Shire of Irwin

Area ~360 km north of Perth and covers ~2,374 square kilometres.
Towns Port Denison, Dongara and Arrowsmith.
Average Temperature Maximum temperature of 32°C in January and minimum of 9°C in July.
Annual Rainfall Average of 445 mm.
ABS Profile  Irwin ABS profile
Click features on the map for more information. View full page map

A total of 3,780  people reside in the Shire of Irwin (ABS 2014) and the town of  Dongara is the most populated with over 2,700 residents.

The population of  the Shire of Irwin is increasing, with a total growth percentage of 3% since 2011.

In the Shire of Irwin, 19% of the population are residents who were born overseas and 81% being born in Australia and approximately 2.2% are of indigenous heritage.

Estimates of the resident populations as at 30 June are released annually for Local Government Areas (LGAs) in Australia by the Australian Bureau of Statistics. The estimates are generally revised 12 months later and final estimates are available after the following census. Visit the ABS website for further details.

Economy in the Shire of Irwin is broadly based on agriculture, rock lobster fishing, olive growing and tourism and oil/gas (MWDC, 2011). Employment by sector (Service related industry, Retail related industry, Agriculture, fishing and forestry, Mining, Manufacturing, Construction, Other) is depicted in the chart below.

The main land uses as shown in the Local Planning Scheme for the Shire of Irwin includes reserves, agriculture, residential, commercial and industrial.

For more information about land use in the region, visit the Land Use theme page.

Nature Reserves

The Yarragadee formation underlies the majority of the Shire of Irwin. The Yarragadee formation was formed during the Jurassic period form volcanic and sedimentary rock. The Yarragadee formation consists of fine to coarse grained sandstone with thin interbeds of shale. The geology underlying the southern coastal boundary of Shire of Coorow and Irwin the Cattamarra Coal Measures. The Cattamarra was formed during the Jurassic period from volcanic and sedimentary rocks. The formation comprises of siltstone, shale, claystone, coal and sandstone. The geology underlying the coastal boundary between the CGG and Shire of Irwin is the Kockatea Shale, which was formed during the triassic period from volcanic and sedimentary rock. The Kockatea Shale consists of shale, minor siltstone, sandstone with deposits of calcareous sandstone.

Deep calcareous sands overlies a series of coastal dune systems and low hills with relict dunes and limestone outcrops along the coastal area of Shire of Irwin. The eastern portion of the Shire consists of deep siliceous sandy soils overlying a complex undulating landscape.

Please go to the below link for more information on soil and geology in the region

Priority Fauna Species

IBRA Regions

  • Lesueur Sandplains (Geraldton Sandplains 2)

    The Geraldton Hills is located in the LGAs in the middle portion of the region. This subregion is characterised by Proteaceous scrub heath dominates the undulating sandplain lying over the Permian and Cretaceous strata. Outwash plains associated with the drainage lines are dominated by York Gum and Jam woodlands. The lateritic mesas, sandplains, coastal sandplains and limestone are rich in shrub-heaths (Desmond and Chant, 2001c).

  • Geraldton Hills subregion (Geraldton Sandplains 1)

    The Geraldton Hills is located in the LGAs in the middle portion of the region. This subregion is characterised by sand heaths of emergent Banksia and Cypresses, York Gum woodlands on alluvial plains. Areas of limestone are dominated by proteaceous heath and Acacia scrubs. Low closed Acacia shrublands occupies much of the alluvial plains associated with the Greenough and Irwin Rivers (Desmond and Chant, 2001b).

Threatened Ecological Communities

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Priority Ecological Communities

  • Coastal sands dominated by Acacia rostellifera, Eucalyptus oraria and Eucalyptus obtusiflora

    Floristically, this community is similar to other Acacia rostellifera communities but is differentiated on structure, being dominated by mallee eucalypts. The community occurs on limestone ridges, in some swales in the coastal dunes between Cape Burney and Dongara, on the Greenough Alluvial Flats on limestone soil and near Tarcoola Beach. Some very small occurrences have also been recorded on the limestone scarp north of the Buller River.

    Threats: Clearing

    Category (WA) – Priority 1

    For more information visit the DPaW website.

Coastal Assets

  • Primary and Secondary Coastal Dunes

    Primary dunes (from low water mark) and secondary dunes. Valued for recreational, aesthetic and cultural reasons, along with the services provided for storm protection  and habitat.

Marine Assets

  • Seven Mile Beach Rock Lobster Monitoring Site

    This shallow water site is located near the centre of the western rock lobster’s range of distribution. Studies conducted at the site provide much of the published data on rock lobster foraging and recruitment.

  • Seagrass Meadows

    Seagrasses are flowering plants that complete their life cycle submerged in seawater. Western Australia has the world’s highest diversity of seagrasses, with 27 species occurring in shallow waters off the coast. Seagrasses form a vital component of marine ecosystems through their services as primary biomass producers, sources of habitat (including breeding and nursery areas) and dissolved oxygen, sediment traps, and nutrient cycling. Seagrass distribution is determined by a combination of shelter, sediment, turbidity, nutrient, temperature, current and tidal influences.

    Extensive seagrass meadows occur in protected near-shore areas of the NAR, where clear water, low nutrients and sandy sea floors prevail, and are dominated by the long strap-like Ribbonweed or Strapweed (Posidonia spp) and the thin-stemmed Wireweed (Amphibolis spp).

    Seagrass habitats are fragile and susceptible to damage and can take many years to recover from disturbance, such as physical damage/removal and shading due to algal blooms (as a result of increased nutrients), and sedimentation (due to dredging activities and erosion in catchment areas).

    More information on seagrasses in Western Australia can be found in the following publications: Flowers of the Ocean: WA’s Expansive Seagrass MeadowsThe Wonders of Weed Information Sheet; Fisheries Fact Sheet: Seagrasses; Establishing Reference and Monitoring Sites to Assess a Key Indicator of Ecosystem Health (Seagrass Health) on the central west Coast of Western Australia (see references).


Groundwater Areas

  • Gascoyne Groundwater Area

    The Gascoyne Groundwater Area extends north to Kalbarri and bounds the Arrowsmith Groundwater Area east to pastoral country. The largest groundwater aquifer occurs in the Yarragadee Formation, which has an estimated yield of 22.5 million m³/year (NACC, 2005). Groundwater from fractured rock aquifers in the eastern, inland part of the region is predominantly saline and poor yielding. This region of the Gascoyne Groundwater Area falls under the Carnarvon Artesian Basin Allocation Plan.

  • Allanooka Borefield

    Located 50 km south of Geraldton in the Arrowsmith groundwater area, the Allanooka Borefield houses the bores and summit reservoir that provide an integrated scheme water supply for the area between and including the City of Greater Geraldton and the towns of  Dongara/Port Denison in the Shire of Irwin.


  • Irwin River

    Drainage Basin Length (km) Catchment Area (km2) Average Stream Salinity (mg/L) Key Characteristics
    Greenough 160 6,072 3000-35000 Originates east of Mullewa, and has middle and lower reaches with perennial flow due to discharge from the groundwater systems. The river enters the ocean at Dongara and the mouth of the river is a coastal lagoon system, which is blocked by a sandbar for most of the year.
  • Arrowsmith River

    Drainage Basin Length (km) Catchment Area (km2) Average Stream Salinity (mg/L) Key Characteristics
    Greenough 82 1,605 3000-35000 Commences near Arrino, north west of Three Springs. It has no clearly defined ocean outlet, and drains into a subterranean cave system.


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Birdlife Midwest

Contact: Sally Vigilante

Irwin Tidy Towns Sustainable Committee

Contact: Coralie Palmer
Phone: 0409 110 237

Mingenew Irwin Group

Phone: 9928 1645 Website:

Northern Agricultural Catchments Council

Work Geraldton Office 201 Lester Avenue PO Box 7168 Geraldton WA 6530 Work Perenjori Office Corner of Fowler Street and Timmings Street PO Box 95 Perenjori WA 6620 Work Jurien Bay Office 69 Bashford Street PO Box 872 Jurien Bay WA 6516 Phone: (08) 9938 0100 (Geraldton) Phone: (08) 9973 1444 (Perenjori) Phone: (08) 9652 0872 (Jurien Bay) Website: NACC Website
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