Landscapes of the Upper Blackwood


The upper reaches of the Blackwood River flow through the upper Basin area. Chains of wetlands and lakes occur naturally across the landscape in two locations, the northern chain, including Lake Toolibin and the southern chain, running from Dumbleyung to south of Wagin. The upper Blackwood Basin has been extensively cleared with only 16% of remnant vegetation remaining, of which only 3% is within conservation estate or Sate Forest.

Land

The upper Basin (approximately 68% of the overall Blackwood Basin) along with the middle Basin, drains the Archaean (and minor) Proterozoic basement rocks of the Yilgarn Craton. Within the Yilgarn Craton, Permian sedimentary rocks are preserved in the Boyup Basin. Primarily Tertiary-Quaternary age surficial sediments occur in all three geological provinces. Basement rocks of the Yilgarn Craton comprise mainly heterogeneous Archaean gneiss complexes and younger, less intensely deformed Archaean granitoid rocks (Wilde and Walker, 1982; Chin and Brakel, 1986). A number of suites of Proterozoic dykes and veins of predominantly northwest orientation intrude the basement rocks.

Natural Waterways

As well as the Blackwood River, other important rivers and creeks occurring in the upper Basin include Dongolocking creek, Coblinine River, Arthur River, Beaufort River, Carrolup River and the Hillman River. There are broad relatively flat valley floors in the upper Basin with low relief. Due to low annual average rainfall, flat topography and existence of an extensive network of salt lakes, the upper eastern creeks and rivers rarely contribute any flows to the lower Blackwood River. Most of the basin to the east of Darling Range is largely an internally drained system where the chain of salt lakes only connects during extreme rainfall events. Lake Dumbleyung is the largest in the Blackwood Basin. It overflowed into the lower Blackwood River only three times during the twentieth century. This lake was considered to be almost ‘fresh’ prior to European settlement but is now saline to highly saline. The catchment contributing to this lake has an area of 7790 km2, which means that about 33% of the overall Blackwood Basin almost never contributed flow to the rivers downstream of Lake Dumbleyung.

In the past the Blackwood River water quality was fresh enough to supply water for domestic uses to the towns along its route. The clearing of native vegetation for agriculture has made the river flows from the upper catchments too salty for this purpose due to increasing dryland salinity in the upper and middle parts of the basin. Downstream of lake systems from Duranillin, the Blackwood River drops 190 m through the Darling Range and along the deep Blackwood Valley in the middle and lower Basin.

Wetlands

As well as Lake Dumbleyung mentioned above, Toolibin Lake is located within the upper part of the upper Blackwood Basin (east of Narrogin) and is recognised as an area of high conservation value being one of the last remaining inland freshwater lakes found in the area. It is an ecological community, an area of unique and naturally occurring groups of plants and animals, and is the largest remaining wetland of this type in south west Australia.

The Australian Government has listed it as a threatened ecological community and it is internationally classified as a wetland of international importance under the Ramsar Convention. It is recognised as a regional priority by being an integral part of the SWCC identified Toolibin bio-landscape.

Toolibin Lake is a seasonal wetland, meaning it only has water at certain times of the year. When the wetland is full its woodland trees, sheoak (Casuarina obesa) and paperbark (Melaleuca strobophylla) are partially submerged in water.

The wetland has some of the richest habitat found in the region and provides a home for many kinds of plants and animals including waterbirds. An impressive 41 species of waterbirds have been recorded at the wetland, including rare species like the freckled duck. The threatened red-tailed phascogale also lives there.

Other wetlands also occur within the upper Basin including:

  • Lake Taarblin, a neighbouring lake to Lake Toolibin that has been heavily degraded by rising salinity.
  • Lake Ewlyamartup see below for more information.
  • Lake Pakeyerring
  • Martinup Lake
  • Nomans Lake
  • Walbyring Lake
  • Wardering Lake
  • White Lake.

Lake Ewlyamartup is a 100 ha recreation lake that was a source of fresh water and rich hunting ground for indigenous people and early European settlers. It became a popular watersport destination for local people following WW1, however clearing in the 50,000ha catchment for agriculture slowly saw an increase in salinity and nutrient load and a resultant decline in water quality. By the early 2000’s the lake water quality had collapsed with salinity triple that of the ocean and eutrophic, and was no longer used for recreation. Katanning Landcare, partners and the local community are currently undergoing a major wetland restoration program, improving water quality, revegetating and restoring the recreational values. Lake Ewlyamartup is home to 95 species of birds including the Priority Listed Hooded Plover.

Biodiversity

Areas Managed for Conservation 

The upper Basin has been extensively cleared in the past with only 16% of remnant vegetation remaining; within the Katanning landcare zone only 9% remains. Only 3% of the upper Basin area is within conservation estate with many of these reserves being small and irregular in shape, many being located in conjunction with the river and wetland chains. The largest of the reserves is Dumbleyung Lake Nature Reserve at just over 4200 ha in size.

Conservation Areas in the upper Basin

  • Arthur River Nature Reserve
  • Ballast Pit Nature Reserve
  • Birdwhistle Nature Reserve
  • Birdwood Nature Reserve
  • Bockaring Nature Reserve
  • Bokan Nature Reserve
  • Boundain Nature Reserve
  • Brooks Nature Reserve
  • Buchanan Nature Reserve
  • Capercup Road North Nature Reserve
  • Carmody Nature Reserve
  • Carrolup Nature Reserve
  • Casuarina Nature Reserve
  • Cherry Tree Pool Nature Reserve
  • Coblinine Nature Reserve
  • Concaring Nature Reserve
  • Coomelberrup Nature Reserve
  • Coyrecup Nature Reserve
  • Cronin Nature Reserve
  • Culbin Nature Reserve
  • Dead Mans Swamp Nature Reserve
  • Dingerlin Nature Reserve
  • Dongolocking Nature Reserve
  • Dulbining Nature Reserve
  • East Collanilling Nature Reserve
  • Flagstaff Nature Reserve
  • Gnarkaryelling Nature Reserve
  • Gundaring Lake Nature Reserve
  • Haddleton Nature Reserve
  • Harrismith Nature Reserve
  • Highbury Nature Reserve
  • Highbury State Forest
  • Highbury West Nature Reserve
  • Hillman Nature Reserve
  • Hobart Road Nature Reserve
  • Hurdle Creek Nature Reserve
  • Ibis Lake Nature Reserve
  • Jaloran Nature Reserve
  • Johns Well Nature Reserve
  • King Rock Nature Reserve
  • Mallee Plain Nature Reserve
  • Manning Road Nature Reserve
  • Maragoonda Nature Reserve
  • Martinup Nature Reserve
  • McDougall Nature Reserve
  • Miripin Nature Reserve
  • Moojebing Nature Reserve
  • Moornaming Nature Reserve
  • Mount Pleasant Nature Reserve
  • Muja State Forest
  • Murapin Nature Reserve
  • Nallian Nature Reserve
  • Narlingup Nature Reserve
  • Ngopitchup Nature Reserve
  • North Wagin Nature Reserve
  • North Yilliminning Nature Reserve
  • Ockley Nature Reserve
  • Parkeyerring Nature Reserve
  • Quongunnerunding Nature Reserve
  • Sandalwood Block Timber Reserve
  • Strathmore Hill Nature Reserve
  • Taarblin Lake Nature Reserve
  • Tarin Rock Nature Reserve
  • Toolibin Nature Reserve
  • Towerrining Nature Reserve
  • Vagg Nature Reserve
  • Wagin Lake Nature Reserve
  • Walbyring Nature Reserve
  • Wangeling Gully Nature Reserve
  • Whin Bin Rock Nature Reserve
  • Wild Horse Swamp Nature Reserve
  • Wingedine Nature Reserve
  • Woodanilling Nature Reserve
  • Woorgabup Nature Reserve
  • Yackrikine Nature Reserve

Vegetation

The upper Basin can be divided into four bio-regions: the southern and northern Jarrah Forest in the western part; the Avon Wheatbelt 2 in the centre and the Western Mallee in the eastern part of the Basin.

Bio-regions

Northern Jarrah Forest

To the north of Collie the vegetation comprises jarrah-marri forest in the west with bullich (Eucalyptus megacarpa) and blackbutt (Eucalyptus pilularis) in the valleys, grading to wandoo (Eucalyptus wandoo) and marri (Eucalyptus calophylla) woodlands in the east with powderbark wandoo (Eucalyptus accedens) occurring on breakaways.

Across the northern jarrah forest there are extensive but localised sand sheets with banksia low woodlands. Heath is found around granite rocks and as a common understorey of forests and woodlands in the north and east. Most of the diversity in the vegetation communities occurs on the lower slopes or near granite soils where there are rapid changes in site conditions.

Southern Jarrah Forest Bio-region

The Jarrah Forest bio-region occurs on the Darling Plateau, with the southern Jarrah Forest occurring south of Collie, where the Darling Plateau broadens and is less well drained. The forest and woodlands are generally similar to those occurring in the northern jarrah forest, but the understorey reflects the wetter conditions. Rainfall is from 1200 mm in the south-west to 500 mm in the east. Vegetation comprises Jarrah-Marri forest in the west grading to Marri and Wandoo woodlands in the east. There are extensive areas of swamp vegetation in the south-east dominated by Paperbarks and Swamp Yate. The understorey component of the forest and woodlands reflects the wetter nature of this area. The majority of the diversity in the communities occurs on the lower slopes or near granite soils where there are rapid changes in site conditions.

Avon Wheatbelt 2 (Re-juvenated Drainage subregion)

The Avon Wheatbelt is an area of active drainage dissecting a Tertiary plateau in Yilgarn Craton. Gently undulating landscape of low relief. Proteaceous scrub-heaths, rich in endemics, on residual lateritic uplands and derived sandplains; mixed eucalypt, Allocasuarina huegeliana and Jam-York Gum woodlands on Quaternary alluvials and eluvials. Within this, AW2 is the erosional surface of gently undulating rises to low hills with abrupt breakaways. Continuous stream channels that flow in most years. Colluvial processes are active. Soil formed in colluvium or in-situ weathered rock. Includes woodland of Wandoo, York Gum and Salmon Gum with Jam and Casuarina.

Western Mallee

The Mallees bioregion is the south-eastern part of Yilgarn Craton. Its landscape is gently undulating, with partially occluded drainage. Mallee over myrtaceous-proteaceous heaths on duplex (sand overclay) soils are common. Melaleuca shrublands characterise alluvia, and Halosarcia low shrublands occur on saline alluvium. A mosaic of mixed eucalypt woodlands and mallee occur on calcareous earth plains and sandplains overlying Eocene limestone strata in the east. Landscape is fragmented with particular surface-types almost completely cleared as wheat-fields.

Western Mallee (MAL2) sub-region has more relief than its eastern counterpart: main surface-types comprise clays and silts underlain by Kankar, exposed granite, sandplains and laterite pavements. Salt lake systems on a granite basement. Occluded drainage system. Mallee communities occur on a variety of surfaces; Eucalyptus woodlands occur mainly on fine-textured soils, with scrub-heath on sands and laterite. The climate is warm Mediterranean and annual rainfall is 250-500mm

Due to the heavy clearing in the past, many of the plant communities in the upper Basin are considered ‘poorly represented’, i.e. there is less than 30% remaining of the original pre-European extent. Many plant communities are also under-represented within conservation estate. A 2009 study of the Inland NRM Zone by Heckel and Lacey (DEC) for SWCC, attempted to prioritise the vegetation associations (Beard’s and Hopkin’s) and  identified the following vegetation associations as having a high priority for conservation based on the extent remaining and the amount remaining within conservation estate:

  • 1051      Shrublands; teatree thicket with scattered wandoo & yate
  • 1005     Low woodland; Allocasuarina huegeliana
  • 1088     Medium woodland; mallet & blue mallet
  • 1096     Medium woodland; York gum, yate & salmon gum
  • 1091     Low woodland; Banksia prionotes & Allocasuarina huegelianna
  • 1087      Medium woodland; wandoo, morrell & blue mallet
  • 987        Medium woodland; jarrah & wandoo
  • 1093      Succulent steppe with open woodland & thicket; eucalypts & Allocasuarina obesa over teatree & samphire
  • 953        Succulent steppe with thicket; teatree over samphire (m5)
  • 1074      Succulent steppe with open woodland & thicket; wandoo & Allocasuarina obesa over teatree & samphire
  • 131         Mosaic:  Medium woodland; salmon gum & gimlet / Shrublands; mallee scrub, redwood & black marlock
  • 1147      Shrublands; scrub-heath in the south-east Avon-Wheatbelt Region
  • 142        Medium woodland; York gum & salmon gum

Ecological Linkages

As the upper Basin has been heavily cleared in the past, remaining patches of native vegetation provide important landscape functions. Small remnants occur along roadsides and natural waterways, as well as within open paddocks. Regional ecological linkages have been identified across the upper Blackwood Basin where these small remnants have been identified as being important stepping stones across the fragmented landscape. More can be found out about regional ecological linkages here. Local linkages can compliment these regional linkages but are identified at a more local scale.

Flora

Several declared threatened flora species have been recorded from across the middle Blackwood Basin area. These include:

  • Acacia brachypoda (VU)
  • Acacia depressa (EN)
  • Adenanthos pungens subsp. effusus (CR)
  • Banksia oligantha (EN)
  • Caladenia bryceana subsp. bryceana (EN)
  • Caladenia luteola (CR)
  • Calectasia pignattiana (VU)
  • Commersonia erythrogyna (CR)
  • Conostylis drummondii (EN)
  • Conostylis seorsiflora subsp. trichophylla (EN)
  • Conostylis setigera subsp. dasys (CR)
  • Darwinia carnea (CR)
  • Eleocharis keigheryi (VU)
  • Grevillea elongata (EN)
  • Hemigenia ramosissima (CR)
  • Jacksonia velveta (EN)
  • Lasiopetalum rotundifolium (EN)
  • Pultenaea pauciflora (VU)
  • Thelymitra stellata (EN)
  • Tribonanthes purpurea (VU)
  • Verticordia fimbrilepis subsp. fimbrilepis (VU)

A large number of priority flora species have also been recorded within the area.

Fauna

Schedule 1 – Fauna that is rare or likely to become extinct

  • Woylie, Brush-tailed Bettong (CR)
  • Curlew Sandpiper (VU)
  • Forest Red-tailed Black Cockatoo (VU)
  • Baudin’s Black Cockatoo (EN
  • Carnaby’s Black Cockatoo(EN)
  • Chuditch (VU)
  • Malleefowl (VU)
  • Numbat (VU)
  • Red-tailed Phascogale, Kenngoor (EN)
  • Brush-tailed Phascogale, Wambenger (VU)
  • Western Ringtail Possum (EN)
  • Heath Mouse, Heath Rat, Dayang (VU)
  • Australian Painted Snipe (EN)

Priority Fauna (DPaW 2014)

  • Australian Bustard (P4)
  • Bush Stone-curlew (P4)
  • Hooded Plover (P4)
  • Western Shrike-tit, Crested Shrike-tit (P4)
  • Water-rat (P4)
  • Shy Heathwren (western) (P4)
  • Western Brush Wallaby (P4)
  • Western Rosella (inland) (P4)
  • White-browed Babbler (western wheatbelt) (P4)
  • Western Whipbird (Mallee) (P4)
  • Quenda, Southern Brown Bandicoot (P5)
  • Tammar Wallaby (WA subsp) (P5)

To find out the definition of the conservation codes click here.

Threatened Ecological Communities

One threatened ecological community is located within the upper Basin, being the Perched wetlands of the Wheatbelt region with extensive stands of Casuarina obesa and Melaleuca strobophylla at Lake Toolibin, Commonwealth listed as critically endangered.

Three priority communities exist, being:

  • Alluvial soils of the upper Blackwood River (P1)
  • Claypans with mid dense shrublands of Melaleuca lateritia over herbs (P1)
  • Granite outcrop pools with endemic aquatic fauna (P2).

Glimpses thumbnailMore information on the Commonwealth listed community, Lake Toolibin, can be found on the Glimpses into disappearing landscapes website here. Copies of the book “Glimpses into disappearing landscapes. Nationally Listed Threatened Ecological Communities of the South West Region” are also available through SWCC.

 

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