When Waters crashed spectacularly just a few laps into the race, Townley inherited second spot and it was just a matter of time before he hunted down and eventually passed the British GP star.
Townley stretched his advantage to win the race comfortably, but, he confessed afterwards, he had been made to work hard for it.
"I've left things a little bit later in my build-up for the nationals [which start near Timaru in just two weeks] and I guess that showed today," he said.
"It was certainly a tough day at the office.
"I feel pretty battered and bruised. I was hitting track marker pegs all over the place."
Meanwhile, it perhaps came as no surprise that world MX2 No4 Nicholls won the MX2 class, taking three wins from three starts.
In the senior 125cc class it was Atiamuri's Hadleigh Knight (CMR Red Bull KTM) who dominated, winning the day's first two races and then settling for third in the final outing.
The top women's class rider was Taupo's Alex Dillon (Honda CRF250), who won ahead of Atiamuri's Nikita Knight (KTM 250) and Rotorua's Mel Patterson (BikesportNZ.com KTM 250).
As expected, Pahiatua's United States cross-country champion Paul Whibley (Sargent Yamaha BikesportNZ.com YZ450F) won the separate river race event.