The REsource ALlocation Model (REALM) is a Windows based computer program that can simulate the operation of both urban and rural water supply systems during droughts as well as during periods of normal and high streamflows.

REALM is a generalised computer program that can simulate simple water supply systems as well as large and complex ones such as the Goulburn Irrigation system in south eastern Australia. It is general in that any water supply system can be configured as a network of nodes and carriers representing reservoirs, demand centres, waterways, pipes, etc.

It is flexible in that it can be used as a "what if" tool to address various options (i.e. new operating rules, physical system modifications, etc.). System changes can be quickly and easily configured and their effects investigated. A wide range of operating rules can be modelled either directly or indirectly by exploiting the basic set of node and carrier types and their corresponding attributes.

It uses a fast network linear programming algorithm to optimise the distribution of water within the network for each time step of the simulation period, in accordance with user-defined operating rules.

The user can specify the desired level of detail of output from the model. Output can be presented graphically, either in raw form or after post-processing using a suite of utility programs separate from the simulation model. Input and output data (ASCII) files have the same format and can be easily transferred to commercially available word processing and spreadsheet packages such as Microsoft Office to enhance presentation or to perform more detailed statistical analyses.