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 2012–13 year. The water stores and systems included in the region are shown in Figure 1.

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

Figure 1 Schematic diagram of the water stores and systems within the Adelaide region
Figure 1 Schematic diagram of the water stores and systems within the Adelaide region

Information on all water flows to and from each water store and system are presented in the following set of notes, 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. The allocation announcement, forfeiture, and allocation remaining line items associated with each between-store abstraction (brown arrows in Figure 2) are also shown in italics in the following notes.

Surface water

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 2012–13 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 2013 (ML) Volume at 30 June 2012 (ML)
1 Surface water

1.1 Storages 87,330 97,182
1.2 Unregulated river 402 481
1.4 Lakes and wetlands

Total surface water assets 87,732 97,663



Water liabilities

5 Surface water liability

5.1 Surface water allocation remaining 574 377
5.2 Surface water allocation remaining – urban water system 0 0
Total surface water liabilities 574 377



Opening net water assets 97,286 137,376
Change in net water assets (10,128) (40,090)
Closing net water assets 87,158 97,286

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 2012–13 year, is shown in Figure 3.



Figure 3 Location map of the storages within the Adelaide region; the % full volume on 30 June 2013 for each storage is also shown
Figure 3 Location map of the storages within the Adelaide region; the % full volume on 30 June 2013 for each storage is also shown

Surface water storage in the Adelaide region decreased marginally (approximately 5% across all storages) during the 2012–13 year (Table 1). While several reservoirs recorded small storage increases, this was not realised for Adelaide's total surface water storage, due predominantly to a substantial decrease in storage volume (10,749 ML) for South Para Reservoir, Adelaide's second largest reservoir. Mount Bold (Adelaide's largest storage) and Millbrook reservoirs also recorded decreases in storage volume. At the end of the 2012–13 year, the volume of water held in storages as a proportion of total storage capacity was 44% across the Adelaide region, down from 49% at the end of the 2011–12 year (Figure 3).

The decrease in surface water storage volume is attributed to below average rainfall conditions (refer to the Rainfall section of the "Contextual information") experienced across much of the Adelaide region during the 2012–13 year. Rainfall was very much below average in the northern parts of the Adelaide region, where South Para and several other reservoirs are located. These conditions contributed to below average streamflows in the major river systems, and, overall, decreased inflows into the storages during the 2012–13 year.

Despite below average rainfall conditions in the Adelaide region, a small increase in runoff was observed during the 2012–13 year compared to the 2011–12 year. This can be explained by high soil moisture levels and groundwater storage left over from the 2011–12 year; June 2012 was the wettest June since 2005. Thus wetter soils at the beginning of the year and greater groundwater base flows contributed to a small increase in runoff in the 2012–13 year, compared to the 2011–12 year.

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 (numbers in brackets are negatives).

Table 2  Statement of Changes in Water Assets and Water Liabilities
Water asset increases 2012–13 volume (ML) 2011–12 volume (ML)
9 Surface water increases

9.1 Precipitation on surface water 6,783 9,770
9.3 Groundwater discharge 72,148 72,148
9.4 Runoff to surface water 286,463 280,833
9.6 Overbank flood return to channel

9.9 Discharge from urban water system 4,620 2,203
Total surface water asset increases 370,014 364,954



Water liability decreases

13 Surface water liability decreases

13.1 Adjustment and forfeiture of surface water allocation 2,210 1,919
13.2 Adjustment and forfeiture of surface water allocation – urban water system 85,719
0
Total surface water decreases 87,929
1,919



Water asset decreases

17  Surface water decreases

17.1 Evaporation from surface water 14,741 15,943
17.2 River outflow from the region 100,442 137,375
17.3 Discharge from surface water to groundwater

17.4 Surface water leakage to landscape

17.5 Overbank flood spilling

17.6 Surface water diversions – other statutory rights 2,006 2,230
17.8 Entitled diversion of non-allocated surface water to urban water system 0 101,099
Total surface water asset decreases 117,189 256,647



Water liability increases

21 Surface water liability increases

21.1 Surface water allocation announcements 3,417 3,412
21.2 Surface water allocation announcements – urban water system 143,000 0
Total surface water liability increases 146,417 3,412



Balancing item—surface water 204,465
146,904



Change in net water assets (10,128) (40,090)

Table 3  Statement of Water Flows for the surface water store
Water inflows 2012–13 volume (ML) 2011–12 volume (ML)
9 Surface water inflows

9.1 Precipitation on surface water 6,783 9,770
9.3 Groundwater discharge 72,148 72,148
9.4 Runoff to surface water 286,463
280,833
9.6 Overbank flood return to river channel

9.9 Discharge from urban water system 4,620 2,203
Total surface water inflows 370,014
364,954



Water outflows

17 Surface water outflows

17.1 Evaporation from surface water 14,741
15,943
17.2 River outflow from the region 100,442 137,375
17.3 Discharge from surface water to groundwater

17.4 Surface water leakage to landscape

17.5 Overbank flood spilling

17.6 Surface water diversions – other statutory rights 2,006 2,230
17.8 Entitled diversion of non-allocated surface water to urban water system 0 101,099
17.11 Entitled diversion of allocated surface water to users 1,010 1,116
17.12 Entitled diversion of allocated surface water to urban water system 57,281 0
Total surface water outflows 175,480
257,763



Balancing item—surface water 204,465
146,904



Change in net water storage (9,931) (39,713)



Opening water storage 97,663 137,376
Change in water storage (9,931) (39,713)
Closing water storage 87,732 97,663

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 2012–13 year; line item numbers are in brackets
Figure 4 Schematic diagram of water inflows and outflows for the surface water store within the Adelaide region during the 2012–13 year; line item numbers are in brackets


Surface water diversions

The total volume of surface water diversions in the Adelaide region during the 2012–13 year was 60,297 ML comprising of line items 17.8, 17.11 and 17.12. The majority of surface water diversions in the Adelaide region during the 2012–13 year were for delivery of water to the urban water system (line item 17.12 Entitled diversion of allocated surface water to urban water system), accounting for approximately 95% of all surface water diversions. The volume diverted to the urban water system in the 2012–13 year is considerably less (43%) than the volume diverted during the 2011–12 year (Figure 5), reflecting the shift towards other water sources for urban supply, such as desalinated water and River Murray water (refer to Figure 10 in the Urban water section of the 'Water resources and systems' note).

During the 2012–13 year, SA Water was issued with a licence to divert up to an annual maximum of 143,000 ML of surface water from the Western Mount Lofty Ranges Prescribed Water Resources Area for the purposes of public water supply. Consequently, the volume of water diverted from surface water during the 2012–13 year was reported at line item 17.12 Entitled diversion of allocated surface water to urban water system, rather than line item 17.8 Entitled diversion of non-allocated surface water to urban water system used in 2011–12. It is suitable to compare the two volumes to show changes in the volume of surface water diverted for urban water supply between reporting years.

Collectively, licenced surface water diversions for private use (line item 17.11 Entitled diversion of allocated surface water to users) and unlicenced surface water diversions (line item 17.6 Surface water diversions – other statutory rights) accounted for only a very small portion 3,016 ML, which is 5% of surface water diversions in the Adelaide region during the 2012–13 year, and were marginally less than during the 2011–12 year (3,346 ML).

Figure 5 Graph of surface water diversions from storages within the Adelaide region during the 2012–13 year and the 2011–12 year; line item numbers are given in brackets
Figure 5 Graph of surface water diversions from storages within the Adelaide region during the 2012–13 year and the 2011–12 year; line item numbers are given in brackets

* Volumes represented in graph are for line item 17.12 for the 2012–13 year and line item 17.8 for the 2011–12 year.
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 4.

Table 4  Balancing item for the surface water store for the 2012–13 year
 Account Volume (ML)
Opening water storage (at 1 July 2012)
97,663
Total water inflows (see Table 3)
370,014
Total water outflows (see Table 3) (175,480)
Closing water storage (at 30 June 2013)
(87,732)
Balancing item—surface water 204,465

The calculation of the water balance on the surface water store yielded a balance of 204,465 ML. This is approximately 233% of the total surface water store volume at the end of the 2012–13 year and 55% of the total surface water inflows during the 2012–13 year. It also represents a 40% increase in the surface water store balancing item compared to 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 or only partly quantified include evaporation from and precipitation to rivers (except at certain weirs), as well as some surface water/groundwater and surface water/landscape interactions.

River outflow to sea was only partially quantified and 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. River outflow is also only quantified where there are appropriate gauging stations. In the 2012–13 Account three streamflow gauging sites were removed from the quantification of this line item as the period of record for these three sites ended in August 2010 and it was not suitable to interpolate data for these sites (refer to Water accounting policies for further information). As such, river outflow to sea is likely to be underestimated by 10–20% (up to +/–  20,000 ML).

A large component of the balancing item is also attributed to the quantification of rainfall-runoff (line item 9.4 Rainfall runoff). The volume is derived from a rainfall-runoff model and it is reasonable to expect a level of uncertainty in the modelled runoff volume.

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 volume reported as the groundwater asset at 30 June 2013 (88,017 ML) comprised of the managed groundwater volume described by the relevant water allocation plan, and the carryover balance of managed aquifer recharge credits (refer to line item 2.5 Other groundwater assets for a more detailed explanation). The groundwater asset did not include the Northern Adelaide Plains, Central Adelaide Plains and Dry Creek prescribed wells areas.

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 negative).

Table 5  Statement of Water Assets and Water Liabilities for the groundwater store
Water assets Volume at 30 June 2013 (ML)
Volume at 30 June 2012 (ML)
2 Groundwater

2.1 Water table aquifer
2.2 Underlying aquifers
2.5 Other groundwater assets 88,017 90,858
Total groundwater assets 88,017 90,858



Water liabilities

6 Groundwater liability

6.1 Groundwater allocation remaining 3,941 6,641
Total groundwater liabilities 3,941 6,641



Opening net water assets 84,217 84,705
Change in net water assets (141) (488)
Closing net water assets 84,076 84,217

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.

Inflows to the groundwater store were largely due to recharge from the landscape, which increased in the 2012–13 year compared to the 2011–12 year. Despite below average rainfall conditions in the Adelaide region, an increase in groundwater recharge  was observed during the 2012–13 year compared to the 2011–12 year. This can be explained by high soil moisture levels left over from the 2011–12 year (June 2012 was the wettest June since 2005) and the duration, frequency and intensity of rainfall events during the 2012–13 year.

Outflows from the groundwater store mainly comprised discharge to the landscape, which increased in the 2012–13 year compared to the 2011–12 year.


Table 6  Statement of Changes in Water Assets and Water Liabilities for the groundwater store
Water asset increases 2012–13 volume (ML) 2011–12 volume (ML)
10 Groundwater increases

10.1 Groundwater inflow from outside region 31 38
10.2 Groundwater inflow from outside region at coast 1,562 1,938
10.3 Recharge from landscape 373,428
303,370
10.4 Recharge from surface water to groundwater

10.5 Leakage from off-channel water storage 999 1,038
10.6 Leakage from urban water system 16,529 14,718
10.7 Leakage from irrigation scheme 0 33
10.8 Managed aquifer recharge – other schemes

10.9 Managed aquifer recharge – urban water system 113 0
Total groundwater assets increases 392,662 321,135



Water liability decreases

14 Groundwater liability decreases

14.1 Adjustment and forfeiture of groundwater allocation 23,515 24,851
Total groundwater liability decreases 23,515 24,851



Water asset decreases

18 Groundwater decreases

18.1 Groundwater outflow to outside region 510 405
18.2 Groundwater outflow to outside region at coast 842 921
18.3 Discharge to landscape 108,290
102,443
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 26,647
18.10 Entitled extraction of non-allocated groundwater to irrigation scheme 112 0
Total groundwater decreases 208,549
175,917



Water liability increases

22 Groundwater liability increases

22.1 Groundwater allocation announcements 48,343 43,923
Total groundwater liability increases 48,343 43,923



Balancing item—groundwater
159,426 126,634



Change in net water assets (141) (488)


Table 7  Statement of Water Flows for the groundwater store
Water inflows 2012–13 volume (ML) 2011–12 volume (ML)
10 Groundwater inflows

10.1 Groundwater inflow from outside region 31 38
10.2 Groundwater inflow from outside region at coast 1,562 1,938
10.3 Recharge from landscape 373,428
303,370
10.4 Recharge from surface water to groundwater

10.5 Leakage from off-channel water storage 999 1,038
10.6 Leakage from urban water system 16,529 14,718
10.7 Leakage from irrigation scheme 0 33
10.8 Managed aquifer recharge – other schemes

10.9 Managed aquifer recharge – urban water system 113 0
Total groundwater inflows 392,662 321,135



Water outflows

18 Groundwater outflows

18.1 Groundwater outflow to outside region 510 405
18.2 Groundwater outflow to outside region at coast 842 921
18.3 Discharge to landscape 108,290
102,443
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 26,647
18.10 Entitled extraction of non-allocated groundwater to irrigation scheme 112 0
18.11 Entitled extraction of allocated groundwater to users 27,528 17,379
Total groundwater outflows 236,077
193,296



Balancing item—groundwater 159,426
126,634



Opening water storage 90,858 89,653
Change in water storage (2,841) 1,205
Closing water storage 88,017 90,858

A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Adelaide region is provided in Figure 6. 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 2012–13 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 2012–13 year; line item numbers are provided in brackets

Groundwater extractions

The total volume of groundwater extractions in the Adelaide region during the 2012–13 year was 54,287 ML, comprising of line items 18.7, 18.10 and 18.11. Groundwater extractions for private licenced use accounted for 51% of all groundwater extractions in the Adelaide region during the 2012–13 year (line item 18.11 Entitled extraction of allocated groundwater). Non-licenced groundwater extractions accounted for the remaining 49% of all groundwater extractions in the Adelaide region during the 2012–13 year (line item 18.7 Groundwater extractions – other statutory rights), including a very small volume (112 ML) of groundwater extracted and provided to the irrigation scheme (18.10 Entitled extraction of non-allocated groundwater to irrigation scheme) for subsequent reuse as part of a managed aquifer recharge program.

Figure 7, shows that the volume of licensed groundwater extracted (line item 18.11) increased substantially (almost 60%) in the 2012–13 year and was approximately 60% of the total volume allocated (line item 22.1 Groundwater allocation announcements). This increase may be the result of below average rainfall experienced throughout the Adelaide region, increasing demand on other water resources such as groundwater. Non-licensed groundwater extractions were not quantified for the 2011–12 year; however, a comparable volume (29,589 ML) was extracted during the 2010–11 year (refer 2011 Account for further information).

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  Graph of extractions from aquifers within the Adelaide region during the 2012–13 year and the 2011–12 year; line item numbers are given in brackets
Figure 7  Graph of extractions from aquifers within the Adelaide region during the 2012–13 year and the 2011–12 year; line item numbers are given in brackets

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 8.

Table 8  Balancing item for the groundwater store for the 2012–13 year
 Account Volume (ML)
Opening water storage (at 1 July 2012)
90,858
Total groundwater inflows (see Table 7)
392,662
Total groundwater outflows (see Table 7
(236,077)
Closing water storage (at 30 June 2013
(88,017)
Balancing item—groundwater
159,426

The calculation of the water balance on the groundwater store yielded a difference of 159,426 ML, approximately 41% of the total groundwater inflows during the 2012–13 year. This value is considerably larger than that reported for the 2011–12 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 because:

  • 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 2012–13 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, the Adelaide Plains, and the Fractured rock (Figure 8). The change in groundwater levels were estimated using all bores within the water table and using a buffer around the bores. The results are shown in the Table 9 for the 2012–13 year.

Table 9  Change in aquifer storage estimated for the 2012–13 year

Management area

Volume (ML)

McLaren Vale PWA water table

1,639

Adelaide Plains water table

(5,768)

Fractured rock aquifers

(4,304)

Total

(8,433)

 

The decrease in aquifer storage for the 2012–13 year shown in Table 9 is inconsistent with an increase in groundwater inflows during the 2012–13 year (392,662 ML) compared to the 2011­–12 year (321,135 ML). The recharge volume estimate does not take into consideration the time lag that occurs between the rainfall infiltrating into the soil and water actually reaching the watertable. The recharge in 2012–13 may not have fully reached the watertable within the year. In addition evapotranspiration from groundwater may prevent part of the modelled recharge actually reaching the watertable. Therefore, it is feasible for groundwater storage levels to decrease, while modelled recharge estimates increase. Missing terms in the groundwater balance also prevent a meaningful comparison with groundwater inflows and groundwater outflows.

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 Geographic Information System (GIS) approach based on measured groundwater levels and aquifer properties. Firstly, groundwater levels at the start (1 July 2012) and the end (30 June 2013) of the 2012–13 year were estimated. This was achieved by considering all groundwater level measurements between March 2012–October 2012 and March 2013–October 2013, 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 in the sedimentary aquifers and within a 3 km radius around each bore in the Fractured rock 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


Approximation, assumptions, caveats and limitations

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 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 for the sedimentary aquifers in agreement with the Adelaide Plains groundwater model report (Aquaterra 2011). A constant specific yield of 0.01 was used for the Fractured rock aquifers (Stewart and Green 2010; Healy and Scanlon 2010).

Uncertainty

The uncertainty in the field-measured data (e.g., groundwater levels, specific yield) was not specified and hence the impact 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

The urban water system within the Adelaide region is discussed in the Other water resources and systems section 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 did not change during the 2012–13 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 2013 (ML) Volume at 30 June 2012 (ML)
3 Urban water system

3.1 Urban water supply system 1,414 1,414
3.2 Wastewater system 96 96
3.3 Recycled water system 17 17
3.4 Urban inter-region claim on water 0 0
3.7 Urban claim on surface water 0 0
Total urban water system assets 1,527 1,527



Opening net water assets 1,527 1,524
Change in net water assets 0 3
Closing net water assets 1,527 1,527


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.

Table 11  Statement of Changes in Water Assets and Water Liabilities for the urban water system
Water asset increases 2012–13 volume (ML) 2011–12 volume (ML)
11 Urban water system increases

11.2 Entitled diversion of non-allocated surface water to urban water system 0 101,099
11.4 Wastewater collected 91,043 90,921
11.6 Delivery of desalinated water to urban water system 36,472 3,816
11.15 Increase of inter-region claim on water by urban water system 130,000 130,000
11.18 Increase of urban claim on surface water 143,000 0
Total urban water system asset increases 400,515 325,836



Water asset decreases

19 Urban water system decreases

19.3 Urban water system leakage to groundwater 16,529 14,718
19.4 Delivery to urban water system users 141,892 133,356
19.5 Discharge from urban water system to surface water 4,620 2,203
19.6 Discharge from urban water system to irrigation scheme 21,586 17,322
19.7 Wastewater discharge outside of region 59,264 63,032
19.9 Managed aquifer recharge 113 0
19.11 Transfer of water outside of region 4,053 3,739
19.14 Adjustment and forfeiture of urban inter-region claim on water 61,580 82,523
19.17 Adjustment and forfeiture of urban claim on surface water 85,719
0
19.20 Other urban water system decreases 1,591
8,460
Total urban water system asset decreases 396,947
325,353



Balancing item—urban water system
3,568
480



Change in net water assets 0 3

 

Table 12  Statement of Water Flows for the urban water system
Water inflows 2012–13 volume  (ML) 2011–12 volume  (ML)
11 Urban water system inflows

11.2 Entitled diversion of non-allocated surface water to urban water system 0 101,099
11.4 Wastewater collected 91,043 90,921
11.6 Delivery of desalinated water to urban water system 36,472 3,816
11.9 Delivery of water to urban water system under inter-region agreement 68,420 47,477
11.12 Entitled diversion of allocated surface water to urban water system 57,281
0
Total urban water system inflows 253,216 243,313



Water outflows

19 Urban water system outflows

19.3 Urban water system leakage to groundwater 16,529 14,718
19.4 Delivery to urban water system users 141,892 133,356
19.5 Discharge from urban water system to surface water 4,620 2,203
19.6 Discharge from urban water system to irrigation scheme 21,586
17,322
19.7 Wastewater discharge outside of region 59,264 63,032
19.9 Managed aquifer recharge 113 0
19.11 Transfer of water outside of region 4,053 3,739
19.20 Other urban water system decreases 1,591 8,460
Total urban water system outflows 249,648 242,830



Balancing item—urban water system 3,568
480



Change in net water storage 0 3



Opening water storage 1,527 1,524
Change in water storage 0 3
Closing water storage 1,527 1,527

 

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 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 within the Adelaide region during the 2012–13 year; line item numbers are provided in brackets
Figure 9  Schematic diagram of water inflows and outflows for the urban water system within the Adelaide region during the 2012–13 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:


Figure 10   Sources of water for the Adelaide region's urban water supply system during the 2012–13 year and the 2011–12 year; line item numbers are given in brackets
Figure 10   Sources of water for the Adelaide region's urban water supply system during the 2012–13 year and the 2011–12 year; line item numbers are given in brackets


* Volumes represented in graph are for line item 11.12 for the 2012–13 year and line item 11.2 for the 2011–12 year.

During the 2012–13 year, SA Water was issued with a licence to divert up to an annual maximum of 143,000 ML of surface water from the Western Mount Lofty Ranges Prescribed Water Resources Area for the purposes of public water supply. Consequently, the volume of water diverted from surface water during the 2012–13 year was reported at line item 11.12 Entitled diversion of allocated surface water to urban water system, rather than line item 11.2 Entitled diversion of non-allocated surface water to urban water system used in 2011–12, due to the fact that there was no entitlement issued. It is suitable to compare the two volumes to show changes in the volume of surface water diverted for urban water supply between reporting years.

During the 2012–13 year there was a small increase (approximately 6%) in the total volume of water supplied to the urban water system from 152,392 ML in 2011–12 to 162,173 ML. Despite this increase in demand on urban water sources, there was a considerable decrease (43%) in the volume of surface water harvested from the Adelaide region's catchments and diverted for urban water supply, compared to the 2011–12 year. This is not surprising given the below average rainfall conditions and decreasing surface water storage volumes (refer to the 'Surface water' section of the Water resources and systems note). The decreased use of surface water for urban supply within the Adelaide region was reflected by a shift towards other water sources. Desalinated water supplied to the urban water system (line item 11.6 Delivery of desalinated water to urban water system) increased by almost ten times the volume supplied in the 2011–12 year. The volume of River Murray water imported into the region (line item 11.9 Delivery of water to urban water system under inter-region agreement) also increased by almost 45% compared to the 2011–12 year.

As shown in Figure 10, the shift in proportions of water resources contributing to the urban water supply system resulted in 35% of urban water sourced from surface water harvested within the Adelaide region (line item 11.12 Entitled diversion of allocated surface water to urban water system), 23% of urban water sourced from desalination (line item 11.6 Delivery of desalinated water to urban water system), and 42% of urban water sourced from the River Murray (line item 11.9 Delivery of water to urban water system under inter-region agreement).

Discharge from the wastewater system

Most of the treated wastewater from the wastewater system is discharged to the sea (line item 19.7) accounting for approximately 64% of wastewater in the Adelaide region. The remaining treated wastewater is either discharged to surface water (line item 19.5: 2,197 ML or 2%), lost through treatment processes (line item 19.20: 1,591 ML or 2%) or recycled for use (32%).

The majority of recycled water produced (75%) was provided to the region's irrigation schemes (line item 19.6). Approximately 17% was supplied for urban consumption (part of line item 19.4) and a very small volume (<1%) was injected to groundwater as part of the Aldinga Aquifer Storage and Recovery Scheme (line item 19.9 volume:113 ML). The remaining recycled water (approximately 8%) was recirculated back into the wastewater system (and therefore not reported in the water accounting statements). 

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 2012–13 year
  Volume (ML)
Opening water storage (at 1 July 2012)
1,527
Total water inflows (see Table 12)
253,216
Total water outflows (see Table 12)
(249,648)
Closing water storage (at 30 June 2013)
(1,527)
Balancing item—urban water system 3,568

 

The calculation of the water balance on the urban water system yielded a balance item of 3,568 ML. This is 1.4% of the total urban water system inflows during the year 2012–13 year. This misbalance may be due to a number of factors such as metering inaccuracies, unaccounted losses and inaccuracies in the estimation of certain volumes.

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 2012–13 year in the Adelaide region.

Table 14 Statement of Water Assets and Water Liabilities for the irrigation scheme
Water assets Volume at 30 June 2013 (ML) Volume at 30 June 2012 (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 29
Change in net water assets 0 0
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 tables 15 and 16 respectively.

Table 15 Statement of Changes in Water Assets and Water Liabilities for the irrigation scheme

2012–13 volume (ML) 2011–12 volume (ML)
Water asset increases

12 Irrigation scheme increases

12.1 Precipitation on irrigation scheme

12.3 Entitled extraction of non-allocated groundwater to irrigation scheme 112 0
12.4 Discharge from urban water system to irrigation scheme 21,586
17,322
12.12 Increase of irrigation scheme inter-region claim on water 7,852 6,653
12.18 Other irrigation scheme increases 600 228
Total irrigation scheme asset increases 30,150
24,203



Water asset decreases

20 Irrigation scheme decreases

20.1 Evaporation from irrigation scheme

20.3 Leakage to groundwater 0 33
20.4 Delivery to irrigation scheme users 26,170 19,478
20.9 Adjustment and forfeiture of irrigation scheme inter-region claim on water 486 2,662
Total irrigation scheme asset decreases 26,656 22,173



Balancing item—irrigation scheme
3,494
2,030



Change in net water assets 0 0


Table 16  Statement of Water Flows for the irrigation scheme
Water inflows 2012–13 volume (ML) 2011–12 volume (ML)
12 Irrigation scheme inflows

12.1 Precipitation on irrigation scheme

12.3 Entitled extraction of non-allocated groundwater to irrigation scheme 112 0
12.4 Discharge from urban water system to irrigation scheme 21,586 17,322
12.6 Delivery of water to irrigation scheme under inter-region agreement 7,366 3,991
12.18 Other irrigation scheme increases 600 228
Total irrigation scheme inflows 29,664
21,541



Water outflows

20 Irrigation scheme outflows

20.1 Evaporation from irrigation scheme

20.3 Leakage to groundwater 0 33
20.4 Delivery to irrigation scheme users 26,170 19,478
Total irrigation scheme outflows 26,170 19,511



Balancing item—irrigation scheme
3,494 2,030



Change in net water storage 0 0



Opening net water assets 29 29
Change in net water assets 0 0
Closing net water assets 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 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 2012–13 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 2012–13 year; line item numbers are provided in brackets


During the 2012–13 year 29,664 ML of water was supplied to the irrigation scheme within the Adelaide region, representing a 38% increase compared to the 2011–12 year (see Table 16). As shown in Figure 12, this increased demand was observed across all irrigation scheme water sources, likely due to the below average rainfall conditions experienced across the Adelaide region during the 2012–13 year.

Recycled water supplied from the urban water system (12.4 Discharge from urban water system to irrigation scheme) makes up the largest proportion (73%) of water sourced for the irrigation scheme, with River Murray water (12.6 Delivery of water to irrigation scheme under inter-region agreement) being the other major water source (25% of total water supplied). Recycled water supplied by community wastewater management schemes (12.18 Other irrigation scheme increases) and recycled water injected to groundwater and subsequently recovered (12.3 Entitled extraction of non-allocated groundwater to irrigation scheme) made up the remaining 2% of water sources for the irrigation scheme.


Figure 12  Sources of water for the Adelaide region's irrigation scheme during the 2012–13 year and the 2011–12 year; line item numbers are given in brackets
Figure 12  Sources of water for the Adelaide region's irrigation scheme during the 2012–13 year and the 2011–12 year; line item numbers are given in brackets


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. 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 irrigation scheme store balance.

The balancing item is calculated according to Table 17.

Table 17  Balancing item for the irrigation scheme for the 2012–13 year
  Volume (ML)
Opening water storage (at 1 July 2012)
29
Total water inflows (see Table 16)
29,664
Total water outflows (see Table 16) (26,170)
Closing water storage (at 30 June 2013)
(29)
Balancing item—irrigation scheme
3,494

 

The calculation of the water balance on irrigation schemes yielded a balancing item of 3,494 ML. This is approximately 12% of the total irrigation schemes inflows during the 2012–13 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.
  • Inconsistent time periods for measurement: The irrigation year is October–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 from 16,764 ML at the beginning of the 2012–13 year to 14,913 ML at the end of the 2012–13 year.

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.

Change in water store

The majority of volumes reported for inflows and outflows to off-channel water storages were modelled (see individual item quantification approaches). 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 2012–13 year. Inflows to off-channel water storages during the 2012–13 year were approximately 6% less than in the 2011–12 year, primarily driven by reduced precipitation and below average rainfall conditions experienced throughout the 2012–13 year (refer to the Rainfall section of the 'Contextual information').

Despite below average rainfall conditions in the Adelaide region, a small increase in runoff was observed during the 2012–13 year compared to the 2011–12 year. This can be explained by high soil moisture levels and groundwater storage left over from the 2011–12 year; June 2012 was the wettest June since 2005. Thus wetter soils at the beginning of the year and greater groundwater base flows contributed to a small increase in runoff in the 2012–13 year, compared to the 2011–12 year.

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 2012–13 year compared to the 2011–12 year.

Table 18  Inflows and outflows for the off-channel water store in the Adelaide region during the 2012–13 year

 

2012–13 volume (ML)

2011–12 volume (ML)1

30 Off-channel water inflows

 

 

30.1 Precipitation on off-channel water store

9,063

11,385

30.2 Groundwater discharge into off-channel water store

30.3 Runoff harvesting into off-channel water store

12,286

11,290

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

21,349

22,675

 

 

 

31 Off-channel water outflows

 

 

31.1 Evaporation from off-channel water storages

15,952

15,995

31.2 Leakages from off-channel water storages

999

1,038

31.3 Off-channel water abstraction

6,248

6,654

Total 31 Off-channel water outflows

23,199

23,687

 

 

 

Balancing item—off-channel water storage

1

0

 

 

 

Change in off-channel water storage

(1,851)

(1,015)

 

 

 

Opening off-channel water storage

16,764

17,779

Closing off-channel water storage

14,913

16,764

1 The volumes reported for the 2011–12 year are different from those presented in the 2012 Account due to a change in quantification approach and an error in the method used to calculate the volumes reported in the 2012 Account.

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 2012–13 year
Account Volume (ML)
Opening balance (at 1 July 2012) 16,764
Total off-channel water inflows (see Table 18) 21,349
Total off-channel water outflows (see Table 18) (23,199)
Closing balance (at 30 June 2013) (14,913)
Balancing item—off-channel water storage 1


The calculation of the water balance on the off-channel water storages yielded a balance of one. The volumes reported were derived from modelled data and the modelling process essentially constrains the data to achieve a water balance, hence removing any large balancing difference.