It quickly became clear the girls were in trouble and the New Zealand bodybuilding champion leapt into action.
Sprinting about 50m down a bank to the water, Ms Dowling - also a qualified lifeguard - threw off her shoes and dived in.
Two of the girls had reached the shore but swam back out to help their friend and were unable to make it back.
"It was almost like an eddy, the water was just swirling around. I could see them trying to swim but it was just pulling them back to the middle of the river. The two girls were trying to hold their friend up. She was swallowing water and choking."
Ms Dowling and another woman swam out to the trio. The constable told the two girls who could swim to head ashore, the other woman helped them. Another woman on the riverbank called 111 and ran to get lifejackets from a nearby jetboat operator, while Ms Dowling dragged the struggling 13-year-old through the water.
"My energy was draining big-time. The lady was standing on the shore holding a lifejacket and I said, 'throw me that'. That gave us just that little bit of buoyancy to get us back to shore."
The teenager was treated by paramedics at the scene, then taken to Waikato Hospital.
After the event Ms Dowling told Coastal News she had only done what anyone would have done in the same situation.
"The girl was exhausted and going nowhere but down. You don't just stand there and watch a child drown. The first thing I did when I reached her was promise I would help her. But at one point I thought we were both going to go under. It was a very frightening experience."
The citation for her award, signed off by police commissioner Mike Bush, says: "Without a doubt, Constable Dowling saved the life of at least one of the girls. Her actions were in the highest traditions of New Zealand Police."
The award was made at the Waikato district Police Pay Parade at the Hamilton Gardens pavilion.
At the event, 23 police staff members were recognised for service ranging from 14 to 42 years.
