Westernport and Mornington Waterways
About the Westernport catchment
The Westernport catchment has an area of 3433 square kilometres and some 2232 kilometres of rivers and creeks. Average annual rainfall ranges from 750mm along the coast to 1200mm in the northern highlands. Approximately 70% of the catchment is rural land, 20% is Crown land and five per cent is urban. The waterways in the area are diverse in both their form and health. Lowlands in the Westernport hinterland were once largely covered by the Koo Wee Rup Swamp, which extended for some 400 square kilometres. With settlement, the swamp was drained for agricultural use and, as a result, many of the waterways in the lower catchment are mostly made up of channelised drains.
Waterway condition in the Westernport catchment and western Mornington Peninsula.
On the Mornington Peninsula, waterways are relatively small and discharge to Western Port, Port Phillip Bay or Bass Strait. Most of the waterways that discharge to Port Phillip Bay and Western Port on the western and southern parts of the peninsula are not within Melbourne Water's management area.
Waterway health
Waterway health within the catchment varies considerably, from good or very good in the northern highlands, to poor or very poor in the rural and urban sections in the central lowlands. These waterways are extremely important, as they are home to 14 species of native fish (including the dwarf galaxias and Australian grayling), 11 species of native frogs (including the growling grass frog), platypus and several species of native plants.
Water quality is generally good in the upper catchments, but tends to decline downstream of Princes Highway. Clearing and draining of the catchment for agricultural use has resulted in significant erosion of the waterways, particularly in the smaller, upper sections. Sediment run-off to the bays caused by the erosion has become a major issue, and Melbourne Water is working to control this.
Although waterways on the Mornington Peninsula generally have a good level of water flow, there is some stress to the Lang Lang and Tarago rivers and the Clyde and Cardinia creek systems. The condition of vegetation is mostly good, but there are some issues throughout the lower sections of the peninsula.
Improving the Westernport catchment
The most significant threats to the health of rivers and creeks in the Westernport catchment are rapid residential growth and major road building. Additional issues to be addressed include reducing the impact of agriculture, industry and septic tanks on water quality reducing sediments, ensuring that planting continues along the banks of the waterways, improving habitat, removing barriers that hinder native fish migration and protecting threatened flora and fauna.
The rivers and creeks in the Westernport catchment are described and rated in the links below. The highlighted red section of the map indicates the catchment area for the individual waterway. Information on improvement works that have been undertaken or are planned is included.