The Thomson River is a river in Gippsland

Gippsland

Gippsland is a large rural region in Victoria, Australia. It begins immediately east of the suburbs of Melbourne and stretches to the New South Wales border, lying between the Great Dividing Range to the north and Bass Strait to the south...

, Victoria

Victoria (Australia)

Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. It starts below Newlands at the north western end of the Baw Baw Plateau

Baw Baw National Park

Baw Baw is a national park in Victoria, Australia, 111 km east of Melbourne. It contains the Baw-Baw Plateau and Mount Baw Baw, a small ski resort, including nearby town, technically outside the national park....

 at an elevation of 972 m, where it shares a watershed with the Yarra River

Yarra River

The Yarra River, originally Birrarung, is a river in east-central Victoria, Australia. The lower stretches of the river is where the city of Melbourne was established in 1835 and today Greater Melbourne dominates and influences the landscape of its lower reaches...

 and Tanjil River, and ends at an elevation of 1.55 m merging with the Latrobe River

Latrobe River

The La Trobe River is a river in Gippsland, Victoria, Australia. It begins in the area between Powelltown and Noojee where it shares a watershed with the Little Yarra River, a tributary of the Yarra River, and has a number of tributaries joining it from the southern slopes of the Baw Baw plateau,...

 near Sale

Sale, Victoria

Sale is a city in the Gippsland region of the Australian state of Victoria. It is the seat of the Shire of Wellington as well as the Roman Catholic Diocese of Sale and the Anglican Diocese of Gippsland. It has a population of around 13,336, and is expected to reach a population of 14,000 soon...

. The Thomson River drops around 970 m over its 170 km length.
The Thomson Valley was intensively mined for gold during the latter half of the 19th and early 20th centuries. Prospector "Ned" Stringer discovered significant quantities of alluvial gold at the junction of what is now known as Stringers Creek. A short distance up that creek the gold mining township of Walhalla

Walhalla, Victoria

Walhalla is a small town in Victoria, Australia, founded as a gold-mining community in early 1863 and at its peak home to around 2,500 residents. Today, the town has a population of fewer than 20 permanent residents, though it has a large proportion of houses owned as holiday properties. It...

 was established.

The river is dammed not far below its source by the Thomson River Dam

Thomson River Dam

The Thomson Dam is located on the Thomson River about 130 km east of Melbourne in Gippsland near the former township of Beardmore and the Baw Baw National Park....

, which provides around 70% of Melbourne's water storage and supplies about 30% of Melbourne's water needs.

This takes about 50% of the river's natural flow, which places a great environmental stress downstream. It particularly affects the Gippsland Lakes

Gippsland Lakes

The Gippsland Lakes are a network of lakes, marshes and lagoons in east Gippsland, Victoria, Australia covering an area of about 600 km2. The largest of the lakes are Lake Wellington , Lake King and Lake Victoria. They are fed by the Avon, Thomson, Latrobe, Mitchell, Nicholson and Tambo...

, which include Lake Wellington, Lake Victoria and Lake King. This area has international significance as a Ramsar

Ramsar Convention

The Ramsar Convention is an international treaty for the conservation and sustainable utilization of wetlands, i.e., to stem the progressive encroachment on and loss of wetlands now and in the future, recognizing the fundamental ecological functions of wetlands and their economic, cultural,...

listed wetland site.