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.