Stormwater management in general is important for the world – helping to keep our cities clean, our children safe, and our waterways chemical-free. However, stormwater harvesting has special benefits.
In large rural settings, the most common stormwater harvesting system is a retention or detention pond, discussed at length below. In the city, however, land is at a premium and most people/businesses are working with far less acreage. Stormwater harvesting systems must accordingly shrink as well, which is why you’ll find most of them on rooftops or in people’s yards.
These usually take the form of rain barrels or large gutters leading to a storage reservoir. Once the water is collected, you can use it in a number of ways, including:
- Filtering it and using it as potable water for drinking, washing dishes, and showering
- Using it unfiltered for flushing toilets, doing laundry, or watering the yard
- Funneling it into the ground to recharge aquifers
This is a better strategy than using downspouts to redirect water away from your roof and into the street, where it will simply add to the runoff problem.
If you don’t particularly care about reusing water inside your home, you can direct it toward green areas. This is another great form of harvesting or reuse, because it beautifies your home or business and provides shelter and food for native animals. Consider solutions such as:
Planters
Any raised bed made of wood or concrete, especially if it is lined with a durable, waterproof liner, can help trap stormwater. This “harvesting” strategy is extremely simple, because it then waters the plants already in the planter, so you don’t need to take the water anywhere.
Rain Gardens
Usually built in shallow areas of the yard or at the bottom of hills, rain gardens collect water to nourish moisture-loving plants. Sometimes the water runs off relatively quickly, so you can use plants that tolerate “wet feet.” Other times it stands for days or weeks, in which case you’ll need to make sure you buy plants that grow directly in water.
Trenches or Bioswales
Trenches and bioswales do not so much “harvest” water as they do direct it somewhere else. However, if your soil is nice and soft – easier to accomplish with plant roots growing into it and breaking it up – then a trench or bioswale will dramatically increase the penetration of water into the ground.
If you prefer, you can line your trench with something waterproof. That will still keep your plants healthy but will harvest overflow water for redirection into a pond. On small properties, you can still funnel water into a small pond, which is both aesthetically and environmentally beneficial.
Green Roofs and Rooftop Gardens
Green roofs (also known as living roofs) are a truly excellent strategy not only for harvesting stormwater and putting it to good use, but also for improving our cities. The heat island effect in urban areas is a serious problem today. Because our cities contain so many impermeable surfaces that collect and trap the sun’s heat (think asphalt and concrete), they become much warmer than surrounding areas where greenery prevails.
The EPA says that “Daytime temperatures in urban areas are about 1–7°F higher than temperatures in outlying areas and nighttime temperatures are about 2-5°F higher.” Although this might not seem like a lot, it is more than enough to increase the chances of heat-related illness (heat stroke), asthma, and respiratory trouble. Often this is related to pollution, which also becomes more serious in higher temperatures.
Happily, green roofs and rooftop gardens offer a great solution. They are cooling, reducing the temperatures in houses and buildings beneath them as well as in the city overall. And because you can construct them with native plants that are accustomed to the rain and snowfall in your area, you can harvest stormwater as it comes down rather than watering them for most of the year.
Typically, these rooftop gardens and living carpets only need watering in the hottest part of summer. If you combine them with a rain barrel for stormwater harvesting, you can water them from that, avoiding the municipal water supply and our aquifers completely.
Best of all, green roofs are capable of harvesting stormwater for use elsewhere. If constructed to do so, green roofs can filter water down into lower catch basins that hang onto the water, either for use in the green roof when hot weather hits – it will evaporate upward – or for collection. In fact, “blue roofs” are becoming more popular in cities. They use a top layer of greenery and harvest stormwater below for use elsewhere.
Trees
Trees are, without a doubt, one of the best strategies for stormwater harvesting. They suck down dozens of gallons of water a day. According to the U.S. Forest Service, “A healthy 100-foot-tall tree has about 200,000 leaves. A tree this size can take 11,000 gallons of water from the soil and release it into the air again, as oxygen and water vapor, in a single growing season.”
By putting trees on properties, urban or rural, you can ensure better stormwater absorption into the soil. You also receive the other benefits of trees. That includes shade for properties and, like green roofs, a reduction in the temperature on that property and the city overall.
Hands-Free Stormwater Management
And if you really don’t want to do much to manage stormwater and don’t care about harvesting, you can use the following systems:
- Drywells: Perhaps the simplest system of all, a drywell is a hole in the earth dug at a low point on your property. The water will funnel there and collect, then evaporate when the rain ceases. It’s dirty, so it’s not usually good for anything, but it is a low-cost solution that still helps manage runoff. Be careful if you use this solution to manage the water so it doesn’t breed mosquitoes, which are not only a nuisance but also dangerous to human health in many areas.
- Permeable pavers: These are shallow pavers that allow water to penetrate into the ground. Sometimes they have holes running through them from top to bottom in a design, and other times they are put down as bricks with large spaces in between. While these are a pretty utilitarian stormwater solution, you can still “harvest” it to grow species such as herbs or grasses, which will attract native pollinators.
A Pond a Day Keeps the Stormwater Away …
Lastly, ponds are always an excellent way to dress up a property and deal with stormwater at the same time. Residential ponds, as we talk about on our blog, “give homes a unique and special feeling. When designing the landscape of your yard, be it a koi pond in the front yard or a cascading waterfall in the back, adding an attractive water feature will increase the value of your property and give you comfort in your own home.”
What’s not to like?
A small koi pond can’t address stormwater on a grand scale, however. If you’re dealing in acres – as many farmers, rural property owners, and contractors are – then you’re going to need a more intensive solution. That’s where large-scale stormwater harvesting comes in.
