History of the MID

Most of Gippsland has a rainfall of 30 inches or more a year, but the Macalister area is in a rain shadow. Rain bearing winds are interrupted by the Baw Baw Plateau, the Haunted Hills near Yallourn and the Strzelecki Ranges. As a result the average annual rainfall at Maffra is only 23½ inches and is also highly variable from year to year.

From the earliest days of white settlement after 1839, it was realised the region offered some of Australia’s most valuable grazing land. But the early settlers were at the mercy of rivers that dried up one year and flooded the next, and rainfall that came - or failed to come - in the most unpredictable way.

The first significant irrigation projects in Victoria began in the north west of the State around the turn of the century as a means of regulating the water supply. In the Macalister region, the first steps towards providing water for irrigation were taken in 1912 when the Water Commission became responsible for "closer settlement" - the name given to the process of encouraging people to relocate to and open up rural Victoria.

The Commission was asked by the Department of Agriculture to investigate the provision of temporary works to supply water to the sugar beet areas of Boisdale. Surveys were also made in that year to enable estimates to be prepared for a scheme to serve 2,400 hectares at Kilmany Park near Sale.

A study of possible storage sites on one of the major rivers was initiated in 1914 following the disastrous drought of that year. The First World War intervened, however, and it was not until 1920 that a dam was begun on the Macalister River near the junction of Bradleys Creek, to be known as the Glenmaggie Dam. The Macalister was selected because it has a much larger average annual flow than the nearby Avon River.

In the meantime, surveys were made to determine the feasibility of an irrigation scheme in the Maffra district to aid the sugar beet industry.

In 1919, Maffra landholders supported a proposal to supply water to irrigate an area of 9,000 hectares on the Avon flats, including Boisdale and the Newry and Maffra flats on the northern side of the Macalister River. This resulted in first priority being given to the construction in 1924 of the Main Northern Channel to supply the Boisdale and Newry River flats. A feature of that channel was its location in hill country on the northern fringe of the district. Very careful attention had to be given to the earthworks and the many water courses that had to be crossed with siphons (water carrying tunnels). By 1926, the Glenmaggie Dam was sufficiently advanced for water to be supplied to 3,600 hectares in Boisdale, Airly, Cobains and other estates near Sale.

With the completion of the Glenmaggie Dam to crest level in 1929, the area under irrigation was progressively extended. To overcome problems of drainage, the Boisdale and Nuntin flats were drained to Nuntin Creek and the Sale and Bundalaguah areas to Lake Wellington . The Main Nuntin and Airly-Nuntin Drains were completed in 1930 and Myrtlebank Drain in 1931. By 1933 the area under irrigation was approximately 7,400 hectares, served by 310 kilometres of channels and 90 kilometres of drains.

The Maffra and Sale Districts were united to form the Maffra-Sale Irrigation District in 1935. After irrigation began, the area sown with sugar beet increased from 820 hectares in 1927 to 1,600 hectares in 1940. The amount of beet that was treated rose from around 20,000 tonnes per annum to over 40,000 tonnes in 1940. In the early 1940s however, butterfat prices began to increase and dairy farming became more profitable. The production of sugar beet declined and eventually ceased altogether in 1945, following which the processing factory was removed.

In 1942 a report was prepared for a Parliamentary Public Works committee on the utilisation of the waters of the Thomson River and their potential for irrigation of 24,000 hectares of land in the Nambrok and Denison areas, between the Thomson and Latrobe Rivers. These works were undertaken as part of the Central Gippsland Project, commenced in 1952 and completed in 1958.

The Maffra-Sale Irrigation District was also extended in 1952 to include the Nuntin, Clydebank and West Boisdale areas, but it had become evident that the storage capacity of Lake Glenmaggie would be inadequate to meet both existing commitments and the projected requirements of the new Nambrok-Denison Scheme. Investigations were therefore made into the construction of crest gates on the Glenmaggie Dam and of a weir on the Macalister River at Maffra.

This weir, the Maffra Weir, was a vertical lift gated structure completed in 1954. It enabled flows from the Macalister River to be diverted into the Main Eastern Channel (constructed in 1958) to join with the Main Sale and Main Airly channels. These works removed the overloading on the Main Northern System by supplying the Airly, Sale and The Heart areas.

The enlargement of Lake Glenmaggie from 130,800 megalitres to its present capacity of 190,410 megalitres by the addition of crest gates was completed in 1957. This was followed by construction of the Cowwarr Weir on the Thomson River in 1959, to divert water to the Central Gippsland Irrigation Area along the Cowwarr Channel to supplement water from Lake Glenmaggie. The weir also maintains a supply of water in the old course of the Thomson River after a permanent breakaway course - Rainbow Creek - was formed during a severe flood in 1956.

In 1959, the Maffra-Sale and Central Gippsland Irrigation Districts were amalgamated to form the Macalister Irrigation District as it now exists, and the two former districts became irrigation areas within the district.

Operating the MID

To distribute irrigation water from Lake Glenmaggie three main channels have been built - the Main Northern, the Main Southern and the Main Eastern. Construction began on the Main Northern Channel in the 1920s; the first delivery of water was made in 1925 to the Boisdale area, and within a few years the northern channel system had been extended to near Sale. The Main Northern channel has a capacity of 550 ML/day.

These years also saw the construction of the Main Southern Channel (capacity 1,460 ML/day), which irrigates the area north of Tinamba. In 1939, it was extended to the Riverslea area and in 1952 was taken under the Thomson River via a 1,800 mm diameter pipe 1.3 km long, to the Nambrok-Denison area and to the east of Heyfield. Under a Soldier Settlement Scheme, 131 farms were laid out around Nambrok. Water was first taken there from Glenmaggie in 1952.

Eight years later, the Cowwarr Weir was constructed on the Thomson River six miles west of Heyfield, together with the Cowwarr Channel which augments irrigation supplies to the Nambrok Denison area when there are sufficient flows in the Thomson River. Today the Macalister Irrigation District has 410 miles of supply channels and 305 miles of drainage channels.

The Main Eastern Channel was built in 1958, following the construction of Maffra Weir on the Macalister River. This channel takes water from the weir to irrigators between Maffra and Sale and has a capacity of 600 ML/day.

The MID is a gravity irrigation system and relies solely on the capacity of the system infrastructure to generate sufficient pressure to move the water from Glenmaggie, Cowwarr and Maffra weirs through the channel system to the farmer.

Water movement is controlled by a complex series of checks and regulators, which are manually operated and can be set to pass specified flow rates downstream to the next check point.

Low lying parts of the Nambrok-Denison area began to suffer from rising groundwater levels soon after irrigation was introduced in 1952. The rising groundwater brought salt deposits to the surface, damaging crops. By 1959 a considerable area had been seriously affected by salting, and other areas were threatened as the water table continued to rise.

After intensive investigations, the problem was tackled by a system of deep surface drains, together with pumps and free flowing bores to remove the groundwater from under lying aquifers.

Salt water intrusion continues to be a threat, however, and in 1996 SRW formally established the Wellington Salinity Group as a sub-committee of the Authority under section 108 of the Water Act 1989. The group, which had already been very active in salinity control for many years aided by Government funding, now generates funds from a Salinity Mitigation Levy (currently 40¢ per Ml) on farmers in salt affected areas of the MID and its surrounds. It is continuing to address salinity intrusion by groundwater pumping and farmer education, having become an implementation committee of the West Gippsland Catchment Management Authority. SRW continues to provide administrative support to this group.

The above information has been supplied courtesy Southern Rural Water, for more detailed information please visit srw.com.au

Links to related information.

Southern Rural Water, Lake Glenmaggie Update Levels
Waterwatch Organisation
Watermark Association