Yarra Tribs.

The 1960s saw more prolonged droughts and water restrictions.  There were also deadly bushfires on the fringes of Melbourne in 1962, and again in 1968.

Growing concerns about long term water security led to a Parliamentary Public Works Committee inquiry between 1965 and 1967.

In response to the inquiry, the Bolte Government immediately approved works for a 20 km diversion tunnel from the Thomson River and began planning for the massive Thomson Dam in Gippsland (the Upper Yarra Dam had been completed in 1957).

In addition to the Thomson, several smaller diversion catchments known as the Yarra Tributaries were set aside in 1968 under a 10-year lease agreement between the Forests Commission Victoria (FCV) and the Melbourne and Metropolitan Board of Works (MMBW).

Five small concrete weirs on the Armstrong (east and west), Starvation, McMahons and Cement Creeks were built to divert water directly into the Silvan Conduit which connected the Upper Yarra Reservoir to Melbourne.

All the newly designated “Yarra Tribs” as they became known, as well as the Thomson Catchment, sat on State forest, unlike the major Yarra water catchments which were vested with the MMBW in 1891.

The Forests Commission had long opposed the closed catchment policy of the MMBW, arguing that timber harvesting, controlled public access and the protection of water supplies were all compatible.

Previously, in 1958–60, the State Development Committee held an Inquiry into the utilisation of timber in watersheds of the State and the Forests Commission advocated strongly, but unsuccessfully, for access for logging in closed catchments.

However, during the latter 1965-67 Parliamentary Inquiry, the Commission remained more concerned that access to timber in the Thomson catchment would be restricted with construction of a new reservoir. The Commission once again advanced as evidence its successful conduct of harvesting in many proclaimed catchments across Victoria.

The State Government had no appetite to overturn the long standing MMBW closed catchment policy but resolved that timber harvesting would continue in the Yarra Tributaries and Thomson catchments but with some additional protections and they were closed to public access and gates were erected.

Releasing water from the Yarra Tribs was also important to maintain environmental flows in the Yarra River.

Construction on the new Thomson Dam and diversion tunnels commenced in the early 1970s and was completed in 1985.

Long term agreements were eventually negotiated between Melbourne Water and the Forest Service to manage activities in both the Thomson catchment and the Yarra Tribs.

Source: McHugh, Peter. (1991). Statement of resources, uses & values for the Dandenong forest management area (Yarra forests). Dept. of Conservation and Environment. ISBN 978-0724198498.