Irish Water is going ahead with plans to bring water from the River Shannon to Dublin and the Midlands.
The €1.3 billion pipeline will supply 40% of the population from 2025.
The plans will see water taken from the Parteen basin in North Tipperary and pumped up to 170 kilometres to the Midlands and Greater Dublin area.
Irish Water says it will offer a "secure, reliable and sustainable long-term" water supply.
The company is hoping to submit a planning application for the project in 2019.
Critics have said the money would be better spent repairing leaks in the capital.
However, Irish Water's Sean Laffey argued: “The future water needs of Dublin and the Midlands cannot be met by fixing leaks alone. Leakage in the Greater Dublin Area network is at 36% and there are 9,000km of water pipes with over 600,000 connections."
He said that the agency is rolling out a 'comprehensive Leakage Reduction Programme', but added: "This industry standard approach is the most technically and economically achievable way of managing network leakage and will deliver major savings through a number of investment cycles. However, this cannot keep pace with growth needs."