The rain garden, a new type of garden springing up in yards across the country, can improve quality of lakes and streams and protect drinking water supplies — while adding an attractive, low-maintenance landscape feature to lawns and gardens.

“It’s beautiful,” said Roger Bannerman, describing a rain garden in his yard on Madison’s West Side. “The rain garden blooms all summer long with blazing star, black-eyed Susans and aster.”

Bannerman says the concept is catching on. “I think a lot more people will be making rain gardens.”

Rain gardens are designed to receive and filter rainwater from rooftops, driveways and other impermeable surfaces. Typically, rain gardens incorporate a dip or depression to catch rain run-off. Experts recommend hardy native perennials for rain gardens because they will be better able to withstand extreme weather conditions and survive with minimal maintenance. Rain gardens don’t require watering or fertilizer, and they typically need mowing only once a year.

Yet Bannerman appreciates his rain garden for more than its beauty. As a water pollution specialist with the Wisconsin Department of Natural Resources, Bannerman knows how beneficial the rain garden is for water quality. He says rain gardens can counteract the harmful effects of development on waterways.

“There’s a pretty good body of evidence that increased urbanization hurts the quality of lakes and streams,” Bannerman said.

When cornfields, marshes or meadows are paved over or developed into houses, strip malls and office buildings, the land is removed from the natural water cycle.

Under natural conditions, rain and snow melt percolate slowly into the ground, allowing the water to be gradually filtered as it makes its way to the water table underground. But when the soil is covered with impermeable surfaces, the water doesn’t get filtered, nor does it replenish the water table — instead it rushes into the nearest water body, picking up pollutants along the way.

During rainstorms, water that pours from roof downspouts and driveways often flows directly into street gutters. These small but rushing torrents can carry sediment, nutrients, toxic metals and other pollutants into creeks, rivers and lakes.

This sudden influx of warm, dirty water kills fish and other wildlife, while the added nutrients from lawns and soil feeds bacteria and algal growth. Scientists say that’s one reason that lakes in urbanized areas become choked with lake weeds and algae.

Most developments contribute to water pollution, according to Bannerman, but with rain gardens and other landscaping features, run-off pollution can be reduced “by maybe 90 percent without much trouble at all.”

Rain gardens reduce run-off pollution from residential areas by encouraging the natural process of rain infiltration. The gardens, set in a low area in the yard, are designed to receive the rain as it comes down roof gutter downspouts or off of driveways and parking areas. Then, when, rainwater flows into the rain garden, it helps plants grow while it slowly percolates into the ground, filtering and recharging our ground water — the primary source of drinking water.

To construct a rain garden in his yard, Bannerman dug a shallow depression, 2 to 3 inches deep, with a level bottom. Then, he used the dirt he dug out to create a berm or small hill on the downside slope to keep water in. “It’s a very simple idea,” he said.

Rain garden plantings can include ornamental grasses, wet-loving prairie plants and other perennials, such as cardinal flower and Joe-pye-weed. As an added bonus, rain gardens provide habitat for wildlife such as birds, butterflies and other insects.

During the first couple of years, the rain garden requires regular tending as the perennial plants get established, but, according to Bannerman, “at some point the plants will get dense enough so the weeds can’t grow.” He looks forward to that time when maintenance is “next to nothing.” And, in the bargain, he’ll be making Dane County waterways cleaner while enjoying an improved view from his window.