Next month, 120 farms will start drawing water from the first stage of Canterbury's central plains irrigation scheme.
The completed scheme will eventually irrigate about 60,000 hectares of farmland.
The first stage, which includes a 17km canal and 130km of pipeline, will irrigate around 20,000 hectares between the Rakaia and Hororata Rivers.
Central Plains Water chief executive Derek Crombie said 90 percent of the water from stage one had been allocated.
About 120 individual properties were connected up to the scheme which Mr Crombie said had had outstanding support from the farmers.
"Each of the farms gets 5mm of rain per hectare per day. That's equivalent to a light rainfall each day. Across the district it works out to be about 10 cubic metres per second in the head race when you add all the individual farms together."
"The overall predictions are that there will be equivalent of $1 billion a year of increased productivity across the whole scheme. It's about 1000 new jobs that are developed. So it will have a big impact."