National Water Account 2015

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Region overview

Contextual information

Physical information

Administration

Water rights

Climate and water overview

Water Accounting Statements

Water Assets and Water Liabilities

Changes in Water Assets and Water Liabilities

Water Flows

Notes

Accounting policies

Supporting information

Quantification approach

Reconciliations

Water resources & systems

Water access & use

Future outlook

References

Accountability statement

Adelaide: Supporting information

Introduction

The following set of notes provides consolidated reports for each of the water stores and systems within the Adelaide region during the 2014–15 year. The water stores and systems included in the region are shown in Figure N1.

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

Figure N1 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 N2.

Figure N2 Between-store flows that occur within the Adelaide region

The between-store flows and transfers (Figure N2), which are eliminated from the region's water accounting statements, are shown in italics throughout the following set of notes.

Surface water store

The Adelaide region's surface water store has two components:

• storages
• unregulated rivers.

A reconciliation of the surface water Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N2. Further details on assets, liabilities, and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical assets

Physical surface water asset volumes in the Adelaide region at 30 June 2015 were 95,231 ML, representing the volume of water held in storages (94,769 ML) and water held in river weirs (462 ML).

The volume of water in rivers, lakes, and wetlands could not be quantified due to a lack of available data; however, the volume of water held in channels and lakes is considered to be relatively small compared to the volume held in storages.

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 2014–15 year is shown in Figure N3.

 
Figure N3 Percentage-full volume on 30 June 2015 for each storage

The overall storage volume within the Adelaide region during the 2014–15 year was 23% less than that during the previous year at 48% capacity. The volume of water in all six of the largest storages decreased compared to the previous year (Figure N4). Below average inflows resulting from below average rainfall are the main reason for the decrease in storage volumes. There was also an increase of water supplied to the urban water system in the 2014–15 year due to a decrease in the supply of desalinated water which put added pressure on storage volumes.

Catchment runoff was the main contributor to storage volumes. During the 2014–15 year, 88,300 ML of surface water runoff reached the storages within the region. This volume is just 37% of the total runoff that reached rivers, storages, and wetlands within the region. The runoff volume to storages was 43% less than that observed for the previous year reflecting the effects of below-average rainfall during the year.

Total volume of water within each storage at 30 June 2015 compared with the previous year and the 5-year average is given in Figure N4.

Figure N4 Total volume of water in each storage at 30 June 2015 compared with the previous year and the 5-year average

Non-physical assets

There are no non-physical surface water assets in the region.

Liabilities

Surface water liabilities in the Adelaide region refer to the volume of surface water allocation remaining on licence entitlements at the end of the 2014–15 year for:

• individual users (614 ML)
• urban water system (0 ML).
  

The surface water licences in the Adelaide region have a management year which ends on 30 June. In the Barossa Prescribed Water Resources Area, licensees for the North Para River and tributaries may carry-over the unused portion of their allocation up to a maximum of 30% of the annual allocation, whereas for Little Para Prescribed Water Course carry-over is not permitted (Adelaide and Mount Lofty Ranges Natural Resources Management Board 2013).

Allocation remaining for individual users was 614 ML at the end of 2014–15. For the urban water system, carry-over of unused surface water allocation held by SA Water from the Western Mount Lofty Ranges Prescribed Water Resources Area is not permitted; therefore, the allocation remaining is zero. The allocation remaining for each licence entitlement is provided in tables N3–N4.

A more detailed description of surface water allocations and associated water rights in the Adelaide region is given in the Surface water rights note.

Inflows and outflows

A schematic diagram representing all surface water inflows and outflows is provided in Figure N5.

Figure N5 Water inflows and outflows for the surface water store during the 2014–15 year

Inflows

Inflows to surface water decreased (approximately 33%) compared to the previous year. Total inflows to surface water were 384,557 ML and comprised:

• Precipitation—7,096 ML
• Runoff—237,520 ML
• Discharge: groundwater—73,921 ML
• Discharge: urban supply—18 ML
• Discharge: wastewater—2,175 ML
• Delivery: inter-region—63,827 ML.

The largest water inflow was runoff to surface water (237,520 ML) during the 2014–15 year. This volume is about 53% of that during the previous year, which reflects the below average rainfall experienced across the region (see Climate and water overview). The volume comprised of inflow to rivers and surface water storages. Inflow to surface water storages was 88,300 ML, which is 37% of total runoff volume (see Physical assets). Similarly, precipitation that fell on the major storages within the region also decreased compared to the previous year.

Groundwater discharge to surface water (73,921ML) included annual baseflow from groundwater to watercourses within the Western Mount Lofty Ranges Prescribed Water Resources Area and baseflow measured at the Yaldara gauging station on the North Para River. 

A volume of 2,175 ML was discharged to rivers from several wastewater treatment plants, including Angaston, Bird-in-Hand, Hahndorf, and Heathfield. It also included treated wastewater from Victor Harbor wastewater treatment plant, which is temporarily stored in Hindmarsh Reservoir during summer before being released to the Inman River in the winter months.

Discharge: urban supply, is the transfer of 18 ML from Swan Reach–Stockwell pipeline to the South Para River during the 2014–15 year.

Delivery: inter-region, represents receiving entitled River Murray water through three pipelines; Murray Bridge-Onkaparinga, Mannum-Adelaide, and Swan Reach-Stockwell. The volume received during the 2014–15 year (63, 827 ML) is almost double that of the previous year's volume. The increase is to match with reduced storage volumes and decreased desalinated supply within the region.

Surface water outflows

Outflows from surface water decreased (approximately 5%) compared to the previous year. Total outflows from surface water were 273,187 ML and comprised:

• Evaporation—24,651 ML
• Outflow—106,422 ML
• Non-allocated diversion: urban water system—56,943 ML
• Allocated diversion: individual users—2,940 ML
• Allocated diversion: urban water system—78,200 ML
• Other outflow— 4,031 ML.

The largest water outflow is river outflow from the region (106,422 ML), which refers to the annual volume of flow to the sea from most major rivers in the region including Gawler, Torrens, Little Para, and Onkaparinga rivers during the 2014–15 year. This outflow is approximately 64% of river outflow during the previous year, reflecting below-average rainfall during the 2014–15 year compared to the 2013–14 year (see Climate and water overview).

Evaporation from surface water during the 2014–15 year was 24,651 ML, which represents evaporation from the major storages within the region. Total evaporation during the 2014–15 year was approximately 45% higher than the volume estimated during the previous year.

Recharge: groundwater (– ML), Recharge: Landscape (– ML) and Diversion: Other statutory rights (0 ML) were not recognised due to a lack of available data and a suitable quantification approach.

Entitled surface water diversions

Non-allocated diversion: urban water system (56,943 ML) represents a part of River Murray water transferred to surface water storages within the region for urban use. The remainder of transferred River Murray water for urban use is recorded as other outflow (4,031 ML). This volume received through Swan Reach–Stockwell pipeline was delivered directly to the urban water system in the north of the region, from the Swan Reach (WTP).

Allocated diversion: urban water system represents surface water harvested within the Western Mount Lofty Ranges Prescribed Water Resources Area for urban water supply. The volume (78,200 ML) accounts for more than 90% of the total allocation diverted by SA Water from the Western Mount Lofty Ranges Prescribed Water Resources Area for public water supply. Allocated diversion: individual users, (2,940 ML) represents the water diverted for non-urban purposes in Western Mount Lofty Ranges and Barossa prescribed water resources areas (PWRAs). Volumes diverted on PWRA basis are shown in Figure N6. Diversion of 362 ML of the volume carried over from the previous year in Barossa PWRA is not included in Figure N6.

Figure N6 Surface water diversions during the 2014–15 year; percentage of allocation diverted is also shown

Surface water balancing item

The surface water balance (Table N5) yielded a balance of 139,297 ML, indicating that inflows are greater than outflows. The balancing volume is larger than the total surface water store volume at the end of the 2014–15 year and more than a third of the total surface water inflows during the year. The positive balancing item indicates that either the inflows are too high or the outflows are too low.

There are several reasons for the balancing item:

• Some items are not quantified, or very small due to lack of data. This includes evaporation from and precipitation to rivers as well as some surface water/groundwater interactions. River and floodplain losses cannot be quantified in the account. It is likely that these losses are a relatively large source of surface water decrease throughout the region.
• There is uncertainty associated with the meteorological inputs into the rainfall-runoff model and the model structure, estimated to be in the range of 10–20% (up to +/– 45,000 ML). This is common in dry years where runoff models tend to overestimate inflows.
• 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 20,000 ML).

Groundwater store

The Adelaide region's groundwater store has two components:

• water table aquifer
• underlying aquifer.

A reconciliation of the groundwater Statement of Water Assets and Water Liabilities, and Statement of Water Flows is provided in Table N6. Further details on assets, liabilities, and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical Assets

Groundwater in the Adelaide region is described in the Groundwater section in the 'Contextual information'.

There is no information regarding the actual physical volume held in the groundwater aquifers in the Adelaide region. The volume quantified as the groundwater asset refers to the managed groundwater volume reported in relevant water allocation plans. The managed groundwater volume includes groundwater extraction limits and the non-licensed groundwater extractions described by each water allocation plan and does not change from year to year, unless the allocation plan is amended.

Non-physical assets

There are no non-physical groundwater assets in the region.

Liabilities

Groundwater liabilities in the Adelaide region refer to the volume of groundwater allocation remaining on licence entitlements at the end of the 2014–15 year for individual users (7,321 ML)

The groundwater licences in the Adelaide region have a management year that ends on 30 June, and licensees are permitted to carry over up to 30% of their annual water allocation, depending on the management area. There is also provision for a portion of the recharge credit to be carried forward into the following year.

Details on groundwater allocation remaining are provided in table N7.

Inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Adelaide region is provided in Figure N7.

Figure N7 Water inflows and outflows for the groundwater store during the 2014–15 year

Inflows

Inflows to groundwater decreased by 20% compared with the previous year. Total inflows to groundwater were 432,444 ML and comprised:

• Inter-region inflow—27 ML
• Inter-region coastal inflow—1,603 ML
• Recharge: landscape—408,445 ML
• Leakage: farm dams —888 ML
• Leakage: urban system—18,085 ML
• Manage aquifer recharge: individual users—3,186 ML
• Managed aquifer recharge: urban system—210 ML.

Total groundwater inflows from natural sources for the Adelaide region for the 2014–15 year were 429,048 ML made up of recharge from landscape, inter-region inflows, leakage from both the urban system and farm dams. The volume represents 99% of total inflows and 21% less than the volume recorded in the previous year.

The decrease in natural inflow is mostly from recharge: landscape, which represents 95% of the natural inflow volume. The below average rainfall experienced in 8 months of the previous year would provide some explanation for the decrease in recharge. Rainfall during the 2014–15 year was very much below average; however, there is not often an immediate correlation between rainfall that falls within a year and the amount of groundwater recharge within the same year because there is some lag in groundwater movement.

Inter-region inflow represents regional groundwater inflows to the Adelaide region at the northern boundary, through the major sedimentary aquifers in the Adelaide Plains (T1 and T2 aquifers). Inter-region coastal inflow represents the flow at coast through the major sedimentary aquifers in the McLaren Vale Prescribed Wells Area (Maslin Sands, and Port Willunga aquifers) and the Adelaide Plains (T1 and T2 aquifers). Coastal groundwater inflow may be either fresh or saline groundwater and is not meant to represent sea water intrusion into the Adelaide region aquifers; however, localised cones of depression due to groundwater pumping have been identified as a potential problem, particularly for saline sea water intrusion, in the McLaren Vale Prescribed Wells Area (Martin and Hodgkin 2005) and in the Adelaide Plains (Aquaterra 2011). In the McLaren Vale Prescribed Wells Area and Adelaide Plains, salinity monitoring suggests some seawater intrusion may be occurring (Martin 1998; Gerges 1999).

Other sources of natural groundwater inflow was leakage from farm dams and leakage from urban system. Leakage from urban system, which is the second largest inflow, shows an 18% increase during the 2014–15 year compared to the previous year (for more details see Urban water system). 

Local councils and some private organisations in the Adelaide region harvest and treat stormwater through constructed wetlands and storage in aquifers. Harvested storm volume for nine licences is included under managed aquifer recharge: individual users. Data were not available in previous years for the National Water Account.

Managed aquifer recharge: urban system represents the volume of recycled water injected to groundwater as part of the Aldinga Aquifer Storage and Recovery Scheme. Recycled water is supplied from the Christies Beach wastewater treatment plant and injected to the Port Willunga Formation aquifer for temporary storage and then subsequently supplied to the Willunga Basin Water Company for irrigation (see Irrigation inflows below). The reported volume for the 2014–15 year is over three times the volume reported for the previous year.

Recharge: surface water (– ML) and  Leakage: irrigation (0 ML) were not recognised due to a lack of available data and a suitable quantification approach.

Outflows

Outflows from groundwater increased by (27%) compared to the previous year. Outflows from groundwater were 461,859 ML and comprised:

• Inter-region outflow—368 ML
• Inter-region coastal outflow—966 ML
• Discharge: landscape—335,143 ML
• Discharge: surface water—73,921 ML
• Extraction: statutory rights—1,108 ML
• Non-allocated extraction: irrigation—210 ML
• Allocated extraction: individual users—50,143 ML.

Total groundwater outflows excluding extractions (natural outflow) for the 2014–15 year was 410,398 ML. Over 80% of this volume is discharge to landscape. This is an outflow resulting from evapotranspiration from shallow groundwater.

The remainder of natural outflow is mostly due to groundwater discharge to surface water during the 2014–15 year. Discharge to surface water quantifies annual average baseflow to watercourses within the Western Mount Lofty Ranges PWRA and baseflow recorded at Yaldara gauging station.

Inter-region outflow groundwater outflow from Adelaide Plains T1 and T2 aquifers, and inter-region coastal outflow from the major sedimentary aquifers in the McLaren Vale Prescribed Wells Area (Maslin Sands and Port Willunga aquifers) and the Adelaide Plains (T1 and T2 aquifers) also contributed to the natural outflow. The volumes for the 2014–15 year were almost same as the previous year.

The volume of 1,108 ML reported for 'Extraction: statutory rights' represents non-licensed groundwater extractions in Kangaroo Flat portion of the Northern Adelaide Plains Prescribed Wells Area. These extractions are managed by authorisations under ss 128, 132, and 164N of the Act. For further information on these authorisations, refer to Water entitlements and other statutory water rights in 'Contextual information'. The volume reported for the 2014–15 year is different from the previous year volume. This is due to inclusion of allocated extraction volume within the statutory right extraction volume reported for the previous year 2014 NWA due to difficulties in data-sorting.

'Non-allocated extraction: irrigation' represents the volume supplied to the Willunga Basin Water Company for irrigation. This water forms part of the Aldinga Aquifer Storage and Recovery Scheme. In the scheme, the recycled water is supplied from the Christies Beach wastewater treatment plant and injected to the Port Willunga Formation aquifer for temporary storage.

Allocated extractions

All allocation diversions reported for the Adelaide region were for individual use. The volume of 50,143 ML is water that was extracted from the Barossa PWRA, McLaren Vale and Northern Adelaide Plains prescribed wells areas (PWAs), and Western Mount Lofty Ranges PWRA. No data was available for Dry Creek PWA.

The volume extracted from each management area is shown in Figure N8.

Figure N8 Groundwater extractions during the 2014–15 year; percentage of allocation extracted is also shown

The volume for Western Mount Lofty Ranges PWRA was reported under 'Extraction: statutory rights' in the 2014 Account. Therefore, the allocated extractions for the 2014–15 year and reported volume for the 2013–14 year are not matching.

Groundwater balancing item

The groundwater balance (Table N8) yielded a balance of (29,415) ML, approximately 6% of the total groundwater inflows during the 2014–15 year. This volume actually represents the net change in groundwater store throughout the 2014–15 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 (Table N8).

The volume reported as the balancing item is the difference between total inflows and total outflows because the groundwater asset in the Adelaide region is equivalent to the managed groundwater volume reported in relevant water allocation plans and does not reflect fluctuation of groundwater levels over time. Therefore, estimated inflows and outflows were compared to the change of water stored in the aquifers to know if the change in the storage reflects the balancing item (inflow-outflow difference). The change in aquifer storage was calculated using groundwater levels for McLaren Vale, Adelaide Plains, and fractured rock areas within the region. The change in storage for was estimated as (49,513) ML, which is a decrease in storage. Decrease in the storage aligns with reduced recharge volume (see Inflows) and explains the balancing item which is an unaccounted outflow.

The other reasons potentially contributing to the balancing item are:

• the omission of some items such as recharge from surface water to groundwater and discharge to farm dams due to a lack of data.
• uncertainty associated with the meteorological inputs in the estimation of recharge from / discharge to landscape (in the range of 10–20% of the estimated volume).
• consideration of the average annual baseflow as discharge to surface water, which does not necessarily represent the flux during the year.

Urban water system

Adelaide's urban water system has three core components:

• Water supply: raw water transfers, water treatment, and potable water supply
• Wastewater: collections, transfers, and treatment
• Recycled water supply.

A reconciliation of the urban water Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N9. Further details on assets, liabilities and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical assets

Physical asset volumes, including water held in pipes, service reservoirs, storage tanks and lagoons at 30 June 2015 were:

• Water supply (1,414 ML)
• Wastewater (96 ML)¹
• Recycled water (17 ML).

^'1' The wastewater asset volume decreased from 133 ML reported in the 2014 NWA to 96 ML in the 2015 NWA, due to the exclusion of wastewater treatment lagoon data.The time required to calculate the wastewater treatment lagoon data was considered inappropriate for the value that this information adds to the Adelaide Account.  The stored volume for wastewater treatment lagoons is insignificant (37 ML in 2014 NWA) and does not have a material impact on the urban water balance.

Nonphysical assets

Nonphysical assets refer to the Claims: surface water, which was 0 ML. This claim represents the volume of surface water allocation remaining for water supply entitlements at the end of the year.

Details are provided in table N10. As there are no carry-over provisions for this entitlement, unused water is forfeited and the claim at year end is zero.

Further information on all entitlements and allocation arrangements are detailed in the Surface water rights section.

Liabilities

There are no urban water liabilities in the region.

Inflows and outflows

A schematic diagram representing all urban inflows and outflows is provided in Figure N9.

Figure N9 Water inflows and outflows for the urban water system during the 2014–15 year

A detailed breakdown of the inflows and outflows of the urban water system components are provided in the Urban water balance diagram.

Water supply inflows

Total inflows to the water supply system were 161,899 ML and were sourced from:

• Non-allocated diversion: surface water—56,943 ML
• Allocated diversion: surface water—78,200 ML
• Delivery: desalinated water—22,725 ML.
• Supply system delivery: inter-region—4,031 ML.

In the Adelaide region, two sources of surface water are supplied to the urban water system. This includes surface water harvested within the Western Mount Lofty Ranges PWRA (allocated diversion: surface water) and the remaining surface water is assumed to be River Murray water (non-allocated diversion: surface water), which is transferred to surface water storages within the region (Refer to the surface water section of the 'Supporting information' note.) River Murray water is also delivered directly to the urban water system in the north of the region, from the Swan Reach water treatment plant (Supply system delivery: inter-region).

During the 2014–15 year, surface water harvested from the Western Mount Lofty Ranges PWRA was the primary source of urban water (48%); 35% was sourced from the River Murray; 14% was sourced from desalinated water; and the remaining 3% was sourced via the Swan Reach and Mount Pleasant. Figure N10 provides comparative information for the 2014 and 2015 years.

Desalinated water production decreased by more than 60% during the 2014–15 year. This decrease was offset by notable increases in the volume of both surface water (18%) and imported River Murray water (80%) supplied to the urban system. Changes in SA Water's operations policy for the Adelaide desalination plant, combined with improved water availability arising from above average rainfall experienced in the previous year may explain this shift in water sources.

Further information on supply system inflows is available in the Supply inflows table.

Figure N10 Water sources used in Adelaide's urban water system during the 2014–15 year compared with the previous year

Wastewater and recycled water inflows

Total wastewater collected and delivered to Adelaide's twelve wastewater treatment plants (WWTPs) was 94,463 ML during the 2014–15. The volume of wastewater collected at each treatment plant is given in Figure N11.

 
Figure N11 Wastewater inflows and outflows at each wastewater treatment plant

 Further information on wastewater and recycled water system inflows is available in the Wastewater inflows table.

Water supply outflows

Total outflows from the water supply system were 159,869 ML and comprised the following:

• Leakage: groundwater—18,085 ML
• Supply system delivery: urban users—136,092 ML
• Supply system transfer: inter-region—4,417 ML
• Supply system discharge: surface water—18 ML
• Other supply system decreases—1,257 ML.

A comparison of water supply outflows (excluding other supply system decreases) to the previous year is provided in Figure N12.

Figure N12 Outflows from the water supply system 

A small increase in consumption of potable and nonpotable water was evident and consistent with a small increase in overall supply (inflows) to the water supply system during the 2014–15 year. 

Further information on supply system outflows is available in the supply outflows table.

Wastewater and recycled water system outflows

Total outflows from the wastewater and recycled water system were 94,719 ML and comprised the following:

• Evaporation—8,942 ML
• Recycled water delivery: urban users—3,906 ML
• Recycled water delivery: irrigation—21,024 ML
• Wastewater and recycled water discharge: surface water—2,175 ML
• Discharge: sea—58,462 ML
• Managed aquifer recharge—210 ML.

Total outflows from Adelaide's wastewater and recycled water system are given in Figure N13. 

Figure N13 Outflows from the wastewater and recycled water systems

The majority of treated wastewater is disposed of through discharge to sea (62%). A small portion is discharged to surface water (2%) and lost to evaporation during wastewater treatment processes (9%). The remaining treated wastewater is recycled for use, primarily delivered to the irrigation schemes within the region (22%), but also supplied to urban users (4%), and a small volume is injected as managed aquifer recharge less than (1%) for later use by the region's irrigation scheme.

Recirculation of treated wastewater and recycled water occurs in the system. This recirculated water may be subjected to additional treatment and/or re-use on site. The reported outflows exclude any such recirculated volumes in the system.  

Urban water system balancing item

The urban water balance (Table N11) yielded a balance item of 1,811 ML. As urban water utilities collect and report a high level of data, the balancing item represents only 1% of the total inflows to the urban water system during the year. The misbalance may be due to a number of factors, such as metering inaccuracies, unaccounted losses and inaccuracies in the estimation of certain volumes.

Irrigation scheme

The Adelaide region's irrigation scheme represents irrigation areas managed by Barossa Infrastructure Limited (BIL), Virginia Pipeline Scheme (VPS), and Willunga Basin Water Company (WBWC).

A reconciliation of the irrigation scheme Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N12. Further details on assets, liabilities and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical assets

The volume of water reported as the irrigation store water asset (29 ML) represents the volume of water held within the pipe and tank infrastructure from BIL and VPS at 30 June 2015. As WBWC drains all its pipes and tanks from May to October, the volume within its storage system was assumed to be zero. Unless the pipe network is augmented or partly decommissioned, the volume of water in the irrigation supply system remains unchanged.

Non-physical assets

There are no non-physical irrigation scheme assets in the region.

Inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the irrigation scheme in the Adelaide region is provided in Figure N14.

Figure N14 Water inflows and outflows for the irrigation scheme during the 2014–15 year

Around 75% of the 29,101 ML of inflows to the irrigation scheme is the delivery of recycled water. A volume of 21,024 ML of recycled water was delivered to VPS and WBWC from Bolivar, Christies' Beach, and Aldinga WWTPs. A further 584 ML was delivered through community wastewater management systems during the 2014–15 year: 245 ML to BIL from Nuriootpa, and 339 ML to WBWC from Willunga.

There was a delivery of 210 ML of groundwater for irrigation purposes under the Aldinga Aquifer Storage and Recovery Scheme. In the scheme, the recycled water is supplied from the Christies Beach WWTP and injected to the Port Willunga Formation aquifer for temporary storage (see Outflows in Groundwater store section).

A volume of 7,283 ML was delivered to BIL through the import of River Murray water under their Class 3a water access entitlement (WAE) in the 2014–15 year. This was 17% increase in the volume imported compared with the previous year. River Murray water is delivered either via the Mannum-Adelaide pipeline, or the Swan Reach–Stockwell pipeline. The Mannum–Adelaide pipeline is the preferred route. It conveys untreated water abstracted from the River Murray and then discharges it into Warren Reservoir.

Delivery of water for irrigation was the only outflow reported for the irrigation schemes. The volume for the 2014–15 year comprised of delivery of 7,545 ML from BIL, 14,800 ML from VPS, and 4,647 ML from WBWC. The total delivery for the 2014–15 year is 12% more than the volume delivered in the previous year.

Irrigation scheme balancing item

The irrigation scheme water balance (Table N17) yielded a balancing item of 2,109 ML, which is approximately 7% of the total irrigation scheme inflows for the year.

The balancing volume may be due to following reasons:

• Application of different methods of measuring flows to and from the irrigation scheme for different data suppliers.
• There is an inconsistency in time periods for measurement: The irrigation year is October–September and customer meters are not read on 30 June. 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.
• There is no reporting of evaporation and precipitation on the irrigation scheme or leakage to groundwater, due to lack of available data.

Unaccounted-for difference

The volume recognised in the water accounting statements 113,802 ML represents the total unaccounted-for difference for the Adelaide region for the 2014–15 year.

The unaccounted–for difference is the volume necessary to reconcile the opening water storage and closing water storage with the total water inflows and total water outflows reported in the water accounting statements. It is calculated according to Table N14

The unaccounted–for difference can also be calculated by summing the volumes necessary to reconcile (balance) the opening and closing storage with the water inflows and outflows of each of the separate water stores of the region, as shown in Table N15.

Table N15 shows that the unaccounted-for difference volume is primarily explained by the balancing item of the surface water and groundwater store.

The surface water balancing item is attributed to uncertainty associated with runoff and river outflow, and several items not being able to be quantified (see Surface water store note).

The groundwater balancing item is attributed to storage change and some items not being able to be quantified, uncertainty associated with estimation of recharge and discharge volumes, and consideration of average annual baseflow as discharge to surface water (see Groundwater store note).