National Water Account 2019

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Key findings

Climate and water

Water Accounting Statements

Supporting information

Region description

Reference information

Adelaide: Methods

Summary of methods

There were five key methods for establishing item volumes in the 2019 Account. Click the down arrow in the table below to view the list of items derived by each method type. For detailed information about each method scroll down this page or click on the links in the table.

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, which in turn affects the accuracy of the storage–volume curves.

Detail of methods

AWRA-R model

AWRA-R is a river network model that represents key hydrological processes and diversions at a daily time step (Dutta et al. 2017; 2015). The model was used in the National Water Account to quantify river fluxes and stores along the river network.

The river system is conceptualised in AWRA-R as a node-link network comprising nodes connected by river reaches. Gauged streamflow data are used where available. For ungauged portions of catchment, the landscape runoff from the AWRA-L model is used (Viney et al. 2015). River processes represented in the AWRA-R model are shown in Figure N1.

Figure N1 Conceptual diagram of AWRA-R reach showing model components (from Dutta et al. 2015)

Rivers

The volume of water in the river channels at 30 June was estimated by using the daily water balance approach within the AWRA-R model. The water balance includes inflow at the upstream nodes and outflow at the downstream nodes; contributing catchment runoff, diversions for consumptive use; overbank flooding and floodplain return; rainfall; evaporation; and losses.

Precipitation and evaporation

Rainfall and evaporation into/from storages and rivers were calculated using climate data from the Bureau of Meteorology interpolated to 0.05 degree (5 km) national grids (Jones et al. 2009). Calculations were done on a daily time step, with the annual totals summed from the daily values.

Climate data for each water body at each time step were estimated from the proportionally weighted average of grid-cells that intersected the water body. Evaporation was estimated using Morton's shallow lake formulation (Morton 1983). Rainfall and evaporation volumes were then estimated by multiplying the surface area of each waterbody by the weighted average rainfall and evaporation respectively. The average daily surface area of rivers was estimated using the AWRA-R model and the average daily surface area of storages was calculated from daily storage levels and capacity tables.

Runoff

Runoff to surface water was estimated using the modelled runoff from the AWRA-R model. Runoff within AWRA-R is in turn derived from landscape runoff modelled in the AWRA-L model, with a scaling factor applied within AWRA-R during the calibration process.

The AWRA-L model is a daily grid-based water balance model that is conceptualised as a small unimpaired catchment (Viney et al. 2015). It simulates the flow of water through the landscape from rainfall entering the grid cell through the vegetation and soil, and then out of the grid cell through evapotranspiration, runoff or deep drainage to the groundwater. Its inputs include gridded climate, soil, vegetation and topographic data. For more information see the Bureau's Australian Landscape Water Balance webpage.

Outflow

River outflow is estimated with the AWRA-R model using dummy nodes assigned at the end of of each river flowing out of the region. Observed flows (or simulated flows if observed flow is not available) at the most downstream gauges are routed to the dummy nodes. The residual catchment inflows not covered by the most downstream gauge are estimated using the AWRA-L model and are added to the routed flow to obtain the total outflow at the river mouth.

Overbank flow and flood return

The AWRA-R floodplain module was used to model the volume of overbank flow from the river onto the floodplain, and the return flow from the floodplain back into the river. The module applies a simple storage-based floodplain model to each river reach. The floodplain modelling method is detailed in Dutta et al. (2013).

Groundwater recharge: landscape

Groundwater recharge from landscape was estimated using the AWRA-L model version 5.0 (Viney et al. 2015). The AWRA-L model is a regionally calibrated water balance model. It estimates daily diffuse deep drainage, 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 estimated as the weighted mean of the relevant grid-cells within the regions. The estimated deep drainage volume was considered as the groundwater recharge from landscape. 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 et al. 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 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 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 aquifers.
• The average deep drainage was determined as the weighted mean of the relevant grid-cells within the regions. 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 the consideration of more recent vegetation and soil type datasets, and a calibrated water balance approach in the AWRA-L model. AWRA-L results lie comfortably within acceptable ranges and are of comparable magnitude and spatial distribution to the long term mean annual recharge estimates recently produced by CSIRO (Shi et al. 2015).

Bureau of Meteorology: groundwater modelling

Inter-region flows

Regional and coastal groundwater flow into and out of the Adelaide region was calculated using a simple GIS approach based on Darcy's Law. 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 2017–18 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 2018–19 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 N2 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 the outside region was calculated.

Figure N3 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.
• The summer groundwater levels in the Willunga and T2 aquifers were the same as the 2018 spring levels and 2018 summer levels, respectively.

Water licencing and management systems, water allocation plans and annual reports

Other groundwater assets

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. Carryover of water allocations was extracted from the Water information licensing and management application (WILMA) database. The DEW 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 2018–19 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 2018–19 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 abstraction

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 DEW.

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 2019.

Managed aquifer recharge: individual users

'Managed aquifer recharge: individual users' volume was estimated by balancing recharge credit details for active licences as available with DEW.

Other irrigation water increases

Barossa Infrastructure Limited

The volume of recycled water delivered to Barossa Infrastructure Limited (BIL) from the Nuriootpa Community Wastewater Management System was taken from BIL's 2017–18 annual report.

Willunga Basin Water Company

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

Delivery to irrigation scheme users

Barossa Infrastructure Limited

The volume of water supplied to customers during the 2018–19 year was taken from BIL's 2018–19 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 Virginia Pipeline Scheme (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 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 non potable 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).

It is assumed that 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: groundwater

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%. It is assumed that 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.

It is assumed that 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%.