The climate of the Gascoyne is semi-arid to arid, with hot summers and mild winters. Temperatures are highest between January and February, during this time inland average temperatures generally exceed 37°C. Due to sea breezes, coastal temperatures are kept well below those inland. Average winter temperatures range below 18°C in the far south to 23°C in the North. In July the overnight minimum averages about 10°C in coastal area’s and 6°C in the far east.
The average annual rainfall of the Gascoyne is between 190 mm to 250 mm and is relatively uniform throughout most of the region; however, it is highly variable particularly in the central and eastern parts. Most of the rainfall occurs in 2 “seasons” – January to March and May to July. Summer rainfall is less reliable than the May to July rainfall, but it can be very significant especially when it is produced by tropical lows and cyclones.
The watercourses of the Gascoyne are ephemeral, meaning the rivers dry up for at least part of the year. The western half of this region is dominated by the catchment areas of the Ashburton and Gascoyne Rivers. The Gascoyne River Basin has a total area of approximately 77,600 km2 and discharges into the ocean at Carnarvon. Tributaries of the Gascoyne River include Lyons River, Turner Creek, Thomas River, Dalgety Brook. The Lyndon and Minilya Rivers are 2 relatively small rivers originating in the inland rangelands and discharging into Lake Macleod, a wetland of national significance.
Although much of the subregion’s surface water is ephemeral, there are a number of permanent pools and soaks that survive the summer as wetlands. Wetlands of national significance in the Gascoyne region are Cape Range Subterranean Waterways (including the associated karst system), Exmouth Gulf east, Lake Macleod and the McNeil Claypan System. The northern end of Lake Macleod has been proposed for listing as a wetland of international significance under the Ramsar agreement.
Wetlands of regional significance within river systems of the subregion include Cattle Pool and Edithana Pool (Lyons River), Rocky Pool, Fishy Pool, Erong Spring, Mibbley Pool, Yinnitharra Cattle Pool and Mooka Springs (Kennedy Ranges) (all part of the Gascoyne River system) and Callytharra Spring (Wooramel River).
The Gascoyne coastline can be broken up into 3 broad areas; the Shark Bay Area in the south, the Ningaloo Coast and Exmouth Gulf in the north and the Quobba Coast in between. Shark Bay is Australia’s largest enclosed marine embayment and Ningaloo Reef is Australia’s only fringing coral reef.
Flora and Fauna
The biodiversity of the Gascoyne is rich and varied across extensive terrestrial ecosystems. The region also has an exceptional marine and coastal zone which includes the Ningaloo fringing reef and the Shark Bay World Heritage Area.
As at July 2013, this subregion supports two threatened ecological communities, four Declared Rare Flora (DRF), 35 Priority One Flora, 37 Priority Two Flora, 81 Priority Three Flora and 13 Priority Four Flora.
Vegetation of the Gascoyne is predominantly chenopod and Acacia shrublands and woodlands, however many other vegetation types can be found within this region. Much of the Gascoyne region can be described as the “mulga zone”. The natural vegetation of this region consists of Spinifex (Triodia), Wattle (Acacia) and Poverty Bush (Eremophila) shrub varieties.
Along the subregion’s rivers and adjacent floodplains a number of eucalypt varieties grow along with Paperbarks (Cadjeputs). On the alluvial flats shrubs of Bluebush (Maireana) and Saltbush (Atriplex) species are present. In coastal areas Mangroves grow. The hardpan plains support open mulga woodlands and scrub, the ranges are dominated by Eremophila shrublands and the salt lakes are characterised by succulent steppes.
The Gascoyne contains two IBRA sub-regions: Carnarvon and Gascoyne. To read more about IBRA subregions, and to access the Australian Government's detailed descriptions of each, see the IBRA subregions page.