Organisers hope there will be more than 2000 competitors for the first time and, counting spectators for the semifinals and finals, that 8000 to 10,000 people will be attracted to a town that has a permanent population of about 1100.
The Maadi Cup has attracted secondary school rowers from more than 100 schools.
In 2008, the last time the regatta was held at Lake Ruataniwha, there were about 1700 rowers competing from 105 schools.
Rowing starts on Monday, with the finals being held next weekend.
Ruataniwha rowing centre manager Trevor Wilson said competition had got so tough, some teams and their support crews were arriving today, to train and prepare for the event on the international course.
All accommodation in Twizel, and as far away as Otematata and Tekapo, has been booked.
Some schools are even renting farm accommodation, such as shearers' quarters, to house their teams.
"There is more interest because of the world championships at Lake Karapiro later this year," he said.
The event will have more than 400 races, starting with between 120 and 130 on the first day.
No study had been done on how much the event was worth to Twizel.
"We may be too scared to," Wilson said.
But it had been estimated people could spend up to $1000 each during the week.
The Twizel regatta will continue with the tradition, started last year at Lake Karapiro, of a dawn service at 6.30am on Monday to honour those who served in World War 2, from whom the Maadi Cup was passed.
