"That green lawn has got to go."

After three dry summers watching the water bills skyrocket as she battled to save the lush manicured grass surrounding her Denver home, Jan Dvorak has made a difficult but firm decision.

"We were always proud of the beautiful green grass outside," she says. "But eventually you come to realize that it makes no sense to keep a big, thirsty lawn in a part of the country where water is more precious than oil. Keeping a lawn in Colorado is like trying to grow cactus in Alaska."

Thus it was that Dvorak prepared detailed charts of her lawn and garden and paid $65 for a planning session with an expert who showed her how to switch from traditional green landscaping to "xeriscape" -- the use of plants and ground covers specifically chosen for the semi-arid climate of the southwestern United States.

The xeriscape revolution taking hold across this drought-stricken region promises to bring a startling new look to cities such as Denver, Phoenix, Salt Lake City and Los Angeles, where residential neighborhoods have traditionally been marked by block after curving block of pampered lawns of Kentucky bluegrass or similar species imported from the rainy East Coast.

"This whole section of the country is undergoing a paradigm shift," says Ken Ball, a Denver landscape architect who was one of the pioneers of the xeriscape concept two decades ago. The term, coined by the Denver Water Board in 1981, stems from the ancient Greek word for "dry," xeros.

"I'm not saying that people in the West want to give up their lawns," Ball continues. "But if this drought goes on like it has, they'll have no choice. The water districts are going to ban all watering. And all those turf lawns that drink tons of water are going to brown up and die."

Last summer's severe drought spawned wildfires across the parched West -- and left reservoirs from Dallas to San Diego at their lowest levels since the Dust Bowl of the 1930s. Heavy early snowfall last autumn initially raised hopes that spring snowmelt would refill the reservoirs this year. Since December, though, precipitation has been disappointing across the West.

At the start of February, reservoirs in Colorado were 30 percent below the average water level for this time of year, the state government says.

That's a little better than the bone-dry levels a year ago, but still so low that water-use restrictions are likely for 2003.

Because lawn watering is by far the biggest form of residential consumption, water districts have issued warnings that sprinkling could be limited or banned this summer. Homeowners are deciding that switching to xeriscape is better than watching their lawns endure a long, slow death by drought.

"We have been running xeriscape seminars every winter and spring for 10 years or more," says Chris Call, a conservation specialist with the Denver Water Board. "But this year, attendance has been triple what we've ever seen before. There's nothing like a drought to make people realize the time has come."

The grass is not greener on the xeriscape side of the fence -- indeed, green turf areas generally comprise less than half of a xeriscaped landscape plan -- but the new landscaping is not all brown, either.

"I always thought xeriscape meant rocks and cactus," said Denverite Diane Esquerra, who tore out her bluegrass lawn last fall "because the water bill was getting bigger than the car payment." But when Esquerra attended a recent seminar, she came away pleasantly surprised.

"The landscape guy showed us that we can have a lot of color," she said. "There are roses, and day lilies, and let's see, lavender, bright yellow daisies. Once they're established, you only have to water once in three weeks."

For gardeners who want to retain something like a lawn, there are grasses that require much less water than the standard bluegrass varieties.

"We often put in Canadian blue fescue," says Ball, the Denver landscape architect. "It will be green all summer with less than 50 percent of the water that a Kentucky bluegrass lawn requires."

Xeriscape also makes use of native grasses such as blue avena, blue grama and flame grass, which don't form the neat low carpet of traditional lawn grasses but do bring new hues of yellow, red and maroon to the yard.

The semi-arid gardens also feature the kind of perennial flowers described in seed catalogues as "drought tolerant," such as penstemon, evening primrose and gazania. Day lilies, which bloom reliably each morning throughout the summer with nary a drop of water, are among the xeriscape gardener's best friends.

But with hundreds of thousands of homeowners across the West making the switch, prices are rising for low-water plants. Ball estimates that the cost for complete conversion of a fairly standard quarter-acre lawn would run about $6,000.

And the xeriscape gardener faces a Catch-22: At first, at least, it takes a lot of water to save water. "After a year or two, the low-water plants will get by with much less," says Call, of the Denver Water Board. "But when they are newly planted, getting rooted, they need as much water as anything else."

Accordingly, the water commissioners here have issued a warning to homeowners thronging the xeriscape seminars. "We're telling people to make their plans and draw up a shopping list, but don't actually buy anything until mid-April," Call says.

"By then, we'll know how much snowmelt we've had, and we can predict how much watering will be allowed this summer. We may have to ban watering altogether. So we don't want people to go out and spend their money on plants that will never be able to establish themselves."

This Denver home switched from a lawn to "xeriscape" -- the use of plants and ground covers chosen for the semi-arid climate of the Southwest.After three dry summers watering and mowing her lawn, Jan Dvorak decided to give xeriscape a try.