Rainwater harvesting: Rain gardens combine form & function

Rainwater harvesting is becoming an important consideration in many parts of the world, including South Africa.  Whether rain is used for rain gardens or whether it is stored in rain water tanks for domestic or industrial use, rainwater harvesting has many beneficial environmental and financial aspects.
There are photos of many garden design ideas, including a fairly new topic new to many — rain gardens. Now is the time that many gardeners start planning for the spring season and the addition of new gardens and rain gardens are worth a look. Not only can they beautify a yard, but also provide real environmental benefits.

Each time it rains, large quantities water flows off impermeable surfaces such as roofs, driveways and patios. On its way to nearest storm drain, it collects garden chemicals, oils, dirt and bacteria which in many cases end up directly in nearby rivers or other bodies of water. These chemicals can have a devastating effect on the organisms, fish and wildlife that call the river home. Rain gardens can prevent some of this water from reaching the storm drain in the first place, creating healthier waterways.

A rain garden is nothing like a water garden, pond or wetland, in fact the majority of the time it’s dry. Planted in a small depression, the garden contains native shrubs, perennials and flowers and is most often found on a natural slope. The garden only holds water for a short period of time during and immediately after it rains. The advantage of a rain garden is that it allows the collection of rainwater so that it can slowly percolate into the ground, recharging underground aquifers. The gardens have been proven effective at removing 90 per cent of chemicals from rainwater runoff and up to 80 per cent of sediments, neither of which we want flowing into our rivers and streams.

The design of a rain garden is quite different from a traditional garden, mostly because of the type of soil used and its shape. In most cases, six inches to as much as a foot of soil is removed and replaced with tillage, compost and sand. This varies depending on soil conditions at your location. If the soil is sandier, and naturally allows water to easily filter through, less will have to be removed and replaced.

Native plants are key to any rain garden. These plants are naturally hardy, don’t typically require fertilizers and are better at using the water that already exists in the soil, not requiring to be watered frequently. Native plants also require less maintenance than their non-native, exotic counterparts.

When designing a rain garden, size is key. The garden should have a size of at least 20 per cent of the roof, patio or driveway draining into it. Generally, the size for a home is between 100 and 400 square feet. The garden should be shaped longer than it is wide to catch as much rain as possible and be placed at least 10 feet from any structure.

When designing a rain keep the following best practices in mind:

• The site is fed by one or two downspouts.
• There are no heavy clay soils.
• The water table is at least two feet from the surface at its shallowest.
• The slope of the site is not more than 12 per cent.
• The site is at least 10 feet from buildings with basements.
• The site is not over any utilities.
• The site is not over or near a septic tank, drain field, or wellhead.
• The site does not interfere with any trees.

As we move further into spring and gardeners are looking for something to keep their green thumbs busy, planning the addition of a rain garden is worth considering. Not only will it be a beautiful addition to any property, it also has important environmental benefits.

Source: St. Albert Leader

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