Adelaide
10.3 Recharge from landscape

Supporting information

The volume reported (299,451 ML) includes recharge to groundwater from both rainfall and irrigation. The volume reported is itemised in the following table by groundwater management and fractured rocks areas.

Recharge from lndscape for each management area and for irrigation recharge in the 2011–12 year
Process

Region

Recharge from landscape (ML) 

Rainfall recharge Adelaide Plains

80,410

McLaren Vale

20,682

Western Mount Lofty Ranges (fractured rocks1)

193,577

Subtotal

294,669

Irrigation recharge Adelaide region

4,782

Total  

299,451


1 Recharge to the fractured rocks of the Myponga River catchment and Fleurieu Peninsula is not included in the 2012 Account as described in the 'Quantification approach' section.

The recharge from landscape is calculated using the Water Atmosphere Vegetation Energy and Solutes (WAVES) model. The output from WAVES is best considered to be potential diffuse groundwater recharge that potentially could reach the water table under the conditions of rainfall, land use and soil type in the region. The recharge volume estimate does not take into consideration the time lag that occurs between the rainfall infiltrating into the soil and water actually reaching the watertable. In addition, the groundwater discharge from the water table through the evapotranspiration from the water table is possibly largely underestimated which will have the effect of increasing the net groundwater recharge value presented in the 2012 Account. In the WAVES model application used in the 2012 Account, the evapotranspiration from the water table and the unsaturated zone cannot occur at depths greater than four metres, although it is known that deep-rooted vegetation can access groundwater at greater depths.

For more information on additional estimates of annual recharge for the Western Mount Lofty Ranges see the draft Western Mount Lofty Ranges water allocation plan and for the Adelaide Plains, Aquaterra (2011).

Quantification approach

Irrigation recharge

Data source

Irrigation efficiency literature (Binks 2004).

Provided by

Bureau of Meteorology.

Method

The estimate of recharge to groundwater from irrigated areas was based on the findings of a study that evaluated irrigation practices within the Mount Lofty Ranges (Binks 2004). This study found that recharge from irrigated areas averaged approximately 5% of the total irrigation water use between 2000 and 2003. Therefore, recharge from irrigation and other activities that apply water to the landscape was estimated to be 5% of all water applied to the landscape as itemised in the following table.

 
Irrigation recharge in the Adelaide region during the 2011–12 year

Line Item

Location

Notes 

Volume applied to the landscape (ML)

Recharge estimate (ML)

18.7 Groundwater extractions – other statutory rights

 

No data on extractions

 –

 –

18.11 Entitled extraction of allocated groundwater1

Barossa Prescribed PWRA

95% extractions used for irrigation

2,059

103

McLaren Vale PWA

100% extractions used for irrigation

5,391

270

Northern Adelaide Plains PWA

90% extractions used for irrigation

13,385

669

All extractions for industrial purpose

All extractions for industrial purpose

0

0

Subtotal

20,835

1,042

17.6 Surface water diversions – other statutory rights

Western Mount Lofty Ranges

Assumes 100% diversions used for irrigation

2,230

112

17.11 Entitled diversion of allocated surface water2

Barossa PWRA 

92% diversions used for irrigation

1,027

51

Little Para River Prescribed Watercourse

No data on diversions

 –

 –

Subtotal

1,027

51

20.4 Delivery to irrigation scheme users

All irrigation schemes

Assumes 100% water delivered used for irrigation

19,478

974

31.3 Off-channel water abstraction

Adelaide region

Assumes 100% farm dams abstractions used for irrigation

6,213

311

19.4 Delivery to urban water system users

Potable water consumption

Outdoor water use based on SA Water land use codes (see following tables) 

45,376

2,269

Recycled wastewater

474

24

Subtotal

45,850

2,293

Total

95,633

4,782

PWA = Prescribed Wells Area, PWRA = Prescribed Water Resources Area

1 Groundwater extractions reported at line item 18.11 are not all used for irrigation purposes. The proportion of the volume allocated for irrigation purposes, detailed at line item 22.1 Groundwater allocation announcements, was used to estimate the proportion of the volume of groundwater extracted for irrigation purposes.

2 Surface water diversions reported at line item 17.11 are not all used for irrigation purposes. The proportion of the volume allocated for irrigation purposes, detailed at line item 21.1 Surface water allocation announcements, was used to estimate the proportion of the volume of water diverted for irrigation purposes.

According to this approach:

  • In the Barossa PWRA,  95% of groundwater and 92% of surface water were allocated for irrigation purpose
  • In the McLaren Vale PWA, 100% of groundwater was allocated for irrigation purpose
  • In the Northern Adelaide Plains PWA, 90% of groundwater was allocated for irrigation purpose.

 

Potable water used for irrigation or other outdoor activities in the Adelaide region in the 2011–12 year

SA Water land use code

National Water Account land use code

Potable water consumption (ML)

Percentage used for irrigation and other outdoor activities

Volume applied to the landscape (ML)

Residential

Residential

86,060

40%

34,424

Commercial

Commercial

7,429

0%

0

Industrial

Industrial

7,032

0%

0

Mining

Industrial

130

100%

130

Public institution

Municipal

6,414

40%

2,566

Public utility

Municipal

1,531

100%

1,531

Recreational

Municipal

2,536

100%

2,536

Country lands

Other – agriculture

2,412

100%

2,412

Primary production

Other – agriculture

1,060

100%

1,060

Sundry

Remaining other

11,331

0%

0

Vacant land

Remaining other

1,792

40%

717

Total

127,727

 

45,376

 

Recycled wastewater used for irrigation activities in the Adelaide region in the 2011–12 year

Wastewater treatment plant

Application

Volume (ML)

Aldinga

Agriculture irrigation

212

Angaston

Agriculture irrigation

46

Gumeracha

Commercial irrigation

45

Myponga

Livestock irrigation

12

Victor Harbor

Municipal and agricultural irrigation

159

Total

474

Assumptions, limitations, caveats and approximations

  • This approach assumes that irrigation recharge was directly related to the total irrigation volume applied independent of soil type, crop type, topography and irrigation practices. It also assumes that the irrigation recharge for the period 2000 to 2003 was representative of recharge occurring during the 2010–11 year.

Uncertainty information

The uncertainty estimate was not quantified.

Rainfall recharge

Data source

Bureau of Meteorology (the Bureau): National Climate Centre (NCC) daily climate grids (rainfall, temperature, solar radiation and vapour pressure deficit); CSIRO: Australian Soil Resources Information System (ASRIS) soil information; Australian Bureau of Agricultural and Resource Economics – Bureau of Rural Sciences 2010: land use mapping; South Australian Department of Environment, Water and Natural Resources (DEWNR): Drillhole Enquiry System, bore locations and groundwater level data from online groundwater database; Aquaterra 2012.

Provided by

The Bureau.

Method

Groundwater recharge was estimated using the Water Atmosphere Vegetation Energy and Solutes (WAVES) model described in Zhang and Dawes (1998) and Dawes et al. (1998). WAVES is a one dimensional soil-vegetation-atmosphere-transfer model that integrates water, carbon and energy balances. Climate, depth to water table (only for the sedimentary areas), soil and vegetation data were used as inputs to the model. The climate data include rainfall, rainfall duration, maximum and minimum temperatures, vapour pressure deficit and solar radiation.

The WAVES model has been used by the CSIRO in its sustainable yields projects (Crosbie et al. 2008) and the Bureau has built on this methodology.  WAVES was run at selected points from across the Adelaide region for all combinations of soil type, vegetation type and depth to water table. The point estimates of the groundwater recharge fraction were interpolated to a 1 km grid based on soil type, vegetation type and depth to water table and multiplied by a grid of annual rainfall for the 2011–12 year.

The recharge within the Adelaide region was determined by summing the spatially interpolated positive recharge estimates.

The following figure illustrates the net groundwater discharge (in red) and recharge (in grey) across the Adelaide region during the 2011–12 year using the WAVES model.


Map showing net groundwater recharge and discharge in the Adelaide region during the 2011–12 year
Map showing net groundwater recharge and discharge in the Adelaide region during the 2011–12 year

Assumptions, limitations, caveats and approximations

  • The assumptions of the WAVES model as described in Dawes et al. (1998) were all applicable to the recharge estimates for the Adelaide region.
  • The national land-use grid (Australian Bureau of Agricultural and Resource Economics – Bureau of Rural Sciences 2010) was reclassified to three vegetation classes that include annuals, perennials and trees. The major vegetation classes modelled were C3 annual pasture, C3 perennial pasture and eucalypt trees with a grass understorey.
  • Annual recharge was estimated for the whole of Adelaide region including both sedimentary and fractured rock areas. Recharge was modelled using a shallow water table surface area estimated by interpolating measured groundwater levels. The water table depth was interpolated using the methodology presented in Peterson et al. (2011). This method uses groundwater elevation and the 9" digital elevation model to improve groundwater levels interpolation in data poor areas within this area of high relief.
  • Rainfall recharge was estimated for the fractured rock area contributing to the flow in the confined sediments only (see fractured rock boundaries in the figure above for diffuse rainfall recharge). Recharge to the fractured rocks of the Fleurieu Peninsula and Myponga River catchment is not included in the balance.

Uncertainty information

The uncertainty estimate was not quantified.

Comparative year

Compared to the 2011 Account, an improved quantification approach for rainfall recharge was applied in the 2012 Account:

  • A different bore data set was used for the 2012 Account corresponding to data available at the time of compiling the report.
  • The water table depth was interpolated using the methodology presented in Peterson et al. (2011) throughout the region, while in the 2011 Account this method had not been used for the Adelaide Plains and McLaren Vale areas.

As shown in the following table, the differences in the volume of rainfall recharge calculated for the 2010–11 year with the 2011 Account and 2012 Account quantification approaches are important for the Adelaide Plains and McLaren Vale areas. When calculated for the whole region, the line item volume difference is not material though. Therefore, the volume of rainfall recharge in the 2010–11 year was not restated.

Comparison of volumes of rainfall recharge in the 2010–11 year calculated with the 2012 Account and 2011 Account quantification approaches

Groundwater management area

Volume calculated with 2012 Account quantification approach (ML)

Volume calculated with 2011 Account quantification approach (ML)

Additional information

Adelaide Plains 188,676 136,164 Bore data and methodology change
McLaren Vale 27,734 16,052 Bore data and methodology change
Western Mount Lofty Ranges (fractured rocks) 516,854 527,613 Bore data change
Total 733,264 679,829  


The value of line item 17.6 Diversions - other statutory rights used to calculate irrigation recharge was restated for the 2010–11 year from 2,728 ML in the 2011 Account to 2,494 ML in the 2012 Account. Considering a 5% recharge rate, the difference in recharge (12 ML) was not material though and the volume of irrigation recharge in the Adelaide region for the 2010–11 year was not restated.