Urban River Torrens Recovery Project

The River Torrens / Karrawirra Pari runs 85 kilometres from the hills to the sea, providing essential flood management for Adelaide. Targeted rehabilitation along the urban stretch of the river over almost 10 years has helped make it a refuge for local animals, and a peaceful escape in the middle of a busy city.

Nowadays, the river is well known for its 30-kilometre shared-use trail from Athelstone to Henley Beach, with public barbecues, picnic areas, playgrounds and fitness equipment – but there was a time when the river wasn’t such a pleasant place to visit.

After European settlement and widespread land use changes, the river corridor was highly altered – changes were made to drainage channels, wetlands, rivers and streams that fed into the River Torrens / Karrawirra Pari, native vegetation was removed, riverbanks eroded, and the water became polluted.

In response, the River Torrens Recovery Project commenced in 2014, targeting priority sites to improve water quality for both the river and the coast, where it enters the sea.

Through the ongoing commitment of the 8 councils along the linear park, National Parks and Wildlife Service South Australia, the Botanic Gardens State Herbarium, Green Adelaide and the local community, the River Torrens Recovery Project has transformed – and continues to transform – the river for the better.

Combatting key issues

Exotic trees

The problem:

Introduced tree species can impact water quality by dropping their leaves into the river during autumn – this is uncommon in Australian native trees. Leaves increase nutrients in the water, decreasing the availability of dissolved oxygen that is needed by aquatic animals. This can result in poor health or even the death of fish and other water creatures. The roots of some exotic tree species also contribute to erosion or instability of riverbanks, trap debris and divert flows.

The solution:

Removing invasive exotic trees and replacing them with locally indigenous species improves water quality, bank stability and habitat for local wildlife, while also reducing riverbank erosion.

Exotic trees targeted through this project include willow, olive, pepper tree and desert ash. These have been replaced with locally native species such as gold dust wattle (Acacia acinacea).

Weeds

The problem:

In addition to exotic trees, the River Torrens / Karrawirra Pari had been invaded by introduced species, such as soursob (Oxalis pes-capre), castor oil plant (Ricinus communrs), giant reed arundo (Donax) and silver leaf nightshade (Solanum elaeagnifolium). These weed species can reduce available homes and food for the many animals that call the river home, as well as compete with and smother native plants reducing the diversity of plants.

The solution:

Combatting weeds along the river requires a collaborative approach. Controlling weeds upstream is the key to stopping them from flowing down to sites where work has already been done to control these plants. Success requires regular long-term maintenance, to eradicate where possible.

Through this project a long-term pest management plan was developed and is being implemented with a review and update underway to set future directions. Thanks to the success of the program to date, this review can focus even more on rehabilitation with native species.

Some local native plants that can now be seen along the river thanks to this project include chocolate lily (Arthropodium strictum), sweet apple berry (Billardiera cymosa), blue flax-lily (Dianella revoluta) and ruby salt bush (Enchylaena tomentosa).

European carp

The problem:

European carp are an introduced, feral species. They are a bottom feeder, which means they stir up mud on the bottom of the river in search of food, making the river turbid and murky. This is problematic for native fish, irrigation and fishers.

The solution:

To control European carp, a technique called ‘electrofishing’ has been used in the River Torrens / Karrawirra Pari to remove large volumes of this species. This technique involves temporarily stunning fish and removing carp manually from the river. Native fish are not harmed by this process.

Other ways we help

The River Torrens Recovery Project is not the only thing we’re doing to look after Adelaide’s most prominent river. Explore our other projects.

Help look after our waterways

Everyone can play a part in looking after the River Torrens / Karrawirra Pari and our other creeks, rivers, wetlands and the ocean. Here’s how:

• Get rid of invasive exotic plants in your garden and replace them with native species that naturally filter water.
• Keep run-off surfaces free of pollutants – remember that stormwater flows directly to the nearest creek and the water is not treated, so bin your cigarette butts, clean up oil leaks, cut down on plastic usage and wash your car at a car wash or on a grassy/gravel area (not on the street).
• Consider installing a raingarden.
• Join a volunteer group to help care for the essential habitats for our native plants and animals.

If you have a waterway on your property, there are even more ways you can help keep our waterways clean.