Kapiti Coast District Council will this week decide on how to secure the water supply of three of the district's main towns for the next 50 years.
The council will vote for one of four options on Thursday.
Technical consultants have recommended a scheme in which extra water is siphoned from the Waikanae River and replaced with bore water to maintain the river's statutory minimum flow. The River Recharge option is estimated to cost of $24 million.
Kapiti mayor Jenny Rowan says a plan to build a $33 million dam is also on the table.
Ms Rowan says the council will also on Thursday choose a back up option in case there are difficulties securing resource consent for their preferred choice.