Lake Muir

Lake Muir National Park and the associated Lake Muir Wetlands complex in WA's Southern Forests region protect one of the most significant freshwater wetland systems in the southwest. Lake Muir itself is a large, shallow fresh to brackish lake that attracts extraordinary concentrations of waterbirds and is recognised as a wetland of national significance. The broader national park protects the lake, surrounding heath, and forest habitats that together form one of the most ecologically complete wetland systems remaining in the southwest. The area is also an important refuge for the threatened oblong tortoise (Chelodina oblonga) and diverse frog species. Spring wildflower displays in the surrounding heath add botanical appeal.

Lake Muir is a nationally important waterbird site, attracting tens of thousands of birds in productive seasons. Australian pelicans, black swans, and royal spoonbills form spectacular roosting and feeding congregations. The globally threatened Australasian bittern inhabits dense reed beds. The oblong turtle (Chelodina oblonga) — a long-necked freshwater turtle — is a priority species for the wetland system. Over 20 frog species have been recorded, including several that are endemic to the southwest. Water rats (rakali) inhabit the lake margins. Carnaby's black cockatoos feed in the surrounding banksia heath.

Lake Muir's wetland vegetation includes extensive reed beds (Typha domingensis), sedge communities, and paperbark (Melaleuca) fringes around the lake margin. The surrounding national park protects coastal heath and jarrah-marri forest. Spring wildflowers in the heath include banksias, sundews (Drosera), and various orchids. The wetland complex provides the full range of aquatic habitats from deep open water to shallow seasonal swamps that support the park's exceptional biodiversity.

The lake occupies a large deflation basin on the coastal plain — a depression scoured by wind from ancient dune systems and filled with fresh water from seasonal rainfall. The surrounding landscape is underlain by the ancient Yilgarn Craton, with coastal plain sediments overlying the basement. The lake's shallow basin is characteristic of the many wetland systems that dot the southwest coastal plain, formed as sea levels changed and dune systems were deflated and reformed.

Annual rainfall of 700–800 mm. Winters cool and wet, filling the lake to maximum level. Summers warm and dry, with the lake potentially reducing in drought years. Best visited August–November for wildflowers and peak waterbird activity. The Southern Forests location moderates temperatures somewhat.

Within Bibbulmun Noongar country. Lake Muir was a significant resource — freshwater, fish, waterbirds, and aquatic plants. European pastoral settlement gradually displaced Noongar people from the 1870s. The lake was progressively enclosed by farmland.

Lake Muir National Park was established to protect the nationally significant wetland system. The park represents one of the most important conservation outcomes for Southwest wetlands. Management focuses on maintaining wetland hydrology, controlling invasive species including carp and introduced vegetation.

Waterbird watching at the lake, particularly in winter and spring. Walking trails through heath and forest. Spring wildflowers August–November. Tortoise and frog observation opportunities.

Access from Manjimup or Walpole on unsealed roads. Basic facilities. Nearest services in Manjimup. Best visited July–November.

Wetland hydrology management, control of invasive European carp (which devastate aquatic vegetation and increase turbidity), weed management, and maintaining native riparian vegetation are priority conservation actions.