The study also indicated irrigation will affect the way farm land is used.
Existing unirrigated land use is 22 per cent dairy, 24 per cent sheep/beef, and 40 per cent mixed/arable.
If irrigated, dairy land use is expected to increase to 45 per cent and orchards to 3 per cent, while sheep and beef and mixed/arable will decline to 12 per cent and 30 per cent respectively.
Wairarapa Water Use Project director Michael Bassett-Foss said there would be an increase in migrant workers as dairy farming grew.
"There's definitely a boost in employment and population depending on the scale of irrigation."
The report suggests farm size will continue to increase, especially in irrigated areas, with more employees and fewer employers per hectare.
The economic study was not a cost-benefit analysis and did not include the cost of the schemes and therefore the cost of the water, Mr Bassett-Foss said.
Several recreation opportunities such as waka ama and dragon boating were identified, however angling, particularly at the Mangatarere site, was raised as an area of possible concern.
So far none of the five preferred storage sites in Tividale, Black Creek, Te Mara, Mangatarere and White Rock Rd have been discounted.
It was expected the list would be narrowed down to one or two sites by April or June next year, Mr Bassett-Foss said. "We don't need five sites so we are looking for the ones that are most cost appropriate."
The next stage of the project will be a full feasibility study, which is expected to begin in 2015.