Perth
18.11 Groundwater allocation extraction

Supporting Information

This line item refers to all groundwater extracted from licensed bores in the Perth region not related to urban water systems or irrigation schemes. It includes groundwater extracted by individual users in the agricultural and industrial sectors.

The groundwater supply licences are divided into licence entitlement purposes. Total groundwater extracted for each licence purpose during the 2010–11 year is given in the following table. The following figure shows the percentage of the total volume of water extracted for each licence category.


Graph of the percentage of the total volume of groundwater extracted for each licence category
Graph of the percentage of the total volume of groundwater extracted for each licence category


Total groundwater extracted for each licence purpose during the 2010–11 year

Licence category – groundwater

Allocation extraction (ML)

Agriculture

139,269

Commercial and institutional

12,179

Environment and conservation

6,086

Industry and power generation

33,286

Mining

2,363

Parks, gardens and recreation

75,159

Stock and domestic

18,241

Other

461

Total

287,044

 

Quantification Approach

Data Source

Department of Water: Water Resource Licensing database.

Provided by

Department of Water.

Method

The Department does not have sufficient metering information relating to actual extraction from licensed bores to determine the total volume of water extracted. Consequently, the allocation extraction during the 2010–11 year is estimated based on the licensed allocation.

The volume of extraction is estimated to be the full allocation, divided by the number of days that each licence was active during the 2010–11 year. The number of days the licences were active is calculated using the issue date of each individual licence.

  • For licences that expired during the 2010–11 year (and were not renewed), the volume of extraction is estimated to be the full allocation, divided by the number of days from 1 July 2010 until its expiry date.
  • For new licences that were created during the 2010–11 year, the volume of extraction is estimated to be the full allocation, divided by the number of days from the licence issue date until 30 June 2011.

Some licences are issued in perpetuity and do not have a finalisation date. In these cases, the volume of extraction is estimated as the amount of one full year's allocation for licences in force during the 2010–11 year.

Assumptions, Limitations, Caveats and Approximations

There is not sufficient information relating to actual extraction to provide more accurate estimates of extraction for all licences. The pro-rata estimates of extraction assume that the full annual allocation is extracted each year, and that the rate of extraction is uniform throughout the year. It is unlikely on both counts that this will be the case for all licences.

Uncertainty Information

The uncertainty estimate was not quantified.

Comparative year

The following table presents substantive changes in the line item reported in this 2011 Account with the corresponding line item in the 2010 Account.

 

Comparative year information for line item 18.11

2011 Account line item

2010 Account line item

2011 Account volume for the 2009–10 year (ML)

2010 Account volume for the 2009–10 year (ML)

Change from the 2010 Account to the 2011 Account

18.11 Groundwater allocation extraction

16.5.3.7 Groundwater allocation extraction–other lumped holders

273,321

294,482

Prior period error: incorrect dates used when calculating the allocation extraction

Change in line item name and number