In these recent House Beautiful years, one landscape design element has become de rigueur, the item that no backyard can be without: the water feature.

This broadly encompassing term includes designs that range from fountains no bigger than a plaster rabbit employing a battery to dribble water over their surfaces to elaborate koi ponds that engulf an entire yard and seem on the verge of establishing their own ecosystems.

Jessica McGowan/Special (ENLARGE)

Harvey Siskin, shown in September, keeps a koi pond in his Atlanta backyard. In 70-degree weather, about 1/2 inch evaporates daily, he estimates.

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Gardening magazines tout the peace and sense of well-being people experience from the sound of running water. It attracts songbirds and masks the sound of traffic — always a plus in Atlanta.

We won't even broach the feng shui implications.

But now that we're in a historic drought, should we even have water features in our yards?

Do they lose too much of the precious commodity to spray and evaporation?

Is the elaborate water feature the gardening equivalent of driving a Hummer?

The answer: It depends.

Backyard fountains generally recirculate their water with little loss, says Bill Parker, an owner of Atlanta Water Gardens, installer of home water features.

"For the average fountain, the amount of water you'd lose to evaporation in a week's time is the equivalent of flushing your toilet once," Parker says.

Now that temperatures have gone down, he says, water holds more oxygen and evaporates less.

But larger water features, such as koi ponds, will lose a lot more to evaporation. The rule is simple: The larger the surface area, the faster the rate of evaporation.

Harvey Siskin, whose intown urban oasis was profiled this past September in The Atlanta Journal-Constitution, looks out to an 8,000-gallon koi pond with a waterfall, currently home to 27 koi. He also has a 900-gallon pond for his six red-eared slider turtles.

Because his ponds support living creatures, he is exempt from water-use restrictions.

So how much does he lose to evaporation?

During the 70-degree weather, he lost about 1/2 inch a day, he estimated. For his 20-by-24-foot koi pond, that translates to 20 cubic feet, or just shy of 150 gallons.

Siskin also must backwash his filter twice a week.

"At least I can release that water into the garden," says Siskin, adding, "It's just like fertilizer."

So the message seems to be this isn't a good time to consider installing a swimming pool or pond, but a small fountain won't put you amiss of conservation.

Even so, homeowners concerned about wastefulness during the drought have been less likely to install new fountains or ponds in recent months.

"I'd estimate that our business has been down around 15 percent this year," Parker says. "Still, we're a lot more fortunate than a number of other industries, such as irrigation. All we can hope is that next summer we'll be out of this."