National Water Account 2015

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Accountability statement

Adelaide: Quantification approaches

Summary of quantification approaches

Table N16 outlines the quantification approaches used to derive the item volumes for the Adelaide region. For a more detailed description of the quantification approach, click on the relevant item name in the table.

Table N16  Quantification approaches used to derive item volumes

Detail of quantification approaches

Water storage product data

Storages

Surface water storage volume was measured using gauged water level height(s) in metres with respect to the Australian height datum for individual storages. The height measurement was converted to a volume using the storage—volume relationship(s) provided by SA Water.

The storage volume of individual surface water storages was aggregated to present the total volume for this item. The uncertainty range for the storage volume is +/–5%.

The assumptions made were as follows:

• Storage–volume curves represent specifically surveyed parts of the storage and may not reflect the storage—volume relationship across the entire storage.
• Storages are subject to sedimentation and other physical changes over time, that in turn affects the accuracy of the storage–volume curves.

Water and wastewater system data and Geographic information system (GIS) database

Unregulated river

Storage volume of surface water storages (weirs) was measured using gauged water level height(s) in metres with respect to the Australian height datum for individual storages. The height measurement was converted to a volume using the storage—volume relationship(s) of SA Water. The storage volume of individual surface water storages (weirs) was aggregated to present the total volume for this item.

The assumptions made were as follows:

• Storage–volume curves relationships were derived from surveys of specific parts of the individual storage (weir), and may not reflect the storage—volume relationship across the entire storage.
• Storages are subject to sedimentation and other physical changes over time, that in turn affects the accuracy of the storage–volume curves.
• This volume does not include water that is held in unregulated river channels or private on-channel storages.

Supply system, wastewater system and recycled water system

Geographic information system (GIS) analysis was used to identify potable, wastewater, and recycled water pipes and potable water tanks within the Adelaide region. The volume of water in these tanks and pipes was estimated from their total capacity.

The volumes of water held in pipes were estimated from pipe lengths and nominal diameters using the following formula:

V = π × (d/2)² × PL
where:
  V = volume
  d = nominal pipe diameter
  PL = length of section

The volumes of water held in tanks were collected from SA Water's storage tank register and Maximo system.

Some tanks did not have volumes recorded in the database (< 5%). In such cases, SA Water personnel provided the volumes.

The assumptions were made as follows: 

• Given the small variation between reporting years, it was assumed that the pipe length and tank volume remained unchanged in the 2014–15 year from the 2013–14 year.
• Process tanks and pipes are assumed to be 100% full in winter, while balancing tanks were assumed to be 50% full.
• Pipes and tanks without recorded construction dates are assumed to have been constructed before the 2014–15 year.
• Only tank and pipe assets that are owned by SA Water were included in the calculations.
• Nominal diameters of pipes were used to calculate volumes.
• The volume of treated wastewater stored in the region's wastewater system via open lagoons was not available in all treatment plants and also the available volume was not considered significant or material to this account.

Pipe storage data

Irrigation water supply system

Barossa Infrastructure Limited

The total pipe lengths (approximately 189 K) and corresponding pipe diameters were obtained from a 2009 hard copy map of the BIL pipe network. Lengths and diameters were then used to calculate the total volume stored in the pipes if 100% full, according to the equation:

V = π × (d/2)² × (L/1,000)
where:
  V = volume (ML)
  d = nominal pipe diameter (m)
  L = length of section (m).

Virginia Pipeline Scheme

The VPS includes approximately 130 km of pipes and a storage pond which receives water directly from Bolivar WWTP. The volumes of water held in these pipes and the storage pond were estimated from their total capacity. The storage pond holds approximately 5 ML of water and the pipeline network holds 4.5 ML.

The assumptions made with these methods are as follows:

• Pipes were under pressure and therefore were 100% full at all times.
• The storage pond is assumed to be at 100% capacity.
• The nominal pipeline diameters recorded on the map represent the internal diameter of the pipeline.

Gridded climate data

Precipitation and evaporation

Monthly precipitation grids for the region were produced using daily data from approximately 6,500 rain gauge stations around Austalia and interpolated to a 0.05 degree (approximately 5 km) national grid (Jones et al. 2007).

Potential evaporation was estimated using the Australian Water Resources Assessment system landscape model (AWRA-L) version 5.0 (Viney et al. 2015). The AWRA-L model uses the Penman method to produce the potential evaporation. Daily AWRA-L potential evaporation grids for the region were produced based on daily gridded climate data that were available on a 0.05 degree (approximately 5 km) national grid. The daily gridded climate datasets used to produce this estimate included downward solar irradiance, and maximum and minimum air temperature. The methods used to generate these gridded datasets are outlined in Jones et al. (2007).

The precipitation and evaporation at each waterbody was estimated from the proportionally weighted average of grid-point cells that intersected each storage or weir (water feature). The precipitation volume was then estimated using the surface area of each waterbody. Surface area varied dynamically with changing storage level for storages, where the relationship between storage level and surface area has been derived. The surface area of storages was either calculated dynamically or was a static value produced from the Australian Hydrological Geospatial Fabric (AHGF). The surface area of all weirs was a static value produced from the AHGF.

The limitations associated with this approach are:

• The estimates were subject to approximations associated with interpolating observation point data to a national grid detailed in Jones et al. (2007).
• The dynamic storage surface areas calculated from the levels and capacity tables represent a monthly average and therefore do not capture changes that occur on a shorter temporal scale.
• The use of the static default AHGF surface area is an approximation only. It represents the water features at capacity and therefore is likely to result in an overestimation of precipitation on the water features.
• Precipitation and evaporation was only estimated for the surface water storages and weirs (for which data were available) within the Adelaide region and does not include river channels.

Runoff

Runoff to surface water was estimated based on the AWRA-L version 5.0 (Viney et al. 2015) model output and a water balance algorithm written by the Bureau.

Using gridded climate data for the Adelaide region (including precipitation, temperature and solar radiation data), AWRA-L estimated the runoff depth at each grid point within the region. Only runoff from the landscape was considered; therefore, the surface areas of the major storages and the off-channel water storages (local catchment reservoir, e.g., farm dams) were excluded from the analysis.

Runoff from the landscape is divided into two components: runoff into the surface water (surface water storages and weirs, rivers and drains) and runoff into off-channel water storages. Only runoff into the surface water store was considered here because in the context of the National Water Account; off-channel water storages are not included in the definition of surface water.

The average runoff depth from the landscape into surface water was determined as the weighted mean of the relevant grid-points within the region boundary. Points were weighted based upon the area they represented within the reporting region to remove edge effects (where the area represented is not wholly within the reporting region), and the effect of changing area represented with changing latitude. Runoff depth was converted to a runoff volume by multiplying runoff depth by the total area of the region (excluding surface water storages, weirs and off-channel storages) and was used as input to the into the water balance algorithm.

The assumptions made were as follows:

• Runoff estimates were subject to the assumptions of the AWRA-L model detailed by Viney et al. (2015).

Stream monitoring data

Outflow

Streamflow data were obtained from the following sources:

• Adelaide and Mount Lofty Ranges Water Data website (Water Data Services 2015)
• WaterConnect website (Department of Environment, Water and Natural Resources 2013).

The total flow volume was obtained by summing the 2014–15 year streamflow from gauging stations on most major rivers in the Adelaide region (Figure N16). Each gauging station monitors stream height, which is converted to a flow volume using a rating table.

Figure N16 Map showing location of streamflow gauges used to calculate river outflow

 The following assumptions were made in the calculations:

• Streamflow data were not available for all major rivers. The Myponga River is the most significant omission; it is not measured downstream of the Myponga Reservoir.
• The rating table used to obtain the flow volume from the measured water level is assumed to be valid for the full range of the measured water level.

Bureau of Meteorology—groundwater modelling

Inter-region inflow and outflow

Regional and coastal groundwater flow into and out of the Adelaide region was calculated using a simple GIS approach based on Darcy's Law (Bureau of Meteorology 2010). A set of bores with current data was selected, including any bores within 20 km of the region's boundary.  Where no bores were present close to the boundary, the interpolated groundwater level surface was extended to the boundary and used to estimate groundwater flow across the boundary (this flow is small in magnitude).

Groundwater levels measured at monitoring bores were interpolated to a groundwater-level grid for each season during the 2014–15 year using the ArcGIS Topo-to-Raster tool. Seasonal groundwater-flow grids were then derived from these groundwater-level grids along with aquifer thickness and hydraulic conductivity data, using a modification of the ArcGIS Darcy velocity tool. Regional groundwater inflow/outflow was subsequently calculated across selected regional groundwater boundaries in the Adelaide Plains, using a simple GIS analysis. Coastal groundwater inflow/outflow was subsequently calculated across selected coastal boundaries in the Adelaide Plains and McLaren Vale PWAs using a simple GIS analysis.

Seasonal inflow/outflow volumes were summed to determine the total volume for the 2014–15 year.

The following two maps are presented to aid interpretation of the methodology used to quantify this item. The first map illustrates the location and concentration of bores used in the quantification approach.

Figure N17 Map showing the location and concentration of bores used to quantify groundwater inflow to and outflow from the region

The second map identifies the lateral groundwater flow boundaries used in the quantification approach. The purple line at the north of the Adelaide region illustrates the area across which groundwater outflow to outside region was calculated.

Figure N18 Map of lateral groundwater flow boundaries in the Adelaide region

The assumptions made in the calculations were as follows:

• Regional groundwater outflow was estimated for the confined and semi-confined aquifers only (T1, T2, Maslin Sands and Port Willunga Formation). These productive aquifers are considered to be the most hydraulically conductive units and flow in other units is assumed to be insignificant.
• Flow across boundaries not included in this quantification was assumed to be negligible on an annual basis either due to limited flow (e.g., in fractured rock) or could not be estimated because limitations of the method prevented its application.

Recharge/discharge: landscape

Groundwater recharge and discharge to landscape was estimated using the 'Water atmosphere vegetation energy and solutes' (WAVES) model described in Zhang and Dawes (1998) and Dawes et al. (1998). WAVES is a one-dimensional soil-vegetation-atmosphere-transfer model that integrates water, carbon and energy balances. Climate, depth to water table (only for the sedimentary areas), soil and vegetation data were used as inputs to the model. The climate data include rainfall, rainfall duration, maximum and minimum temperatures, vapour pressure deficit, and solar radiation.

The WAVES model has been used by the CSIRO in its sustainable yields projects (Crosbie et al. 2008), and the Bureau has built on this methodology.  WAVES was run at selected points from across the Adelaide region for all combinations of soil type, vegetation type and depth to water table. The point estimates of the groundwater recharge fraction were interpolated to a 1-km grid based on soil type, vegetation type, annual rainfall for the 2014–15 year and depth to water table.

The recharge within the Adelaide region was determined by summing the spatially interpolated positive recharge estimates.

The following figure illustrates the net groundwater discharge (in red) and recharge (in grey) across the Adelaide region during the 2014–15 year using the WAVES model.

Figure N19 Map showing net groundwater recharge and discharge in the Adelaide region during the 2014–15 year

The assumptions made were as follows:

• The assumptions of the WAVES model as described in Dawes et al. (1998) were all applicable to the recharge estimates for the Adelaide region.
• The national land-use grid (Australian Bureau of Agricultural and Resource Economics – Bureau of Rural Sciences 2010) was reclassified to three vegetation classes that include annuals, perennials, and trees. The major vegetation classes modelled were C3 annual pasture, C3 perennial pasture, and eucalypt trees with a grass understorey.

Annual recharge was estimated for the whole of Adelaide region including both sedimentary and fractured rock areas. Recharge to and discharge from the region were modelled using a shallow water table surface area estimated by interpolating measured groundwater levels. The water table depth was interpolated using the methodology presented in Peterson et al. (2011). This method uses groundwater elevation and the 9 arc-second digital elevation model taking into account the effect of the coastline to improve groundwater levels interpolation in data poor areas within this area of high relief.

Rainfall recharge and diffuse groundwater discharge were estimated for the fractured rock area contributing to the flow in the confined sediments only (see fractured rock boundaries in the figure above for diffuse rainfall recharge). Recharge to and discharge from the fractured rocks of the Fleurieu Peninsula and Myponga River catchment are not included in the balance.

Internal records, annual reports and meter readings

Other irrigation water increases

Barossa Infrastructure Limited

The volume of recycled water delivered to BIL from the Nuriootpa Community Wastewater Management System was taken from BIL's 2014–15 annual report.

Willunga Basin Water Company

The metered volume of recycled water delivered to from Willunga Community Wastewater Management System was provided by WBWC from its internal records.

Delivery to irrigation scheme users

Barossa Infrastructure Limited

The volume of water supplied to customers during the 2014–15 year was taken from BIL's 2014–15 annual report. Although some pipe infrastructure extends beyond the Adelaide region boundary, it was assumed that all water reported in the annual report was delivered to users in the Adelaide region, because the volume delivered beyond the region was considered negligible.

Virginia Pipeline Scheme

The volume reported is from a meter at the VPS pump station. Customers' meters are not read in June or July as this does not correspond to the irrigation water year. The volume reported was from the VPS pumping station and therefore the volume actually delivered to customers may differ due to leakage between the pumping station and customer meters.

Willunga Basin Water Company

The volume of water supplied to customers was provided by WBWC from their internal records.

Leakage from irrigation scheme

Barossa Infrastructure Limited

BIL reported leakages in the irrigation scheme had been eliminated following completion of the installation of electronic meters and pressure sensors in the 2012–13 year (BIL 2013).

Virginia Pipeline Scheme

Data regarding leakage were not available for the VPS. This volume is assumed to be small, and its omission is unlikely to have a material impact on the irrigation scheme balance.

Willunga Basin Water Company

Leakage from the WBWC pipes was assumed to be negligible. Numerous pressure monitoring sites are able to rapidly identify leaks which are fixed quickly.

Water information licencing and management application system, Water allocation plans, annual reports, meter readings, and internal estimates

Other groundwater asset

The groundwater asset is comprised of the following:

• Barossa PWRA: the sum of estimated underground water allocation volumes, detailed in the current Barossa Prescribed Water Resources Area Water Allocation Plan.
• McLaren Vale PWA: the estimated sustainable yield and estimated stock and domestic extraction detailed in the current McLaren Vale Prescribed Wells Area Water Allocation Plan.
• Western Mount Lofty Ranges PWRA: the sum of groundwater extraction limits and existing non-licensed extraction volumes as detailed in the Western Mount Lofty Ranges Prescribed Water Resources Area Water Allocation Plan.

The volume reported for the groundwater asset did not include the following prescribed groundwater resources:

• Northern Adelaide Plains PWA: although the Northern Adelaide Plains has an operational water allocation plan, the capacity of the resource is insufficient to meet the water use demands and as such the managed groundwater volume is not recognised as a groundwater asset.
• Central Adelaide Plains PWA and Dry Creek PWA: these do not have operational water allocation plans and therefore a managed groundwater volume has not been determined for these resources.

Allocation remaining

Allocation remaining corresponds to the unused volume of allocated inter-region, surface water, or groundwater that is carried forward to the following year and recharged groundwater credits that can be carried to the following year. Carry-over of water allocations was extracted from the Water information licensing and management application (WILMA) database. The DEWNR database detailing managed aquifer recharge credit calculations was used to differentiate new recharged water credits from previously applied but not used or not expired recharged water credits carried over at the end of the 2014–15 year.

Carryover rules vary depending on the water resource and/or allocation and are as follows:

• Carry-over of unused allocation is not permitted for the Northern Adelaide Plains PWA, Dry Creek PWA and Little Para Prescribed Water Course (PWC).
• Carry-over of unused water allocated to SA Water from the Western Mount Lofty Ranges PWRA for the purposes of public water supply is not permitted.
• Carry-over of unused water allocated to SA Water from the River Murray for the purposes of public water supply is not permitted.
• Carry-over of unused water allocated against BIL's entitlement to River Murray Water was not permitted by the Government (BIL 2015).
• In the Barossa PWRA licensees may carry over the unused portion of their allocation up to a maximum percentage of the annual allocation, according to the rules stated in the water allocation plan.
• Diversions from surface water resources located outside of the Barossa PWRA and Little Para PWC are managed by authorisations under ss 128,132 and 164N of South Australia's Natural Resources Management Act 2004. In these instances, carryover arrangements do not exist.

Allocation

The volumes of inter-region, surface water and groundwater allocations during the 2014–15 year were extracted from the WILMA database.

• Surface water and groundwater allocations for individual users are typically equal to the licensed extraction limit throughout Adelaide’s PWRAs and PWAs.
• The surface water inter-region claim to River Murray water allocation increase was 130,000 ML. The South Australian Minister for Sustainability, Environment and Conservation announced a 100% allocation of 1 kL/unit share for the Class 6 WAE. Based on this allocation rate and the number of Class 6 shares held, the volume of water reported was 130,000 ML.
• The irrigation scheme inter-region claim to River Murray water allocation increase was the volume of water that BIL were entitled to under Class 3 WAE owned or leased.
• Recharged water is allocated based on the volume injected as part of managed aquifer recharge (MAR) and may also depend on the quality of the water injected.

Allocated diversion/allocated extraction

The entitled abstraction of allocated water (inter-region, surface water, and groundwater) during the licensed water year is derived from a combination of metered data and estimates.

Metered abstraction data were obtained from the WILMA licensing database, including volumes for inter-region claims and individual users.

Non-metered abstraction data for individual users were estimated and provided by DEWNR staff.

The assumptions made were as follows:

• There was 100% usage for stock and domestic licences
• The data and estimates do not include allocated abstractions for individual users in the Western Mount Lofty Ranges PWRA; these are considered as abstraction water for other statutory rights.

Allocated diversion: urban water system

The volume of allocated surface water diverted to the urban water system was obtained from the WILMA licensing database.

In the Adelaide region, two sources of surface water are supplied to the WTPs for urban water supply: water harvested from within the Western Mount Lofty Ranges PWRA (reported at this volume), and remaining water which is typically equivalent to River Murray water imported. As metered data is not available at the inlet to each WTPs to distinguish between each water source, this volume is based on SA Water's total licensed diversion volume from the Western Mount Lofty Ranges PWRA as recorded in the WILMA database.

Adjustment and forfeiture

The portion of water allocation that has not been abstracted or carried over at the end of the water year is forfeited. Therefore, forfeiture is calculated as the total annual allocation for each licence, less the allocation abstraction during the water year, less the volume carried over into the following year.

Extraction: other statutory rights

Metered extraction data for the Kangaroo Flat portion of the Northern Adelaide Plains PWA were obtained from the WILMA licensing database.

Discharge: surface water

Groundwater discharge to surface water in the Western Mount Lofty Ranges PWRA was summed from the annual baseflow figures detailed in the Western Mount Lofty Ranges PWRA Water Allocation Plan.

The streamflow gauge for the North Para River at Yaldara (A5050502) was deemed the only streamflow site with a significant baseflow component outside the Western Mount Lofty Ranges PWRA. Baseflow was calculated for this site using a Lyne and Hollick filter (Grayson et al. 1996) with a filtering factor of 0.925 and daily flow records for 1 July 1975–30 June 2010.

Entitlement trade/lease

Trade and lease details were obtained from a WILMA database extract designed to supply the Water Regulations 2008 category 6a (permanent water access entitlement trades) and 6b (temporary water allocation trades and leases) information.

Water access entitlements (WAEs) associated with the Adelaide region's prescribed water resources are bundled, whereby the value of the entitlement is equivalent to the annual volumetric allocation. Trade duration and permanency were used to differentiate between entitlement and allocation trades according to the following table:

Trades and leases were individually investigated to remove trades and leases that relate to off-channel water licences. A 'change of entitlement holder' refers to when the bundled water licence is modified to reflect a change in the entitlement holder name. The point of take and other authorisations endorsed on the licence remain unchanged.

Managed aquifer recharge: individual users

'Managed aquifer recharge: individual users' volume was estimated by balancing recharge credit details for active licences as available with DEWNR. There were nine active licences for the local councils and some private organisations for the 2014–15 year.

Water and wastewater system data

Wastewater collected

The wastewater collected volume is estimated using the aggregated metered inflow to WTPs and sewer-mining plants within the region:

• minus any recirculation such as treated wastewater volume that was reported as discharge back to sewer in the region, to avoid double counting.
• plus any reported wastewater losses or egress from the system before the metering point measuring inflow to the treatment plants (e.g., through emergency relief structure).

The assumptions made were as follows:

• Given wastewater volumes are typically measured at the treatment plants (and not at customer connections), the collected wastewater volume includes any variation due to (a) ingress of stormwater; (b) infiltration of groundwater; (c) unreported wastewater overflows to stormwater; and (d) exfiltration of wastewater to groundwater.
• Where inflow meter readings are not available, outflow meter readings have been used, which could underestimate the volume as it assumes no losses during wastewater treatment.
• This volume does not include wastewater collected for individual or community wastewater management systems.

The uncertainty range for these volumes is +/– 20%.

Delivery: desalinated water

The volume is metered at the outlet of the Adelaide Desalination Plant.

The uncertainty range for these volumes is +/– 20%.

Non-allocated diversion: urban water system

In the Adelaide region, two sources of surface water are supplied to the water treatment plants for urban water supply: water harvested from within the Western Mount Lofty Ranges PWRA (reported at this volume), and remaining water which is typically equivalent to River Murray water imported.

As metered data is not available at the inlet to each water treatment plant to distinguish between each water source, this volume is the total inflow to water treatment plants, less SA Water's total licensed diversion volume from the Western Mount Lofty Ranges PWRA as recorded in the WILMA licensing database.

Supply system delivery: inter-region

The 'supply system delivery: inter-region volume, consists of potable and nonpotable water and is based on metered information at the distribution infrastructure.

The volume imported from Swan Reach–Stockwell into the region is estimated using metered water consumption by urban users plus metered unused water returned back to South Para Reservoir.

The uncertainty range for these volumes is +/– 20%.

Evaporation

The volume of evaporation from the urban water system is calculated using a water balance approach through available inflow and outflow metering data for the relevant WWTPs.

The assumptions made were as follows:

• Evaporation losses are only reported for the wastewater system.

The uncertainty range for these volumes is +/– 20%.

Leakage: groundwater

The leakage: groundwater, volume is assumed to be the non-revenue water associated with real losses, specifically due to background pipe leakage from the urban water supply system. Where volumes are available with only pipe bursts, this is reported in leakage: landscape,

Non-revenue water is estimated using:

• the difference based on a water balance between metered water sourced and supplied to customers: and/or
• modelling software of network real losses (leakages and bursts) and apparent losses (unauthorised/authorised unbilled use)
• time to repair leaks.

SA water used internal models to estimate real losses of 4.57 kL/km/day from their infrastructure leakage index (ILI) and multiplied this by the length of its mains pipes within the Adelaide region.

The assumptions made were as follows:

• Leakage in the wastewater system is not reported and therefore the total leakage to groundwater is likely underestimated.
• Where non-revenue water real losses are reported as a combined volume for pipe bursts and background leakage, these are also reported in this volume, which may overestimate the volume
• Assumed water main length in Adelaide region's boundary is approximately 40 percent of total water length in Country and Metro areas estimated by GIS database analysis.

The uncertainty range for these volumes is +/– 20–40%.

Supply system delivery: urban users

The supply system delivery: urban users volume, includes urban consumption of potable and nonpotable water and is derived from:

• customer meters
• billing meters
• estimated non-revenue water volumes.

The customer meters used to derive the volume were extracted from the SA Water GIS database and categorised based on different land uses.

Urban consumption consists of residential, commercial, industrial, municipal, and small scale agriculture irrigation.

The uncertainty range for these volumes is +/– 20%.

Recycled water delivery: urban users

The recycled water delivery: urban users  is derived from:

• customer meters,
• billing meters
• onsite re-use meters.

The volume excludes recycled water re-circulated within the wastewater treatment process.

Urban consumption consists of residential, commercial, industrial, municipal, onsite (WWTP) use, and small scale agriculture irrigation.

The uncertainty range for these volumes is +/– 20%.

Supply system discharge: surface water

The supply system discharge; surface water volume, is metered and includes return of excess water from the urban water supply system back to surface water / reservoirs for balancing.

The uncertainty range for these volumes is +/– 20%.

Wastewater and recycled water discharge: surface water

The wastewater and recycled water discharge: surface water, volume is metered and includes:

• disposal of treated wastewater to rivers
• discharge of recycled water for environmental purposes
• known egress to stormwater from the wastewater collection system occurring before metered inflow to WWTPs.

Egress to stormwater is estimated based on observation or monitoring of the sewer network. This may occur at emergency relief systems built into the network or uncontrolled points at manholes and network leaks.

The assumptions made were as follows:

• Treated wastewater disposal to rivers and streams which are estuarine in nature, or subject to tidal impacts, are not reported in this volume, but reported as discharge outside the region (to sea).

The uncertainty range for these volumes is +/– 20%.

Recycled water delivery: irrigation scheme

The recycled water delivery: irrigation, volume is the metered volume of recycled water supplied for use in Irrigation Schemes.

The uncertainty range for these volumes is +/– 20%.

Discharge: sea

The discharge: sea, volume is the metered volume of disposals from the wastewater system and recycled water system to the sea, estuaries, inlets and portions of rivers and streams with tidal impacts (which are considered outside of the region).

The assumptions made were as follows:

• Where metered disposal data is not available, the volume is estimated based on the difference between metered inflow to a wastewater treatment plant and metered volume of recycled water used.

The uncertainty range for these volumes is +/– 20%.

Managed aquifer recharge/non-allocated extraction: irrigation scheme

The volume of managed aquifer recharge is based on metered data measuring the water recharged to aquifers– including potable, nonpotable and recycled water.

The injected recycled water is subsequently supplied to the irrigation scheme for re-use.  

The uncertainty range for these volumes is +/– 20%.

The assumptions are made as follows:

• The volume reported does not include water injected to groundwater by MAR schemes that are not operated by SA Water.

Supply system transfer: inter-region

The supply system transfer: inter-region, volume measures the transfer of potable and nonpotable water outside of the region. The volumes are based on metered information at the distribution infrastructure.

The customer meters used to derive the volume were located outside the Adelaide region as determined by the SA Water GIS database.

The uncertainty range for these volumes is +/– 20%.

Other supply system decreases 

The other supply system decreases, volume is the remaining non-revenue water from the urban water supply system (if not reported in 'leakage to landscape' and 'leakage to groundwater' respectively).

Remaining non-revenue water is estimated using:

• the difference based on a water balance between metered water sourced and supplied to customers, and/or
• the difference between metered supply into the urban water supply system and metered volume of water consumed (revenue water) and subtracting real losses; and/or
• modelling software of network real losses (leakages and busts) and apparent losses (unauthorised/authorised unbilled use), and/or
• time to repair leaks, and/or
• difference between inlet meter and outlet meter of water treatment plants for treatment losses

The uncertainty range for these volumes is +/– 20–40%.

Delivery: inter-region agreement

Delivery of water to the surface water store under inter-region agreement, is metered water which includes raw water, potable, and nonpotable water.

For Adelaide, this consists of an inter-region agreement to River Murray water sourced from three pipelines:

• the volume of water delivered via the Murray Bridge–Onkaparinga pipeline.
• the volume of water delivered via the Mannum–Adelaide pipelines that excludes the volume of water delivered to BIL because this volume is reported at 'Delivery: inter-region agreement' for irrigation schemes.
• the volume delivered from the Swan Reach–Stockwell pipeline to the Swan Reach WTP. As the Swan Reach WTP is located outside of the Adelaide region boundary, only a portion of the Swan Reach WTP potable water produced is supplied for use within the Adelaide region, and no meter is available to monitor this volume. Therefore, the volume imported from Swan Reach-Stockwell pipeline into the region is estimated using metered water consumption by urban users plus metered unused water returned back to South Para Reservoir. This could underestimate the volume of surface water abstracted from the Swan Reach-Stockwell pipeline into the region, as it assumes no treatment losses or distribution losses.

The uncertainty range for these volumes is +/– 20%.

The Adelaide region was split into two subregions for the purpose of estimating the water balance of the farm dams. The region was divided using the boundaries of the AHGF contracted catchments between McLaren Vale and the Onkaparinga Valley. The northern region includes the Barossa Valley; the Northern Adelaide Plains; and the River Torrens, Patawalonga and the Onkaparinga catchments. The southern region includes catchments throughout McLaren Vale and the Fleurieu Peninsula.

The farm dam algorithm written by the Bureau was used to determine the volume of water held in and the movement of water to/from farm dam. Data input to the model included gridded climate datasets; runoff from the AWRA-L version 5.0 (Viney et al. 2015) model; and dam details derived from spatial data (surface area, volume, location, and catchment area). Model parameters included a leakage factor of 5% per year and irrigation (Binks 2004) and stock and domestic demand factors (Luke 1987).

The farm dam algorithm performs a water balance on each individual storage at each time step using runoff and precipitation as inflows; and spills, evaporation, and usage as outflows. The volume of water held in storage is an output of this water balance. The farm dam algorithm estimates leakage to groundwater  based on the assumption that water will leak from the storage unless the storage empties, at which time leakage will cease. Similarly, the algorithm estimates abstraction based on the assumption that water will be abstracted from the off-channel water store at the rate required unless the off-channel water store empties, at which time abstraction will cease.

Precipitation on, evaporation from and runoff to off-channel water storages were estimated using the same methods for surface water storages.

The assumptions made were as follows:

• The estimated volumes are subject to the assumptions associated with the farm dam algorithm written by the Bureau and the parameters used.
• The spatial extent of water bodies was subject to the assumptions and methods associated with the spatial data provided by DEWNR.
• The use of a 9 arc-second digital elevation model (DEM) to determine catchment area may result in farm dam being assigned a catchment much larger or smaller than the true catchment. In some cases, farm dams may be assigned to the catchment of a streamline hundreds of metres away.