Environmental Issues: Water

Advanced Ways to Clean Up Our Water
Three ambitious projects to reduce the flow of polluted runoff.

Runoff from lawns, sidewalks, roads and driveways is a major contributor to surface water pollution. By making some simple changes to your everyday activities, you can reduce the flow of runoff. But if you're willing to commit a bit more time and money, you can take an even bigger dent out of the runoff problem. Here are three advanced suggestions.

Install A Water Storage Cistern
Photo of a rain barrelCisterns collect rainwater from rooftops, driveways and patios before it becomes runoff. The cistern itself is a storage tank that is part of a larger rainwater collection system. A pump and a system of pipes deliver the water from the tank to a faucet or sprinkler for household uses other than drinking water. Cisterns reduce runoff, but they have the added benefit of lowering household water consumption. They can also come in handy as an extra water source during dry periods, when water from your local utility might be rationed and watering lawns, washing cars or filling pools might be prohibited. Most cisterns are below ground, but they can also be placed above ground. Residential cisterns come in sizes that range from 100 to 1,400 gallons.

Plant A Rain Garden
Bioretention areas, also known as rain gardens, are low-lying areas of soil and vegetation that are constructed in yards or gardens to channel and collect polluted runoff. When runoff flows from downspouts and off driveways and patios, the plants in the garden block the water flow, slowing it and allowing it to filter into the ground, rather than washing quickly over the surface and carrying pollutants to street gutters and storm drains. Rain garden plants and soil also filter pollutants from water that passes through them. The typical rain garden is composed of trees, shrubs and grasses planted in a medium that includes layers of gravel, sand and soil. Local soil types, native plant species, site conditions and nearby land uses influence rain garden design.

Install A Vegetated Roof
Installing a vegetated roof, or green roof, may sound extreme, but it's a proven way to curtail polluted runoff in congested urban areas. These systems use plants in a lightweight soil mixture to absorb and slow runoff that would otherwise pour from rooftops. They typically consist of three layers: subsurface drainage, soil and plants. The vegetated roof mimics vegetation's natural ability to capture and hold precipitation. For small amounts of rain, little runoff occurs. During heavier storms, the roofs reduce runoff volume. The systems conserve energy in winter by insulating rooftops. They also protect the underlying roof from the elements, extending its life by several years. Vegetated roofs are especially effective on extensive roofs in urban areas, where space for other stormwater runoff controls is limited. If you'd like to explore this idea, we suggest you consult an expert. You'll need the experience of someone who is familiar with such systems to tackle considerations such as the load-bearing capacity of your roof and the design of the system itself.

If you'd like to read more about the types of projects briefly described above for decreasing polluted runoff, see the U.S. EPA's report Low Impact Development as well as its fact sheets on Vegetated Roof Covers and Bioretention Applications. (These publications, which contain additional sources and contacts, are available in Adobe Acrobat format.)

Related NRDC Pages
How to Clean Up Our Water

Related Websites
The Low Impact Development Center offers publications and fact sheets

Photo: Courtesy of Larry S. Coffman, Prince George's County, MD

last revised 4.11.01

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