Adelaide
Water resources and systems

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

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

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.

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

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

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).

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

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

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).

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

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

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

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

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.

• 10.4 Recharge from surface water
• 10.8 Managed aquifer recharge – private user
• 18.5 Discharge to off-channel water storage
• 18.7 Groundwater extractions – other statutory rights

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.

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).

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 

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.

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'.

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).

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	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

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

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.

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%).

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.

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.

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'.

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

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

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.

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.

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.

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

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.