1.1.4.4 Current and historical groundwater use


Groundwater resources in the Namoi are the most intensively developed in NSW and the subregion has one of the highest levels of groundwater extraction within the MDB (CSIRO, 2007). There are over 18,000 bores in the Namoi catchment which are licensed to provide over 343,000 ML of groundwater entitlement per year. Aquifer licences cover a variety of purposes including irrigation, industrial, stock and domestic water.

Over-allocation of the alluvial aquifers in the past has led to the Namoi being included in the Achieving Sustainable Groundwater Entitlements program; a program to reduce allocation in key inland catchments in NSW. The program is being implemented through the water sharing plans in the region as discussed above, and by 2016 will result in a reduction of the groundwater allocation in the Upper Namoi groundwater source of almost 60% (179,800 ML/year) and in the Lower Namoi groundwater source of 50% (86,200 ML/year) (MDBA, 2012).

Figure 32 below shows annual groundwater usage in the Lower Namoi from 1991–92 to 2007–08 with predicted water use based on the annual extraction limit set by the water sharing plan. Groundwater use in the Lower Namoi groundwater source has fluctuated significantly since 1991, ranging from approximately 45,000 ML in 1998–99 to 165,000 ML in 1994–95, usually in response to rainfall variability and the associated variability in surface water and groundwater use. In the Lower Namoi a combined total of 228,999 ML was pumped in the two seasons 2006–07 and 2007–08. Groundwater use was high in these years due to the low availability of surface water as a result of the Millennium drought. Groundwater use between 2008–09 and 2012–13 has been considerably lower than the early 2000s, ranging from approximately 30 to 80 GL. This is likely to be a result of in the introduction of the water sharing plan, limiting the amount of water irrigators can extract, and higher rainfall resulting in greater availability of surface water and reduced additional water requirements for irrigation.

Figure 32

Figure 32 Lower Namoi groundwater usage since 1991-92

Source: Figure 3 in Smithson (2009).This figure is not covered by a Creative Commons Attribution. It has been reproduced with permission from NSW Department of Primary Industries.

There are approximately 1100 production bores in the Upper Namoi groundwater source, all of which are metered with usage recorded two to six times a year (Barrett, 2010). A comparison of annual groundwater usage since 1997–98 against the estimated average annual recharge for all zones in the Upper Namoi groundwater source is presented in Figure 33. Groundwater use in the Upper Namoi has varied significantly, ranging from approximately 55,000 ML in 2010–11 to 147,000 ML in 2001–02. Similar to the Lower Namoi, this variability has been driven by the rainfall pattern and associated availability of surface water, and the introduction of the water sharing plan. Usage across the Upper Namoi groundwater source has generally been well below the estimated average annual recharge since 2007–08.

Figure 33

Figure 33 Total groundwater use in the Upper Namoi groundwater source 1997-98 to 2010-11

Source: Figure 4 in Barrett (2012)

A comparison of annual groundwater usage against the water sharing plan’s extraction limits for the groundwater source of the Upper Namoi is provided in Table 9 (see Figure 34 for zone locations). Usage in Upper Namoi Zones 2, 3 and 5 was close to or greater than the plan extraction limit for 2006–07. However since the first year of the plan, both the water available for extraction and the annual usage in these zones have been declining. Since the plan began, the three-year average usage for all the zones in the Upper Namoi has been well below the extraction limits, attributed to a combination of wetter climatic conditions and greater availability of surface water, and the introduction of the water sharing plan.

Table 9 Comparison of annual groundwater usage against the water sharing plan extraction limits for zones in the Upper Namoi groundwater source (in ML)


Water Source

Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

Zone 6

Zone 7

Zone 8

Zone 9

Zone 10

Zone 11

Zone 12

Total

EXTLIM

2,100

7,200

17,300

25,700

16,000

14,000

3,700

16,000

11,400

4,500

2,200

2,000

122,100

2006–2007

EXTLIM plus SWAL Access plus 5%

4,009

13,186

25,787

39,874

19,648

14,700

3,892

21,499

11,970

4,725

2,326

2,914

164,530

Usage

2,238

12,218

28,068

30,654

19,697

1,952

2,678

19,028

3,258

0

988

1,266

122,045

% of Usage per WSP Extraction Limit

56%

93%

109%

77%

100%

13%

69%

89%

27%

0%

42%

44%

2007–2008

EXTLIM plus SWAL Access plus 5%

4,009

12,561

24,940

38,442

19,648

14,700

3,892

20,977

11,970

4,725

2,326

2,914

161,104

Usage

1,530

10,635

10,008

23,455

16,438

1,023

946

11,495

1,911

0

467

573

78,481

% of Usage per WSP Extraction Limit

38%

85%

40%

61%

84%

7%

24%

55%

16%

0%

20%

20%

2008–2009

EXTLIM plus SWAL Access plus 5%

3,792

11,935

24,094

37,010

19,648

14,700

3,892

20,455

11,970

4,725

2,326

2,914

157,461

Usage

1,260

10,314

9,501

20,291

12,428

676

941

9,043

2,141

17

641

432

67,685

% of Usage per WSP Extraction Limit

33%

86%

39%

55%

63%

5%

24%

44%

18%

0%

28%

15%

2009–2010

EXTLIM plus SWAL Access plus 5%

3,576

11,310

23,247

35,578

19,648

14,700

3,892

19,933

11,970

4,725

2,326

2,914

153,819

Usage

1,425

6,560

17,809

19,623

16,542

1,132

698

11,628

1,449

0

591

628

78,085

% of Usage per WSP Extraction Limit

40%

58%

77%

55%

84%

8%

18%

58%

12%

0%

25%

22%

EXTLIM – Extraction limit

SWAL – Supplementary water access licences

WSP – Water sharing plan

Source data: Table 3 in Barrett (2010)

Figure 34

Figure 34 Upper Namoi groundwater source zones

Source: NSW Department of Environment, Climate Change and Water (Barrett, 2010)

Last updated:
10 January 2019