This task has been made easier by the advent of the modern computer at about the same time as a change in attitudes to water resource planning and management. Computer-aided modelling techniques have been developed in Australia for use in improving the operation of existing systems and the planning of new projects. One of the earliest such models was evolved in 1971 for the Goulburn Murray Irrigation System, one of the largest in Australia, with an average annual diversion at river offtakes of 2.8 million ML. This system is supplied by releases from storages and unregulated tributary flows of a highly variable nature. Reserves must be carried over from wet years for use in dry years to minimize drought losses.

A simulation model was developed using historical stream flow data, with the objective of determining the design security of the system and identifying operational criteria. This model was quickly shown to be capable of quantifying the effects of proposed changes in the prototype system, thus facilitating the choice of priorities in future works programs aimed at enlarging the system. The model has been progressively updated and refined with new computer developments and progressive monitoring of system operation.

Also in about 1971, a simulation model was developed for the Canberra water supply system, an expanding region supplied from several reservoirs and requiring augmentation. The objective was to determine the maximum population that the existing and future systems could serve, with a given degree of security in dry periods, and when augmentation of the supply would be desirable. A digital computer was used in these early studies, which pioneered the way for more detailed studies with modern equipment.

The Melbourne and Metropolitan Board of Works (MMBW) commenced development of a simulation model of Melbourne's water supply system in the early 1970s. This system has become increasingly complex in recent years, with new storages remote from the utilization area and rising operating costs. It has therefore become necessary to develop sophisticated techniques for managing the existing system, so that maximum performance and efficiency can be attained prior to future storages becoming operational.

One current approach being developed by the MMBW is the use of computers, (a) as an aid to automated operation of critical control points in the system and (b) in processing real-time data as a management tool in exploring options in system management. Presentation is the key in communicating simulation model results, and interactive computer graphics are being increasingly used for this purpose in Australia as well as overseas.

The computer hardware and basic programs used in these developments originate outside Australia. The enhancement and adaptation of the methods, however, has been carried out by local engineers in response to local conditions, in particular where the comparative scarcity of water has led to the creation of large and complex harvesting, storage and distribution systems. Australian work in this field is acknowledged as being of world class.

Australian Academy of Technological Sciences and Engineering