The Werribee River catchment is made up of the basin in which the Werribee River system flows. It is separated from other major catchments across Melbourne as shown on our maps by the high land from which water will flow into the Werribee River basin or into other basins.

The Werribee River system comprises two major rivers and a number of tributaries. But, in the basin as well are a number of streams which flow independently to Port Phillip Bay, such as Little River, Skeleton Creek, Laverton Creek, Kororoit Creek, Cherry Creek and others of smaller sizes.

The basin was formed by a number of geological forces over eons, and has been altered due to major land movement, Volcanics, erosion and sea level changes. There are three major bio-regions of the catchment, the central Victorian uplands from which most flows occur into the streams, the Victorian Volcanic plain, through which the streams have made their way to the sea, and a small part of the Otway plain in the lower Werribee. These areas had their own species of flora and fauna, with a few species being common across the basin. Human inhabitants have changed over time with indigenous people living in the basin from tens of thousands of years ago, and European settlers from the late 1700s.

Now the catchment is subject to a warming climate and a growing urban population which are having their own effects on the basin.