When I was about 12, I worked as a greenskeeper. My responsibilities included and were limited to farting about in the barn at the top of the hill where Johnny Mooney -- The Greenskeeper -- housed and tended to the mowers. Back then, watering a green involved attaching a hose to a spigot buried somewhere nearby, and then dragging it Carl Spackler-style around the putting surface with just enough of your thumb pressed over the hole to create the Nozzle Effect (accidentally discovered in 1971 by theoretical hydrologist Dr. Garfield McCord while washing his VW Microbus). When your sneakers began to soak through, the job was done.
The keeping of the greens has changed quite a bit since then, but until recently the amount of water a playing surface required was still largely a matter of guesswork. The modern greens superintendant would take a look at the course, then the weather forecast, and set the timers on his automatic system according to his best guess. However, water's evolution into a commodity has new technology quickly popping up, so sprinkler heads do so less often. For instance, a company called UGMO is manufacturing underground sensors that give exact digital readouts of soil conditions, calculate the amount of water needed for healthy turf, and apply it with the accuracy of a rifle instead of scattershot-style. Grass that doesn't need water doesn't get it, in some cases reducing the amount of water used by a third, and electricity, too. These little ugmos are under the stadia that serve the Dodgers and Dolphins and beneath holy golf dirt such as Merion, Seminole, TPC Sawgrass, Los Angeles C.C., and coming soon to a golf course near you.