Davis was joined on the site tour by former Regional Economic Development Minister Shane Jones, who secured a PGF loan for the water storage scheme while in government.
Once the access road is complete work on the dam itself can begin.
The Te Tai Tokerau Water Trust, which plans a number of reservoirs and water schemes around the drought-prone Mid North and Kaipara, hopes Matawii will be operational by summer 2021-22.
The 750,000cu m reservoir will be filled by pumping water from nearby streams in times of high flow.
Trustee Dover Samuels, a former MP for Te Tai Tokerau, said the project would bring new investment and opportunity.
"You just have to look at Kerikeri to see what a reliable source of water can do for a community,'' he said.
Reservoirs planned by the trust would allow a combined 7000ha of land to be converted to high-value horticulture.
The trust has asked the Minister for the Environment for permission to apply for fast-tracked consent for two more reservoirs in the Mid North — Ōtawere near Waimate North and Te Ruaotehauhau near Ōhaeawai. A decision is expected this month.
If built, Te Ruaotehauhau would cover about 30ha and hold 1.4 million cubic metres of water, making it almost twice the size of Matawii.
The trust is also looking into building a reservoir north-west of Kaikohe which would be called Rakauwhai.
That project is in its earliest stages with the trust talking with affected parties about feasibility.
The site is currently owned by state farming company Pamu, formerly LandCorp, so the land could be included in a future Treaty settlement. That means the project can't be considered for fast-tracked consent.
The trust has submitted an application through the normal channels — in this case the Kaipara District and Northland Regional councils — to build a reservoir near Glinks Gully, south of Dargaville.
Fast-tracking was not required in that case because it is a relatively simple project. The trust hopes construction will start before winter.
The Glinks Gully reservoir could be expanded in future if demand for water in the area grows.