Annual permitted take (APT) is a critical component of sustainable resource management, balancing the need for water resource utilisation with the preservation of ecosystems. It is a crucial mechanism for ensuring the long-term annual sustainable diversion limits (SDLs) set under the Murray-Darling Basin Plan are not exceeded, and that enough water is available for the environment. APT is the maximum amount of water permitted to be taken for consumptive purposes each year, and has been enforced since July 2019

A method for determining APT is part of each water resource plans (WRPs) developed by the Basin states under the Commonwealth Water Act 2007. When the method is applied over the Basin Plan reference period (1895–2009), the annual APT must be equal to or less than SDL.

An APT model is a major component of the APT calculation method. It is used to calculate the APT that would be expected in a year, given that year’s water availability and climatic conditions. APT is calculated at the end of each year and compared to actual take in that year, with the difference added to a public register of take. SDL compliance is tracked using the cumulative difference (from water year 2019–20).

APT models are configured using estimates of the river management and development (public and private infrastructure) conditions in a river system across the water resource plan period. These estimates include:

• irrigated crop area and planting decisions

• water entitlement holders’ distribution and use patterns

• how storages are operated to supply water for consumption and the environment.

The data set provided contains flows at several gauges in each river system, as simulated by the annually extended APT model. Notwithstanding the model’s inherent limitations, these are a fair representation of those we would expect under current conditions development and operation rules. They can be compared with flows simulated by other key scenario models, such as long-term average annual extraction limit (LTAAEL) model or without development (WOD) model.