She won four medals - three gold and a bronze - at the New Zealand rowing championships at Lake Ruataniwha.
The gold medals were in the women's under-22 eight, the women's under-20 coxless four and coxless pair. She also won a bronze medal in the women's premier coxless four.
The Kearneys live on a mixed farm close to Oamaru. Johannah and twin sister Caitlin started rowing five years ago under the eye of coach Stewart Mitchell at the Oamaru Rowing Club.
''Johannah was a star in the making from the outset,'' Mitchell said.
''She had a quiet and determined resolve and applied herself. Rowers like her don't come along too often.''
Johannah Kearney, who will study at the University of Otago this year, made her international debut in the coxless four at the world junior championships in Bulgaria last year. The stroke of the New Zealand crew was Holly Greenslade (Avon), whom Kearney beat in the women's under-20 pair on Saturday.
The Southern RPC crew of Kristen Froude and Kearney won the title in 7min 55.08sec from Holly Greenslade and Alice Darry (Avon), 7min 58.8sec. Auckland RPC was third in 8min 5.73sec.
The Wanaka Rowing Club was formed in 2007 and made history on Saturday when it won its first gold medal at a New Zealand championship.
The men's under-19 coxed four of Jamie Bowley, James Redai, Jarrod Wellman, Nic Jackson and cox Hamish Roulston won the title in 6min 45.57sec.
''It was six years in the making,'' coach Dave Varney said.
''It was a red-letter day for us.''
Bowley, Redai and Wellman started rowing three years ago and were in the combined Otago University-Wanaka novice eight that won a silver medal at the national championships at Lake Ruataniwha two years ago.
The crew had trained all season without a cox and Roulston (13)
came into the crew only three weeks ago.
It was level pegging in the race after 500m when Wanaka applied pressure and led by a length at halfway and three lengths at 1500m.
It was a successful final day with Otago provincial rowers winning an additional eight medals - four gold and four silver.
Otago rowers won a record 19 medals - 10 gold, seven silver and two bronze. It was the most gold medals won by Otago crews at a New Zealand championship. The previous best medal haul was at Lake Ruataniwha two years ago when Otago rowers collected 18 medals - seven gold, eight silver and three bronze.
There was also a milestone for Lucy Strack (North End), who won her first red coat in the Southern RPC premier women's eight. The other Otago rower in the crew was Fiona Bourke (Otago University), who won her second red coat.
Southern won convincingly in 6min 20.65sec from Central (6min 25.06sec) and Waikato (6min 25.71sec).
Bourke also won a silver medal when finishing behind Olympian Emma Twigg (Auckland), who won her fifth successive title in the women's premier single sculls.
Twigg won in 7min 28.42sec from Bourke (7min 33.78sec) and Waikato's Genevieve Armstrong (7min 39.67sec).
Hamish Bond (North End) won his 16th red coat when he stroked the Southern RPC crew to a win in the men's premier eight in 5min 40.22sec. It was a tight tussle with the Waikato RPC crew (5min 41.93sec). Auckland RPC was third in 5min 46.82sec.
The following crews won silver medals on Saturday: Emma Winders and Anna O'Leary (Otago) in the women's under-19 double sculls (8min 02.85sec); Zoe McBride and Hannah Duggan (Otago) in the women's under-20 double sculls (7min 19.66sec); Jack O'Leary and Eachann Bruce (Otago) in the men's club double sculls (6min 37.99sec).
NZ championships
Otago winners
Johannah Kearney (Oamaru), Jamie Bowley, James Redai, Jarrod Wellman, Nic Jackson, Hamish Roulston (Wanaka), Hamish Bond, Lucy Strack (North End), Fergus Fauvel, Fiona Bourke (Otago University), Zoe McBride (Otago).
