Nature conservation

Threatened species

Pilliga Outwash Ephemeral Wetlands in the Brigalow Belt South Bioregion - profile

Indicative distribution

   Loading map...
The areas shown in pink and/purple are the sub-regions where the species or community is known or predicted to occur. They may not occur thoughout the sub-region but may be restricted to certain areas. ( click here to see geographic restrictions). The information presented in this map is only indicative and may contain errors and omissions.
Scientific name: Pilliga Outwash Ephemeral Wetlands in the Brigalow Belt South Bioregion
Conservation status in NSW: Endangered Ecological Community
Commonwealth status: Not listed
Gazetted date: 04 Dec 2015
Profile last updated: 06 Apr 2022


Pilliga outwash ephemeral wetlands are found in a small area of Pilliga scrub generally associated with ephemeral creeks and waterways. Two water dependant threatened plant species (Eriocaulon australasicum – endangered, and Myriophyllum implicatum - critically endangered) are known to occur in this EEC.

Benson (et al 2010) described the Pilliga wetlands as tank gilgais because they are formed on cracking, clay, alluvial soils and they form a chain of ponds. Most of these wetlands are under one hectare in size. Morphologically they can be divided into two types, tank and shallow basin wetlands. The  water of tank wetlands is more turbid and permanent than in shallow basin wetlands. Tank wetlands are unevenly circular to irregularly oblong basins with distinctive lip to 30 cm high. They have higher clay content in the soil. The shallow basin wetland soil has a higher sand content at the margin. They are surrounded by Allocasuarina luehmannii and form a boundary between woodland edge and shallow basin wetland.

Bell and others (2012) observed three types of vegetation communities in the Pilliga outwash ephemeral wetlands. Community 1 consists of Cyperus gunnii subsp. gunniiNymphoides crenata sedgeland/herbfield. Dominated by tall sedge Cyperus gunnii subsp. gunnii, sometimes Nymphoides crenata found in the deepest part of basin. Ruderal species appears on the damp mud as water recedes. Community 2 consists of Eleocharis pusillaMyriophyllum simulansNymphoides crenataMarsilea hirsutaPseudoraphis spinescens herbfield/sedgeland with an ephemeral part dominated by Goodenia gracilisCentipeda minima subsp. minimaGratiola pedunculataAlternanthera denticulata. This community is more species rich than community 1.  Community 3 is mainly Diplachne fusca grassland and has a low species richness and lacks floating leaved and submerged species.


Pilliga Outwash Ephemeral Wetlands have an exceptionally restricted geographic distribution. It is estimated that these wetlands are 2,342 km2 in extent where one third of them is located within conservation reserves such as Pilliga National Park and Pilliga State Conservation Area; they may also occur in the Pilliga West State Conservation Area. South west of Narrabri some ephemeral wetlands are found in the Pilliga forest which do not conform to the basic type of this community (Bell et al. 2012).

Habitat and ecology

  • Species richness is highly variable with the wetland depth gradient. Deepest part of the wetland shows lower species richness but those with damp soil are very high in species richness. Water in the wetlands are slightly acidic to slightly alkaline (Bell et al 2012).
  • Pilliga Outwash Ephemeral Wetlands are generally dominated by Allocasuarina luehmanii, Eucalyptus pilligaensis, Eucalyptus chloroclada, Melaleuca densispicata and Eucalyptus sideroxylon (Benson et al. 2010; Hunter 2010). They commonly occur on the Pilliga outwash within a mosaic of woodlands and shrublands, or formerly wooded areas.
  • Six species are considered regionally significant since they are disjunct or thought to be at or near their geographic limits. These taxa are: Centrolepis eremica, Drosera burmanni, Hydrocotyle tripartita, Isoetes muelleri, Peplidium foecundum and Philydrum lanuginosum. Nymphoides geminata is usually homostylous but populations in the Pilliga Outwash are consistently heterostylous.

Regional distribution and habitat

Click on a region below to view detailed distribution, habitat and vegetation information.


Recovery strategies

Activities to assist this species

IBRA Bioregion IBRA Subregion Known or predicted Geographic restrictions region