The region’s Vulnerable platypus population will be given a boost with a freshening flow down the Coliban River in mid-April.

Before the Millennium Drought, platypus foraging around the banks of the Coliban River downstream of Malmsbury Reservoir was a common sight.

However, climate change and challenging flow patterns have had an impact on them, and dams at either end isolate that section of the river preventing regular natural flows.

The lower Coliban River is one of the few regulated rivers in Victoria that does not have any water entitlements. 

It flows between Malmsbury and Eppalock reservoirs, and there are no irrigation customers and no water for the environment entitlements. 

However, passing flows, of up to 8ML/day, are managed for the health of the river. Passing flows can be partially accumulated for future use. 

The accumulated passing flows are then released at the right time to have the best-possible environmental impact for the river and the plants and animals that rely on it to survive.

North Central Catchment Management Authority (CMA) Water for the Environmental Project Manager Darren White said up to 260 megalitres of water will flow down the Coliban from mid to late April.

“The main target of this fresh is juvenile platypus. We know in at least one part of the river, directly below the Malmsbury Reservoir, there is a strong breeding population of platypus,” he said.

“This is the time of year when the juveniles start leaving home and we need to make sure there is enough water in the river to help them roam up and downstream.

“This flow will reconnect any pools and help make it easier for them to find food and explore new areas. And it will provide protection for them from predators.

“As we see low numbers across the state, this platypus population is one that really needs to be protected.”

The flow will also help other plants and animals in the river.

“It will also improve the health of the vegetation on the riverbank and scrape any slime off surfaces,” Mr White said.

“When the slime regrows, it’s brilliant food for waterbugs, which are key parts of the diet of platypus.”

The North Central CMA manages environmental flows on behalf of the Victorian Environmental Water Holder. The flows are authorised by VEWH in line with its Seasonal Watering Plan 2021-22. 

The Plan is available for download from www.vewh.vic.gov.au, with regular watering updates posted on the Current Flows section of the North Central CMA website.