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Why and How to Promote Water Infiltration in the Garden?

By Céline Schaldembrand
Communication Campaigns and Projects Manager

According to NASA, 2020 was the hottest year on record. And the summer of 2021 again began with extreme temperatures, drought and water shortages throughout much of North America. In this context, a good gardener has to know how to make good use of the water in their yard!

Let Water Soak In!

Water infiltration has many benefits for everyone. First, any water that seeps into the ground will at least not carry away runoff. Runoff water brings with it all the contaminants and pollutants present on impermeable surfaces (concrete, asphalt, compacted soils, etc.) such as hydrocarbons and heavy metals from roads, excess pesticides and herbicides, particles of bitumen from asphalt shingle roofs as well as all the waste left behind by neglectful landowners. In fact, storm water (runoff following a major precipitation event) is one of the major sources of river and lake pollution. This pollution from runoff in turn leads to the degradation of water quality and leads to the loss of biodiversity and sometimes even to the prohibition of certain water uses such as fishing or swimming.

Some readers may have had the unpleasant experience of a sewer backing up in their basement because of a water overload in the sewer system during a heavy rainfall. Still others will have seen drinking water advisories imposed. Tap water is, after all, water: it comes from lakes, rivers or groundwater and always returns to those sources!

Conversely, the water that infiltrates the soil is cleansed of a large part of its contaminants thanks to the purifying nature of the plants and micro-organisms found in every type of soil. This filtered water helps recharge groundwater tables and unclogs municipal sewer systems! And that’s where the gardener comes in!

There are several options available to gardeners when it comes to increasing the amount of water that seeps into the soil:

1. Collecting Rainwater

Rain barrel in a rain storm
Rain barrel in a rain storm. Photo:

Installing a rain barrel or other reservoir on a roof downspout is very easy and inexpensive to do. Once the system is up and running, it will provide you with free, room-temperature water all summer long to quench your plants’ thirst. And water you can use freely, at that, as it is exempt from municipal watering restrictions!

You can also hook a rain barrel to a drip irrigation system or to a garden hose.

2. Prefer Native Species

In most areas in most years, there is more than enough to meet the needs of plants, provided the plants are local!

Native plants (ones naturally present in a given area) have the great advantage of being adapted to local climatic conditions and soil. In fact, they require less water and fewer chemicals (fertilizers and pesticides) in order to grow well. In addition, they better support insects and therefore the birds that visit our gardens.

The Canadian Wildlife Foundation has developed an online native plant encyclopedia that can be searched by province and plant category. In the US, the USDA’s Natural Resources Conservation Service offers a similar service through its PLANTS Database.

3. Plant Trees and Shrubs

Trees and shrubs, because they are larger, have a larger root system. In fact, they promote the infiltration of more water, in addition to being themselves more resistant to drought. They also reduce erosion, absorb carbon dioxide from the air and cool the air during hot weather.

4. Develop Your Own Rain Garden

Rain Garden.
Rain garden. Photo: OBV Matapédia-Restigouche

Rain gardens are planted arrangements created in a depression and designed to collect stormwater in the immediate aftermath of a heavy rain, then let the water drain away naturally over time. They can vary in size and shape and can include only edible plants, but most often consist of trees and shrubs. Plants chosen need to be able to tolerate being partly immersed for a certain period during their growing season.

5. Build a Filter Trench

Filter trench. Photo: OBV Matapédia-Restigouche

A filter trench plays the same role as a rain garden, but is more suitable for small yards. As the name suggests, it is usually elongated in shape and typically measures 15 inches (40 cm wide) and 30 inches (80 cm) deep. It usually consists of a filter material such as stones overtop an agricultural drain.

6. Add a Touch of Permeability to Your Hard Surfaces

Driveway with pavers for tire traffic and sod down the middle.
A driveway can be made largely of grass rather than concrete or asphalt and thus allow water to soak into the soil rather than run off. Photo: OBV Matapédia-Restigouche

When the time comes to renovate your driveway or patio, it’s the perfect occasion to consider alternatives to conventional surfacing materials such as concrete and asphalt.

There are currently several alternatives on the market that offer the same benefits as conventional permeable surfaces while promoting water infiltration and remaining esthetically pleasing.

Grass block pavers planted with grass
Grass block pavers planted with grass. Photo: AY Amazefoto/Shutterstock

This is particularly the case with grass block pavers (also known as turf block pavers or grow through pavers) with plentiful open spaces into which you can integrate grasses or even creeping or woolly thyme. Other ground covers are also possible, depending on the frequency of parking. These pavers are very attractive in addition to being extremely long-lasting, weather resistant, able to withstand snow removal and easy to install.

There are also pavers, such as interblocks, bricks or concrete blocks whose sand or gravel joints are more widely spaced and thus allow grass to grow and water to infiltrate.

Permeable paver with water flowing through it.
Permeable pavers let water flow right through them. Photo: JJ Harrison, Wikimedia Commons

Think too of permeable or porous pavers. You’ll find them on the market and they look quite similar to conventional pavers, but have the advantage of allowing water to flow right through into the ground below.

And consider using not a classic but impermeable cement walkway to your back door or tool shed, a surface that will just shed water, but rather stepping stones (flat pavers or flagstone) set in grass or some other groundcover. 

In addition to being very attractive, these products are easy to install yourself and, of course, allow most of the rainwater to infiltrate the soil.

As you can see, there are lots of means of making sure the precipitation that falls on your property stays on your property so it can soak in and benefit the environment rather than running off and causing problems. Which ones can you incorporate into your property?

Article provided by the Regroupement des organismes de bassins versants du Québec (ROBVQ) 
and translated and adapted from the French by Larry Hodgson.

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, will continue its mission of demystifying gardening and making it more accessible to all.

5 comments on “Why and How to Promote Water Infiltration in the Garden?

  1. I’m currently house hunting and it’s disheartening how many backyards have been mostly, or even completely, paved over. Even if you tear up all the concrete and paving stones and restore the yard to a green space, you’ll be sending a ton (possibly literally) of waste to the landfill. It’s a completely lose-lose situation because some people don’t want to have to bother with grass or a garden.

    • My yard was paved with asphalt (a surprise: we bought the house in the winter in a snowy climate: we had no idea). I broke it up (over several years) and used the pieces to create raised areas to add a bit of relief to an otherwise flat yard. Once covered in soil, plants grow well on them.

      • Thank you– that’s great to know. I would never have expected you could re-use asphalt that way. Gives me hope for whatever yard we might end up with 🙂

  2. I have let my weed killed stone chip drive green over. It is stunningly beautiful, covered in native flowers and butterflies. All rain water soaks down, no herbicides pollute the world and there is plenty of space to drive my car into the garage

  3. Rain water harvesting was a fad here for a while, and should make sense where rain is limited. The problem is that it is limited by season. All the rain falls within a very limited time, with none between March or April and October or so. So, if rain water is collected in big tanks during the rain season, all that water gets used early in the season, without replenishment. Then, the big empty tanks occupy garden space without really doing much of anything.

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