The Rainwater Observer

“When designing rainwater collection systems for sustainable buildings, we should think about creating systems that require little to no maintenance and will perform their function without the continued input of outside energy. Passive rainwater harvesting is the perfect example of this concept.”

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by Jeremy Delost

Rainwater systems are often divided into two basic types- active systems and passive systems.  Active systems use pipes, tanks and pumps while passive systems use no moving parts and store the water in the soil rather than a tank.

Some common landscape elements that utilize passive rainwater collection are:

• Rain gardens
• Swales
• Permeable pavement
• Detention basins
• Injection wells

Once a rain garden, swale or infiltration basin has been created, it will detain, purify and slowly release water into the groundwater supply for an indefinite amount of time making it a long-term solution to our storm water problems.  Trees planted along a swale will grow quickly, providing shade to the soil and further improving the ecology of the site while the deep layer of fibrous roots helps to purify the water as it travels down the soil column. Maintenance costs are minimal and a smart landscape design will take advantage of perennial plants versus energy-intensive turf grass.

5 Things I Love About Passive Rainwater Systems

1. It is the least expensive way to collect rainwater because it uses the soil as the storage tank.
2. Water collected in a passive system is purified by plants and microbes.
3. It recharges the groundwater rather than creating storm water.
4. Passive rainwater harvesting is a long-term solution to water management.
5. Eliminates mowing and does not require a sprinkler system!

A Simple Example From My Front Yard

The green space between a residential street and the sidewalk is sometimes called a “parkway strip”.  The parkway strip provides protection for pedestrians and a place for dogs to relieve themselves outdoors.  It is not uncommon for this narrow (4 ft.) strip of land to be regularly irrigated, mowed, trimmed and fertilized along with the rest of the yard.

Last year, we decided to remove the grass in the parkway strip in front of our house, then excavate some of the top soil to create a basin and back fill with a mixture of gravel, compost and native soil .  Then we planted with native plants from small one-gallon pots and finally covered the soil with mulch.  Since the sidewalk is sloped towards my parkway strip, the water from the sidewalk goes into the garden and trickles down into the soil helping the native plants send their roots deep into the soil.  Before I installed this passive rainwater collection system, rainwater would run down the sidewalk and out into the street since the parkway strip was raised slightly higher than the sidewalk.

Here’s how it looked before I started.

Here is how it looks after 12 months of establishment.