Adelaide

The volume reported in the water accounting statement (1,875 ML) represents non-licensed groundwater extraction for stock and domestic purposes from across the Adelaide Region, excluding the Northern Adelaide Plains Prescribed Wells Area. Stock and domestic groundwater extraction is licensed in this area.

Data source

Stock water use literature (Luke 1987; McLaren 1997; Farmer 2004; Dixon-Thompson pers comm. 2010).

Stock statistics (ABS 2010a).

Domestic water use literature (NWC & WSAA 2009; NWC 2011).

Population statistics (ABS 2008; ABS 2010b).

Data provider

South Australian Department for Water (DFW).

Method

Unmetered groundwater extraction for stock and domestic purposes was calculated based on water demand within the Adelaide Region (BoM 2010). The volume excludes the Northern Adelaide Plains Prescribed Wells Area (PWA) in which stock and domestic extraction is metered and covered in line item 16.5.3.5.

Unmetered groundwater extraction for stock and domestic purposes was calculated as the sum of:

• stock demand
• domestic demand in rural areas
• domestic demand in metropolitan Adelaide.

Stock demand

Stock water use was calculated based on a method similar to the equation underlying the software package ‘Damcat’ (Luke 1987; Farmer 2004). Australian Bureau of Statistics (ABS) stock numbers in 2008–09 for the Adelaide and Mount Lofty Ranges Natural Resource Management region were converted to dry sheep equivalents (DSE) (Luke 1987; McLaren 1997). The seasonally adjusted DSE (for production patterns) and monthly average daily maximum temperatures for Adelaide (Kent Town) were used to calculate a stock drinking rate using an empirical equation (Luke 1987). The supply volume was increased based on advice from a farm water supply businessman, who suggested that 40% of the supply volume was lost in the delivering of water to stock (Dixon-Thompson pers comm. 2010). The source of stock water was identified by spatially disaggregating grazing land use with a 500m buffer of potential water sources as detailed in the table below.

Domestic demand in rural areas

The volume of domestic water use was calculated by applying a demand of 190 kL/year (average annual residential water per household) to the number of dwellings assumed to have used bore water as their primary water source (NWC & WSAA 2010; NWC 2011). The number of dwellings was revised upwards by 1.1% per year to represent population growth since the 2006 census (ABS 2010b). The sources of domestic water were identified by spatially disaggregating the areas in the ABS mesh block layer with a 500m buffer around potential water sources. The proportion of mesh block area was used to derive the number of dwellings accessing each water source as detailed in the table above.

Domestic demand in metropolitan Adelaide

It is estimated that an additional 250 ML of unmetered groundwater was used in metropolitan Adelaide based on an assumption frequently used in water resource planning (DFW Planning and Management pers. comm. 2010).

Uncertainty

Ungraded.

Assumptions, approximations and caveats/limitations

• Overall, the calculated volume of unmetered groundwater extraction for stock and domestic purposes was slightly less than the volumes stated in the relevant water allocation plans (AMLRNRMB 2007, 2010).
• The assumed water source differs for stock and domestic purposes due to different water quality requirements. It was assumed domestic purposes favour SA Water as a water supply, while SA Water would not typically supply stock water. The assumed water sources were identified by applying a 500m buffer around each GIS feature (SA Water pipes, bores and dams). In the Adelaide metropolitan area, an estimate of domestic groundwater extraction was applied to the area otherwise serviced by SA Water.

Stock water demand

• Grazing land within 500m of one type of water source (SA Water pipelines, dams or bores) relied solely on that water source. Other grazing areas were assigned to a water source based on the table above
• An additional 67% of water consumed by stock was supplied to cover the 40% of the supplied volume lost in distribution.
• The long-term average monthly maximum temperature for the Adelaide (Kent Town) weather station represented the monthly temperatures for grazing areas in the Adelaide Region.
• Seasonal stock production intensity followed a crossbred merino flock autumn lambing pattern typical in Victoria (McLaren 1997). Stocking rates were uniform across grazing land in the Adelaide Region.
• Stock numbers for the slightly larger Adelaide and Mount Lofty Ranges Natural Resource Management region approximate numbers in the Adelaide Region.
• Stock fed solely on dryland pasture and supplied water was fresh. Saline water or different feed may increase stock water requirements.

Domestic water demand in rural areas

• Dwellings preferentially used water from SA Water when they were located within 500m of a SA Water pipeline rather than other sources. Dwellings in other areas were assigned to a water source based on the table above.
• The estimated domestic water use is sensitive to the average water supplied to households (NWC 2011).
• The number of households and dwellings in the ABS census was assumed to be evenly distributed within each mesh block.
• The estimate depended on the regional South Australian annual population growth rate of 1.1% representing the growth rate of the number of dwellings extracting groundwater for domestic use since 2006.

Domestic demand in metropolitan Adelaide

• Unmetered domestic groundwater extraction in metropolitan Adelaide was an estimate of consensus, which is typically used for water resource planning.