The water resources within the Port Phillip and Western Port region are the lifeblood of the region’s economy, communities and ecosystems.
The region’s waterways form a complex network of interconnected and interdependent rivers, wetlands and estuaries, which collectively gather rainwater, stormwater and groundwater from the landscape (the catchments), ultimately carrying this water to the bays and ocean via Port Phillip Bay, Western Port and Bass Strait.
The health of our water, and the vegetation and wildlife it supports, underpins the region’s amenity, biodiversity and economy.
The region’s waterways are also very significant for Traditional Owners. Cultural stories and physical evidence of thousands of years of Aboriginal peoples’ caring for Country are connected to the water and waterways.
Complex relationships and interactions exist between the region’s water resources. Some are obvious, such as the flow of rivers into the bays, or our collection and storage of fresh water in reservoirs for domestic use. Others, such as the contribution of groundwater to base flow levels in streams, or the role of wetlands and estuaries in filtering sediments and nutrients to improve water quality, are less obvious but just as important.
Rivers can include large river systems, smaller creeks, and smaller tributaries. The include the water, bed, banks, and adjacent land (known as riparian land).
Rivers and creeks collect water for drinking, industry and agriculture, and contribute to critical ecosystem services including nutrient-cycling and carbon sequestration. They are also popular recreational destinations for residents and tourists, with around 90 million visits each year.
There are more than more than 25,000 kilometres of rivers and creeks in the Port Phillip and Western Port region.
Wetlands are areas, whether natural, modified or artificial, that hold static or very slow moving water and develop, They include coastal wetlands, dominated by salt tolerant vegetation, ephemeral wetlands on the Victorian Volcanic Plain, which may be dry for significant periods, and billabong wetlands on the floodplains which are filled intermittently when rivers spill their banks.
Wetlands filter out suspended sediments and store nutrients which contribute to natural food chains. They are important habitats, and provide feeding and breeding grounds for many aquatic animals that move between wetlands, rivers, estuaries and bays. They may also be places of refuge in times of drought.
There are over 14,000 natural wetlands in the Port Phillip and Western Port region, including three listed as internationally significant under the Ramsar Convention.
Estuaries are where a river meets the sea. They include the lower section of a river where fresh water and saline (salty) water mix together. The downstream section of an estuary is where the banks of the river end and the waterway meets the bay or ocean.
Estuarine ecosystems are highly complex and dynamic environments. Since estuaries are at the bottom end of catchments, their condition can be affected by activities occurring within the upstream freshwater catchment. Where the condition of catchments, rivers or estuaries is poor, there are likely to be additional impacts on the marine receiving waters and coastal areas.
There are 33 estuaries in the Port Phillip and Western Port region.
Groundwater is water that is found below the surface of the ground. It may be out of sight, but it is a highly valuable resource which supports the economic, environmental and social needs of our region.
Groundwater mainly comes from rainfall and is stored in aquifers – a layer of fractured rock, gravel, sand or limestone below the ground surface. Depending on the type of aquifers, this rainfall may have occurred recently or many thousands of years ago.
About 30% of the world’s fresh water is stored as groundwater while less than 1% is stored in streams, rivers, lakes and other surface water bodies.
A reservoir is a large natural or artificial storage of water usually formed by constructing a dam across a river.
There are two types of reservoirs – on-stream reservoirs, where rainfall across the catchments drive the amount of water that flows into these reservoirs, and off-stream reservoirs, where water is transferred from on-stream reservoirs or other sources.
10 major reservoirs store water collected around the Port Phillip and Westernport region. Together, they have a storage capacity of 1,810 billion litres.
Water for the environment
Many of Victoria’s rivers and wetlands are modified as our population grows, so that water can be used for towns, industry and food production. This means each year, some rivers part with up to half of the water they would have naturally had before dams and reservoirs were built.
Water for the environment means that a portion of water is reserved for maintaining the long-term health of our rivers and groundwater ecosystems, and the plants and animals that depend on them.
Water for the environment benefits everyone. It ensures there are plenty of recreational opportunities like fishing, rowing and birdwatching; country is healthy for Traditional Owners, who have a long-standing cultural connection to waterways and floodplains; and it means better water quality, which has economic benefits for farmers and water supply.