I know this because it was printed on my free map of the slopes, but I was also reminded by Dave, a square-jawed young American. We were travelling up the mountainside in a gondola towards the 11,053ft summit; he, smart and confident in the bright blue uniform of a "host" (one of a team hired to keep an eye on ordinary skiers); me, bulging in an ill-fitting and out-of-date jump suit.
"If I hear someone cussing, I'll put a slash across his ski pass [one- day price: $40] as a warning," Dave explained happily. "Most people only do it because they are so excited. But if they continue, I'll tear up their pass - at least, if they're using four- letter words. We want this to be a place where families can enjoy themselves."
These are, of course, admirable sentiments. But in the circumstances they were also rather unreasonable. For, peering out of the gondola windows at the surrounding white expanse, it was almost impossible not to utter an expletive in sheer amazement. Those little green bushes in the snow below were not, as they seemed, young Christmas trees, but full grown 30ft pines, buried to their leaf-tips.
This year, parts of the Sierra Nevada mountains, a range that begins north of the Mojave Desert in eastern California and runs northwards for 400 miles, have been covered by more than 20ft of snow. This is not merely good news for the thousands of wealthy young southern Californians, who pour northwards in their Jeeps and Broncos to their winter playground, and who can now look forward to skiing on 4 July, Independence Day; it is also a godsend for the vast metropolis of Los Angeles. This year's heavy rains have ensured - albeit briefly - that the desert city, so often plagued by drought, can be sure that it has a healthy supply of the one commodity it usually lacks: water.
To get to Mammoth, the skiers weaving around the slopes beneath our gondola had completed a journey that should have reminded them that this is a profoundly serious issue in America's far west. Most of the resort's visitors come from the LA area, and make the five-hour journey northwards up the Interstate 395 and along the arid bottom of the Owens River Valley, scene of the most bitter war over water in US history.
Ninety-odd years ago, the valley was a thriving farming community, marketed by eager estate agents to newcomers as America's Switzerland. But that was before LA city officials covertly bought up most of the local land and water rights and built a 233-mile aqueduct, channelling the water southwards to their rapidly expanding city. These days it is one of a complex of giant canals and aqueducts which feed water from the Rockies and Sierras to heavily-populated southern California.
Evidence of this huge water grab - which prompted a spate of bombings during the Twenties and was the theme of the movie Chinatown - is still impossible to avoid. The highway sweeps across mile after mile of barren waste, a seemingly endless expanse of rubble and sagebrush. There are no fruit orchards, no wheat fields, and little agriculture beyond grazing. What were once the valley's booming farming towns are now service centres, mostly comprising motels, garages, fast food joints and bric--brac shops for tourists.
To what extent any of this worries Mammoth's non-swearing guests as they sweep through the valley floor in their smart new four-wheel drive vehicles is hard to assess, but there are precious few signs they care. You only have to drive the other way down the highway - south into LA - past the swimming pools, the scores of golf courses, the endless lush gardens, to realise that the recent seven years of drought has done nothing to abate the city's profligate use of water. At the moment the city's reservoirs are full to bursting, but LA will eventually suffer for this - when the next dry spell comes along, and the snow is not so thick at the top of Mammoth Mountain.