South East Queensland
Supporting information

Introduction

The following set of notes provides consolidated reports for each of the water stores and systems within the South East Queensland (SEQ) region during the 2013–14 year. The water stores and systems included in the region are shown in Figure 1.

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

Figure 1 Water stores and systems within the South East Queensland region

Information on all water flows to and from each water store and system are presented in the following set of notes, including between–store flows and transfers that are not presented in the water accounting statements. The between-store flows and transfers that occur in the region are presented in Figure 2.

Figure 2 Between-store flows that occur within the South East Queensland region

The between-store flows and transfers (Figure 2), which are eliminated from the region's water accounting statements, are shown in italics throughout the following set of notes. The allocation announcement, forfeiture, and allocation remaining volumes associated with each between-store abstraction (brown arrows in Figure 2) are also shown in italics in the following notes.

Surface water store

Surface water assets

The volume of surface water assets represents water held in storages (2,320,939 ML).  The volume of water in regulated rivers, unregulated rivers, and lakes and wetlands could not be quantified due to lack of available data; however, it is considered to be relatively small compared to the volume held in storages.

The location of each storage within the SEQ region and the volume of water in each storage (including dead storage) as a percentage of total storage capacity at the end of the 2013–14 year is shown in Figure 3.

Figure 3 Percentage-full volume on 30 June 2014 for each storage

Total volume of water within each storage at 30 June 2014 and at the end of the previous three years (2013, 2012 and 2011) is given in Figure 4.

Figure 4 Surface water storage for South East Queensland region

The volume of water held in all storages within the SEQ region decreased by approximately 10% during 2013–14 from that of the previous year. The overall storage volume at the end of the 2012–13 year was at almost 99% of total capacity whereas at the end of the 2013–14 year the overall storage was 89% of the total capacity. The decrease in the storage was due to a 43% decrease in rainfall and subsequent runoff in the SEQ region (see Climate overview).

Surface water liabilities

Water liabilities in the SEQ region refer to the volume of surface water allocation remaining on licence entitlements at the end of the 2013–14 year for:

• individual users (12,153 ML)
• urban water system (0 ML).

Allocation carryover from one water year to the next water year does not occur in the SEQ region and all unused allocation at the end of a water year is forfeited.

The allocation remaining for each licence entitlement is provided in tables 1–2.

The largest water outflow is the river outflow from the region (904,491 ML), which refers to the annual volume of flow from the SEQ region rivers to the Pacific Ocean during the 2013–14 year. This outflow is approximately 13% of that during the 2012–13 year, which primarily reflects the impact of less than average rainfall that occurred during the 2013-14 year (see Water overview).

Evaporation from surface water storages during 2013-14 year was 286,303 ML. More than 40% of the evaporation from surface water occurred at Wivenhoe storage. Total evaporation during the 2013-14 yearwas slightly higher than that during the 2012–13 year, which might be due to higher temperature in the 2013–14 year (see Climate overview).

The total annual leakage from surface water storages within the SEQ region during the 2013–14 year was 279,567 ML, approximately 8% higher than that in 2012–13.

There are two non-allocated diversions and one riparian water diversion from the surface water store:

• entitled diversion of non–allocated surface water to users (9,152 ML)
• entitled diversion of non–allocated surface water to urban water system (3,787 ML)
• surface water diversions – other statutory rights (3,670 ML).

A small amount of was water delivered from surface water stores within SEQ region to the Toowoomba regional council area (6,742 ML).

Entitled water abstractions from the surface water store are described in Surface water allocation diversions.

The volume of river and floodplain losses  could not be quantified due to a lack of available data; however, these losses are considered to be relatively large and its omission may have a material impact on the water balance of the surface water store (see Balancing item).

Surface water allocation diversions

Entitled diversion of allocated surface water to the urban water system (235,836 ML) during the 2013–14 year accounts for more than 90% of the total surface water abstraction in the SEQ region. This volume represents the water diverted from storages to the SEQ water grid system. It also includes water (169 ML) diverted by Toowoomba Regional Council to the Crow's Nest area lying within the SEQ region.

In the 2013–14 year, surface water allocation announcement for urban water system by Seqwater was 442,841 ML in the region for different WSSs under three different WRP areas as follows:

• Gold Coast WRP: Nerang WSS was allocated with 84,000 ML and out of that 53,634 ML was diverted
• Logan Basin WRP: Logan River WSS was allocated 8,920 ML and out of that 933 ML was diverted
• Moreton WRP: there are 6 WSSs – Central Brisbane River and Stanley River, Central Lockyer, Cressbrook Creek, Lower Lockyer Valley, Pine Valleys and Warrill Valley. The amount of water allocation was 349,921 ML, out of which 181,269 ML was diverted.

The allocation of water in the 2013–14 was relatively unchanged compared to the previous year; however, the diversion increased by approximately 7%,  due to low rainfall prevailed in the 2013–14 year. The volume of water diverted from each WRP area is shown in Figure 6. Approximately 77%  of the entitled diversion of allocated surface water in the SEQ region was within Moreton WRP.

Figure 6 Surface water allocation diversion for urban supply within the South East Queensland region during the 2013–14 year

Entitled diversion of allocated surface water for individual users during the 2013–14 year was 5,986 ML, which accounts for approximately 8% of the total announced allocation for individual users. Licences primarily relate to different water resource plan priority groups as described in the WRPs.

Water allocation announcements in the SEQ region during the 2013–14 year refer to surface water supply to:

• individual users (73,294 ML)
• urban water system (442,841 ML).

The distribution of water allocation announcements to individual users are based on WRP areas as shown in Figure 7.

Figure 7 Surface water allocation to individual users in the South East Queensland region for the 2013-14 year

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

Surface water balancing

The balancing item volume represents the difference between the measured opening and closing balances of the surface water store, after physical inflows and outflows have been applied. This item is an indication of both the accuracy of the volumes reported and the degree to which the reported water flows represents a complete surface water store balance.

The balancing item is calculated according to Table 3.

The calculation of the water balance on the surface water store yielded a balancing item of 387,005 ML, which is approximately 20% of the total surface water inflows during the 2013–14 year. The positive balancing item indicates that either the inflows are too high or the outflows are too low. The rainfall-runoff volume is derived from a rainfall–runoff model, and it is reasonable to expect a 10–20% uncertainty around the estimated runoff volume that could account for the balancing item. The surface water outflow to sea was based on flow gauge data and estimated flow from the area downstream of the gauging station. The surface water balancing item is attributed to uncertainty associated with runoff and river outflow and the volume of river and floodplain losses not being able to be quantified.

Groundwater store

Groundwater assets

The aquifers in the SEQ region are described in the Groundwater section of the 'Contextual information'. The groundwater asset volume for the SEQ region represents permissible consumptive volumes for water table aquifers (9,340 ML).

Groundwater liabilities

Water liabilities in the SEQ region refer to the volume of groundwater allocation remaining on licence entitlements at the end of the 2013–14 year for individual users as shown in Table 4.

Allocation carryover from one water year to the next does not occur in the SEQ region. All unused allocation at the end of a water year is forfeited. Therefore, the groundwater allocation remaining is 0 ML. The announced allocation of groundwater to individual users in the 2013–14 year was 9,335 ML, and the entitled extraction of allocated groundwater to individual users was 3,340 ML. The reaming balance was forfeited at the the end of the year.

Groundwater inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the groundwater store in the SEQ region is provided in Figure 8.

Figure 8 Water inflows and outflows for the groundwater store within the South East Queensland region during the 2013–14 year

The only inflow to aquifers in the SEQ region that could be quantified was leakage from the urban water system (20,021 ML). Groundwater movement across the region boundary as well as surface water—groundwater interactions are considered to occur within the region; however, these flows could not be quantified.

The only outflows from aquifers in the SEQ region that could be quantified are the entitled abstractions (see 'Entitled groundwater extractions').

The only water movement to and from aquifers in the SEQ region that can be quantified is the entitled abstractions for individual users. Groundwater movement across the region boundary as well as surface water—groundwater interactions are considered to occur within the region; however, these flows could not be quantified.

Infiltration of groundwater into the urban water system could not be quantified in a way that is complete, neutral, and free from material error due to the lack of both data and a suitable quantification approach. As urban water supply systems and recycled water supply systems are typically pressurised, it would be expected that little groundwater infiltration into these systems occurs. This flow is not a significant proportion of the groundwater store inflows and would not be considered material to the water balance for the groundwater store.

Groundwater extractions from other statutory rights occur in the SEQ region, but the volume could not be quantified in a way that is complete, neutral, and free from material error due to the lack of both data and a suitable quantification approach. This extraction is not a significant proportion of the groundwater store outflows and would not be considered material to the water balance for the groundwater store.

Groundwater allocation extractions

There are the following non–allocated and allocated groundwater extractions in the region:

• entitled extraction of non–allocated groundwater to urban water system (182 ML)
• entitled extraction of non–allocated groundwater to users (3,994 ML)
• entitled extraction of allocated groundwater to users (3,340 ML).

Most of the extractions from the groundwater store were benefitted area extractions within the Central Lockyer Valley WSS in the Lockyer Valley groundwater management area (GMA). The allocation extraction was 3,340 ML out of an announced allocation of 9,335 ML.  The volume from other statutory rights cannot be quantified due to lack of available data. In addition, extraction data were not available for a number of other GMAs or for the non–benefitted area of Implementation Area 1 of the Lockyer Valley GMA.

The entitlement, allocation announcement, and forfeiture for each of these water rights during the 2013–14 year are provided in the Groundwater rights section of the 'Water access and use' note.

Groundwater forfeitures

The portion of groundwater allocation that has not been abstracted at the end of the water year is forfeited, i.e. there is no carry over of entitlements into the next water year. Water forfeitures in the SEQ region during the 2013–14 year relate to licence entitlements for individual users for adjustment and forfeiture of groundwater allocation (5,995 ML).

Groundwater allocation announcements

Water allocation announcements (see Groundwater rights section of the 'Water access and use' note) in the SEQ region during the 2013–14 year refer to groundwater supply to individual users on groundwater allocation announcements (9,335 ML).

Groundwater balancing item

The balancing item volume (Table 5) represents the difference between the measured opening and closing balances of the groundwater store, after physical inflows and outflows have been applied.

The balancing item is calculated according to Table 5.

The calculation of the water balance on the groundwater store yielded a balance of 12,505 ML, approximately 62% of the total groundwater inflows during the 2013–14 year.

As the volume of water in the groundwater stores within the SEQ region could not be quantified physically, the volume disclosed in the balancing item of 12,505 ML represents the net change in groundwater store and other measurement errors throughout the 2013–14 year.

Urban water system

Urban water assets

South East Queensland’s urban water system comprises three subcomponents:

• urban water supply system (4,742 ML)
• wastewater system (43 ML)
• recycled water system and advanced water treatment (422 ML).

The volume of water in the urban water supply system changes little from year to year and comprises water in the distribution pipe network (2,113 ML) and reservoirs (2,629 ML).  Water in the wastewater system was 43 ML, as reported by the Council of the City of Gold Coast and the Toowoomba Regional Council. The recycled water and advanced water treatment volume comprises water in the distribution pipe network (40 ML) and service reservoirs (382 ML), as reported by  Council of the City of Gold Coast.  There was no reporting on wastewater system or recycled water and advanced water treatment systems from other utilities.

Urban water claims

Water claims in the SEQ region refer to the volume of surface water allocation remaining for urban water supply licence entitlements at the end of the 2013–14 year. Entitled extraction of allocated groundwater to urban water system is not applicable for SEQ region. As there is no carryover in the SEQ region, surface water allocation remaining will always be zero, as shown in Table 6.

Urban water system inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the urban water system in the SEQ region is provided in Figure 9.

Figure 9 Water inflows and outflows for the South East Queensland's urban water system during the 2013–14 year

Urban water supply system inflows

The SEQ urban water supply system, also referred to as the 'SEQ water grid', is the infrastructure network of two-way pipes that connects water storages, weirs, water treatment plants (WTPs), groundwater bore fields, and the Gold Coast desalination plant (Tugun Desalination Plant) across the region.

Seqwater operates the storages and SEQ water grid including WTPs in the SEQ region, which supplies to Queensland Urban Utility (QUU), Logan City Council, Redland City Council, Unitywater and Council of the City of Gold Coast. Some of these WTPss are connected to the water grid and some are supplying into local reticulation networks only.

The operations of both Toowoomba Regional Council and South Burnett Regional Council are also partially located within the SEQ region boundary. They mostly source water directly and manage their own urban water supply system without any connection to the SEQ water grid.

The SEQ water grid also extends outside the SEQ region boundary and therefore imports and exports of water occur in the SEQ account. Important imports to note are the Eastern Interceptor Pipeline, which sources surface water and groundwater from North Stradbroke Island within the Redland City Council operational area, and the Northern Interceptor Pipeline that extends to the Sunshine Coast. There are also minor imports from the neighbouring Toowoomba Region Council to the Preston community which is located within QUU operational area. Desalinated water from the Gold Coast desalination plant feeds directly into the SEQ water grid.

There are four sources of water for the urban water supply system:

• allocated and non-allocated surface water (239,623 ML)
• allocated groundwater (182 ML)
• desalinated water (1,435 ML)
• Inter-region import (20,007 ML).

The water supply to urban water system from different sources is shown in Figure 10.

Figure 10 Water sources used in South East Queensland's urban water system and total volume for the years ending 30 June 2011, 2012, 2013 and 2014

Entitled extraction of allocated  and non-allocated surface water to the urban water supply system (239,623 ML) is the SEQ region’s primary source of water for urban water supply and comprised approximately 92% of the inflows to the system during the 2013–14 year (Figure 11).  Delivery of desalinated water contributed approximately 1% of urban water supply  in this reporting year, a decrease of 1370 ML from the 2012–13 year.

Delivery of water from outside the region (20,007 ML) contributed 8% of urban water supply, which is 18% less that reported in the previous year. This delivery refers to water imported via the Norther Pipeline Interconnector (11,073 ML), delivery of mostly surface and some groundwater via Eastern Pipeline Interconnector from North Stradbroke Island (8,874 ML), and supply to the Preston community within QUU operations, which takes water (60 ML) from neighbouring Toowoomba Regional Council and Logan City Council outside the of the SEQ region boundary.

Desalinated water was supplied from the Tugun Desalination Plant (1,435 ML).

Wastewater and recycled water system inflows

The wastewater in the region is collected and treated within WWTPs operated by the following water authorities: QUU, Logan City Council, Redland City Council, Unitywater, Council of the City of Gold Coast, Toowoomba Regional Council and South Burnett Regional Council. There is an exported volume of wastewater outside of the region. This is, however, wastewater estimated to be collected by Unitywater and sent to WWTPs located outside of the SEQ region boundary but still within Unitywater’s operational area to the north of the SEQ region's boundary.

Total wastewater collected during the 2013–14 year was 207,971 ML, approximately 15% less than the previous year.

Precipitation on urban system occurs in the SEQ region, but the volume could not be quantified in a way that is complete, neutral, and free from material error due to the lack of both data and a suitable quantification approach. No information on storage surface area was available for wastewater lagoons or uncovered tanks and storage reservoirs that form part of the urban water supply, collection or recycled water supply systems. The surface area of these storages would be minor in comparison to the surface area of storages. The omission of the precipitation volumes affecting these structures is not material for the water balance of the urban water system store.

Urban water supply systems and recycled water supply systems are typically pressurised; therefore, it would be expected that little stormwater ingress (entry) into these systems occurs, but the volume could not be quantified in a way that is complete, neutral and free from material error due to the lack of both data and a suitable quantification approach. Wastewater collection systems consist of gravity sewers and pumping mains. Stormwater ingress into the gravity sewers may occur where illegal connections, flooding or leakage occur. Stormwater ingress into wastewater collection systems could not be quantified in a way that is complete, neutral, and free from material error in the SEQ region as data were not available from the urban utilities. The inclusion of stormwater ingress is not considered to be material to the water balance for the urban water system store.

Infiltration of groundwater occurs into the urban water system, but the volume could not be quantified in a way that is complete, neutral, and free from material error due to the lack of both data and a suitable quantification approach. As urban water supply systems and recycled water supply systems are typically pressurised, it would be expected that little groundwater infiltration into these systems occurs. The inclusion of groundwater infiltration is not considered to be material to the water balance for the urban water system store. This flow is not a significant proportion of the groundwater store inflows and would not be considered material to the water balance for the groundwater store.

The volume of wastewater collected by each water utility is given in Figure 11.

Figure 11 Wastewater collected by different utilities in the South East Queensland region for the year 2013-14 (source data)

Urban water supply system outflows

The largest water outflow from the urban water system is the delivery of water to consumers. During the 2013–14 year, the total delivery of water was 263,380 ML, of which 238,016 ML was delivered from the urban water supply system. The remaining  25,364 ML was delivered from the recycled water system and advanced treated water system (Wastewater and recycled water system outflows).

Losses from the urban water supply system included leakage to groundwater (20,021 ML), which was 39% less than that in the previous year. Other losses from the system (3,306 ML) include all other non-revenue water from the urban water supply system, such as consumer meter inaccuracies and unauthorised consumption. This was an improvement by approximately 30% compared to that in the previous year.

There is also a minor export of potable water to Tweed Shire Council via the Gold Coast City Council infrastructure (10 ML).

Wastewater and recycled water system outflows

The outflow from the wastewater and recycled water systems was 210,984 ML. The largest outflow is treated wastewater discharge (138,324 ML). Recyled and advanced water treatment discharge (304 ML) to estuary/sea is approximately 67% of the total inflow to the wastewater and recycled water systems (207,971 ML).  Treated wastewater is also discharged to surface water (41,905 ML) and landscape (1,527 ML). Treated wastewater exported out of the SEQ region was 3,110 ML.

Six of the WWTPs within the SEQ region sends recycled water to advanced water treatment plants (AWTPs) located in Bundamba, Gibson Island, and Luggage Point, all operated by Seqwater. The AWTPs produce high-quality treated water for industrial use. The Western Corridor Recycled Water Scheme (WCRWS) is currently being placed in 'care and maintenance' mode to preserve the asset and allow reactivation if required.

A portion of wastewater was further treated in the recycled water and advanced water treatment systems and delivered for urban use (25,364 ML) in the 2013–14 year.  Approximately 12% of the total wastewater collected to the system was recycled and delivered to users. The use of recycled and advanced treated water increased by approximately 45% in 2013–14 compared with the 2012–13 year, however the majority of this increase can be attributed to additional data received in 2013-14.

Estimated losses in the wastewater and recycled water system totalled 450 ML.

Total wastewater outflows from SEQ's wastewater and recycled water system is given in Figure 12. Outflows from each utility are given in Figure 11.

Figure 12 Wastewater outflows from South East Queensland's wastewater system during the 2013–14 year

Decrease of urban water claims

The portion of urban water claim that is not abstracted at the end of the water year is forfeited, that is, there is no carryover of entitlements into the next water year. Water forfeitures in the SEQ region during the 2013–14 year relate to licence entitlements for surface water supply (207,005 ML).

Increase of urban water claims

Increase of water claims for the urban water system refers to allocation announcements during the 2013–14 year for surface water supply (442,841 ML).

Surface water annual allocations for urban water supply for the WRP areas for the year are given in Figure 6.

Urban water system balancing item

The balancing item volume represents the difference between the measured opening and closing balances of the urban water system, after physical inflows and outflows have been applied (Table 7). This item is an indication of both the accuracy of the volumes reported and the degree to which the reported water flows represents a complete urban water system balance.

The calculation of the water balance on the urban water system yielded a balancing item of –4,177 ML. This is approximately 80% of the total urban water system store volume at the end of the 2013–14 year and less than 0.9% of the total urban water system inflows during the year.

Unaccounted-for difference

The volume recognised in the water accounting statements (395,333 ML) represents the total unaccounted-for difference for the SEQ region for the 2013–14 year.

The unaccounted–for difference is the volume necessary to reconcile the opening water storage and closing water storage with the total water inflows and total water outflows reported in the water accounting statements (Table 8).

The unaccounted–for difference can also be calculated by tallying the volumes necessary to reconcile (balance) the opening and closing storage with the water inflows and outflows of each of the separate water stores of the region, as shown in Table 9.

Table 9 shows that the unaccounted-for difference volume is primarily explained by the balancing item of the surface water and groundwater store. The surface water balancing item is attributed to uncertainty associated with runoff and river outflow, and the volume of river and floodplain losses not being able to be quantified (see Surface water note).

Off-channel storages

The Queensland Government Department of Environment and Resource Management (DERM) has indicated that there are approximately 1,700 off-channel storages within the SEQ region with a combined estimated storage volume of 59,080 ML.

The information from 2010 has been extracted from the Large Referable Farm Dam Identification Program dataset (Queensland Government Department of Energy and Water Supply), which identified farm dams greater than 0.25 ha in area using Landsat 30-metre imagery. Some dams may have been omitted during this selection process due to the remote sensing methods used. The data is not intended as a complete count of off-channel storages but is an indication of the number of larger dams within the SEQ region.