Vasse-Wonnerup Estuary facts for kids
The Vasse-Wonnerup Estuary is a special water area in Western Australia. It's near the town of Busselton. An estuary is where a river meets the sea, mixing fresh and salt water. This estuary is very important for nature.
Quick facts for kids
Designations
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| Official name: Vasse-Wonnerup System | |
| Designated: | 7 June 1990 |
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| Reference #: | 484 |
The Vasse-Wonnerup Estuary is listed as an important wetland in Australia. It was also named a wetland of international importance on June 7, 1990. This happened under the Ramsar Convention. About 1,115 hectares (2,755 acres) of the estuary are a special dry-season home for waterbirds. It is also a main part of the 2,038-hectare (5,036-acre) Busselton Wetlands, which is an Important Bird Area.
Contents
What is the Vasse-Wonnerup Estuary?
The Vasse-Wonnerup Estuary is shaped by ocean waves. It has changed a lot from how it used to be naturally. There are special gates called the Vasse and Wonnerup Floodgates. These gates have controlled the water flow since about 1907. They accidentally helped create a freshwater wetland. These floodgates were added to the Western Australian heritage list in 2005.
Size and Surroundings
The estuary covers a total area of about 17.8 square kilometers (6.9 square miles). Its main middle part is about 7.5 square kilometers (2.9 square miles). In winter, large open water areas are surrounded by plants like samphire and rushes. Behind these plants, you can find paperbark trees. On higher ground, there are eucalypt woodlands.
Where Does the Water Come From?
The land area that drains into the estuary is called its catchment. About half of this land (52%) has been cleared. It is mostly used for growing crops and for pastures. Some areas are also used for tree plantations.
Water Quality Concerns
The water in the estuary can get polluted easily. This is because houses in Busselton are built right next to it. Rain can wash things like fertilizers and other chemicals from farms and homes into the water. The Abba River, Ludlow River, Sabina River, and Vasse River all flow into the estuary.
Catchment Area and Drainage
The whole catchment area is about 961 square kilometers (371 square miles). It is part of the larger Geographe Bay catchment. The coastal plain has sandy soils that can get waterlogged easily. A big network of drains has been built. This helps protect Busselton and Wonnerup from floods. It also helps create more land for farming.
Amazing Birds of the Estuary
The Vasse-Wonnerup Estuary is a very important home for birds. It's estimated that over 20,000 waterbirds use this area. More than 80 different kinds of waterbirds have been seen here!
Bird Species You Might See
Some of the birds found in the estuary include the black-winged stilt, banded stilt, Australasian shoveller, Australian shelduck, and the red-necked avocet. The estuary is also home to the biggest group of black swans that breed in Western Australia. There are over 150 pairs of swans here!
Why Do Fish Die Here Sometimes?
Sadly, sometimes many fish die in the estuary. This has happened in 2009, 2011, and 2013. In 2013, about 7,000 fish died in just two days. This made people worry about how healthy the waterway is.
What Causes Fish Kills?
Experts think that several things cause these fish deaths. Low water flow, poor water quality, and high levels of phosphorus are often to blame. When it rains, nutrients from the land wash downstream into the estuary. Then, if there's a warm spell, these nutrients can cause a lot of algae to grow very quickly. This algae uses up all the oxygen in the water, which then kills the fish.
