Rotorua Rowing Club captain Glen Reichardt says clubs gain points by finishing first, second or third in each final.
He said the clubs with the most rowers were generally the ones which challenged for the top prize.
Rotorua had not won the Dewar Challenge Shield in about 10 years and many of the rowers were hopeful of changing that this year - with a group of 38 rowers from the club taking part.
Reichardt said about two-thirds of the rowers competing at the regatta this weekend were still in high school.
"It is a short course regatta so good for the juniors and a lot use it for build-up to the secondary school regattas," he said.
Reichardt said it was great to get big numbers along to the event, with about 680 entered.
"We got up to just under 900 one year but we had a really bad regatta, it got blown out, and it dropped back to about 400 the following year." He said it had been growing since then.
While each club has the opportunity to win the Dewar Challenge Shield, they are not allowed to take it home with them.
The winning club gets a chance to take photos with the massive shield after the regatta but the trophy is kept in Rotorua.
It went missing in the 1960s and was not recovered for about four decades. As a result, it is now kept safely in Rotorua.
Whakatane Rowing Club won the top award last year after a nail-biting finish. Heading into the final event - the men's open coxed eight final - Hawke's Bay Rowing Club were ahead of Whakatane on points. But a spirited bid led by two-time Olympian Jozef Klaassen saw Whakatane win the race to claim the Dewar Challenge Shield.
Heats will be held today with most finals staged tomorrow at the Blue Lake Rowing Regatta.
Racing starts at 8am, and runs until about 4pm today and 3pm tomorrow.
- Spectators are welcome to watch but the lake will be closed to the public during the regatta and will reopen at 5pm on Sunday.
