Wānaka's new Beacon Point drinking water reservoir has capacity for 5.5 million litres of water.
The new steel-plate reservoir was recently completed by Fulton Hogan, giving a significant boost to the capacity of 3.5 million litres already being provided by a concrete tank reservoir.
The water network infrastructure upgrade would prove critical for firefighting in a wildfire scenario, Queenstown Lakes District Council property and infrastructure manager Tony Avery said last week.
The additional capacity also means older infrastructure can be safely taken offline for maintenance if required.
The council and Fulton Hogan also completed two new steel-plate reservoirs in Glenorchy recently, replacing four concrete tanks and increasing capacity there from 90,000 litres to 500,000 litres.
"Council continues to invest in Three Waters infrastructure throughout the district, and the completion of these key projects will ensure we meet current and future water supply demands, while also providing for firefighting demands if the need arises," Mr Avery said.
With the arrival of a long, dry summer, everyone should continue using water but increased water usage could strain the infrastructure and increase the potential need for temporary water restrictions, he said.