Murray–Darling Basin
Water resources and systems

Introduction

The following set of notes provides consolidated reports for each of the water stores and systems within the Murray–Darling Basin (MDB) region during the 2012–13 year. The water stores included in the region are shown in Figure 1.

Figure 1  Schematic diagram of the water stores within the MDB region
Figure 1  Schematic diagram of the water stores within the MDB region

 

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

Information on all water flows to and from each water store and system is 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 2.

The numbers on the diagram refer to the line item numbers in the water store notes. For each between-store flow, there are two line item numbers: one refers to flow out of a water store and the other refers to flow into a water store.

Figure 2  Schematic diagram of between-store flows that occur within the MDB region: line item numbers are provided next to the flows
Figure 2  Schematic diagram of between-store flows that occur within the MDB region: line item numbers are provided next to the flows

 

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.

Surface water

Background

A description of the MDB region's surface water resources is provided in the Surface water section of the Contextual information.

Water in store

Table 1 shows that the total surface water store decreased during the 2012–13 year in the MDB region.

 

Table 1  Statement of Water Assets and Water Liabilities for the surface water store for the MDB region as at 30 June 2013

Water assets

Northern Basin

Southern Basin

Whole region

2013
ML

2012
ML

2013
ML

2012
ML

2013
ML

2012
ML

1 Surface water

 

 

 

 

 

 

1.1 Storages

2,972,416

4,314,709

13,039,374

16,872,487

16,011,790

21,187,196

1.2 Unregulated river

 –

 –

 –

 –

 –

 –

1.3 Regulated river

20,885

16,249

998,377

1,309,763

1,019,262

1,326,012

1.4 Lakes and wetlands

1,799,526

1,811,372

1,799,526

1,811,372

1.5 Inter-region claim on water

0

0

306,397

913,776

306,397

913,776

1.10 Other surface water assets

0

0

20,592

19,952

20,592

19,952

Total surface water assets

2,993,301

4,330,958

16,164,266

20,927,350

19,157,567

25,258,308

 

 

 

 

 

 

 

5 Water liabilities

 

 

 

 

 

 

5.1 Surface water allocation remaining

1,368,322

2,092,669

2,835,992

5,204,783

4,204,314

7,297,452

5.2 Surface water allocationremaining - urban water system

0

0

0

0

0

0

Total surface water liabilities

1,368,322

2,092,669

2,835,992

5,204,783

4,204,314

7,297,452

 

 

 

 

 

 

 

Opening net water assets

2,238,289

2,010,873

15,722,567

14,059,906

17,960,856

16,070,779

Change in net water assets

(613,310)

227,416

(2,394,293)

1,662,661

(3,007,603)

1,890,077

Closing net water assets

1,624,979

2,238,289

13,328,274

15,722,567

14,953,253

17,960,856

  – = Data not available

Table 1 includes information only for nine lakes: Dock Lake, Pine Lake, Lake Batyo Catyo, Green Lake, Lake Albert, Lake Alexandrina, Lake Burley Griffin, Lake Ginninderra, and Lake Tuggeranong. Volume of water stored in other lakes and wetlands could not be quantified accurately due to a lack of available data.

The location of major storages within the MDB region, and the volume of water, including dead storage, in each storage as a percentage of total storage capacity (% full) at the end of the 2012–13 year, is shown in figures 3 and 4.


 

Figure 3 Location map of major storages within the Northern Basin; the % full volume on 30 June 2013 for major storages is also shown
Figure 3 Location map of major storages within the Northern Basin; the % full volume on 30 June 2013 for major storages is also shown


 

Figure 4 Location map of major storages within the Southern Basin; the % full volume on 30 June 2013 for major storages is also shown
Figure 4 Location map of major storages within the Southern Basin; the % full volume on 30 June 2013 for major storages is also shown

The water volume in majority of the storages within the MDB region at the end of the 2012–13 year was less than that at the start (see line item 1.1 Storages). The decrease in surface water storage during the year is primarily attributed to low inflows into the storages during the 2012–13 year. This situation reflects the below average rainfall conditions observed in the region in the 2012–13 year (see Rainfall in 'Climate overview').

Changes in water store

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the surface water store are provided in tables 2 and 3, respectively. In addition to flows reported in the water accounting statements, the tables also show flows between the surface water and groundwater stores within the region.

 

Table 2  Statement of Changes in Water Assets and Water Liabilities for the surface water store for the year ended 30 June 2013

Description

Northern Basin

Southern Basin

Whole region

2013
ML

2012
ML

2013
ML

2012
ML

2013
ML

2012
ML

Water asset increases

 

9 Surface water increases

9.1 Precipitation on surface water

157,744

247,093

1,002,385

1,401,857

1,160,129

1,648,950

9.2 River inflow to region

0

0

2,156,320

4,547,315

451,000

0

9.3 Groundwater discharge

61,788

35,207

496,982

7,159

558,770

42,366

9.4 Runoff to surface water

10,679,507

27,429,924

14,464,367

30,168,072

25,143,874

57,597,996

9.5 Point return from irrigation scheme

0

0

212,773

198,314

212,773

198,314

9.6 Overbank flood return to river channel

 –

 –

 –

 –

 –

 –

9.9 Discharge from urban water system

0

0

31,636

34,325

31,636

34,325

9.10 Direct discharge by user

 –

 –

 –

 –

 –

 –

9.15 Direct discharge by user

0

0

1,748,700

2,560,022

1,748,700

2,560,022

9 Total surface water increases

10,899,039

27,712,224

20,113,163

38,917,064

29,306,882

62,081,973

 

13 Surface water liability decreases

13.1 Adjustment and forfeiture of surface water allocation

112,563

163,023

1,894,975

2,052,327

2,007,538

2,215,350

13.2 Adjustment and forfeiture of surface water allocation - urban water system

20,929

30,021

152,510

256,722

173,439

286,743

13 Total surface water liability decreases

133,492

193,044

2,047,485

2,309,049

2,180,977

2,502,093

 

Water asset decreases

 

17 Surface water asset decreases

17.1 Evaporation from surface water

311,829

313,670

2,725,037

2,672,732

3,036,866

2,986,402

17.2 River outflow from the region

1,705,320

4,547,315

5,179,600

9,565,600

5,179,600

9,565,600

17.3 Leakage to groundwater

35,736

104,977

645,142

244,817

680,878

349,794

17.4 Leakage to landscape

 –

 –

 –

 –

 –

 –

17.5 Overbank flood spilling

437,901

299,151

0

0

437,901

299,151

17.6 Surface water diversions - other statutory rights

37,687

37,686

30,523

30,523

68,210

68,209

17.7 Entitled diversion on non-allocated surface water to users

1,398,405

1,090,894

668,541

523,155

2,066,946

1,614,049

17.8 Entitled diversion of non-allocated surface water to urban water system

4,177

3,567

8,896

6,294

13,073

9,861

17.10 River and floodplain leakage, evaporation and errors

6,847,029

19,638,619

7,652,345

17,942,623

14,499,374

37,581,242

17.17 Decrease of inter-region surface water claim on water

0

0

215,000

625,000

215,000

625,000

17 Total surface water asset decreases

10,778,084

26,035,879

17,125,084

31,610,744

26,197,848

53,099,308

 

Water liability increases

 

21 Surface water liability increases

21.1 Surface water allocation announcements

825,265

1,599,474

6,933,312

7,412,187

7,758,577

9,011,661

21.2 Surface water allocation announcements - urban system

42,492

42,499

496,545

540,521

539,037

583,020

21 Total surface water liability increases

867,757

1,641,973

7,429,857

7,952,708

8,297,614

9,594,681

 

 

 

 

 

 

 

Balancingitem—surfacewater

0

0

0

0

0

0

 

 

 

 

 

 

 

Change in net water assets

(613,310)

227,416

(2,394,293)

1,662,661

(3,007,603)

1,890,077

– = Data not available

  1. Please note 1,705,320 ML for the 201213 year and the whole volume for the 201112 year for the Southern Basin for line item 9.2 'River inflow to region' was eliminated in the whole region.
  2. Please note the volume for the Northern Basin for line item 17.2 'River outflow from the region' was eliminated in the whole region.

 

Table 3  Statement of Water Flows for the surface water store for the year ended 30 June 2013

Description

Northern Basin

Southern Basin

Whole region

2013
ML

2012
ML

2013
ML

2012
ML

2013
ML

2012
ML

Water asset increases

 

9 Surface water increases

9.1 Precipitation on surface water

157,744

247,093

1,002,385

1,401,857

1,160,129

1,648,950

9.2 River inflow to region

0

0

2,156,320

4,547,315

451,000

0

9.3 Groundwater discharge

61,788

35,207

496,982

7,159

558,770

42,366

9.4 Runoff to surface water

10,679,507

27,429,924

14,464,367

30,168,072

25,143,874

57,597,996

9.5 Point return from irrigation scheme

0

0

212,773

198,314

212,773

198,314

9.6 Overbank flood return to river channel

 –

 –

 –

 –

 –

 –

9.9 Discharge from urban water system

0

0

31,636

34,325

31,636

34,325

9.10 Direct discharge by user

 –

 –

 –

 –

 –

 –

9.11 Delivery of water under inter-region agreement to surface water

0

0

2,141,079

1,491,312

2,141,079

1,491,312

9 Total surface water increases

10,899,039

27,712,224

20,505,542

37,848,354

29,699,261

61,013,263

 

Water asset decreases

 

17 Surface water asset decreases

17.1 Evaporation from surface water

311,829

313,670

2,725,037

2,672,732

3,036,866

2,986,402

17.2 River outflow from the region

1,705,320

4,547,315

5,179,600

9,565,600

5,179,600

9,565,600

17.3 Leakage to groundwater

35,736

104,977

645,142

244,817

680,878

349,794

17.4 Leakage to landscape

 –

 –

 –

 –

 –

 –

17.5 Overbank flood spilling

437,901

299,151

0

0

437,901

299,151

17.6 Surface water diversions - other statutory rights

37,687

37,686

30,523

30,523

68,210

68,209

17.7 Entitled diversion on non-allocated surface water to users

1,398,405

1,090,894

668,541

523,155

2,066,946

1,614,049

17.8 Entitled diversion of non-allocated surface water to urban water system

4,177

3,567

8,896

6,294

13,073

9,861

17.10 River and floodplain leakage, evaporation and errors

6,847,029

19,638,619

7,652,345

17,942,623

14,499,374

37,581,242

17.11 Entitled diversion of allocated surface water to users

1,437,049

685,467

7,407,128

5,593,729

8,844,177

6,279,196

17.12 Entitled diversion of allocated surface water to urban water system

21,563

12,478

344,035

283,824

365,598

296,302

17 Total surface water asset decreases

12,236,696

26,733,824

24,661,247

36,863,297

35,192,623

59,049,806

 

Balancingitem—surfacewater

0

0

0

0

0

0

 

Opening water storage

4,330,958

3,352,558

20,013,574

19,028,517

24,344,532

22,381,075

add/(less): Change in water storage

(1,337,657)

978,400

(4,155,705)

985,057

(5,493,362)

1,963,457

Closing water storage

2,993,301

4,330,958

15,857,869

20,013,574

18,851,170

24,344,532

  – = Data not available
  1. Please note 1,705,320 ML for the 201213 year and the whole volume for the 201112 year for the Southern Basin for line item 9.2 'River inflow to region' was eliminated in the whole region.
  2. Please note the volume for the Northern Basin for line item 17.2 'River outflow from the region' was eliminated in the whole region.

 

A schematic diagram representing all the inflows and outflows associated with the surface water store in the MDB region is provided in Figure 5. The numbers in brackets on the diagram refer to the line item numbers in Table 3.


 


Figure 5 Schematic diagram of water inflows and outflows for the surface water store within the MDB region during the 2012–13 year: line item numbers are provided in brackets; irrigation diversions are included in line items 17.7 and 17.11
Figure 5 Schematic diagram of water inflows and outflows for the surface water store within the MDB region during the 2012–13 year: line item numbers are provided in brackets; irrigation diversions are included in line items 17.7 and 17.11


 

 

Surface water diversions

Allocation diversions, non-allocated diversions, and water abstraction under other statutory rights are the main forms of surface water diversions within the MDB region.

The allocation diversions are associated with a water access entitlement. When an allocation is announced, an obligation (water liability) is created on the surface water to deliver water to the user. The entitlement holder (an individual, water supply organisation or environmental water provider, where necessary) then orders the release or delivery of the allocated water and diverts it, which reduces the water liability. Allocation diversions, 9,209,775 ML, account for 81% of all diversions within the region for the 2012–13 year. Allocation diversion volume includes 569,695 ML supplied for the environment.

Non-allocated diversions are also associated with a water access entitlement, but are primarily unregulated diversions. Other statutory rights for surface water diversions are non-entitled water rights. They may be conferred by jurisdictional water acts or be written in water management plans and include land owner basic rights, riparian rights, Indigenous rights and stock and domestic rights.

The entitlement, allocation announcement and forfeiture for water rights associated with surface water diversion during the 2012–13 year are provided in the Water rights, entitlements, allocations and restrictions note.

Figure 6 compares surface water diversions within the MDB region for the 2011–12 year and the 2012–13 year. Non-allocated and allocated diversions have increased compare to diversions made during the 2011–12 year.


 


Figure 6 Surface water diversions from storages within the MDB region during the 2012–13 year and the 2011–12 year
Figure 6 Surface water diversions from storages within the MDB region during the 2012–13 year and the 2011–12 year



 

Balancing item—surface water store

The volume of the balancing item represents the volume necessary to reconcile the opening and closing balances of the surface water store with the physical water inflows and outflows (Table 4). Inter-store flows between groundwater and surface water stores were included in calculating balancing volume for the surface water store (these flows were excluded in calculating unaccounted-for difference for the water accounting statements because water accounting statements were prepared considering all stores together on an elimination approach, eliminating inter-store flows).

  

Table 4  Balancing item for the surface water store for the 2012–13 year

 Description

Volume (ML)

Northern Basin

Southern Basin

Whole region

Opening balance (30 June 2012)

4,330,958

20,013,574

24,344,532

Total 9 Surface water inflows

10,899,039

20,505,542

29,699,261

Total 17 Surface water outflows

(12,236,696)

(24,661,247)

(35,192,623)

Closing balance (30 June 2013)

(2,993,301)

(15,857,869)

(18,851,170)

Balancingitem—surfacewater store

0

0

0

  

 

The volume of the balancing item for the MDB region should be zero. This is because line item  17.10 River and floodplain leakage, evaporation and errors was calculated applying a water balance approach. Therefore, any balancing volume for the region is included in that line item.

Groundwater

Background

A description of the MDB region's groundwater resources are provided under Groundwater in the 'Physical information' section in the 'Contextual information'.

Water in store and groundwater asset

Information on groundwater assets in the region is shown in Table 5. Long-term estimates of volumes for extraction (including the volume of supplementary access licence that was available for use in New South Wales in the 2012–13 year) and basic landholder rights are defined as the groundwater assets considered for the region. These assets do not reflect temporal fluctuation of groundwater levels. Therefore, groundwater assets for the region are not responsive to groundwater storage changes resulting from water table fluctuations. As a result, groundwater assets are constant except for administrative changes to long-term estimates of volumes for extraction and landholder rights. Increases to administrative groundwater asset volumes may be the result of the commencement of a water resource plan for a groundwater source area within the basin. Decreases in administrative groundwater asset volume in New South Wales may be a result of the reduction of supplementary access licence volumes as outlined in the relevant water resource plans. Information for asset volumes separated into water table aquifers and underlying aquifers are not available for the region.

  

Table 5  Statement of Water Assets and Water Liabilities for the groundwater store for the MDB region as at 30 June 2013
Water assets

Northern Basin

Southern Basin

Whole region

2013
ML

2012
ML

2013
ML

2012
ML

2013
ML

2012
ML

2 Groundwater
2.1 Water Table aquifer  –  –  –  –  –  –
2.2 Underlying aquifers  –  –  –  –  –  –
2.5 Other groundwater assets 1,537,388 1,548,941 2,655,778 2,464,674 4,193,166 4,013,615
Total groundwater assets 1,537,388 1,548,941 2,655,778 2,464,674 4,193,166 4,013,615
 
6 Water liabilities
6.1 Groundwater allocation remaining 0 0 1,907 2,498 1,907 2,498
6.2 Groundwater allocation remaining - urban water system 0 0 0 0 0 0
Total groundwater liabilities 0 0 1,907 2,498 1,907 2,498
 
Opening net water assets

1,548,941

440,728

2,462,176

911,359

4,011,117

1,352,087

Change in net water assets

(11,553)

1,108,213

191,695

1,550,817

180,142

2,659,030

Closing net water assets

1,537,388

1,548,941

2,653,871

2,462,176

4,191,259

4,011,117

– = Data not available

 

Changes in water store

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the groundwater store are provided in Table 6 and Table 7, respectively. In addition to flows reported in the water accounting statements, the tables also show flows between the surface water and groundwater stores within the region.

 

Table 6  Statement of Changes in Water Assets and Water Liabilities for the groundwater store for the year ended 30 June 2013

Description

Northern Basin

Southern Basin

Whole region

2013
ML

2012
ML

2013
ML

2012
ML

2013
ML

2012
ML

Water asset increases

 

10 Groundwater increases

10.1 Groundwater inflow from outside region

0

0

2,646

2,797

2,646

2,797

10.2 Groundwater inflow from outside region at coast

0

0

50

53

50

53

10.3 Recharge from landscape

546,103

254,547

992,995

2,871,380

1,539,098

3,125,927

10.4 Recharge from surface water

35,736

104,977

645,142

244,817

680,878

349,794

10.5 Leakage from off-channel water storage

 –

 –

 –

 –

 –

 –

10.6 Leakage from urban water system

 –

 –

 –

 –

 –

 –

10.7 Leakage from irrigation scheme

 –

 –

 –

 –

 –

 –

10.8 Managed aquifer recharge - private user

0

0

631

2,340

631

2,340

10.13 Other groundwater increases

53,825

1,116,554

216,284

1,567,106

270,109

2,683,660

10 Total groundwater increases

635,664

1,476,078

1,857,748

4,688,493

2,493,412

6,164,571

 

14 Groundwater liability decreases

14.1 Adjustment and forfeiture of groundwater allocation

299,379

385,945

905,863

692,254

1,205,242

1,078,199

14.2 Adjustment and forfeiture of groundwater allocation - urban water system

14,329

11,874

17,463

5,205

31,792

17,079

14 Total groundwater liability decreases

313,708

397,819

923,326

697,459

1,237,034

1,095,278

 

Water asset decreases

 

18 Groundwater asset decreases

18.1 Groundwater outflow to outside region

0

0

21

19

21

19

18.2 Groundwater outflow to outside region at coast

0

0

1,446

1,551

1,446

1,551

18.3 Discharge to landscape

34,933

7,104

2,698,664

2,511,257

2,733,597

2,518,361

18.4 Discharge to surface water

61,788

35,207

496,982

7,159

558,770

42,366

18.7 Groundwater extractions - other statutory rights

74,329

48,948

156,087

145,228

230,416

194,176

18.18 Other groundwater decreases

65,378

8,341

25,180

15,930

90,558

24,271

18 Total groundwater asset decreases

236,428

99,600

3,378,380

2,681,144

3,614,808

2,780,744

 

Water liability increases

 

22 Groundwater liability increases

22.1 Groundwater allocation announcements

661,110

634,486

1,485,883

1,051,042

2,146,993

1,685,528

22.2 Groundwater allocation announcements - urban system

27,350

19,107

41,466

6,886

68,816

25,993

22 Total groundwater liability increases

688,460

653,593

1,527,349

1,057,928

2,215,809

1,711,521

 

Balancing itemgroundwater1

36,037

12,491

(2,316,350)

96,063

(2,280,313)

108,554

 

Change in net water assets

(11,553)

1,108,213

191,695

1,550,817

180,142

2,659,030

 – = Data not available

1 See Supporting information of line item 25.1 Unaccounted-for difference for details.

 

Table 7  Statement of Water Flows for the groundwater store for the year ended 30 June 2013

Description

Northern Basin

Southern Basin

Whole region

2013
ML

2012
ML

2013
ML

2012
ML

2013
ML

2012
ML

Water asset increases

 

10 Groundwater increases

10.1 Groundwater inflow from outside region

0

0

2,646

2,797

2,646

2,797

10.2 Groundwater inflow from outside region at coast

0

0

50

53

50

53

10.3 Recharge from landscape

546,103

254,547

992,995

2,871,380

1,539,098

3,125,927

10.4 Recharge from surface water

35,736

104,977

645,142

244,817

680,878

349,794

10.5 Leakage from off-channel water storage

 –

 –

 –

 –

 –

 –

10.6 Leakage from urban water system

 –

 –

 –

 –

 –

 –

10.7 Leakage from irrigation scheme

 –

 –

 –

 –

 –

 –

10.8 Managed aquifer recharge - private user

0

0

631

2,340

631

2,340

10.13 Other groundwater increases

53,825

1,116,554

216,284

1,567,106

270,109

2,683,660

10 Total groundwater increases

635,664

1,476,078

1,857,748

4,688,493

2,493,412

6,164,571

 

Water asset decreases

 

18 Groundwater asset decreases

18.1 Groundwater outflow to outside region

0

0

21

19

21

19

18.2 Groundwater outflow to outside region at coast

0

0

1,446

1,551

1,446

1,551

18.3 Discharge to landscape

34,933

7,104

2,698,664

2,511,257

2,733,597

2,518,361

18.4 Discharge to surface water

61,788

35,207

496,982

7,159

558,770

42,366

18.7 Groundwater extractions - other statutory rights

74,329

48,948

156,087

145,228

230,416

194,176

18.11 Entitled extraction of allocated groundwater to users

361,731

248,541

580,611

358,429

942,342

606,970

18.12 Entitled extraction of allocated groundwater to urban water system

13,021

7,233

24,003

1,681

37,024

8,914

18.18 Other groundwater decreases

65,378

8,341

25,180

15,930

90,558

24,271

17 Total surface water asset decreases

611,180

355,374

3,982,994

3,041,254

4,594,174

3,396,628

 

Balancing item – groundwater1

36,037

12,491

(2,316,350)

96,063

(2,280,313)

108,554

 

Opening water storage

1,548,941

440,728

2,464,674

913,498

4,013,615

1,354,226

add/(less): Change in water storage

(11,553)

1,108,213

191,104

1,551,176

179,551

2,659,389

Closing water storage

1,537,388

1,548,941

2,655,778

2,464,674

4,193,166

4,013,615

 

– = Data not available

1 See Supporting information of line item 25.1 Unaccounted-for difference for details.
Allocations and extractions

 Allocation extraction and water abstraction under other statutory rights are the main forms of groundwater extractions within the MDB region. The allocation extractions are associated with a water access entitlement.

Allocation extractions reported in line item 18.11 Entitled extraction of allocated groundwater to users (primarily for non-urban purposes), 942,342 ML, account for 78% of all extractions within the region for the 2012–13 year. Extractions for all three entitlement / right categories showed increase in water extractions compare to 2011–12 extractions.  Increased volume for other statutory rights were primarily due to availability of data from the water sharing plans implemented during the 2012–13 year.

The entitlement, allocation announcement and forfeiture for water rights associated with groundwater extraction during the 2012–13 year are provided in the Water rights, entitlements, allocations and restrictions note.

Balancing itemgroundwater store

 

Table 8  Balancing item for the groundwater store for the 2012–13 year

 Description

Volume (ML)

Northern Basin

Southern Basin

Whole region

Opening balance (30 June 2011)

1,548,941

2,464,674

4,013,615

Total 10 Groundwater inflows

635,664

1,857,748

2,493,412

Total 18 Groundwater outflows

(611,180)

(3,982,994)

(4,594,174)

Closing balance (30 June 2012)

(1,537,388)

(2,655,778)

(4,193,166)

 Balancingitem—groundwaterstore

36,037

(2,316,350)

(2,280,313)

The balancing item—groundwater store represents the volume necessary to reconcile the opening and closing balance of the groundwater asset with all the water inflows and outflows. Groundwater asset (see line item 2.5 Other groundwater assets) was quantified as the long-term annual extractable limits plus basic landowner water rights defined in water sharing plans. The change in groundwater asset during the 2012–13 year can be explained solely by the inclusion of additional sustainable diversion limit (SDL) areas in the scope of the groundwater asset (see line item 10.13 Other groundwater increases) and the reduction of supplementary groundwater entitlements on issue in the New South Wales water sharing plans (see line item 18.18 Other groundwater decreases). Therefore, the balancing item—groundwater store is the difference between physical water inflows and outflows occurring during the 2012–13 year. More information on balancing item—groundwater store is available under Supporting information of line item 25.1 Unaccounted–for difference.

Changes in groundwater stored in aquifers

Changes in the groundwater store volume of the water table aquifers for which data are available during the 2012–13 year were evaluated using aquifer characteristics and groundwater level measurements (see quantification methods given below). Table 9 reports on changes in the groundwater store volume of the watertable aquifers for the sustainable diversion limit (SDL) areas within region for which data were available.

Table 9  Volumetric values of changes in groundwater storage in the MDB region for the 2012–13 year
Groundwater resource plan area

Groundwater sustainable diversion limit area  

State

Change in groundwater storage in the 2012–13 year (ML)1

Method used to quantify change in groundwater storage2

Code

Name

Condamine-Balonne GS64 and GS65 Upper Condamine Alluvium (Central Condamine Alluvium and  Tributaries) and Upper Condamine Basalts Qld

(137,420)

The Bureau method
Gwydir Alluvium GS24 Lower Gwydir Alluvium  NSW

(9,799)

NSW model
Namoi Alluvium GS29 Lower Namoi Alluvium  NSW

(32,277)

NSW model
GS47 Upper Namoi Alluvium  NSW

5,508

NSW model zone 1-12  
Macquarie-Castlereagh Alluvium GS26 Lower Macquarie Alluvium  NSW

9,128

NSW model zone 1 to 6
Sub-total Northern Basin

(164,860)

 
Lachlan Alluvium GS25 Lower Lachlan Alluvium  NSW

(21,493)

NSW model
GS44 Upper Lachlan Alluvium   

(56,071)

NSW model
Murrumbidgee Alluvium GS28 Lower Murrumbidgee Alluvium, shallow; Shepparton Formation  NSW

(44,044)

NSW model
GS31 Mid Murrumbidgee Alluvium, shallow; Shepparton Formation  

(17,150)

NSW model zone 2-3
Murray Alluvium GS27 Lower Murray Alluvium, shallow; Shepparton Formation  NSW

64,358

The Bureau method
GS46 Upper Murray Alluvium, Shallow Shepparton Formation

NSW

(32,409)

The Bureau method
Goulburn-Murray GS8 Goulburn-Murray: Ovens–Kiewa Sedimentary Plain  Vic.

(139,898)

The Bureau method
GS8 Goulburn-Murray: Victorian Riverine Sedimentary Plain, shallow; Shepparton Formation Vic.

(580,695)

The Bureau method 
Wimmera-Mallee (groundwater)  GS09 Wimmera Mallee Sedimentary Plains Vic. (649,581) The Bureau method
Eastern Mount Lofty Ranges GS01 Angas Bremer (Quaternary Sediments and Murray Group Limestone) Vic. (4,062) The Bureau method
South Australian Murray GS03 Mallee (Murray Group Limestone) SA (54,293) The Bureau method
GS05 Peake–Roby–Sherlock, watertable SA 2,228
Sub-total Southern Basin

(1,533,110)

 
Total for the region

(1,697,970)

 

 1Change in groundwater storage is the estimated difference between all inflows to the store and outflows from the store for the 2012–13 year (see 'Method' in 'Quantification approaches' for more details). Changes in store volumes (based on aquifer characteristics) shown in the table for selected sustainable diversion limit areas are not reflected in the water accounting statements for the MDB region. Therefore, there is no relation between the changes in storage volumes shown in the table, and included in Table 7 and the water accounting statements.

2 See 'Method' in quantification approaches for more details.

NSW = New South Wales, Vic. = Victoria, SA = South Australia, The Bureau = Bureau of Meteorology

 

Table 9 also indicates what method was used to quantify the change in groundwater storage in each sustainable diversion limit (SDL) area: either the Bureau method based on measured groundwater levels or the New South Wales groundwater model results (New South Wales models).

With time, trends in the yearly changes in groundwater storages will provide more useful information about the adequacy of the extraction limits set in the groundwater management plans. For instance, a long-term trend of negative changes in groundwater storage may indicate that groundwater in an area may be over allocated. This year most of the changes indicate an decrease in groundwater storage which is consistent with the below average rainfall observed during the 2012–13 year.

Quantification approaches for the estimation of changes in groundwater stored in aquifers

Data source: The Bureau method

Bore locations and groundwater level data in South Australia were sourced from the Drillhole Enquiry System (Department of Environment, Water and Natural Resources 2012).

Bore locations and groundwater level data in Victoria were sourced from the Department of Sustainability and Environment and Victorian Department of Primary Industries through a database developed by the University of Melbourne.

Bore locations and groundwater level data in New South Wales were sourced from New South Wales Office of Water.

The geographic information system (GIS) data relating to the boundaries of the aquifers and SDL regions were received from the Murray–Darling Basin Authority.

Data source: NSW model

The outputs of the New South Wales groundwater models available within selected SDL areas provided by New South Wales Office of Water were used.

Data provider

The Bureau and New South Wales Office of Water.

Method: The Bureau method

Change in extractable storage is estimated using a simple geographic information system (GIS) approach based on measured groundwater levels and aquifer properties. Firstly, groundwater levels at the start (1 July 2012) and the end (30 June 2013) of the 2012–13 year were estimated. This was achieved by considering all groundwater level measurements between March 2012 – October 2012 and March 2013 – October 2013, respectively, and using the measurements closest in time to interpolate the start and end levels. The estimated groundwater levels on the start and end dates were then spatially interpolated to grids using kriging with external drift and the 9" digital elevation model as an external driver following the methodology presented in Peterson et al. (2011). The change in volume within the sedimentary area was calculated using these interpolated groundwater level surfaces.

These total volumes between interpolated groundwater level surfaces were multiplied by appropriate specific yield values (Commonwealth Scientific and Industrial Research Organisation and Sinclair Knight Merz 2010a and 2010b) to convert to a water volume (change in groundwater storage). Finally, change in storage was only considered within a 10-km mask of each groundwater observation bore to ensure an appropriate influence from the change in each bore and the volume was reported for the water table aquifer only. Groundwater storage outside these buffer areas was assumed constant throughout the year given that there is no data available.
 

Method: NSW model

New South Wales groundwater (see list of applicable SDL areas in Table 9) model outputs were used to evaluate the changes in groundwater storage. The change in groundwater storage derived from the groundwater models in New South Wales included all the groundwater model layers (not just the water table aquifer layer).

Uncertainty: The Bureau method

Uncertainty estimate was not quantified.

The uncertainty in the field-measured data (e. g., groundwater levels, specific yield) was not specified and hence the impacts of such uncertainty on the change in storage were not estimated.

The change in storage estimations were calculated from the interpolated groundwater level grids produced using kriging with external drift and the 9" digital elevation model as an external driver. Use of other interpolation methods may impact the values of the groundwater level grids and hence the estimated values for change in groundwater storage.

Uncertainty: NSW model

The uncertainty estimate was not quantified.

It is currently not feasible to estimate the uncertainty of modelled change in extractable storage from outputs of a MODFLOW groundwater model.

Approximations, assumptions, caveats, and limitations

The Bureau method:

  • Change in groundwater storage outside the buffer areas is assumed zero given that no data is available for calculation.

  • Change in groundwater storage was not calculated for confined aquifers. Under normal circumstance, the annual change in storage is considered to be negligible for confined aquifers due to their very low storage coefficient, which is much lower than the specific yield of water table aquifers (Freeze and Cherry 1979, Johnson 1967). As long as confined aquifers remain saturated, changes in piezometric levels (i. e. aquifer pressure) usually cause small changes in water volumes stored in the aquifers; the changes are equivalent to the volumetric expansion/contraction of the water and the pore space.

  • The specific yield values used in each water table aquifer are presented in Table below.

New South Wales groundwater models (see list of applicable SDL areas concerned in Table 9):

  • Details on the limitations of groundwater models used by New South Wales Office of Water can be accessed through its webpage on Water accounting.

 

 

Table 10  Specific yield values used in calculating the change in groundwater storage with the Bureau method (The specific yield values was sourced from Commonwealth Scientific and Industrial Research Organisation and Sinclair Knight Merz 2010a and b)
SDL area

Specific Yield

Northern Basin  
Lower Gwydir Alluvium 

0.200

Southern Basin  
Lower Murray Alluvium, shallow; Shepparton formation 

0.100

Upper Murray Alluvium, shallow, Shepparton formation

0.100

Goulburn–Murray: Ovens–Kiewa sedimentary plain 

0.150

Goulburn–Murray: Victorian Riverine sedimentary plain, shallow; Shepparton formation

0.100

Wimmera–Mallee sedimentary plains

0.115

Angas Bremer (Quaternary sediments and Murray Group limestone)

0.100

Groundwater inflow to a SDL area from other SDL areas and outflows from a SDL area to the other SDL araes within a segment

Groundwater flow into and from for selected SDL areas has been calculated and details are provided in tables 11 and 12 for the Northern Basin and the Southern Basin respectively.

 

Table 11. Details of groundwater inflows to and outflows from SDL areas  within the Northern Basin for the 2012–13 year
SDL area Inflow (ML) Outflow (ML)
Lower Gwydir Alluvium - unconfined 0 0
Lower Gwydir Alluvium - confined 0 0
Lower Namoi - unconfined 0 12,000
Lower Namoi - confined 5,880 18,740

 

 

Table 12. Details of groundwater inflows to and outflows from SDL areas  within the Southern Basin for the 2012–13 year
SDL area

Inflow (ML)

Outflow (ML)

Lower Lachlan – watertable and confined 2,450 27,210
Upper lachlan - Unconfined 0 3,422
Upper lachlan - confined 0 2,981
Lower Murrumbidgee Alluvium, shallow; Shepparton Formation  424 136
Lower Murrumbidgee Alluvium, deep; Calivil Formation and Renmark Group 12,647 24,722
Mid Murrumbidgee Alluvium - watertable 2,545 98
Mid Murrumbidgee Alluvium - confined 1,859 2,303
Lower Murray Alluvium, shallow; Shepparton Formation 34,687 29,241
Lower Murray Alluvium, deep; Renmark Group and Calivil Formation 193,213 108,934
Goulburn-Murray: Upper Murray watertable and Ovens–Kiewa Sedimentary Plains 1,199 11,496
Goulburn-Murray: Upper Murray confined Ovens–Kiewa Confined 1,186 12,985
Goulburn-Murray: Victorian Riverine Sedimentary Plain, shallow; Shepparton Formation  24,820 26,602
Goulburn-Murray: Victorian Riverine Sedimentary Plain, deep; Calivil and Renmark Formations  49,191 138,825
Wimmera Mallee Sedimentary Area - watertable 54,723 76,439
Wimmera Mallee Sedimentary Area - confined 86,079 29,280
Angas Bremer (Quaternary Sediments and Murray Group Limestone) 1,537 1,080
Mallee (Murray Group Limestone) and Peake-Roby Sherlock Unconfined 48,655 38,840
Mallee (Murray Group Limestone) and Peake-Roby Sherlock confined 862 3,445

Quantification approaches for the estimation of inflow to a SDL area from other SDL areas and outflow from a SDL area to other SDL areas within a segmentNorthern Basin

New South Wales Office of Water methods were applied in calculations.

Data provider

New South Wales Office of Water.

Method

The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Uncertainty information

The uncertainty estimate was not quantified.

It is currently not feasible to estimate the uncertainty of modelled regional flow from outputs of a MODFLOW groundwater model.

Assumptions, limitations, caveats, and approximations

Details on the limitations of groundwater models used by New South Wales Office of Water are available in General Purpose Water Accounting Reports – Groundwater methodologies.

 

Quantification approaches for the estimation of inflow to a SDL area from other SDL areas within a segmentSouthern Basin

Two estimation methods, the Bureau method and New South Wales Office of Water method, were applied in calculations (see line Item 10.1 Groundwater inflow from outside region for more details on the methods).

Data source

The Bureau method:

  • Bore locations and groundwater level data in South Australia were sourced from the Drillhole Enquiry System (Department of Environment, Water and Natural Resources, 2012).

  • Bore locations and groundwater level data in Victoria were sourced from the Department of Sustainability and Environment and Victorian Department of Primary Industries through a database developed by the University of Melbourne

  • Bore locations and groundwater level data in New South Wales were sourced from New South Wales Office of Water.

New South Wales Office of Water method:

  • The New South Wales Office of Water has developed a series of groundwater models for selected areas using the groundwater flow simulation computer program MODFLOW. The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Data provider

The Bureau and New South Wales Office of Water.

Method: The Bureau method

The regional groundwater flow across selected SDL areas within the Southern Basin was considered. 

Groundwater flow was calculated using a simple GIS approach based on Darcy's Law. Groundwater levels were interpolated for seasons using kriging with an external drift from 9" digital elevation model following the methodology presented in Peterson et al. (2011), and simple GIS analysis for the water table and confined aquifers, respectively. The seasonal values were aggregated to the 2012–13 year.

Seasonal groundwater flow-grids were derived from groundwater level grids, aquifer thickness and hydraulic conductivity using a modification of the ArcGIS Darcy Velocity tool. Groundwater flow across selected flow boundaries was then calculated using a simple GIS analysis and seasonal values were aggregated to the 2012–13 year.

Method: New South Wales Office of Water method

The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Uncertainty information: The Bureau method

The uncertainty estimate was not quantified.

The uncertainty in the field-measured data (e.g., groundwater levels, hydraulic conductivity) was not specified and unknown and hence the impacts of such uncertainty on the calculated groundwater flow were not estimated.

The regional flow estimations were based on the interpolated groundwater level grids produced using kriging with an external drift from 9" digital elevation model and simple GIS analysis for the water table and confined aquifers, respectively. Use of different interpolation methods may impact on the values of the groundwater level grids and hence the estimated regional flow; however, the regional flow estimated with interpolated groundwater levels using GIS analysis was compared with a simple groundwater flow model developed on MODFLOWmodel (United States Geological Survey 2013). The results from the two methodologies indicated a 6 – 7% difference.

Uncertainty information: New South Wales Office of Water method

The uncertainty estimate was not quantified.

It is currently not feasible to estimate the uncertainty of modelled regional flow from outputs of a MODFLOW groundwater model.

Assumptions, limitations, caveats, and approximations

The Bureau method:

  • Regional flow estimations were provided for the aquifers indicated in Table 12 only and also due to the fact that not all the hydrological processes within the Southern Basin have been taken into consideration, the total regional inflows to the Southern Basin are not comparable with that provided in Table 12.

  • The Geofabric version 2 (Bureau of Meteorology 2011a), and Southern Riverine Plains groundwater model (Goode and Barnett 2008) were used to estimate aquifer thicknesses. The hydraulic conductivity values were sourced from Mallee Prescribed Wells Area – Murrayville Water Supply Protection Area groundwater model (Barnett and Osei-bonsu 2006), Southern Riverine Plains groundwater model (Goode and Barnett 2008) and the report on sustainable extraction limits derived from the recharge risk assessment method – New South Wales (Commonwealth Scientific and Industrial Research Organisation and Sinclair Knight Merz 2010a and 2010b). The transmissivity values were calculated by multiplying the aquifer thickness with the relevant hydraulic conductivity.

  •  It is possible that small differences occur between the University of Melbourne database and the Department of Sustainability and Environment groundwater database (from which bore locations and groundwater level data in Victoria were sourced).

 

Quantification approaches for the estimation of outflow from a SDL area to other SDL areas within a segmentSouthern Basin

Two estimation methods, the Bureau method and NSW Office of Water method, were applied in calculations (see line Item 10.1 Groundwater inflow from outside region for more details on the methods).

Data source

The Bureau method:

  • Bore locations and groundwater level data in New South Wales were sourced from NSW Office of Water.

NSW Office of Water method:

  •  The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Data provider

The Bureau and NSW Office of Water.

Method: The Bureau method

The regional groundwater flow across selected SDL areas within a segment was considered. The selected SDL areas represent major groundwater resources for the segment.

Groundwater flow was calculated using a simple GIS approach based on Darcy's Law.


Method: NSW Office of Water method

The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Uncertainty information: The Bureau method

The uncertainty estimate was not quantified.

The uncertainty in the field-measured data (e.g. groundwater levels, hydraulic conductivity) was not specified and unknown and hence the impacts of such uncertainty on the calculated groundwater flow were not estimated.

The regional flow estimations were based on the interpolated groundwater level grids. Use of different interpolation methods may impact on the values of the groundwater level grids and hence the estimated regional flow; however, a comparison of the methodology was carried out using a simple groundwater flow model developed on MODFLOW model (United States Geological Survey 2013). The results from the two methodologies indicated a 6% to 7% difference.

Groundwater flow was estimated for a simplified boundary constructed from a series of line segments. Groundwater flow across this boundary was calculated using the method described above. The uncertainty surrounding this simplification was not analysed.

Uncertainty information: NSW Office of Water method

The uncertainty estimate was not quantified.

It is currently not feasible to estimate the uncertainty of modelled regional flow from outputs of a MODFLOW groundwater model.

Assumptions, limitations, caveats, and approximations

The Bureau method:

  • Regional flow estimations were provided for the SDL areas shown in Table 12. Due to the fact that not all the hydrological processes within the segments have been taken into consideration, the total regional outflow are not comparable with that provided in Table 12.

NSW Office of Water method:

Details on the limitations of groundwater models used by the NSW Office of Water are available in General Purpose Water Accounting Reports - Groundwater methodologies.

Off-channel storages

Purpose of note

The purpose of this note is to provide a consolidated report on the off-channel water storages within the MDB region during the 2012–13 year. Information on storage volumes, inflows and outflows for the off-channel water storages is provided in this note.

Background

The off-channel water storages consists of all private reservoirs that are used to harvest runoff before reaching the surface water store or that are filled by pumping from a watercourse or groundwater.

The store includes constructed storages that are not connected either seasonally or perennially to rivers, filled predominantly by local catchment runoff. They include off-channel farm dams, run-off dams, hill-side dams, industrial, commercial, and mining water storages. They exclude on-channel farm dams and other storages.

The off-channel water storages for the 2013 Account were determined from waterbody mapping conducted by Geoscience Australia as those that:

  • are not named storages (assuming that any storage with a name is unlikely to be a off-channel storage)

  • are above 600 m in elevation or are in areas that receive greater than 400 mm per annum in precipitation and are not within 50 m of a major or perennial stream.

The above rules attempt to divide storages into those that are likely to be filled primarily by local catchment runoff and those which are filled by abstraction from surface water, groundwater, or floodplain harvesting.

As discussed in General description in 'Physical information' in the 'Contextual information', the off-channel water store has been excluded from the scope of the MDB region for the purposes of the 2013 Account, because it is constituted of water already abstracted from the shared pool of water resources. Therefore off-channel water store reporting line items do not appear in the water accounting statements. Off-channel water storages influence water assets and water liabilities recognised in the water accounting statements though, as they harvest water from the landscape and thus reduce groundwater recharge and runoff into surface water.

Water in store

Table 15 shows that the total off-channel water store decreased during the 2012–13 year in the MDB region.

 

Table 15  Off-channel water storage volume at the start and end of the 2012–13 year for the MDB region
Description

30 June 2013 (ML)

30 June 2012 (ML)

Northern Basin

Southern Basin

Whole region

Northern Basin

Southern Basin

Whole region

27.1 Off-channel water storages

412,096

446,748

858,844

511,397

615,564

1,126,961

27.2 Rainwater tanks

Total

412,096

446,748

858,844

511,397

615,564

1,126,961

 –  = Data not available

Note: The volume reported in the 2012 Account for line item 27.1 Off-channel water storages for the 2011–12 year was 1,152,737. The volume has been recalculated as 1,126,961 for the 2013 Account.  The change was due to the choise of Australian Water Resources Assessment (AWRA) system version 3.0 model in the 2013 Account instead of AWRA version 2.0 in the 2012 Account for the calculations.

The water volume held in off-channel water storages within the MDB region at the end of the 2012–13 year was less than that at the start (1 July 2012). This was primarily attributed to the below average rainfalls and inflows recorded in the region during the 2012–13 year (see Rainfall in 'Climate overview' in the 'Contextual information').

Off-channel water inflows and outflows

The inflow and outflow volumes for the off-channel water store during the 2012–13 year are given in Table 16.

 

Table 16  Volume of inflows and outflows for the off-channel water store during the 2012–13 year
 Description

Volume (ML)

Northern Basin

Southern Basin

Whole region

Off-channel water inflows      
30.1 Precipitation on off-channel water store

531,497

270,875

802,372

30.2 Groundwater discharge into off-channel water store

­–

30.3 Runoff harvesting into off-channel water store

585,981

459,638

1,045,619

30.4 Surface water diversion into off-channel water store

­–

30.5 Groundwater extraction into off-channel water store

­–

Total Off-channel water inflows

1,117,478

730,513

1,847,991

       
Off-channel water outflows      
31.1 Evaporation from off-channel water storages

769,701

488,104

1,257,805

31.2 Leakages from off-channel water storages

­–

31.3 Off-channel water abstraction

447,083

411,225

858,308

Total Off-channel water outflows

1,216,784

899,329

2,116,113

       
Balancingitem—off-channel water

(5)

0

(5)

       
Change in off-channel water storage

(99,301)

(168,816)

(268,117)

       
Opening off-channel water storage 

511,397

615,564

1,126,961

Closing off-channel water storage

412,096

446,748

858,844

 

– = data not available

 

Precipitation on to off-channel water store and runoff harvesting into them decreased by 38% and 21% respectively for the 2012–13 year compared to the 2011–12 year. Most likely due to that reason, water use from off-channel storages decreased by 12% in the 2012–13 year compared to the previous years' use.

Balancing item—off-channel water

This volume represents the volume necessary to reconcile the opening and closing balances of the off-channel water storage with the physical water inflows and outflows. The difference was calculated according to Table 17.

 

Table 17  Balancing item—off-channel water 2012–13 year
Account

Volume (ML)

Opening balance at 30 June 2012

1,126,961

Total Off-channel water inflows

1,847,991

Total Off-channel water outflows

(2,116,113)

Closing balance at 30 June 2013

(858,844)

Balancing itemoff-channel water store

(5)

 

The calculation of the water balance on the off-channel water store yielded a balance of -5 ML. This is negligible compared to the opening and closing balances. Despite this, one should note that the values presented for off-channel storages remain broad estimates based on numerous assumptions and simplifications (see quantification approaches of the various line items linked from the tables).