What are long-term diversion limit equivalent (LTDLE) factors?
Long-term diversion limit equivalent (LTDLE) factors across the Basin were noted by the Murray-Darling Basin Ministerial Council in 2011 to account for the environmental water recovery associated with the development of the Basin Plan.
The LTDLE factors are a water accounting tool used by the Murray-Darling Basin Authority (MDBA) and the Department of Agriculture (DoA) to measure how much water has been recovered for the environment as part of the Murray-Darling Basin Plan and to guide future water recovery decisions.
The LTDLE factors are also referred to as the Cap factors.
LTDLE factors:
- Provide a conversion between the size of a water entitlement and the long-term average use of the entitlement over the timeframe used to develop the Basin Plan.
- Represent the long-term average annual usage of an entitlement by considering the average allocation and utilisation of the entitlement.
- They are only intended to estimate the long-term average environmental water recovery of entitlements. They are not intended to determine the financial value of an entitlement.
Revision of LTDLE factors will not affect reliability as it does not influence the seasonal determination process.
Why do we need LTDLE factors?
There are over 150 different classes of water entitlements across the Basin.
Each valley’s entitlement classes are given an LTDLE factor to translate through to long term average use, so they can be counted on equal terms. This allows the MDBA to report on water recovery in a way that is consistent and accurate across the Basin.
The factors provide a consistent accounting system to ensure water recovery has occurred as planned. It also shows where any future water recovery may be required.
How do the LTDLE factors work?
The factors are a numerical value (from 0.0 to 1.0) given to each entitlement class that reflects estimates of the long-term average actual water use.
This is different to the reliability of an entitlement, which considers water availability.
These factors focus on historical patterns, they are not a prediction or a guide of future water use.
The factors have no impact on entitlements or water availability.
Reviewing and updating the LTDLE factors
In 2015, all Basin Governments committed to reviewing the methodology and the assumptions used to develop the first set of factors. This was in response to concerns that the methodology used was not as accurate as it could be and not consistent across the Basin.
Victoria worked with the MDBA to review and update the Victorian LTDLE factors and developed revised factors using the best available models and data. This work ensures the LTDLE factors give the best representation of water recovered in Victoria under the Basin Plan.
An Independent Review Panel engaged by the MDBA in January 2019 to review Victoria’s LTDLE factors concluded its review in March 2019. The review endorsed the method and assumptions upon which these factors are based – which includes the use of Victoria’s Baseline Diversion Limit (BDL) models – as the best available at the time.
Revision of LTDLE factors for Victoria’s Basin Plan water recoveries report
