Some of that investment is based on the hope proposals to boost irrigation in the district come to fruition.
If two dams are created and another one upgraded, a construction workforce of 200 will be needed, the Vincent Community Board heard yesterday.
Becks farmer and board member James Armstrong said 23 centre pivots were either operating now or planned this year on farms from Chatto Creek to St Bathans.
''If you work that out at $600,000 a pivot being spent ... some of that must filter into Alexandra,'' he said.
Mr Armstrong owned one of those pivots, which would make irrigation on his sheep and beef property more effective, he said.
One of his neighbours had bought three farms and was converting them into two dairy units, and would need seven houses on the combined properties to accommodate the workforce, he told the board.
He had heard of another Lauder farmer who would be bringing three families into the district to work on a farm.
''The change in the Omakau district is quite colossal.''
Manuherikia Catchment Water Strategy Group deputy chairman Gary Kelliher updated the board yesterday on proposals to boost irrigation in the two valleys.
A feasibility study into water management in the Manuherikia catchment was almost complete and an update on the project would be the focus of a public meeting at Omakau on Thursday.
Final dam designs and costs per hectare for existing and new irrigators were being finalised but the options include raising Falls Dam, near St Bathans, by up to 27m to increase its storage capacity and possibly building new dams at either end of the Ida Valley.
At present, about 10,000ha of the Manuherikia Valley is irrigated and that could increase to 25,000ha, while the 5000ha of Ida Valley land being irrigated could double if new dams are built.
''The key thing for us is to keep it cost-effective for irrigators and to protect the Manuherikia,'' Mr Kelliher said.
Land was already changing hands in anticipation of more intensive farming being possible when irrigation was boosted.
''People are doing something on the premise that we will have something sorted for them soon.''
His Springvale farm would be employing ''a couple more staff'' when land use intensified.
''It'll certainly be a very positive thing for the district.''
Asked by board member Stu Millis what Alexandra needed to do to cater for the expected growth, Mr Kelliher said it would need to accommodate a substantial workforce.
If work on all three dams went ahead - raising the Falls Dam and building dams in the Ida Valley, at Hope Creek, Poolburn and another at Hawkdun-Idaburn, a workforce of 200 people would be needed for construction.
Mr Kelliher said the valleys would be sporting ''a lot more'' centre pivots as landowners in the catchment realised they needed to move from flood irrigation to a more effective method.
Landowners would be asked in the middle of next year whether the cost of the upgraded irrigation supply was viable.
If the project gained resource consents, construction would take a couple of years.
