Hobart’s waterbug wonderland reveals secrets of our rivulets

Published on 23 May 2023

The City of Hobart has released its first ever report into the ecological health of Hobart’s four major rivulets: New Town Rivulet, Sandy Bay Rivulet, the Hobart Rivulet and Lambert Rivulet.

“The science behind this report uses the tiny waterbugs native to our rivulets as telltales of the environmental health of our inland waterways,” City of Hobart Water Portfolio Chair Councillor Ben Lohberger said.

“Waterbugs sensitive to negative impacts on water health such as pollution and erosion are like canaries in the coal mine, with their numbers and diversity declining as rivulet health declines.”

The report found all four rivulets were healthier upstream than downstream, with the Hobart and New Town rivulets degrading gradually from the naturally forested headwaters in Wellington Park to their urbanised mouths at the River Derwent.

It found that Sandy Bay and Lambert rivulets suffer more abrupt changes once their waters reach urbanised areas than New Town and Hobart rivulets.

Cr Lohberger said the report sets an important baseline for the management of Hobart’s rivulet system.

“The results of our first ever surveys of the ecological health of Hobart’s inland waterways provide a comprehensive report into the condition of our major rivulets,” Cr Lohberger said.

“This report clearly demonstrates the importance of protecting the upper reaches of our rivulets where they are at their healthiest and taking action downstream to reduce pollutants from entering our waterways.”

The rivulet surveys, conducted in spring 2022, identified a drop in ecological health on New Town Rivulet directly below the Girrabong stormwater outflow.

They also identified the presence of invasive willow trees as potential culprits behind a clear drop in ecological health in Guy Fawkes Rivulet.

The report recommends:

• Removing willows from Hobart’s rivulets will improve ecological indicators over time.
• Revegetating rivulet banks and increasing canopy cover over waterways will create habitat for waterbugs and other aquatic wildlife, such as platypus.
• Surveys should be carried out annually to provide increasingly valuable information about the health of Hobart’s rivulets.

“The City of Hobart will build on this report by producing annual snapshots of our rivulets,” Cr Lohberger said.

“These annual rivulet snapshots will reveal stronger trends in improved health or declines of Hobart’s rivulets, aid water management decisions and help to improve the health of our precious waterways.”

>> Download the full report

>> Download the map