Conserve water, support your local ecosystem, and grow a more sustainable garden with rainwater harvesting. Here are 8 key principles to getting started…
As gardeners, we understand the significance of water for our plants’ growth and health. Yet, in many regions around the world, water scarcity remains a pressing concern. In an era where sustainability is paramount, finding innovative ways to conserve and utilize natural resources has become crucial. This is where rainwater harvesting comes in.
Rainwater harvesting is a centuries-old technique that has gained renewed attention in recent years, primarily due to its environmental benefits and cost-effectiveness. By capturing and storing rainwater, we can not only reduce our reliance on traditional water sources but also minimize the strain on local water supplies and drainage systems.
As sustainable gardeners, we can take advantage of rainwater harvesting to water our gardens without stressing local water resources. From conserving precious water resources to nurturing a thriving garden while reducing your ecological footprint, rainwater harvesting can be a game changer for sustainable gardening!
In Brad Lancaster’s book, Rainwater Harvesting for Drylands, Volume I: Guiding Principles to Welcome Rain into your Life and Landscape, he details how he created a self-sufficient property and garden in Tuscon, AZ, relying only on captured rainwater and greywater.
According to this article, their desert household consumes less than 20,000 gallons of municipal water annually, with over 90 percent of that being recycled in the landscape as greywater. They also harvest and infiltrate over 100,000 gallons of rain and runoff into the soil of their site (and, by extension, the community’s watershed) over the course of their annual average rainfall.
They have also learned to live within their rainwater “budget” (the natural limits of the local environment). As a result, they are enriching the land, growing up to 25 percent of their own food on-site, and contributing to a beautiful home and neighborhood environment.
In the course of creating their sustainable oasis, they arrived at eight basic principles that anyone can use to implement a successful rainwater-harvesting strategy of their own:
#1: Begin with a long and thoughtful observation.
…Wherever you direct rainwater in your landscape, you will be nurturing plant life, so take the time to ensure this vegetation is part of your overall plan.
Next, calculate the rainwater resources available within your site’s “watershed.”
For us, that area included not only the 12 inches of annual rainfall on our roof and 1/8th of an acre property, but the 20-foot-wide public right-of-way adjoining our property, the section of street draining past the right-of-way, and the runoff from our neighbor’s roof… This totaled about 104,600 gallons (397,000 liters) of rainwater in an average year!
#2: Start harvesting rain at the top of your watershed, then work your way down.
In most cases, the top of your watershed means the roof of your house. Take a look. Where do the gutters drain? Where is rainfall currently being directed? This is where you should begin with mulched water-harvesting basins and plantings (at least 10 feet from the building’s foundation.)
…Whatever type of cistern (or water storage vessel) you choose, having your garden located nearby will keep hose length to a minimum (25 ft. ideal). This will reduce water-pressure loss and make watering with rainwater a convenience. Your plants will love it too!
#3: Always plan an overflow route, and manage overflow as a resource.
Eventually, all water-harvesting systems will meet a storm that exceeds their capacity, so don’t get taken by surprise. All rainwater harvesting structures should be managed in such a way that the system can overflow in a beneficial, rather than destructive way.
In that spirit, overflow from our backyard cistern is directed via a 4-inch diameter overflow pipe to a series of adjoining mulched basins that passively irrigate a citrus tree and our garden. In addition, all of our sunken earthworks have an overflow “spillway.” Typically, one earthwork overflows to another and another, until all are full and then, if needed, the lowest earthwork can overflow to natural drainage – or, in a typical urban context, the street.
Your goal should be to harvest the rain, but never get flooded by it. This is key.
#4: Start with small and simple strategies that harvest the rain as close as possible to where it falls.
When people think of rainwater harvesting, usually it’s cisterns and tanks that spring to mind. But the water collected off your roof is typically much less than what’s actually falling on your property. Simple water-harvesting earthworks, such as basins, terraces, contour berms, and check dams will harvest the rain where it falls, on the land.
#5: Spread, slow, and infiltrate the flow of water into the soil.
Cisterns along with mulched and vegetated earthworks with overflow routes will effectively transform your erosive runoff during heavy rainfall into a calm, productive resource while reducing water loss to evaporation and downstream flooding.
Raised pathways and gathering areas are also great strategies for spreading water through the landscape. This pattern of “high and dry” regions that drain to adjoining basins kept “sunken and moist” will help to define those areas through vegetation while spreading and sinking the flow of water.
#6: Maximize living and organic ground cover.
All your basins and other water-harvesting earthworks should be well-mulched and planted. This creates a “living sponge” effect that will utilize the harvested water to create food and beauty in your surrounding landscape while steadily improving the soil’s ability to infiltrate and hold water due to the vast network of growing roots and beneficial microorganisms.
Groundcover is equally important in helping to ensure that, in your enthusiasm for harvesting rainwater, you don’t wind up creating a haven for mosquitoes. Mosquitoes need three days of standing water to transform from eggs to adults. Water-harvesting earthworks allow water to infiltrate below the surface of the soil (typically within one hour) where it won’t be lost to evaporation.
Take a hike in the natural unmanaged areas near your home to determine what native vegetation would be best to plant within or beside your earthworks. Out in the wild, you’ll notice which plants grow naturally in depressions – they can be planted within your basins. Wild plants preferring better drainage can be planted beside, but not within earthworks…
#7: Maximize beneficial relationships and efficiency by “stacking functions.”
As mentioned previously, water-harvesting strategies offer maximum benefits when they’re integrated into a comprehensive overall site plan. We focused on locating the earthworks where we wanted to stack functions (a permaculture principle) with multi-use vegetation.
Through rainwater harvesting earthworks, we’ve nurtured a solar arc of deciduous trees on the east, north, and west sides of our home that cool us in the summer, but let in the free light and warmth of the sun in winter. A living fence of native plants along the property line…forms part of a sun trap, which shades our garden from the afternoon sun, creates on-site stormwater control, and enhances habitat for native songbirds and butterflies.
#8: Continually reassess your system and improve it.
By keeping an eye on what’s working – and what could work better – and making adjustments as needed – you can build an ever-more sustainable yard and garden over time.
Whether you’re an experienced gardener or a beginner with a green thumb, you can learn to incorporate rainwater harvesting into your gardening routine. By harnessing the power of nature’s gift, we can create a more sustainable and resilient future, one garden at a time!