Over the past 6 years, Melbourne Water have been implementing a framework developed by Jacobs to determine and implement water regime management objectives at billabongs in the Melbourne Water catchment. This paper presents the ecological and hydrological responses and key learnings of implementing water regime management objectives at 3 billabongs along the Yarra River; Spadoni’s, Bolin Bolin and Banyule Billabongs. All 3 billabongs have experienced a decrease in frequency of inundation due to river regulation and extraction for water supply. As such, the preferred water regime is to increase the frequency of inundation events.
In 2016 capital works were undertaken at Spadoni’s Billabong to lower the inlet level to allow for overbank flows from the river to enter the billabong more frequently. This has been successful with inflows occurring in 2016 and 2017 that would have otherwise not entered the billabong. Determining water regime management objectives at Bolin Bolin and Banyule Billabongs were more challenging due to the billabong locations higher in the landscape and greater impacts of river regulation on peak flow level. Pumping trials from the river were undertaken to provide information on seepage rates and billabong volumes, and feature surveys were completed on inlet/outlet areas to help inform the feasibility of permanent structures. Based on the information collated, structural works to lower the inlet level at Bolin Bolin Billabong is recommended. For Banyule Billabong, lowering if the inlet level was considered unfeasible, however, the billabong could be inundated more frequently if connected to the local stormwater catchment.