Melbourne
17.7 Entitled diversion of non-allocated surface water to users

Supporting information

The volume presented in the water accounting statements (13,509 ML) represents the volume of water diverted in the Melbourne region under take and use licences issued for irrigation, stock and domestic, commercial and industrial and other purposes. Take and use licences specify a maximum entitlement volume, but this does not represent a surface water liability.

Take and use licences exist for unregulated sections of the Bunyip, Maribyrnong, Werribee, and Yarra rivers, as well as regulated sections of the Maribyrnong and Werribee rivers.

The following table presents the volume of surface water diverted under take and use licences in the Melbourne region during the 2012–13 year. The licenced entitlement volume is also shown. 

Volume of surface water diverted under take and use licence entitlement volume during the 2012–13 year

 

Licence Class

Catchment

Total

Bunyip

Yarra

Maribyrnong

Werribee

Diversion volume (ML)–metered and unmetered

irrigation1

4,074

5,284

2.5

0

9,361

stock and domestic

10

12.2

0

0

22

commercial and industrial

39

4,045

0

0

4,084

other

24

18

0

0

42

Total diversion volume (ML)

4,147

9,359

2.5

0

13,509


1 The volume presented for irrigation does not include:

Quantification approach

Data source

Victorian Water Register.

Provided by

Victorian Department of Environment and Primary Industries.

Method

The volume presented for this item is a combination of metered diversion data and estimates of non-metered diversions. Southern Rural Water meter surface water diversions for take and use licences in the Maribyrnong, Werribee and Bunyip catchments. Melbourne Water meter surface water diversions for take and use licences in the Maribyrnong and Yarra catchments. Diversion data is submitted to the Victorian Water Register.

Metered diversions

Metered diversion volumes were obtained from the Victorian Water Register for all catchments for the 2012–13 year.

Un-metered estimated diversions

Where metered data were not available, the diversion was estimated using the following assumptions; and

  • diversion volume was assumed to be equal to zero for licences in the Yarra catchment (as per Melbourne water assumptions)
  • diversion volume was assumed to be equal to the licensed entitlement volume for licences in the Bunyip, Maribyrnong, and Werribee catchments (as per Southern Rural Water assumptions).

Assumptions, limitations, caveats and approximations

Broad assumptions have been made to estimate unmetered diversions:

  • The assumption that the volume diverted under take and use licences in the Bunyip, Maribyrnong and Werribee catchments is equal to the entitlement volume is likely to overestimate the actual diversion.
  • The assumption that the volume diverted under take and use licences in the Yarra catchment is equal to zero is likely to underestimate the actual diversion.

Uncertainty information

Metered diversions have an uncertainty of +/– 10% due to known errors of meters.

The uncertainty estimate for unmetered estimates of diversion were not quantified.