Olivia Mehaffey took a giant step towards returning to the world's top 10 when she beat Stanford's Albane Valenzuela at the first extra hole to win the prestigious Pac-12 Women's Golf Championship at Palos Verdes Golf Club in California.

The Banbridge native (21) fired rounds of 69 and 70 to go into the final round four strokes behind Switzerland's Valenzuela, the world number five.

But she slowly clawed her way closer to the lead and after making a long birdie putt at the 16th, she closed with a one-under 70 to post a four-under par target that heaped the pressure on her opponent.

Playing some 50 minutes behind Mehaffey, Valenzuela slipped to a 74 and in the playoff at the 401-yard 18th, she bogeyed and Mehaffey got up and down after going through the green, nervelessly holing a six footer for her third collegiate victory and her second in her last five starts.

Pac-12 Championship scores

"I had no idea all day," Mehaffey said of her final round quest to catch the leader. "I was just trying to hit greens and play as well as I could. I was just very focussed on each hole and very present. So I really had no idea.

"I made a really good birdie on 16 and a really good par save on 17 to get myself into a playoff, so that was an amazing feeling.

"I actually struggled with my putting a little bit this week and I have been hitting it really nicely so to make those putts when you need to make them is a really good feeling."

Looking for now to helping ASU challenge for another NCAA Division I title, she said: "It's nice to know I am in some good form now, especially when things get exciting in the season."

After beating a field that  included 22 Top-100 players including the US collegiate No. 1 Andrea Lee, she joins an illustrious list of winners which includes Annika Sorenstam (1992), Grace Park (1999), Lorena Ochoa (2001) and ASU's Carlota Ciganda (2009, 2010).

ASU also took the team title and coach  Missy Farr-Kaye was thrilled for her team, who finished third, and for Mehaffey.

"We are thrilled with Olivia winning her first Pac-12 championship," she said. "She fought hard all week and it paid off. It is a great accomplishment winning the championship because it is the strongest conference in the country.

"As a team we also finished strong beating two teams that are ranked ahead of us. I love how we played today and I want us to continue our great play and fight when we head to NCAA Regionals in two weeks."

Meanwhile, Forrest Little's Julie McCarthy continued her hot run of form when she opened with a four-under 68 to lead the SEC Championship at Greystone Golf & Country Club in Birmingham, Alabama.

SEC Championship scores

Just a week after winning her maiden collegiate title for Auburn University, the Clemson Invitational, McCarthy's brilliant effort helped them take a share of the lead with Florida.

"It's brilliant for us," McCarthy said. "We had always wanted to start strong. We had the same idea at Clemson last week because we knew the weather was coming in, and so I think it's just a great start and we'll try to keep it going."

McCarthy, now ranked No. 4 in the US, finished the round with five birdies, including a hole-out from a bunker at the 14th. She has now shot par or better in nine of her 13 rounds this spring.