Probable Maximum Precipitation

Probable Maximum Precipitation (PMP) Estimates

can be produced for any catchment in Australia. There are 3 Generalised Methods used to estimate PMP, appropriate for different locations and durations:

Generalised Short-Duration Method (GSDM)

- for durations up to 6 hours and areas up to 1000 km2.

GSDM downloadable document merges the method and data from Bulletin 53 with recently introduced amendments.

Revised Generalised Tropical Storm Method (GTSMR)

- for durations up to 120 hours and areas up to 150 000 km2 in the region of Australia where tropical storms are the source of the greatest depths of rainfall.

Generalised Southeast Australia Method (GSAM)

- for durations up to 96 hours and areas up to 100 000 km2 in the region of Australia where tropical storms are not the source of the greatest depths of rainfall.


- previously available on CD, the GSAM/GTSMR USB contains all the data to estimate PMP using the GSAM or GTSMR.

Overseas PMP

- estimates of PMP for catchments overseas can also be provided. Please contact us for details.

West Coast of Tasmania Method of Storm Transposition and Maximisation

- for long durations applicable for catchments located in western Tasmania

Standard charges apply.

A study into the impact of Climate Change and Probable Maximum Precipitation has been undertaken.

A PMP report provides the PMP depth, averaged over the catchment, as a function of duration, from one hour to a maximum of four days depending on the location; the spatial distribution of the rainfall over the catchment; and the temporal distribution of the rainfall during the period of the PMP storm.

What is PMP?

Probable Maximum Precipitation (PMP) is defined by the Manual for Estimation of Probable Maximum Precipitation (WMO,2009) as:

"...the theoretical maximum precipitation for a given duration under modern meteorological conditions."

Hydrologists use a PMP magnitude, plus its spatial and temporal distributions, to calculate the Probable Maximum Flood (PMF) for the catchment of a dam. The PMF is used to design the dam.

What are Generalised Methods?

Generalised Methods of estimating PMP use data from all available storms over a large region and include adjustments for moisture availability and differing topographic effects on rainfall depth. The adjusted storm data are enveloped by smoothing over a range of areas and durations. Generalised methods also provide design spatial and temporal patterns of PMP for the catchment.

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