RENO, August 1, 2014 (AFP) - The tournament uses the Modified Stableford scoring system, awarding points for birdies and eagles and deducting points for bogeys and worse.
Watney's effort gave him a total of 18 points and a good start toward a sixth career victory on the US tour, where he hasn't lifted a trophy since The Barclays in 2012.
"I'm very pleased with the way I played today, and this is pretty close to home," Watney said. "So it's nice to see a lot of friends and family. And I'm enjoying myself so far. And hope it continues like this."
Australia's Geoff Ogilvy and New Zealand's Tim Wilkinson were tied for second on 16 points. Scotland's Martin Laird and American Chad Campbell shared fourth on 13 points at Montreux Golf and Country Club.
There is a four-way tie for sixth between Kevin Chappell, John Huh, John Rollins and Wes Roach at 12 points.
Watney started strong. After a par at the first, he drained his first birdie of the day. He added another birdie at the fourth, then closed out the front nine with birdies at eight and nine.
Watney made it three birdies in a row at the 10th, and he birdied three straight from the 13th before capping his round with a birdie at the last.
"I played really well today. When I did miss a couple of greens, I missed a few greens early and chipped to within tap-ins and hit some really nice wedges. But that was the result of good driving," Watney said.
Ogilvy, whose seven PGA Tour wins include the 2006 US Open title, also had a bogey-free round to put himself in contention for a first US title since 2010.
Wilkinson's nine birdies included four in a row from the 10th through the 14th, but also had two bogeys.
Under the scoring system, players receive eight points for an albatross, five points for an eagle, two points for a birdie and zero for a par. A player loses one point for a bogey and two points for a double-bogey or worse.
Leading scores on Thursday in the first round of the US PGA Reno-Tahoe Open (USA unless noted, scores based on Modified Stableford points system):
18 points - Nick Watney
16 - Geoff Ogilvy (AUS), Tim Wilkinson (NZL)
13 - Martin Laird (SCO), Chad Campbell
12 - Kevin Chappell, John Huh, John Rollins, Wes Roach
11 - Tommy Gainey, Woody Austin, Derek Ernst, Danny Lee (NZL), George Coetzee (RSA), Eric Axley, Doug LaBelle, Patrick Rodgers, Nathan Green (AUS), Rod Pampling (AUS), D.H. Lee (KOR), Kevin Lucas
10 - Thorbjorn Olesen (DEN), Robert Streb, Jim Herman, Tim Petrovic, Bryce Molder, Johnson Wagner, Padraig Harrington (IRL), Nicholas Thompson, Miguel Angel Carballo (ARG)
(Points awarded: 8 for double eagle, 5 for eagle, 2 for birdie, 0 for par, -1 for bogey and -3 for double bogey or worse)