The North Central Catchment Management Authority will deliver the flow to more than 10 wetlands in the lower forest between Cohuna and Koondrook, via the Reedy Lagoon, Barapa Swamp, Little Gunbower and Yarran Creek regulators.
North Central CMA chief executive officer Brad Drust said the watering would build on what July's natural flooding had begun.
"The recent inflows have been a great start in helping protect the floodplain wetlands from a possible El Niño this summer, and we now have an opportunity to make it even better," Mr Drust said.
"The flows would have been higher and stayed on the floodplain longer without river regulation, so we have the opportunity to help Mother Nature finish what she started and ensure the wetlands get the right amount of water they need, for the duration they need it.
"Managing an efficient environmental flow from now until November allows us to piggy-back on the recent high-river flows and top-up wetlands, helping to prepare them for what could be a dry period ahead."
Among the wetlands set to benefit is Reedy Lagoon, which Mr Drust described as the jewel in the forest's crown, after it received minimal inflows in July.
He said the watering would create the conditions wetland plants and animals, such as waterbirds, frogs and turtles, needed heading into spring.
The flow is modest by the international floodplain standards, falling short of the forest's full environmental watering footprint of about 23 per cent of the overall forest.
"It is simply a top-up of wetland areas that, before river regulation, would have received water nine out of every 10 years," Mr Drust said.
Visitors can still expect full access to most of the forest, with main routes including River Track, Koondrook Track and Nursery Track not expected to be affected.
Small sections of some access tracks may be temporarily closed as water moves between wetlands through natural connecting creeks.
"Gunbower Forest is open for business and spring is a great time to see the forest come to life," Mr Drust said.
The flow is authorised by the Victorian Environmental Water Holder under its Seasonal Watering Plan 2026-27.
The Goulburn Valley Environment Group, or GVEG, is calling for environmental top-up flows in the Goulburn River at Shepparton.
