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National Water Account 2016

Adelaide: Methods

City of Adelaide, South Australia (iStock © Ben Goode)

Summary of methods

Table N4 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 N4  Quantification approaches used to derive item volumes

Assets
Approach or data usedItemSource
Water storage product dataStoragesBureau of Meteorology
Water information licencing and management application system; Water allocation plans; annual reports; meter readings
  • other groundwater assets
  • entitlement trade/lease
Department of Environment, Water and Natural Resources

 

Liabilities
Approach or data usedItemSource
Water information licensing and management application system; Water allocation plans; annual reports; meter readingsDepartment of Environment, Water and Natural Resources

 

Inflows and outflows
Approach or data usedItemSource
Stream monitoring dataOutflowDepartment of Environment, Water and Natural Resources; Water Data Services
Gridded climate data and AWRA L modelBureau of Meteorology
Bureau groundwater modelling; GIS dataset of bore locationsBureau of Meteorology; Department of Environment, Water and Natural Resources
Internal records; annual reports; meter readingsBarossa Infrastructure Limited; Willunga Basin Water Company; Virginia Pipeline Scheme
Water information licensing and management application system; Water allocation plans; annual reports; meter readingsDepartment of Environment, Water and Natural Resources
Water and wastewater system dataSA Water

 

Abstractions
Approach or data usedItemSource
Water information licencing and management application system; Water allocation plans; annual reports; meter readingsDepartment of Environment, Water and Natural Resources

 

Detail of methods

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.

 

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). The precipitation at each waterbody (i.e. storages) was estimated from the proportionally weighted average of grid cells that intersected each water feature. The volume was then estimated by multiplying the surface area of each waterbody by the weighted average precipitation. The average monthly surface area of the storages was calculated from daily storage levels and capacity tables.

Evaporation from water bodies was calculated on a daily basis using the Morton's shallow lake formulation (Morton 1983a, 1983b, 1986). For annual evaporation estimate, there is no difference between shallow and deep lake evaporation (Sacks et al. 1994). The climate data required for the Morton's method are maximum temperature, minimum temperature, vapour pressure and solar radiation. The climate data for each waterbody (i.e. storages) was estimated from the proportionally weighted average of grid cells that intersected each water feature and input to the Morton's program to obtain the evaporation values. The volume was then estimated by multiplying the surface area of each waterbody by the evaporation values.

The limitations associated with this approach are:

  • The dynamic storage surface areas calculated from the levels and capacity tables represent a monthly average and therefore, will not capture changes that occur on a shorter temporal scale.
  • The total surface area of the surface water store within the Adelaide region included only the storages and not the rivers, lakes or wetlands.

Uncertainty estimates were not available for the modelled precipitation and evaporation estimates by the Bureau.


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).

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:

The total flow volume was obtained by summing the 2015–16 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
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 2015–16 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 2015–16 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
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
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 was estimated using the deep drainage volumes calculated by the Australian Water Resources Assessment system Landscape model (AWRA-L) version 5.0 (Viney et al., 2015). The AWRA-L model is a regionally calibrated water balance model. It estimates daily diffuse deep drainage (Dd), which is the free drainage at the bottom of the deep soil layer (6m) for each 5km x 5km stand-alone grid cell across the continent. The average deep drainage was determined as the weighted mean of the relevant grid-cells within the regions. The main factors affecting the deep drainage rate at any location are:

  • Rainfall – AWRA-L is driven by daily gridded climate data (including precipitation, solar radiance, and temperature) that were available on a 0.05 degree (approximately 5 km) national grid (Jones, Wang and Fawcett, 2009).
  • Soil properties – rates of drainage through the model's conceptual water stores (0-0.1m, 0.1m-1m, and 1m-6m) are controlled by the estimated soil saturated hydraulic conductivity across those soil depths. AWRA-L makes use of clay content based pedotransfer functions (Dane and Puckett, 1994) to derive conductivities of the various soil layers.
  • Evapotranspiration rates – AWRA-L model divides the landscape into two types of vegetation: deep-rooted and shallow rooted The fraction covered with vegetation (the same for both types) is further estimated by using the Leaf Area Index (LAI) estimate for each grid, and this value responds dynamically to moisture in the ground. This then affects the rate of evapotranspiration from the unsaturated soil stores and groundwater.

The limitations associated with this approach are:

  • Free drainage at a depth of 6m is potential recharge, and may be quite different in magnitude to the net volume that reaches the water table (allowing for transpiration), and is not appropriate to be used for confined aquifer
  • The average deep drainage was determined as the weighted mean of the relevant grid-cells within the region. Estimates of recharge for 5km by 5km grid-cells may not be of the same order of magnitude as any point estimate made within the grid. 
  • Lateral flow from grid-cell to grid-cell, which could affect groundwater levels are not considered.

The AWRA-L annual estimates of deep drainage tends to be lower than previously used WAVES model outputs (~10% of previous value), this is due to AWRA-L using more recent vegetation and soil type datasets, and a calibrated water balance approach. AWRA-L results lie comfortably within acceptable ranges and are moreover of comparable magnitude and spatial distribution to the long term mean annual recharge estimates recently developed by CSIRO (Shi, Crosbie and Vaze, 2015).

 

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 2015–16 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 2015–16 year was taken from BIL's 2015–16 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.

 

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:

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. Carryover 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 2015–16 year.

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

  • Carryover of unused allocation is not permitted for the Northern Adelaide Plains PWA, Dry Creek PWA and Little Para Prescribed Water Course (PWC).
  • Carryover of unused water allocated to SA Water from the Western Mount Lofty Ranges PWRA for the purposes of public water supply is not permitted.
  • Carryover of unused water allocated to SA Water from the River Murray for the purposes of public water supply is not permitted.
  • Carryover of unused water allocated against BIL's entitlement to River Murray Water was not permitted by the Government (BIL 2016).
  • 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 2015–16 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 water access entitlement. 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 water access entitlement 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 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 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:

 

Table N5 Trade duration and permanency in the Adelaide region
DurationEntitlement or allocationPermanencyTrade or lease
greater than 1 yearwater access entitlementnot permanentlease
greater than 1 yearwater access entitlementpermanenttrade
less than 1 yearwater allocationnot permanenttrade

 

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 2015–16 year.

 

Water and wastewater system data

Wastewater collected

The wastewater collected volume is estimated using the aggregated metered inflow to each wastewater treatment plant and sewer-mining plant 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 +/– 10%.

 

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.


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

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 +/– 10%.

 

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.

 

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%.

 

Other wastewater decreases

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%.

 

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 via the Swan Reach-Stockwell pipeline.

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