National Water Account 2015

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Region overview

Contextual information

Physical information

Administration

Water rights

Climate and water overview

Water Accounting Statements

Water Assets and Water Liabilities

Changes in Water Assets and Water Liabilities

Water Flows

Notes

Accounting policies

Supporting information

Quantification approach

Reconciliations

Water resources & systems

Water access & use

Future outlook

References

Accountability statement

Burdekin: Supporting information

• Introduction
• Surface water store
• Groundwater store
• Unaccounted-for difference

Introduction

The following set of notes provides consolidated reports for each of the water stores and systems within the Burdekin region during the 2014–15 year. The water stores and systems included in the region are shown in Figure N1.

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

Figure N1 Water stores and systems within the Burdekin region

Information on all water flows to and from each water store and system are presented in this note, 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 N2.

Figure N2 Between-store flows that occur within the Burdekin region

The between-store flows and transfers (Figure N2), which are eliminated from the region's water accounting statements, are shown in italics throughout the following set of notes.

Surface water store

The Burdekin region's surface water store has four components:

• storages
• regulated rivers
• unregulated rivers
• lakes and wetlands.

A reconciliation of the surface water Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N1. Further details on assets, liabilities, and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical Assets

Physical surface water asset volumes in the Burdekin region at 30 June 2015 were storages (1,479,551 ML).

The volume of water in regulated rivers, unregulated rivers, and lakes and wetlands could not be quantified due to a lack of available data; however, the volume of water held in channels and lakes is considered to be relatively small compared to the volume held in storages.

The location of each storage within the Burdekin region and the volume of water in each storage (including dead storage) as a percentage of total storage capacity at the end of the 2014–15 year is shown in Figure N3.

Figure N3 Percentage-full volume on 30 June 2015 for each storage

The overall storage volume within the Burdekin region decreased during the 2014–15 year from 99% to 73% capacity. The volume of water within each storage at 30 June 2015 compared with the previous year is given in Figure N4.

Figure N4 Total volume of water in each storage at 30 June 2015 compared with the previous year

The water volume in Lake Dalrymple and Eungella dropped from 99% last year to 72 and 79% full respectively during the 2014–15 year. Below average rainfall in the region, particularly during the middle of the wet season, resulted in below average streamflows and storage inflows, leading to a progressive decrease in volume since June 2014 (Climate and water overview).

Non-physical assests

There are no non-physical surface water assets in the region.

Liabilities

Surface water liabilities in the Burdekin region refer to the volume of surface water allocation remaining (or carryover) on licence entitlements at the end of the 2014–15 year for:

• individual users—53,654 ML
• urban system—0 ML
• irrigation scheme—0 ML.

All the listed water supply licences for the region have a water management year that ends on 30 June. Carryover of surface water is allowed for these licence entitlements; however, at the time of publication only a total volume of carryover was available. That is, the carryover could not be separated for individual users, urban system and irrigation scheme. It is considered that the majority of carryover is associated with individual users, so the total volume has been assigned to licence entitlements for individual users. However, given diversions to the irrigation scheme during the 2014–15 year exceeded the allocation volume (Table N4), it can be assumed that a portion of the total carryover volume from the previous year (92,202 ML) was associated with the irrigation scheme. In this case, an adjustment volume of 25,439 ML was applied to the irrigation scheme liability.

A summary of surface water allocation remaining for each licence entitlement is provided in tables N2–N4.

Inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the surface water store in the Burdekin region is provided in Figure N5.

Figure N5 Water inflows and outflows for the Burdekin region's surface water store during the 2014–15 year

Surface water inflows

Total inflows to surface water were 1,730,603 ML and comprised the following:

• precipitation—90,680 ML
• runoff—1,639,923 ML.

The largest water inflow into the surface water store is runoff (1,639,923 ML). The total volume of runoff during the 2014–15 year is less than half that of the previous year (3,510,350 ML). This reflects the relatively poor rainfall experienced across the region during the typically wetter months (February and March) and also the below average soil moisture conditions (see Climate and water overview).

The remaining two natural surface water inflows are precipitation on surface water (90,680 ML) and discharge from groundwater (– ML). The volume of precipitation represents rainfall that fell on the storages within the region. More than 85% of the total volume of precipitation on surface in the region occurs at Lake Dalrymple. Discharge from groundwater represents the water discharged from aquifers to rivers within Burdekin region. The discharge from groundwater volume cannot be quantified accurately due to a lack of available data.

Two transfers of water in the region are point return from the irrigation scheme (– ML), which represents return flow from the irrigation areas to rivers, and discharge from urban supply (– ML). Both of these transfers are not measured and cannot be quantified accurately.

Surface water outflows

Total outflows from surface water were 2,446,226 ML and comprised the following:

• evaporation—504,892 ML
• outflow—1,007,196 ML
• non-allocated diversion: individual users—115,336 ML
• allocated diversion: individual users—150,120 ML
• allocated diversion: urban system—1,957 ML
• allocated diversion: irrigation—666,725 ML.

The largest water outflow is the river outflow from the region (1,007,196 ML), which refers to the annual volume of flow from the Burdekin River (897,852 ML), Haughton River (46,511 ML), and Barratta Creek (62,833 ML) into the South Pacific Ocean during the 2014–15 year. This outflow volume is considerably less than that which occurred during the 2013–14 year (1,862,192 ML), reflecting the below average flow conditions in the regions river systems during the 2014–15 year (see Climate and water overview).

Evaporation from surface water during the 2014–15 year was 504,892 ML, which was higher than the previous year. This may be attributed to the decreased rainfall (and hence cloud cover) that occurred during the year (see Climate and water overview). More than 91% of the total volume of evaporation from surface water in the region occurs at Lake Dalrymple.

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

Recharge: groundwater <(– ML) was not recognised due to a lack of available data and a suitable quantification approach.

No inter-region transfer from the Burdekin region occurred during the 2014–15 year.

Non-allocated surface water diversions to individual users in the region was estimated to be 115,336 ML during the 2014–15 year, which assumes 100% of the licenced entitlement was taken.

Allocation diversions

Most of the allocated diversion in the Burdekin region is for irrigation scheme water supply. During the 2014–15 year, 666,725 ML of surface water was diverted from storages to the Burdekin and Bowen irrigation areas which accounts for approximately 81% of the total allocated diversion (Figure N6). Total surface water diversion to irrigation during the 2014–15 year exceeded the total allocation by 25,439 ML (refer to Surface water rights in the 'Water access and use' note).

Figure N6 Water diversions for irrigation schemes during the 2014–15 year

Allocated diversion to individual users during the 2014–15 year was 150,120 ML, which accounts for approximately 18% of the total allocated diversion. Licences primarily relate to water sourced for the industrial and mining sectors (see Surface water rights note).

Allocated diversions for urban water supply during the 2014–15 year was 1,957 ML, which accounts for less than 1% of the total allocated diversion. This volume includes urban supply associated with the Bowen Broken (869 ML) and Burdekin Haughton (1,088 ML) water supply schemes (Figure N6). 

Surface water balancing item

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 N5.

The calculation of the water balance on the surface water store yielded a balancing item of 191,985 ML. This is approximately 13% of the total surface water store volume at the end of the 2014–15 year and approximately 11% of the total surface water inflows during the 2014–15 year. The positive balancing item indicates that either the inflows are too low or the outflows are too high.

It is likely that the balancing item volume is primarily attributed to uncertainties associated with the runoff to surface water (a large source of surface water increase), river outflow from the region (a large source of surface water decrease), and the lack of an estimate of surface water discharge to groundwater.

Runoff is estimated using a combination of observed streamflow data and rainfall–runoff model outputs (see Quantification approaches) and it is reasonable to expect a 10–20% uncertainty around this estimated runoff volume (+/– 150,000 ML). The river outflow to sea is based on measured flow data collected at the most downstream station along a river. There is no adjustment made for the contributing area below the gauging station (see Quantification approaches). As such, outflow to sea could be underestimated by up to 10% (100,000 ML).

Groundwater Store

The Burdekin region's groundwater store has two components:

• water table aquifer
• underlying aquifer.

A reconciliation of the groundwater Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N6. Further details on assets, liabilities, and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical assets

The aquifers in the Burdekin region are described in the Groundwater section of the 'Contextual information'. While some information exists on water movement to and from the aquifers (see Groundwater inflows and outflows below), no value is available for the volume of water stored in the aquifers as indicated by dashes ('–') in the water accounting statements.

Non-physical assets

There are no non-physical groundwater assets in the region.

Liabilities

Groundwater liabilities in the Burdekin region refer to the volume of groundwater allocation remaining on licence entitlements at the end of the 2014–15 year for individual users (0 ML).

All of the individual users listed water supply licences for the region have a water management year that ends on 30 June. As there are no carryover provisions for these licences, the unused component of annual groundwater allocation is forfeited at the end of the water year. Therefore, the volume of groundwater allocation remaining at the end of the 2014–15 for these licence entitlements is zero.

A summary of groundwater allocation remaining for each licence entitlement is provided in Table N7.

Further information on all entitlements and allocation arrangements are detailed in the Groundwater rights note.

Inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Burdekin region is provided in Figure N7.

Figure N7 Water inflows and outflows for the groundwater store within the Burdekin region during the 2014–15 year

Groundwater inflows

The only water movement to aquifers in the Burdekin region (that can be quantified) is the managed aquifer recharge (discharge to groundwater via artificial pits and channels) from individual users (81,673 ML).

Inter-region groundwater movement across the region boundary and from the coast, discharge from landscape, and surface water recharge to groundwater could not be quantified.

Groundwater discharge from urban supply, and leakage from irrigation schemes are considered to be applicable to the region; however, these flows were also unquantifiable, as indicated by dashes ('–') in Figure N7.

Groundwater outflows

Total outflows to groundwater were 54,860 ML and comprised the following:

• non-allocated extraction: individual users—37,010 ML
• allocation extraction: individual users—17,850 ML.

The only groundwater outflows that can be quantified are the non-allocated and allocated extractions for individual users.

Non-allocated groundwater extractions to individual users in the region was estimated to be 37,010 ML during the 2014–15 year, which assumes 100% of the licensed entitlement was taken (see Groundwater rights note).

The volume of inter-region groundwater flow out of the region and from the coast (– ML) and discharges to landscape and surface water (– ML) could not be quantified due to a lack of available data.

Allocation extractions

Allocated groundwater extractions to individual users was reported to be 17,850 ML and represents water taken specifically from the Haughton A Zone (part of the Burdekin Haughton Water Supply Scheme).

Groundwater balancing item

The balancing item volume represents the difference between the measured opening and closing balances of the groundwater store, after physical inflows and outflows have been applied. Given the volume of water in the aquifers and the natural groundwater movement in the region cannot be quantified, the balancing item is simply the difference between the managed aquifer recharge from individual users (81,673 ML) and the total volume of groundwater extraction (54,860 ML), as shown in Table N8.

Unaccounted-for difference

The volume recognised in the water accounting statements (165,172 ML) represents the total unaccounted-for difference for the Burdekin region for the 2014–15 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. It is calculated according to Table N9.

The unaccounted–for difference can also be calculated by summing 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 N10.

Details regarding the balancing item's calculation are given in the Surface water store note.

The volume of water in the groundwater stores within the Burdekin region could not be quantified.