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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

Two ibis and three duck on a tree in front of water
Ibis and ducks at Lake Murphy

What are the revised LTDLE factors in Victoria?

Revised LTDLE factors in Victoria table

SystemEntitlement classLTDLE Factor versions V2.05LTDLE Factor versions Revised
BrokenHigh reliability0.950.57
 Low reliability0.7670.083
CampaspeHigh reliability0.950.95
 Low reliability0.490.571
 Coliban Urban and Rural0.90.797
GoulburnHigh reliability0.950.967
 Low reliability0.350.583
LoddonHigh reliability0.950.624
 Low reliability0.270.05
VIC MurrayHigh reliability0.950.974
 Low reliability0.240.543
Wimmera-MalleeIrrigation Product including Losses0.8060.828
OvensRegulated irrigation0.950.45

A limited range of unique entitlements have no LTDLE factors. Alternate methods based on the best available information have been used to convert these entitlement volumes to an estimated water recovery volume.

Estimated water recovery volumes for entitlements with no LTDLE factors

SystemEntitlement classFactor
CampaspeVery high-reliability entitlement from Campaspe Irrigation Area decommissioning1
LoddonVery high-reliability entitlement from East Loddon Waterworks District decommissioningSee footnote 1
 Wimmera-Mallee Pipeline Savings Entitlement in the Loddon system1
VIC MurrayUnregulated entitlements associated with Green’s Lake decommissioningSee footnote 2


Footnote 1

Entitlement resulting from the decommissioning of East Loddon Waterworks District has unique rules / conditions that do not make it equivalent to a Loddon high reliability water share. The water savings volume of 1.478 GL is a modelled outcome and the resulting entitlement was determined as 1.480 GL.

Footnote 2

The entitlement resulting from the decommissioning of Greens Lake has no equivalent modelled under BDL. The water savings volume is a modelled outcome resulting from an increase of 7.1 GL and 1.2 GL in end-of-valley flows from Goulburn and Loddon respectively. The resulting VIC Murray unregulated entitlement of 9.0 GL is calculated using an agreed method between DELWP and MDBA.

The methodology used to derive the revised factors was endorsed in an MDBA commissioned independent review. The resulting factors were agreed to by the MDBA who is satisfied that the updated factors are robust and evidence based. They have been peer-reviewed and are the outcome of a thorough process.

Original factors (v2.05) were those used by the Department of Sustainability, Environment, Water, Population and Communities in 2011 and were used in Victoria to calculate recoveries from purchases.

LTDLE factors for Low Reliability Water Shares (LRWS) for Goulburn and VIC Murray are 0.583 and 0.543 respectively.

LTDLE Factors are calculated over the period from 1895-2009, which is on average, a wetter period compared to recent years. This historical period is also the period in which the Baseline Diversion Limit (BDL), Sustainable Diversion Limit (SDL), and water recovery targets are calculated.

The factors are not based on the unusual water demand patterns following the break of prolonged Millennium Drought during the early stages of settling into the current carryover rules.

These unusual water demand patterns have not been observed in recent years, but if it does reoccur, its impact – particularly to low reliability water share allocation is likely to be minimised by Victoria’s current carryover policy.

LTDLE factors do not just reflect availability - they also reflect how much water is used. The average use of available water in the smaller valleys are relatively low compared to larger valleys with irrigation areas.

This is why the LTDLE factors for smaller valleys are low.

No. LTDLE factors are only intended to estimate the long-term average water recovery of entitlements.

They are not intended for determining the financial value of an entitlement.

No. Revision of LTDLE factors will not affect reliability as it does not influence the seasonal determination process.

In fact, the revision of LTDLE factors is intended to protect reliability by preventing over / under recovery and the overissue of water shares from water savings projects.

Page last updated: 08/09/23