Toronto's $1.3 billion Port Lands Flood Protection Project (PLFP) reached a significant milestone on Wednesday when water began to flow into the project's centrepiece, the artificial naturalized Don River mouth carved through former industrial lands.

The gradual process of filling the river mouth with water — one of the final steps before the serpentine river valley comes to life — began on January 31. Waterfront Toronto announced the start of pumping activity for the newly formed river valley on Wednesday, a process that could take several weeks.

The waterfront revitalization agency stated on Wednesday that "flooding the river is a slow and controlled process to protect the plants and riverbank materials we've installed."

Dams or plugs holding back the Don River to the north and Toronto Harbour to the west will only be removed once the river valley's plantings take hold in a process that Waterfront Toronto has warned may seem anticlimactic to some.

"Flooding the new mouth of the Don River is an exciting event – but not the dramatic gush of water many people imagine," reads the announcement. "We've been working towards this moment for years, and now you can follow along as we start the slow and careful process of adding water to the river we built," stated Waterfront Toronto.

Despite the lack of drama, many are indeed reacting to the news with excitement, cheering on a very visible progression for the new river valley.

Okay, this is really cool. After years of design, they're getting ready to flood the new mouth of the Don, in preparation to connect it back to the lake.

I'm excited!https://t.co/TbmfZfxKmd https://t.co/AUriQj0MHr

— Not Vex as in 🏳️‍🌈, but Vex as in 🏳️‍🌈 (@The_Terroirist) January 31, 2024

People can watch the river valley flooding progress from the Cherry South Bridge and the newly-opened Commissioners Street Bridge. Waterfront Toronto will also be releasing regular updates on the river filling for the public to keep tabs on the process.

While the flooding is indeed the most visible leap forward for the river valley, it is not the first section of the project to undergo this process.

A wetland area known as the Don Greenway was flooded in Fall 2023. This area — not normally connected to the river valley — acts as an emergency release valve during storm events, giving water rushing downstream from the Don a direct path into the Ship Channel, bypassing the snaking curves of the river valley.

The completion of the river mouth will eliminate a large floodplain and unlock 240 hectares of barren post-industrial lands for new development.