The Latrobe River in Australia’s south east discharges into the 380 km² Ramsar listed Gippsland Lakes. Significant alterations to the system since the mid-1800s include major river regulation and the permanent opening of the Gippsland Lakes to the sea. This has resulted in reduced freshwater inflows and increasing salinity in the lower reach of the river.

A concerted effort is being made to improve understanding of the lower Latrobe River’s response to riverine inflows, including coordinated environmental water releases from environmental water entitlements held in three (3) storages on three Latrobe River tributaries (Tanjil, Thomson and Macalister rivers).

A hydrodynamic model was developed to quantify the theoretical flow requirements to flush salt water from the river into the Gippsland Lakes. Year 2 of a three (3) year monitoring program to improve the calibration of this model is nearly complete. The program consists of five arrays of continuous flow and salinity loggers and event-based longitudinal salinity profiling over 17 km. A complementary study into the movement of Black bream (Acanthopagrus butcheri) in response to environmental flow releases is also underway.  This has involved fitting fifty Black bream with movement tracking tags.

The physical monitoring undertaken to date has found that the flow magnitudes estimated by the model are relatively accurate, and that flow duration is critical in attenuating the rate and extent of saltwater return.