"Presented by the USGA" (the United States Golf Association) gave me a wry chuckle there.

That said, here are the relevant numbers from that 2012 article in full:

> Most 18-hole golf facilities utilize surface waters (ponds, lakes) or on-site irrigation wells. Approximately 14 percent of golf facilities use water from a public municipal source and approximately 12 percent use recycled water as a source for irrigation.

> Specific water sources for 18-hole courses as indicated by participants are noted below:

> 52 percent use water from ponds or lakes.

> 46 percent use water from on-site wells.

> 17 percent use water from rivers, streams and creeks.

> 14 percent use water from municipal water systems.

> 12 percent use recycled water for irrigation.

It depends on the region. In dryer regions most golf courses are already on greywater system. Irrigation mainly targets fairways, teeboxes, and greens, while the rough is allowed to go to hell in the dryer months.

Some golf courses also are designed to spread floodwater and protect surrounding development. Golf is sort of a happy bonus on top of that.

Private courses are usually far better irrigated than their public counterparts where even the fairway is liable to be left to dry out.