The importance of systematic recording of river levels as an essential tool for assessing available water resources was, however, not realised for many years. The first regular daily records were commenced in 1864 on the River Murray at Mildura and, a year later, at Echuca, as an aid to navigation. At about the same time records were commenced in connection with projected water supply schemes for Geelong, the Coliban system and the Western Australian Goldfields.

The first systematic establishment of stream gauging for water resource assessment followed consideration by Royal Commissions in Victoria and New South Wales in 1884, after widespread concern about water conservation in the colonies. Water conservation agencies were set up in the next two years and by 1890 eleven discharge-measuring stations had been established in New South Wales and 43 in Victoria. Stuart Murray, the first Chief Engineer for Water Supply in Victoria, was able to state in 1889 that -

It is hoped that, in the course of a short time, full and reliable information will be available in regard to all our rivers likely to be drawn upon to any considerable extent for the irrigation of land.

He was also able to claim that the state of the art in Australia was comparable to that in overseas countries, a claim supported by visiting engineers from the U.S.A.

The systematic measurement of stream flows in Australia in the late 19th century was recognized in other parts of the world, as evidenced by an abstract from the French publication La Technologie Sanitaire of 15 May 1897 -

In Australia . . . observations relating to water-courses, springs, artesian wells, etc., are systematically undertaken . . . The reports (of these observations) give the discharges of 30 rivers and streams of the province of Victoria . . . The conclusion . . . is that the hydrography of the water-courses of Australia is generally better known than that of the water-courses of Europe.

Stream gauging networks were expanded progressively in all States in the early years of this century, but many areas remained - and still remain - for which little or no long-term data exist. Automatic continuous recording stations are now used universally.

The most dependable method for estimating run-off from all sizes of catchments is to base the estimates on a long-term sequence of historically recorded stream-flows. Flows at a location with only short-term records can be estimated by correlation with long-term records at a station either in the same river valley or in a nearby valley with similar climatic conditions. For small catchments, rainfall-run-off models can be developed to synthesize the stream flows.

Australian Academy of Technological Sciences and Engineering