"We know around half of this is being used for lawns, gardens, pools and for washing vehicles and boats. We need to make sure we can continue to supply water for homes and so we need people to reduce their outside water use."
Ms Porter says a key part of the decision to move to Alert Level 3 is ensuring supply can be maintained during routine maintenance, in the event of a breakdown or for firefighting purposes in an increasingly-dry region.
Chair of the city's Infrastructure Operations Committee, councillor Angela O'Leary, said "Council staff have held off changing to Alert Level 3 until now, while many other areas of the country have been implementing or increasing their restrictions, including total bans on outdoor water use in some places.
"Water is a precious resource and as a community we need to keep working towards being smarter and more sustainable about how we use it," Ms O'Leary said.
"The council teams will be monitoring the situation closely in coming days and weeks and I'd like to thank those Hamiltonians who are making the effort to conserve water in what is one of the driest and hottest spells our city has seen," Cr O'Leary says.
Hamilton City Council is reducing or eliminating water usage for many of its operations and developing action plans across the organisation to conserve water.
Hamilton's Water Alert Level will also affect residents in Tauwhare, Gordonton, Matangi, Tamahere, Newstead/Eureka, Wallace Rd and Stonebridge estate, as these areas are supplied by Hamilton's water network.
The Waikato District remains without a restriction, but earlier this week Waipa District Council warned its residents that if they do not cut back on water usage, then a total ban on outdoor water usage will be put in place.