The Vasse-Wonnerup Estuary is an estuary

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

 in the South West region of Western Australia

Western Australia

Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

 close to the town of Busselton

Busselton, Western Australia

-Growth and development:According to the Australian Bureau of Statistics the Shire had a permanent resident population of 25,950 in 2004 with the town of Busselton accounting for 67% or 17,400 of the total. The Shire's permanent population is expected to continue to increase significantly to...

. The estuary is listed with DIWA

Diwa

Diwa is a railway junction on the Mumbai Suburban Railway between Mumbra and Dombivli.The nearest cities are Mumbra and Dombivli. Diva junction also connects with rail link to Panvel from where Konkan railways originate to Goa and Mangalore. Diva is primarily a railway junction and was almost...

. It was also recognised as a wetland of international importance under the Ramsar Convention

Ramsar Convention

The Ramsar Convention is an international treaty for the conservation and sustainable utilization of wetlands, i.e., to stem the progressive encroachment on and loss of wetlands now and in the future, recognizing the fundamental ecological functions of wetlands and their economic, cultural,...

 on 7 June 1990 when an area of 1115 ha was designated Ramsar Site 484 as an important dry-season habitat for waterbirds. It is also the main part of the 2038 ha Busselton Wetlands Important Bird Area

Important Bird Area

An Important Bird Area is an area recognized as being globally important habitat for the conservation of bird populations. Currently there are about 10,000 IBAs worldwide. The program was developed and sites are identified by BirdLife International...

.

Description

The estuary is wave dominated and has been severely modified from its natural state. The site of the Vasse and Wonnerup Floodgates

Vasse and Wonnerup Floodgates

The Vasse and Wonnerup Floodgates is a heritage listed site in Western Australia that comprises two locations. The two locations are the site of the Vasse floodgates on the Vasse River and the Wonnerup floodgates on the Wonnerup Estuary...

 that regulated the flow of water in the estuary from about 1907 inadvertently created the freshwater wetland, were listed on the Western Australian Register of Heritage Places in 2005. The estuary covers a total surface area of 17.8 square kilometres (7 sq mi) with the central basin having an area of 7.5 square kilometres (3 sq mi) In winter, wide areas of open water are fringed by samphire

Samphire

Samphire is a name given to a number of very different edible plants that happen to grow in coastal areas.*Rock samphire, Crithmum maritimum is a coastal species with white flowers that grows in the United Kingdom...

 and rushes

Juncaceae

Juncaceae, the rush family, are a monocotyledonous family of flowering plants. There are eight genera and about 400 species. Members of the Juncaceae are slow-growing, rhizomatous, herbaceous plants, and they may superficially resemble grasses. They often grow on infertile soils in a wide range...

. Paperbark

Melaleuca

Melaleuca is a genus of plants in the myrtle family Myrtaceae known for its natural soothing and cleansing properties. There are well over 200 recognised species, most of which are endemic to Australia...

 woodland

Woodland

Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...

 occurs behind the samphire belt, with eucalypt

Eucalypt

Eucalypts are woody plants belonging to three closely related genera:Eucalyptus, Corymbia and Angophora.In 1995 new evidence, largely genetic, indicated that some prominent Eucalyptus species were actually more closely related to Angophora than to the other eucalypts; they were split off into the...

 woodland on higher ground.

Catchment

The catchment of the estuary is 52% cleared and is used primarily for crops and pastures but also for plantations. The waters are susceptible to pollution from run-off as houses in Busselton have been built adjacent to the estuary. The Abba River

Abba River

The Abba River is a river in the South West of Western Australia.The headwaters of the river rise in the Whicher Range in the Millbrook State Forest then flow in a northerly direction...

, Ludlow River

Ludlow River

The Ludlow River is a river in the South West region of Western Australia.The headwaters of the river rise in the Whicher Range near Claymore then flow in a north westerly direction through Yoganup then through Ludlow and discharge into the Wonnerup Estuary and then out into Geographe Bay and the...

, Sabina River

Sabina River

The Sabina River is a river in the South West of Western Australia.The headwaters of the river rise in the Whicher Range near the edge of the Millbrook State Forest and then flowing in the northerly direction...

 and Vasse River

Vasse River

The Vasse River is a river in the South West of Western Australia.The headwaters of the river rise in the Whicher Range below Chapman Hill and flows in the northerly direction until discharging into the Vasse Estuary near Busselton and then the Indian Ocean via Wonnerup Inlet and Geographe Bay.The...

 all discharge into the estuary.

The catchment covers a total area of 961 square kilometres (371 sq mi) and is part of the Geographe Bay

Geographe Bay

Geographe Bay is located in the South West of Western Australia around 220 km southwest of Perth.The bay was named in May 1801 by French explorer Nicolas Baudin; Baudin named the bay after his ship, Géographe. The bay is a wide curve of coastline extending from Cape Naturaliste past the towns...

 catchment. The coastal plain area is composed of sandy and duplex soils that are easily water-logged. An extensive drainage network has been constructed to protect Busselton

Busselton, Western Australia

-Growth and development:According to the Australian Bureau of Statistics the Shire had a permanent resident population of 25,950 in 2004 with the town of Busselton accounting for 67% or 17,400 of the total. The Shire's permanent population is expected to continue to increase significantly to...

 and Wonnerup

Wonnerup, Western Australia

The townsite of Wonnerup is located south of Perth and east of Busselton. It was gazetted a townsite in 1856, deriving its name from the nearby Wonnerup Inlet.The name is Aboriginal, having been shown on maps of the region since 1839...

 from flooding and to create agricultural land.

Birds

It is estimated that over 20,000 waterbirds use the estuary as habitat with over 80 species of waterbird being found. Some of the species found in the area include Black-winged stilt

Black-winged Stilt

The Black-winged Stilt or Common Stilt is a widely distributed very long-legged wader in the avocet and stilt family . Opinions differ as to whether the birds treated under the scientific name H. himantopus ought to be treated as a single species and if not, how many species to recognize...

, Banded Stilt

Banded Stilt

The Banded Stilt is a nomadic stilt from Australia. It belongs to the monotypical genus Cladorhynchus. It gets its name from the red-brown breast band found on breeding adults, but this is mottled or entirely absent in non-breeding adults and juveniles. Its remaining plumage is pied and the eyes...

, Australasian Shoveler

Australasian Shoveler

The Australasian Shoveler is a species of dabbling duck in the genus Anas. It ranges from 46–53 cm. It lives in heavily vegetated swamps. In Australia it is protected under the National Parks and Wildlife Act, 1974...

, Australian Shelduck

Australian Shelduck

The Australian Shelduck, Tadorna tadornoides, is a shelduck, a group of large goose-like birds which are part of the bird family Anatidae, which also includes the swans, geese and ducks. The Anatidae article should be referred to for an overview of this group of birds.This is a bird which breeds...

 and the Red-necked Avocet

Red-necked Avocet

The Red-necked Avocet is a water bird found throughout Australia, except for the northern parts of the Northern Territory....

. The largest breeding colony of Black Swan

Black Swan

The Black Swan is a large waterbird, a species of swan, which breeds mainly in the southeast and southwest regions of Australia. The species was hunted to extinction in New Zealand, but later reintroduced. Within Australia they are nomadic, with erratic migration patterns dependent upon climatic...

s in Western Australia (over 150 pairs) is in the estuary.