Categories Go Green

How To Harvest Rainwater?

From perennially parched California to unseasonably dry Massachusetts, from sea to salty sea, rainwater is a precious resource.

As drought rages in East Africa and groundwater systems are stretched to their limits in India, and global climate changes at an increasing rate, water will become an ever more precious commodity driving the new economic and political landscape of the 21st century.  In such a water world, it is rewarding to understand how this resource may be better used. We have outlined six simple steps that individuals and communities can take to harvest and harness rainwater. Take a look.

1. Install Rain Barrels

A rain barrel is perhaps the most straightforward way to harvest water on-site. Any household with outdoor space can install a rainwater catchment system that fills a barrel with water that can then be used to nourish plants. Given the rain barrel’s revolutionary ability to improve resilience through saving water, it is not surprising that, prior to this past May, backyard rain barrels were illegal in Colorado.

You can purchase a prefabricated rain barrel online or from a local vendor. If you’re feeling adventurous, you can build your own from scratch. Barrels are most easily found on sites like Craigslist or Freecycle, or at local food distributors. Usually fed by a downspout off a gutter, rain barrels should be elevated above the ground for greater water pressure when using a garden hose. DIY instructions can be found here or here.

2. Produce Living Mulch

To many, the word mulch brings to mind the smell and sight of shredded wood chips blanketing the earth. True, this is a form of mulch, usually softwood (from conifer trees) and often used in traditional landscape design. However, mulch, or mulching, refers to a general practice of covering the soil with an organic layer of matter that suppresses weeds and retains soil moisture.

When possible, living mulch is an ideal solution, particularly if it’s edible. In my gardens, we have allowed purslane, a leaf vegetable that is used in certain Indian and Persian cuisine and has become a summer weed in temperate climates, to propagate, while removing most other weeds. This results in a thorough ground cover that suppresses other more noxious weeds while retaining moisture by shielding soil from the sun.


3. Create Lasagna Mulch

Ambitious soil-builders may also apply sheet-mulch, or “lasagna mulching,” to their growing space to catch rainwater and increase yield. This involves the application of layers, made of organic material such as shredded leaves, compost, seaweed, over a base of cardboard that covers the soil. These materials will decompose and fuel a healthy soil ecology while providing protection from water loss.

“Chop and drop” mulching is made possible through comfrey, a plant used for fertilizer and herbal medicine. After the plant has been established, gardeners can cut the prolific leaf growth from comfrey and apply it as mulch to a growing space. Comfrey is known as a “dynamic accumulator” able to pull nutrients from deep within the soil. These nutrients become readily available in comfrey leaves, which quickly decompose after chopping.

4. Build Swales

 A helpful design principle is the efficient use of resources that are available and abundant on-site. The power of gravity is infinite and drives much of the earth’s natural drama. When rain falls on a slope, the runoff quickly finds its way downhill. Unless captured by the local ecology, this running water may cause erosion. Runoff is both a threat and a missed opportunity.

Rainwater runoff can be trapped through the application of swales, a landform that utilizes a raised mound and an immediately uphill ditch to slow downhill runoff. This runoff moisture is then absorbed by the large surface area of the mound, where it is accessible to plant roots. Swales must be built along contour lines to ensure a balanced system. For a small-scale swale, workers may use shovels to dig a ditch and use the removed soil to create a mound. On the mound, growers can plant fruit or nut trees, annual and perennial vegetables, berry bushes, herbs and more to create a food-producing ecosystem that prevents erosion and harvests water through its root networks.

5. Grow Mushrooms and Carnivorous Plants

When designing a growing space, it is helpful to consider the benefits of stacking functions, or including components in a system that perform more than one function. For example, the ditch section of the swale serves to slow and concentrate runoff water so that plants growing on the downhill mound may have access to it. However, the ditch may also serve as a growing space for edible and medicinal mushrooms.

Many mushroom varieties, including oyster and wine cap, can be grown in an inoculated, moist patch of hardwood chips. Chips from hardwood, or deciduous trees can be hard to find as they are not usually available in common hardware or gardening stores. Check with local landscaper companies. After acquiring, these chips may be applied with a layer of mushroom spawn to a swale ditch and voila: functions stacked, mushrooms established.

Even mushrooms grown on logs, such as shiitake, benefit from ready access to rainwater. For best results, mushroom growers should use rainwater, not tap water, to maintain moisture and induce fruiting. However, tap water is usually acceptable if rainwater is not available. But hey, after reading and applying this article, you’ll have rainwater for days. You might as well give your mushrooms the best.

While mushrooms may tolerate treated water, carnivorous plants will not. Pitcher plants, venus fly traps, and others developed their unique consumption habits as an adaptation to poor soil environments. The nutritionally infused tap water will fry the meat-eating flora with excessive nutrients and alkalinity. Carnivorous plants can be found here.


6. Make Beer

Yes, it is true. Harvested rainwater can be used to brew sustainable beer. RainHarvest Systems and 5 Seasons Brewery collaboratively developed a rainwater beer system that redirects fallen precipitation into brewing equipment. Their work, shared to encourage other would-be green brewers to catch the rain, is available to explore here.