National Water Account 2015

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Changes in Water Assets and Water Liabilities

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Accounting policies

Supporting information

Quantification approach

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References

Accountability statement

South East Queensland: Quantification approaches

Summary of quantification approaches

Table N14 outlines the quantification approaches used to derive the item volumes for the South East Queensland region. For a more detailed description of the quantification approach, click on the relevant item name in the table.

Table N14  Quantification approaches used to derive item volumes

Bureau = Bureau of Meteorology
DSITI = Queensland Government Department of Science, Information Technology and Innovation

Detail of quantification approaches

Water storage product data

Storages

Storage volume was measured at the start and end of the 2014–15 year by using gauged water level height(s) for individual storages. The height measurement was converted to a volume using the storage-volume curve(s) of the storage.

The volume of individual storages was aggregated to present the total volume as detailed in the supporting information table. The uncertainty was not quantified.

The assumptions made were as follows:

• Storage-volume (rating) tables are constructed from surveyed parts of the water storage, and may not reflect the storage-volume relationship across the entire storage.
• Water storages are subject to sedimentation and other physical changes over time that affect the accuracy of the storage-volume tables.

Water table aquifer

The entitled maximum volume extractable from the benefitted area of the Central Lockyer WSS was provided by Queensland Department of Natural Resources and Mines (DNRM). Detailed groundwater modelling of the benefitted area of the Central Lockyer aquifer has been undertaken by DNRM to determine the sustainable volumetric limit for extractions.

This volume is applicable to the Implementation Area 1 of the Central Lockyer GMA.

There was no uncertainty associated with the provided volume. The maximum entitled volumetric limit of medium priority interim water allocation that can be extracted from Implementation Area 1 of the benefitted area of groundwater in the Central Lockyer Valley WSS was confirmed.

Service reservoir data

Supply system

The storage volume of the urban water supply system comprises two components: the distribution pipe network and service reservoirs.

The volumes of water in the pipes and tanks were obtained from Seqwater, QUU, Council of the City of Gold Coast, Logan City Council, Redland City Council, Unitywater and Toowoomba Regional Council. Seqwater also supplied volumes in service reservoirs and balance tanks.

Due to lack of availability of actual storage volumes on 30 June 2015, the entire capacity for each tank and water main for the utilities in the South East Queensland region was included for this volume; however, QUU included all the pipes it owns. The pipe volumes for the portion of Toowoomba Regional Council within the South East Queensland region was approximated using average pipe capacity. Service reservoir and balance tank storage volumes at 30 June 2015 were supplied by Seqwater.

Wastewater

The storage volume of the wastewater system includes treated wastewater stored in the region’s wastewater system via tanks and open lagoon systems.

There are a number of other wastewater treatment plants (WWTPs) in the region; however the volumes of their stored treated wastewater was not included as they were not considered material to the Account.

Recycled water

The volume in recycled water pipes and tanks in the Council of the City of Gold Coast was assumed unchanged from 2013–2014.

Water resourcing licence database and meter readings 

Allocation remaining

Announced allocations for the Lower Lockyer WSS's water year (1 April–30 March) were obtained from Seqwater. Metered quarterly use data were extracted from DNRM database 'Water Scheme Operator Report'. Any unused allocation remaining at the end of the water year (i.e. 31 March) was forfeited; and there was no carryover of allocation between water years. The allocation remaining at the end of the 2014–15 year (30 June 2015) was calculated by subtracting the first quarter use (1 April–30 June) from the announced allocation made on 1 April 2015.

It was assumed that all entitlement, allocation and diversion data within the Water Scheme Operator Report were accurate and current at the time of data extraction.

The allocation remaining at 30 June 2015 was calculated, as shown in Table N15.

Adjustment and forfeiture of water allocation

Allocation carryover from one water year to the next does not occur in the South East Queensland region. All unused allocation at the end of a water year is forfeited.

Allocation: individual users

Supplemented allocation diversions were provided by Seqwater for each WRP area. The current ROP reporting requirements do not allow for reporting by type of use. This volume was calculated by removing the urban diversions from the total supplemented allocation diversion. This represents the remaining high-priority holders and all medium-priority holder diversions.

Metered data were obtained from resource operations licence holder for licensed groundwater allocation extractions for the Central Lockyer WSS for the 2014–15 year.

It was assumed that all entitlement, allocation and extraction data within the water management system were correct and up to date at the time of data collection. 

Diversions for the following rural-based WSSs were not necessarily solely for irrigation purposes and may have included some supplemented allocation diversions for urban purposes:

• Central Lockyer WSS
• Lower Lockyer WSS
• Warrill Valley WSS
• Logan River WSS.

The data were derived from measured data and no uncertainty was quantified.

Allocation: urban system

The volume was calculated by multiplying the nominal allocation volume (equivalent to entitlements in the 2015 Account) stated in the ROP or interim resource operations licence (IROL) by the announced allocation percentage. Data were then sorted into water security type and WSS. Urban holders of supplementary licences were then removed individually from the data and included in the surface water allocation announcements for urban water system.

Interim water allocations are provided for the Central Lockyer, Warril Valley, and Lower Lockyer WSSs under IROLs dated July 2008, August 2009, and July 2008 respectively.

The announced allocation percentage varies between priority groups and between WSSs, and is announced on the first day of the water year by the resource operation licence holders. If an announced allocation percentage is initially below 100%, subsequent announcements may be made to increase the percentage. The percentage cannot be reduced during a water year and once the announced allocation percentage reaches 100%, no further increases to the limit can occur.

The urban claim on surface water only includes the Seqwater and Toowoomba Regional Council entitlement allocations, as they have been identified as the high priority urban holders of entitlements in the ROPs. Within the supplemented schemes, water allocations are assigned a priority group (e.g. high priority, medium priority, etc.) which is used in allocating water between groups, and is especially important at times of scarcity. High priority groups will receive a higher level of reliability than medium priority groups to reflect the high level of reliability of supply provided for under the plan. The volumes of entitlement were obtained from the Moreton, Logan Basin, and Gold Coast resource ROPs schedule of water allocations. Announced allocation of 100% was given for all urban utility's entitlements for the 2014–15 year, making the allocation announcements equal to the nominal entitlement volume.

Other organisations may hold supplemented entitlements for some form of urban use but, as urban use is not identified on entitlements, these could not readily be identified.

The uncertainty estimate was not quantified for allocation announcements.

More information on these allocations and the associated water access entitlement is given in the Water rights, entitlements, allocations and restrictions note.

Stream monitoring data

Outflow

The runoff at the most downstream gauges of the major rivers within the South East Queensland region were received from the Queensland Government Department of Natural Resources and Mines (DNRM). The runoff downstream of these gauges was calculated using Australian Water Resources Assessment Landscape (AWRA–L) model version 5.0 Viney et al. (2015) outputs. The gauging stations considered in this calculation covered 65% of the total area of South East Queensland catchments and relevant flow data were received from DNRM. The rest 35% of the total area was ungauged and it had to be modelled to estimate the flow volumes.  It was estimated that out of 4,288,336 ML of runoff to surface water, approximately 40% was stored in the storages and the rest of the runoff went to the rivers. The following river gauging stations and the Pumicestone passage were considered to estimate the outflow from the region (Figure N13):

• Coomera River at Army Camp (Station 146010A)
• Currumbin Creek at Nicolls Bridge (Station 146012A)
• Tallebudgera Creek at Tallebudgera Creek Road (Station 146095A)
• Nerang River at Glenhurst (Station 146002B)
• Logan River at Yarrahappini (Station 145014A)
• Brisbane River at Savages Crossing (Station 143001C)
• Caboolture River at Upper Caboolture (Station 142001A)
• South Pine River at Drapers Crossing (Station 142202A).

Figure N13 Gauging stations used to calculate total outflow to sea 

AWRA–L model was used to estimate total runoff (4,288,336 ML) based on daily gridded climate data that were available on a 0.05 degree (approximately 5 km) national grid. The catchments of the downstream river sections were defined using the Australian Hydrological Geospatial Fabric (AHGF) stream network. The average runoff depth from the landscape into the surface water was determined as the weighted mean of the relevant grid cells within the catchment boundary. Cells were weighted based upon the area they represented within the catchment boundary. Mean runoff depth was converted to a runoff volume by multiplying runoff depth by the catchment area of the relevant end point of the river (excluding reservoirs).

To estimate outflow to the sea, the water balance equation was applied on the measured surface water volume at the upstream gauging station and estimated surface water volume at the near-sea outlet for the listed rivers, water diversion for the WTP, wastewater disposal to the surface water within the catchment from the WWTP, change in storages, rainfall volume directly on to the storages and evaporation from the storages.

It was assumed that the gauging station flow data are reliable and the water balance equations are valid. A comparison of alternative 'extrapolation' methods has not been undertaken.

This contributing area below the gauging stations is 7,310 km², approximately 35% of the total area of the South East Queensland region (Figure N14).

Figure N14 Gauging stations used to calculate runoff

Based on a water balance equation, estimated outflow to the sea is approximately 2,852,675ML, which is approximately 67% of  runoff to surface water reported in the Statement of Water Flows (4,288,336 ML). Given that the ungauged component of the South East Queensland region lies mainly on the Moreton, which contains a large number of rivers, creeks and estuary, it is likely that this area will generate a large amount of runoff. Moreover, river allocation rules were not considered in estimating the flows and outflows within the region. Therefore, the uncertainty in the estimate could not be quantified.

Gridded climate data and AWRA-L model

Precipitation and evaporation

Monthly precipitation grids for the region were produced using daily data from approximately 6,500 rain gauge stations across Australia and interpolated to a 0.05 degree (5 km) national grid (Jones et al. 2009).

Potential evapotranspiration across the region 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 evapotranspiration. Daily AWRA-L potential evapotranspiration grids for the region were produced based on daily gridded climate data (including precipitation, solar radiance, and temperature) available on a 0.05 degree (approximately 5 km) national grid (Jones et al. 2009).

The precipitation and evapotranspiration at each waterbody were estimated from the proportionally weighted average of grid cells that intersected each water feature. The volume was then estimated by multiplying by the surface area of each waterbody. The average monthly surface area of the major storages was calculated from daily storage levels and capacity tables. In the South East Queensland region, the surface area of the fourteen storages was calculated dynamically and the surface area of the six urban lakes was a static value produced from the Australian Hydrological Geospatial Fabric (AHGF). Surface area was not available for two storages.

The limitations associated with this approach are:

• The precipitation and AWRA-L potential evapotranspiration estimates were subject to approximations associated with interpolating the observation point data to a national grid as detailed in Jones et al. (2009).
• The dynamic storage surface areas calculated from the levels and storage rating tables represent a monthly average and therefore will not capture changes that occur on a shorter temporal scale.
• The use of the static default AHGF surface area is an approximation only. 
• The total surface area of the surface water store within the South East Queensland region included only the reservoirs and urban lakes. River channels were not included.

Runoff

Runoff to surface water was estimated based on the AWRA–L version 5.0 Viney et al. (2015) streamflow model outputs.

Using climate grid data for the South East Queensland region (including precipitation, temperature and solar radiation data), AWRA–L model was used to estimate the runoff depth at each grid cell within the region. Only runoff from the landscape is considered; therefore, the surface areas of the major reservoirs were excluded from the analysis.

The average runoff depth from the landscape into the connected surface water store was determined as the weighted mean of the relevant grid cells within the region boundary. Cells 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 storages).

The total runoff to surface water in the 2014–15 year was 4,288,336 ML, which was approximately 152% higher than the runoff generated in the 2013–14 year. The reason behind this increase in runoff was due to higher rainfall (1,066 mm) in 2014-15. It was estimated that 40% of the runoff was stored in the storages in the region and the rest of the runoff entered to the rivers downstream of the storages.

The runoff estimates were subject to the assumptions of the AWRA–L model detailed in 5.0 Viney et al. (2015). The uncertainty could not be unquantified.

Metered and estimated data provided by water authorities

Evaporation

Evaporation from the urban water system includes:

• calculated using the Bureau climate data

• calculated using a water balance approach through available inflow and outflow metering data and/or

• the metered treated wastewater volume disposed to evaporation lagoons.

Evaporation losses are only reported for the wastewater system.

The uncertainty estimate was +/– 20% to +/–40%.

Leakage: landscape

The 'Leakage: landscape' to landscape volume is assumed to be the non-revenue water associated with real losses, specifically due to pipe bursts from the urban water supply system.

The non-revenue volume is calculated based on physical observations of bursts events.

Where pipe bursts and background leakages are provided as a combined volume, for simplification this is reported as Leakage to groundwater because the volume related to leakage to landscape cannot be separated.

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. Real losses related to pipe bursts are reported in Leakage: landscape.

Non-revenue water is estimated using:

• the difference based on a water balance between metered water produced and revenue water (metered/estimated customer consumption charges); and/or
• modelling software of network real losses (leakages and bursts) and apparent losses.

Leakage in the wastewater system is not reported and therefore the total leakage to groundwater is likely to be underestimated.

Where non-revenue water real losses are reported as a combined volume for pipe bursts and background leakage, with no breakdown, this was reported in Leakage: groundwater, which may overestimate the volume.

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).

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.

Some disposals to Brisbane River, Albert River, Logan River, Bremer River, Tingalpa Creek, Eprapah Creek, and Cabbage Tree Creek are considered discharge to sea as these are estuarine at the site of the disposal.

Advanced wastewater treatment plants within the region also discharge reverse osmosis concentrate and excess purified recycled water to sea.

The uncertainty estimate was 0 to +/– 20%.

Discharge: user

Water Tracking and Electronic Reporting System (WaTERS)  contains both wastewater treatment plant discharges, and industrial and commercial  discharges.  WaTERS was queried for commercial and industrial discharge volumes in the 2014–15 year.

This volume includes treated wastewater discharge directly to surface water and sea water from industrial and commercial businesses, rather than discharging to urban wastewater collection system.

The data in the WaTERS have been collected, measured and reported by third parties (licence holders). The QA/QC of this data is not within DSITI control, and it has been assumed that these data are accurate and complete.

The uncertainty  was not quantified.

Discharge: wastewater

Discharge: wastewater is metered and includes:

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

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.

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 estimate was 0 to +/– 20%.

Discharge: landscape

The discharge: landscape volume is the metered treated wastewater discharge to landscape and/or infiltration ponds, where the primary purpose is disposal of the effluent rather than using the effluent for irrigation purposes. Also included in this volume is any other managed treated wastewater discharges not reported in

• Discharge:  surface water
• Discharge: sea.

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.

This volume may include discharges to landscape that make their way into the groundwater.

The uncertainty estimate was 0 to +/– 20%.

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 uncertainty estimate was +/– 20% to +/–40%.

Wastewater collected

The wastewater collected  volume is estimated using the aggregated metered inflow to wastewater treatment 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).

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.

Unitywater estimated the volume of wastewater collected within the region boundary, which is a subset of its total operational area.  The estimation of the volume is based on a pro-rata adjustment of the total wastewater by the customer connections located inside and outside the region boundary done via GIS scan. The difference between this volume and the metered inflow to treatment plants located within the region is the volume of wastewater exported by Unitywater outside the region boundary (but still within Unitywater’s operations). Refer to Wastewater and recycled water system transfer: inter-region.

The uncertainty estimate was 0 to +/– 20%.

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.

Some of the water treatment plants located outside the region boundary may supply water into the South East Queensland account region via the Water grid. The volume imported is derived from meters available at the outflow from the treatment plants as well as meters located within the water grid, or within local reticulation networks.

North Stradbroke Island is located outside the South East Queensland region boundary. It is assumed that the entire volume of water produced at North Stradbroke Island WTP is imported into the region via the Eastern Pipeline Interconnector and none of this volume is used on the island. The imported volume is likely to be overestimated due to this assumption.

The uncertainty estimate was +/– 20% to +/–40%.

Delivery: desalinated water

The delivery: desalinated water volume is metered at the outflow from the Tugun desalination plant.

The uncertainty estimate was 0 to +/– 20%.

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, and
• estimated non-revenue water volumes.

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

The volume delivered to non-urban users (i.e. supply to irrigation schemes and the environment) is not included in the reported volume.

Unitywater estimated the volume of water consumption within the South East Queensland region, which is a subset of its total operational area.  The estimated volume is based on a pro-rata adjustment of the total water use by the customer connections located inside and outside the region determined via GIS scan.

Three water treatment plants operated by Seqwater (Amity, Dunwich and Pt Lookout WTP) are located outside the south East Queensland region. Therefore,  related volumes were excluded from this volume.

Water treated by North Stradbroke Island water treatment plant is assumed to be entirely imported into the region.

For simplification, total urban consumption from Queensland Urban Utilities, Council of the City of Gold Coast and Logan City Council was reported, although small areas of their operations are located outside of the region.

The uncertainty estimate was 0 to +/– 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 groundwater).

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.

No non-potable water losses were reported and likely underestimate of the losses in the system.

The uncertainty estimate was +/– 20% to +/–40%.

Recycled water delivery: urban users

The 'Recycled water delivery: urban users' is derived from :

• customer meters; and
• billing meters onsite re-use water meters.

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

Urban consumption consists of residential, commercial, industrial, municipal, onsite (water and wastewater treatment plant) use and small scale agriculture/irrigation uses.

Unitywater estimated the volume of water consumption within the South East Queensland region, which is a subset of its total operational area.  The estimated volume is based on a pro-rata adjustment of the total water use by the customer connections located inside and outside the region determined via GIS scan. For simplification, total urban consumption from Queensland Urban Utilities, Council of the City of Gold Coast and Logan City Council was reported, although small areas of their operations are located outside of the region.

The uncertainty estimate was 0 to +/– 20%.

Wastewater and recycled water discharge: surface water

The 'Wastewater and recycled water discharge: surface water' is metered and includes:

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

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.

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 estimate was 0 to +/– 20%.

Other wastewater and recycled water system decreases

The other wastewater and recycled water decreases volume is the sum of the following two components:

• losses from the wastewater treatment system (if not reported in Evaporation from urban water system)
• known losses from the wastewater collection system
• known egress or exfiltration from the wastewater collection system occurring before metered inflow to wastewater treatment plants
• this also includes advanced treated water.

Losses from the wastewater system are estimated based on the metered inflow and outflow/disposal/customer meters or estimated based on observations.

Wastewater overflows or spills are 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 uncertainty estimate was +/– 20% to +/–40%.

Wastewater and recycled water system transfer: inter-region

The wastewater and recycled water system transfer: inter-region volume measures the transfer of treated wastewater and recycled water outside of the region. The volumes are based on metered information at the distribution infrastructure.

Wastewater exported by Unitywater is estimated by pro-rata adjustment of the total metered inflow to all its wastewater treatment plants based on the number of customer connections within the region, minus the metered inflow to treatment plants located within the region.

Unitywater customer connections located inside and outside of the region boundary is approximated based on GIS scan.

The uncertainty estimate was +/– 20% to +/–40%.

Other decreases

Other dereases represents transfers of supplemented allocations out of the South East Queensland region. This represents the surface water transfers out of the region; no diversions for use within the region are included.

Although the Queensland Department of Natural Resources and Mines (DNRM) has records of entitlement, allocation and diversions from storages in the water management system (WMS) database, data were needed from Toowoomba Regional Council to determine the diversions transferred out of the South East Queensland region to the town of Toowoomba. Toowoomba is located outside the South East Queensland region, on the Great Dividing Range and obtains much of its town water supply from within the South East Queensland region.

Water is pumped out of Lake Perseverance and Lake Cressbrook by the resource operation licence (ROL) holder (Toowoomba Regional Council) to Toowoomba via a series of tanks and minor storages to Mount Kynoch water treatment plant. Potable water is then supplied to the town of Toowoomba.

Derived from measured data. DNRM reliability and accuracy rating is B2 (Department of Environment and Resource Management 2011).

Operational Data Storage System: seepage data

Leakage: landscape

Storage loss is the loss that occurs in the WSS storages. Where storage loss was not specifically evaluated as part of ROP reporting requirements, the storage loss allowance detailed in the ROPs was used as an estimate. This was done by adding the storage loss allowances calculated for each month, based on the storage surface area at the start of month and the application of the difference between monthly storage loss factors in the applicable ROP tables. The Moreton and Logan Basin ROPs provide storage loss tables for Lake Wivenhoe, Lake Somerset and Lake Maroon, Cedar Grove Weir and Bromelton Off–Stream Storage, Lake Atkinson and Lake Moogerah.

The value for each storage was calculated as follows:

• For a storage, net evaporation loss was calculated by subtracting precipitation on surface water from the evaporation from surface water. If the calculation resulted in a negative value, the net evaporation loss was considered as zero.
• This net evaporation loss was subtracted from ROP loss (provided by DNRM) to calculate the adjusted storage loss for the volume. This is to prevent double counting because ROP loss includes net evaporative loss as estimated by DNRM. If the resulting value was less than zero, no value was considered for the storage.

The volumes are from application of the ROP calculation and therefore include evaporation losses. No adjustment was made to the calculation.

It has been assumed that the water management system database data were current, accurate and correct.

The Moreton and Logan Basin ROPs list loss factors to apply when estimating losses from storages where the storages are part of the WSS. Where the storages are not part of a WSS, losses were not available and could not be quantified accurately.

Losses from the storages that form part of a WSS have been estimated and reported where information was available to allow accurate quantification. Therefore:

• transmission losses were not reported in the Moreton or Gold Coast WRP areas
• storage losses were not reported in the Gold Coast WRP area.

Derived from storage loss estimates. DNRM reliability and accuracy rating is B4 (Queensland Government Department of Environment and Resource Management 2011).

Water resourcing licence database and meter readings

Non-allocated diversion: surface water

The non-allocated diversion: surface water volume is calculated from the volume of surface water diverted (metered at the source) and inflow to water treatment plants.

North Stradbroke Island Water Treatment Plant (WTP) has both surface water and ground water sources. The percentage of surface water inflow to the WTP was estimated based on production logs of treated water from each water source. This percentage was applied to the combined outflow metered volume of the plant.

Where metered inflows to water treatment plants are not available, these volumes are assumed to equal the metered outflow volume (i.e. no water losses occur during the treatment process).

The uncertainty estimate was 0 to +/– 20%.

Non–allocated diversion: urban system

'Non-allocated diversions: urban syetm' volume refers to surface water that is sourced from unregulated water source and/or source not managed using entitlements and allocations. For water sources managed through entitlements and allocations, refer to 'Allocation diversion of surface water'.

The calculation is based on metered raw water extraction from surface water and inflow to WTPs.

Raw water supplied directly as untreated (nonpotable water) is the metered extracted volume from the water source.

Where metered intakes to water treatment plants were not available, the intake volumes were estimated using metered outflow data and assumed that no water losses occurred during the treatment process.

North Stradbroke Island WTP sources water from both surface water and groundwater. The percentage of surface water abstracted was estimated based on production logs of treated water from each water source and this percentage was applied to the combined outflow metered volume of the plant. In previous years, all water was assumed to be sourced from surface water.

The uncertainty estimate was 0 to +/– 20%.

Allocated diversion: individual users 

‘Allocated diversions: individual users’ volume represents the volume of water diverted from surface water by non-urban (excluding Seqwater and Toowoomba Regional Council) holders of supplemented allocations. 

Supplemented allocation diversions were provided by Seqwater for each water resource plan (WRP) area. The current resource operations plan reporting requirements do not allow for reporting by 'type' of use. The volume was calculated by removing the urban from the total supplemented allocation diversion. This represents the remaining high-priority holders and all medium-priority holder diversions.

Seqwater has accepted metered data provided by water supply scheme (WSS) operators. The volume calculated excludes distribution loss.

Diversions for the following rural-based WSSs were not necessarily solely for irrigation purposes and may have included some supplemented allocation diversions for urban purposes:

•  Central Lockyer WSS

•  Lower Lockyer WSS

•  Warrill Valley WSS

•  Logan River WSS.

The data were derived from measured data and no uncertainty was quantified.

Allocated diversion: surface water

'The allocated diversion: surface water' volume is calculated from the volume of surface water diverted (metered at the source) and inflow to water treatment plants.

Where metered inflows to water treatment plants are not available, these volumes are assumed to equal the metered outflow volume (i.e. no water losses occur during the treatment process).

The uncertainty estimate was 0 to +/– 20%.

Non-allocated extraction: groundwater

The non-allocated extraction: groundwater volume is calculated from the volume of groundwater extracted (metered at the source) and inflow to water treatment plants.

Where metered inflows to water treatment plants are not available, these volumes are assumed to equal the metered outflow volume (i.e. no water losses occur during the treatment process).

Groundwater treatment plants on Bribie Island and Stradbroke Island were not considered as they are located outside the South East Queensland region.

The uncertainty estimate was 0 to +/– 20%.

Diversion: statutory rights

‘Diversion: statutory rights’ volume consists of diversions based on riparian water authorisations (RWAs).

An estimate has been made of the RWAs within the South East Queensland region. The total number of properties with RWAs was multiplied by an assumed diversion rate of 2 ML per property to obtain an estimate of the volume abstracted.

The assumed diversion rate of 2 ML per property may not be appropriate for all users and adds uncertainty to the estimated value.