The condensation forming inside the cups on a red-hot Oklahoma afternoon was the first clue that there’s something special about the putting greens at Southern Hills Country Club. The stark contrast between the air and soil temperature causing this effect is thanks to the innovative hydronic cooling (and heating) system installed during a major renovation in 2019. The system was the first of its kind to be deployed on all the greens of a golf course and many in the industry took note. Some, including myself, were a bit skeptical about its capabilities when it came to keeping creeping bentgrass happy in the 105-degree heat of a summer day in Tulsa, but seeing the system in action during the 2024 U.S. Women’s Amateur made a believer out of me.

During the championship, temperatures regularly soared into the 100s, but director of agronomy, Bryant Evans, was as cool under pressure as his greens. The hydronic system was the brainchild of previous Southern Hills superintendent, Russ Myers, whom Evans had worked for as an assistant in years past. Myers had seen the power of hydronics in action on a green at Augusta National and pushed hard for it to be part of Gil Hanse’s renovation of Southern Hills. “It was an absolute game changer,” said Myers. “Before hydronics, to get the conditions our golfers expected we had to keep the greens on the edge, we were always playing defense in summer.” The hydronics helped Evans and his team achieve superb putting surfaces throughout the U.S. Women’s Amateur without worrying about pushing them over the edge. To get a feel for how the system works, here are some key facts and figures.

Southern Hills Hydronics: By the Numbers

• The system is installed on all 26 of Southern Hills’ ‘Pure Distinction’ creeping bentgrass greens: 18 greens on the championship course, two practice greens, five short game greens and the nursery green.
  
  
• Four custom-built units, each containing air-to-water heat pumps, are positioned across the 300-acre property to cool or heat water which is then pumped to individual greens. In cooling mode, water leaves the units at 43 degrees F.
  
  
• The smallest unit services five greens while the largest feeds eight. Each contains multiple compressors and refrigerant circuits, modulating up or down to match changing load requirements.
  
  
• 2-inch polyethylene supply and return lines run from the units to underground manifolds next to each green that feed smaller tubing installed under the green. Heated or cooled water flows through the tubes under the green at 35 to 45 GPM to moderate the soil temperature.
  
  
• Over 38 miles of ¾-inch polyethylene raised temperature (PE-RT) tubing was laid under the greens in a circular pattern at 9-inch spacing and about 12 inches deep.
  
  
• In-ground soil sensors 4 inches below the surface show that, on average, the hydronic system keeps putting greens 12 to 15 degrees cooler than the greens without hydronics on Southern Hills’ West Nine course. This allows soil temperatures to be maintained between 65 and 80 degrees throughout the summer.