater outflow to outside region at coast 921 919
18.3 Discharge to landscape 155,177 54,866
18.4 Discharge to surface water 72,148 72,148
18.5 Discharge to off-channel water storage

18.7 Groundwater extractions – other statutory rights 29,589
Total groundwater decreases 228,651 157,912
     
Water liability increases    
22 Groundwater liability increases    
22.1 Groundwater allocation announcements 43,923 41,555
Total groundwater liability increases 43,923 41,555
     
Balancing item—groundwater 69,873 533,047
     
Change in net water assets (488) (271)

 

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 38 36
10.2 Groundwater inflow from outside region at coast 1,938 2,051
10.3 Recharge from landscape 299,451 685,221
10.4 Recharge from surface water

10.5 Leakage from off-channel water storage 930 1,011
10.6 Leakage from urban water system 14,718 13,962
10.7 Leakage from irrigation scheme 33 62
10.8 Managed aquifer recharge – private user
5,455
Total groundwater inflows 317,108 707,798
     
Water outflows    
18 Groundwater outflows    
18.1 Groundwater outflow to outside region 405 390
18.2 Groundwater outflow to outside region at coast 921 919
18.3 Discharge to landscape 155,177 54,866
18.4 Discharge to surface water 72,148 72,148
18.5 Discharge to off-channel water storage

18.7 Groundwater extractions – other statutory rights
29,589
18.11 Entitled extraction of allocated groundwater to users 17,379 15,019
Total groundwater outflows 246,030 172,931
     
Balancing item—groundwater 69,873 533,047
     
Opening water storage 89,653 87,833
Add/(Less): Change in water storage 1,205 1,820
Closing water storage 90,858 89,653


A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Adelaide 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 in brackets 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 Adelaide region during the 2011–12 year; line item numbers are provided in brackets
Figure 6 Schematic diagram of water inflows and outflows for the groundwater store within the Adelaide region during the 2011–12 year; line item numbers are provided in brackets

Allocations and extractions

Groundwater extractions in the Adelaide region occur under different types of water rights. These water rights, including entitlements, allocation announcements and forfeiture during the 2011–12 year, are provided in the Water rights, entitlements, allocations and restrictions note in the Groundwater rights table. Table 6 also reports groundwater allocation announcements (line item 22.1).

Only extractions associated with an entitlement were reported in the 2012 Account (see line item 18.11) and the volume extracted was approximately 40% of the total volume allocated (line items 22.1). Overall, the majority of groundwater extractions are used for irrigation but the type of crops irrigated differs by area. The primary use of groundwater extractions, described by groundwater management area and hydrology are provided in the Groundwater section of the 'Contextual information'.

Figure 7 shows that allocated groundwater extractions have increased in the 2011–12 year compared to the 2010–11 year, which is likely to be the result of a return to average rainfall conditions. During the 2010–11 year, above-average rainfall was experienced, reducing demand for groundwater (for further information, refer to the Rainfall section of the 'Contextual information').

Groundwater extractions under other statutory rights (line item 18.7) for the 2011–12 year could not be quantified in a way that was complete, neutral and free from material error. Provision of a value for this line item for the 2009–10 year and 2010–11 year required significant transformation of data that had been collected for a different purpose. That data was out of date and not representative for the 2011–12 year.

The impact of this gap is material to the water balance of the groundwater store and the change in net water assets. As a comparison, the 2010–11 year value reported for line item 18.7 was 29,589 ML. Assuming a comparable volume (a reasonable assumption, given that licensed groundwater extractions increased) was extracted during the 2011–12 year, then the change in net water assets has been substantially underestimated and the balancing item overestimated.


  Figure 7  Graph of extractions from aquifers within the Adelaide region during the 2011–12 year and the 2010–11 year
Figure 7  Graph of extractions from aquifers within the Adelaide region during the 2011–12 year and the 2010–11 year


Balancing item—groundwater store

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 8.

Table 8  Balancing item for the groundwater store in the 2011–12 year

 

Account

Volume (ML)

 

Opening balance (30 June 2011)

89,653

add

Total groundwater inflows (see Table 7)

317,108

less

Total groundwater outflows (see Table 7)

246,030

less

Closing balance (30 June 2012)

90,858

 

Balancing item—groundwater store

69,873

The calculation of the water balance on the groundwater store yielded a difference of 69,873 ML, approximately 22% of the total groundwater inflows during the 2011–12 year. This value is considerably less than that reported for the 2010–11 year.

The balancing item can be partly attributed to the omission of several line items that could not be quantified in a way that was complete, neutral and free from material error.

The balancing item can be also be attributed to the fact that that groundwater assets and flows are calculated in ways that do not allow them to reconcile:

  • The groundwater asset is quantified as the average long-term groundwater volume available for extraction without adversely impacting the system. This value is essentially constant from year to year.
  • Inflows and outflows are estimated by models and represent, albeit with calculation errors, the inflows and outflows that change from year to year, depending on climatic conditions, extractions, etc. Nevertheless, because of the limitations of data availability, there is an inherent limitation in accuracy in the groundwater quantities presented in tables 5, 6 and 7.
  • The groundwater asset is only defined for a few of the aquifers of the total aquifers in the Adelaide region.
  • The reported recharge from landscape represents potential diffuse recharge to groundwater. This is the amount of water that potentially could reach the water table given the land use and soil type in the region. This volume is not a direct measure of groundwater recharge and does not take into consideration the lag of time that occurs between the rainfall infiltrating into the soil and its actually reaching the water table.
  • The groundwater discharge to surface water (line item 18.4) was the average annual baseflow and does not necessarily represent the flux during the 2011–12 year.

Estimated inflows and outflows are more sensibly compared to the change of water stored in the aquifers, as shown in the following section, than to the opening and closing balance of the groundwater asset.

Change in aquifer storage

The change in groundwater storage was estimated for the water table aquifer within the sedimentary aquifers of the McLaren Vale Prescribed Wells Area (PWA), the Adelaide Plains and the fractured rocks area aquifers (Figure 8). The change in groundwater levels were estimated using all bores within the water table and using a buffer of 10 km. The results are shown in the Table 9 for the 2011–12 and 2010–11 years (values in brackets are negatives).

 Table 9  Changes in aquifer storage estimated for the 2011–12 and 2010–11 years

Management area

Change in storage 2011–12 (ML)

Change in storage 2010–11 (ML)1

McLaren Vale PWA water table

7,441

5,472

Adelaide Plains water table

(20,156)

88,288

Fractured rocks area
(66,764)
197,068

Total

(79,479)

290,828

1 The 2010–11 year volumes are different from those reported in the 2011 Account as they have been restated using the bore data set of the 2012 Account, which was different from the one used in the 2011 Account.

The decrease in aquifer storage for the 2011–12 year shown in Table 9 is consistent with a decrease of groundwater inflows during the 2011–12 year (317,108 ML) compared to the 2010­–11 year (707,798 ML); however, a meaningful comparison with groundwater inflows (317,108 ML) and groundwater outflows (246,030 ML) for the 2011–12 year can not be done due to missing terms in the groundwater balance (refer to balancing item above for list of items that could not be quantified).


Quantification approach—change in aquifer storage

Data source

South Australian Department of Environment, Water and Natural Management: bore locations, groundwater level data and screened aquifer information from online database; Aquaterra 2011.

Method

Change in extractable storage is estimated using a simple GIS approach based on measured groundwater levels and aquifer properties. Firstly, groundwater levels at the start (1 July 2010) and the end (30 June 2011) of the 2010–11 year were estimated. This was achieved by considering all groundwater level measurements between March 2010 – October 2010 and March 2011 – October 2011, respectively, and using the measurements closest in time to interpolate the start and end levels. 

The estimated groundwater levels at the start and end dates were then spatially interpolated to grids using kriging with external drift and the 9" digital elevation model as an external driver following the methodology presented in Peterson et al. (2011). The interpolated groundwater-level surfaces at the start and the end of financial year were then used to calculate the volume between the two surfaces within the sedimentary and fractured rocks areas. Finally, these volumes were multiplied by appropriate specific yield values to convert to a change in groundwater storage.

In agreement with the Adelaide Plains groundwater model report, the values were calculated only within a 10 km radius around each bore as shown in Figure 8.

Figure 8  Map of Adelaide groundwater buffer zone change in storage
Figure 8  Map of Adelaide groundwater buffer zone change in storage
 

Assumptions, limitations, caveats and approximations

Change in groundwater storage was not calculated for confined aquifers. The annual change in storage was considered to be negligible for confined aquifers due to their very low storativity, which is much lower than the specific yield of unconfined aquifers (Freeze and Cherry 1979; Johnson 1967). Upon lowering of water levels in such aquifers, they remain fully saturated so that no dewatering occurs. The water diverted is volumetrically equivalent to the volumetric expansion of the water and contraction of the pore space.

The Fleurieu Peninsula and Myponga catchment areas were not included in the calculations of the change in storage.

Outside the 10-km buffer zone, where no groundwater level measurements are available, the change in storage is considered zero. This is due to the inability of estimating any change because of lack of data.

Annual change in storage in fractured bedrock was considered negligible as the fractures are the only water-holding structures and these systems have a low specific yield. Furthermore, groundwater extraction in fractured rock areas is limited in volume. On an annual basis, it is assumed that any increase or decrease in rainfall is counterbalanced by an increase or decrease in evapotranspiration and in discharge to rivers through baseflow.

A constant specific yield of 0.1 was used in agreement with the Adelaide Plains groundwater model report (Aquaterra 2011).

Uncertainty

The uncertainty in the field-measured data (e.g. groundwater levels, specific yield) was not specified and hence the impacts of such uncertainty on the change in storage is not estimated. The change in storage estimations were based on interpolated groundwater level grids produced using kriging with external drift and the 9" digital elevation model as an external driver. Use of other interpolation methods may impact the values of the groundwater-level grids and hence the estimated values for change in groundwater storage.

Urban water system

Background

Background information on the urban water system within the Adelaide region is in the Other water resources and urban system section of the 'Contextual information'. The extent of the urban water supply and collection systems within the Adelaide region can be seen in Figure P8 of the 'Contextual information'.

Water in store

The Statement of Water Assets and Water Liabilities for the urban water system (Table 10) shows that the volume of water in the urban water system changed very little during the 2011–12 year in the Adelaide region.

Table 10  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 1,414 1,412
3.2 Wastewater system 96 95
3.3 Recycled water system 17 17
3.4 Urban inter-region claim on water 0 0
Total urban water system assets 1,527 1,524
     
Opening net water assets 1,524 18,310
Change in net water assets 3 (16,786)
Closing net water assets 1,527 1,524

The volume of the urban water system store includes water held in pipes that were part of the potable, wastewater and recycled pipe network, as well as tanks and urban storages. The urban water system excluded water held in wastewater treatment lagoons as these volumes could not be quantified in a way that is complete, neutral and free from material error due to a lack of available data. The decrease of net water asset during the 2010–11 year is due to the reclassification of the off-river storages from the urban water system store to the surface water store (line item 3.1 Urban water supply system).

Changes in water store

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the urban water system are provided in Tables 11 and 12, respectively.

As shown in Table 11, the water asset increases in the 2011–12 year were slightly less than during the 2010–11 year. This is due to a decrease in the River Murray water claim (line item 11.15) that was not fully compensated by an increase in the inflow of water harvested within the Adelaide region (line item 11.2) and the inflow of desalinated water that started in October 2011.


Table 11  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    
11.1 Precipitation on urban water system 0 0
11.2 Entitled diversion of non-allocated surface water to urban water system 101,099 92,965
11.4 Wastewater collected 90,921 92,024
11.6 Delivery of desalinated water to urban water system 3,816 0
11.15 Increase of inter-region claim on water by urban water system 130,000 150,000
Total urban water system increases 325,836 334,989
     
Water asset decreases    
19 Urban water system decreases    
19.1 Evaporation from urban water system 0
19.3 Leakage to groundwater 14,718 13,962
19.4 Delivery to urban water system users 133,356 127,207
19.5 Discharge from urban water system to surface water 2,203 2,425
19.6 Discharge from urban water system to irrigation scheme 17,322 15,977
19.7 Wastewater discharge outside of region 63,032 70,836
19.11 Transfer of water outside of region 3,739 3,476
19.14 Adjustment and forfeiture of urban inter-region claim on water 82,523 101,701
19.20 Other urban water system decreases 8,460 7,993
Total urban water system decreases 325,353 343,577
     
Balancing item—urban water system 480 8,198
     
Change in net water assets 3 (16,786)

As shown in Table 12, outflows in the 2011–12 year were similar to those in the 2010–11 year. A slight increase in water delivered to individual customers (line item 19.4) and irrigation schemes (line item 19.6) was compensated by a decrease in the discharge of wastewater to sea (line item 19.7).

Table 12  Statement of Water Flows
Water inflows 2011–12 volume (ML) 2010–11 volume (ML)
11 Urban water system inflows    
11.1 Precipitation on urban water system 0 0
11.2 Entitled diversion of non-allocated surface water to urban water system 101,099 92,965
11.4 Wastewater collected 90,921 92,024
11.6 Delivery of desalinated water to urban water system 3,816 0
11.9 Delivery of water to urban water system under inter-region agreement 47,477 48,299
Total urban water system inflows 243,314 233,288
     
Water outflows    
19 Urban water system outflows    
19.1 Evaporation from urban water system 0 0
19.3 Leakage to groundwater 14,718 13,962
19.4 Delivery to urban water system users 133,356 127,207
19.5 Discharge from urban water system to surface water 2,203 2,425
19.6 Discharge from urban water system to irrigation scheme 17,322 15,977
19.7 Wastewater discharge outside of region 63,032 70,836
19.11 Transfer of water outside of region 3,739 3,476
19.20 Other urban water system decreases 8,460 7,993
Total urban water system outflows 242,830 241,876
     
Balancing item—urban water system 480
8,198
     
Opening water storage 1,524 18,310
Add/(Less): Change in water storage 3 (16,786)
Closing water storage 1,527 1,524



A schematic diagram representing all the inflows and outflows associated with the urban water system in the Adelaide region is provided in Figure 9. The inflow and outflow volumes for the urban water system during the 2011–12 year are given in Table 12. The numbers in brackets on the diagram refer to the line item numbers in Table 12.


Figure 9  Schematic diagram of water inflows and outflows for the urban water system store within the Adelaide region during the 2011–12 year; line item numbers are provided in brackets
Figure 9  Schematic diagram of water inflows and outflows for the urban water system store within the Adelaide region during the 2011–12 year; line item numbers are provided in brackets

Water sources, allocations and diversions

In the Adelaide region water for urban supply comes from three sources:

  • water harvested from the Mount Lofty Ranges catchments within the Adelaide region (line item 11.2);
  • River Murray water imported via the Mannum–Adelaide, Murray Bridge–Onkaparinga and Swan Reach–Stockwell pipelines (line item 11.9); and
  • desalinated water received from the Adelaide desalination plant (line item 11.6).

Figure 10  Sources of water for the Adelaide region's urban water supply system during the 2011–12 year and the 2010–11 comparison year; line item numbers are given in brackets
Figure 10  Sources of water for the Adelaide region's urban water supply system during the 2011–12 year and the 2010–11 comparison year; line item numbers are given in brackets


Water harvested from the Adelaide region's catchments (line item 11.2) provided the majority of water supplying the urban water supply system during the 2011–12 year (66% of source water). Imported River Murray water (line item 11.9) constituted approximately 31% of the urban water supply system's source water and desalinated water (line item 11.6) made up 3% of urban water sources. Similar proportions of water sources were observed during 2010–11, except for desalinated water that was not supplied during that year.

River Murray water imported via the Mannum–Adelaide, Murray Bridge–Onkaparinga and Swan Reach–Stockwell pipelines occurs via a Class 6 water access entitlement (WAE) to shares in the River Murray consumptive pool for South Australia. This WAE is intended specifically for reticulated public water supply to metropolitan Adelaide and diversions are reported at 11.9 Delivery of water to urban system under inter-region claim. This water source supplements Adelaide's urban water supply system. The volume diverted in any given year will vary depending on prevailing climatic conditions because:

  • rainfall and subsequently stream flows within the River Murray Catchment will determine the volume of water available to be taken, advised via allocation announcement; and
  • rainfall within the Adelaide region's catchments will determine the demand on the River Murray water to supplement the Adelaide region's urban water supply system.
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) accounting for approximately 71% of wastewater in the Adelaide region. The remaining treated wastewater is either discharged to surface water (line item 19.5: 2%), provided to the regions irrigation schemes as recycled water (line item 19.6: 20%), provided to individual users as recycled water (part of line item 19.4: 3,159 ML or 4%) or used on site of the wastewater treatment plants as recycled water (part of line item 19.4: 2,468 ML or 3%).

Balancing item—urban water system

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 13.

Table 13  Balancing item for the urban water system for the 2011–12 year

 

Account

Volume (ML)

 

Opening balance (30 June 2011)

1,524

add

Total urban water system inflows (see Table 12)

243,313

less

Total urban water system outflows (see Table 12)

242,830

less

Closing balance (30 June 2012)

1,527

 

Balancing item—urban water system

480


The balancing item for water flows into and out of the urban water store was 480 ML, less than 1 % of the total urban water inflows for the 2011–12 year. This is due to a combination of meter errors, data measurement and handling errors, calculation and estimation errors (leakage, precipitation and evaporation), and from flows that can not be quantified such as stormwater infiltration and groundwater infiltration.

Urban water restrictions

In times of severe water shortages, SA Water can implement a regime of water conservation or restriction measures on behalf of the South Australian Minister for Water. As of 1 December 2010, level 3 enhanced restrictions were removed and Water Wise Measures introduced. South Australia does not have a defined set of water restriction levels; specific levels and conditions are announced as the need arises.

Irrigation schemes

Background

Three major irrigation schemes operate in the Adelaide region: Barossa Infrastructure Limited (BIL), Virginia Pipeline Scheme (VPS) and Willunga Basin Water Company (WBWC).

Background information on these irrigation schemes in the Adelaide region can be found in the Other water resources and distribution systems section of the 'Contextual information'.

Water in store

The Statement of Water Assets and Water Liabilities for the irrigation scheme (Table 14) shows that the volume of water in the irrigation scheme did not change during the 2011–12 year in the Adelaide region.

Table 14  Statement of Water Assets and Water Liabilities for the irrigation scheme
Water assets Volume at 30 June 2012
(ML)
Volume at 30 June 2011
(ML)
4 Irrigation scheme    
4.1 Irrigation water supply system 29 29

4.2 Irrigation scheme inter-region claim on water

0
0
Total irrigation scheme assets 29 29
     
Opening net water assets 29 2,306
Change in net water assets 0 (2,277)
Closing net water assets 29 29
Changes in water store

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the irrigation scheme are provided in Table 15 and Table 16, respectively.

As shown in Table 15, increases to the irrigation scheme was greater in the 2011–12 year than in the 2010–11 year due to an increase of claim to River Murray water (line item 12.12) and an increase in recycled water transferred from the urban water system (line item 12.4). An increase of River Murray water inflows (line item 12.6 in Table 16) followed the increase of claim to water. During the 2011–12 year, outflows from the irrigation schemes also increased in the 2011–12 year compared to the 2010–11 year, as more water was delivered to customers (line item 20.4).

Table 15  Statement of Changes in Water Assets and Water Liabilities for the irrigation scheme
Water asset increases 2011–12 volume (ML) 2010–11 volume (ML)
12 Irrigation scheme increases    
12.1 Precipitation on irrigation scheme

12.4 Discharge from urban water system to irrigation scheme 17,322 15,977
12.12 Increase of irrigation scheme inter-region claim on water 6,653 3,850
12.18 Other irrigation scheme increases 228 253
Total irrigation scheme increases 24,203 20,080
     
Water asset decreases    
20 Irrigation scheme decreases    
20.1 Evaporation from irrigation scheme

20.3 Leakage to groundwater 33 62
20.4 Delivery to irrigation scheme users 19,478 14,789
20.9 Adjustment and forfeiture of irrigation scheme inter-region claim on water 2,662 3,826
Total irrigation scheme decreases 22,173 18,677
     
Balancing item—irrigation scheme 2,030 3,680
     
Change in net water assets 0 (2,277)


Table 16  Statement of Water Flows for the irrigation scheme
Water inflows
2011–12 volume (ML) 2010–11 volume (ML)
12 Irrigation scheme inflows    
12.1 Precipitation on irrigation scheme

12.4 Discharge from urban water system to irrigation scheme 17,322 15,977

12.6 Delivery of water to irrigation scheme under inter-region agreement

3,991
2,301
12.18 Other irrigation scheme increases 228 253
Total irrigation scheme inflows 21,541
18,531
     
Water outflows
   
20 Irrigation scheme outflows
   
20.1 Evaporation from irrigation scheme

20.3 Leakage to groundwater 33 62
20.4 Delivery to irrigation scheme users 19,478 14,789
Total irrigation scheme outflows
19,511 14,851
     
Balancing item—irrigation scheme 2,030 3,680
     
Opening water storage
29
29
Add/(Less): Change in water storage
0
0
Closing water storage
29
29


A schematic diagram representing all the inflows and outflows associated with the irrigation scheme in the Adelaide region is provided in Figure 11. The inflow and outflow volumes for the irrigation scheme during the 2011–12 year are given in Table 16. The numbers in brackets on the diagram refer to the line item numbers in Table 16.

Figure 11  Schematic diagram of water inflows and outflows for the irrigation scheme within the Adelaide region during the 2011–12 year; line item numbers are provided in brackets
Figure 11  Schematic diagram of water inflows and outflows for the irrigation scheme within the Adelaide region during the 2011–12 year; line item numbers are provided in brackets
Balancing item—irrigation schemes

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 is calculated according to Table 17.

Table 17  Balancing item for the irrigation scheme for the 2011–12 year
  Account Volume (ML)
  Opening balance (30 June 2011) 29
add Total irrigation schemes inflows (see Table 16) 21,541
less Total irrigation schemes outflows (see Table 16) 19,511
less Closing balance (30 June 2012) 29
  Balancing item—irrigation scheme 2,030

The calculation of the water balance on irrigation schemes yielded a balancing item of 2,030 ML. This is approximately 9% of the total irrigation schemes inflows during the 2011–12 year.

The balancing item may be due to:

  • Different methods of measuring flows to and from the irrigation scheme for different data suppliers: The inflow of recycled water to the VPS was provided from SA Water wastewater records, whereas the outflow from the VPS was the metered volume at the VPS pump station. The difference between these two volumes is significant and may be due to meter errors at either end of the flow and unquantified losses between supply from SA Water to VPS and supply to VPS customers.
  • Unquantified line items: The fact that evaporation and precipitation were not quantified is not expected to have had a material impact on the balancing item reported.
  • Inconsistent time periods for measurement: The irrigation year is September to September and customer meters are not read on 30 June 2012. Therefore, the volume reported for delivery to irrigation scheme users for the VPS was the metered volume of water at their pumping station, not at customer meters.

Off-channel storages

Background

A description of the Adelaide region's off-channel water resources is provided in the Other water resources and distribution systems section of the 'Contextual information'.

Where available, water flows to and from off-channel water storages are reported here. Water held in off-channel water storages is not reported in the Water accounting statements because the statements report only on water resources yet to be shared. Water held in off-channel water storages is considered to be abstracted from the shared pool of water resources and, as such, is not included as part of the region.

Water in store

The volume of water held in off-channel water storages (27.1 Off-channel water storages) decreased marginally from 15,158 ML at the beginning of the 2011–12 year to 14,798 ML at the end of the 2011–12 year. This decrease in off-channel water storage is attributed to outflow exceeding inflows (see 'Change in water store'). 

The volume of water reported for off-channel water storages included only storages filled primarily by rainfall-runoff harvesting. Volumes of water held in off-channel water storages filled by groundwater extractions, surface water diversions, or recycled water were excluded as these volumes could not be quantified in a way that is complete, neutral and free from material error, due to a lack of available data; however, it is expected that this volume is not material as these types of off-channel water storages only make up a small proportion of off-channel water storage capacity within the Adelaide region.

Change in water store

The volumes reported in Table 18 do not include flows to or from rainwater tanks. The majority of volumes reported for inflows and outflows to off-channel water storages were modelled (see individual item quantification approaches), with the exception of a small portion of water use (31.3 Water use). Data were unavailable for inflows to off-channel water storages via surface water diversions and groundwater extractions.

The only volumes reported for inflows to off-channel water storages were runoff harvesting and precipitation, both of which made a significant contribution to the overall inflow to off-channel water storages in the 2011–12 year; however, inflows were approximately 40% less in the 2011–12 year, primarily driven by reduced runoff and average rainfall conditions experienced throughout the 2011–12 year compared to the 2010–11 year (refer to the Rainfall section of the Contextual information).

Evaporation from off-channel water storages was the most significant outflow from off-channel water storages, more than twice the volume reported for water use and more than inflows from runoff harvesting. Overall, outflows from off-channel water storages decreased marginally in the 2011–12 year compared to the 2010–11 year, but importantly in the 2011–12 year outflows exceeded inflows.


Table 18  Inflows and outflows for the off-channel water store in the Adelaide region during the 2011–12 year

2011–12 volume (ML)

2010–11 volume (ML)

30 Off-channel water inflows

 

30.1 Precipitation on off-channel water store

11,145
13,768

30.2 Groundwater discharge into off-channel water store



30.3 Runoff harvesting into off-channel water store

12,232
18,643

30.4 Surface water diversion into off-channel water store


 –

30.5 Groundwater extraction into off-channel water store



Total 30 Off-channel water inflows 23,377
32,411



31 Off-channel water outflows

 

31.1 Evaporation from off-channel water storages

17,056
18,639

31.2 Leakages from off-channel water storages

930
1,011

31.3 Off-channel water abstraction

6,213
7,970
Total 31 Off-channel water outflows 24,199
27,620


 
Balancing item—off-channel water store
(462)
(7)


 
Change in off-channel water storage
(360)
4,798


 
Opening off-channel water storage
15,158
10,360
Closing off-channel water storage 14,798
15,158

Balancing item—off-channel water store

This volume represents the volume necessary to reconcile the opening and closing balances of the off-channel water storage with the physical water inflows and outflows. The balancing item was calculated according to Table 19.


Table 19  Balancing item for the off-channel water store for the 2011–12 year
  Account Volume (ML)
  Opening balance (30 June 2011) 15,158
add Total off-channel water inflows (see Table 18) 23,377
less Total off-channel water outflows (see Table 18) 24,199
less Closing balance (30 June 2012) 14,798
  Balancing item—off-channel water store (462)


The calculation of the water balance on the off-channel water storages yielded a negative balance of 462 ML. Although a large balancing item was not observed for the off-channel water store, it should be noted that volumes reported were derived from modelled data. The modelling process essentially constrains the data to achieve a water balance, hence removing any large balancing difference.