Diverting Rainwater From the Roof: Where Should It Go?

From rain gardens and swales to ponds and hydroponics, these ideas go beyond the basic barrel.

Rain Water Falling From Blue Roof
Put that rainwater to use. Natthapong Daeng Leis / EyeEm / Getty Images

So, you've taken the step of diverting and collecting the rainwater that falls on your roof. This is an excellent idea—helping you make the most of this natural resource and use it more wisely on your property. But what next? Many people stop at the stage of collecting harvested rainwater in a barrel or butt. But thinking about where the water goes next can help you make the right choices for water management in your garden.

Diverting Rainwater From a Container to an Irrigation System

The most obvious way to make use of the rainwater from your roof, perhaps, is to direct it from the collection vessel into an irrigation system for your garden. In certain instances, it may be possible to use gravity to divert water to an irrigation system. Water, of course, flows downhill. Raising a barrel or butt off the ground may be sufficient to gravity feed water to irrigate containers, planters, beds, or your vegetable plot.

In many instances, however, you may need to think about pumping the water to where it is needed. Solar-powered pumps are available to pump rainwater for an irrigation system in a more sustainable way.

Using rainwater wisely means thinking about the most efficient way to water your garden. Drip irrigation systems can be the most water-efficient choice. Drip irrigation can not only save water, but it can also make it easier to ensure that the water is delivered to exactly where it is needed—in the soil or growing medium. Watering from above is far less efficient, and wet foliage can also increase the likelihood of plant damage or disease.

Diverting Rainwater to Wicking Beds, Hydroponics, Aquaponics

A wicking bed with a spout for water
A wicking bed with its watering pipe.

Angle Schatz / Flickr

Rainwater can also potentially be diverted from collection vessels into wicking beds. Wicking beds are raised beds with reservoirs of water in the base. Water wicks up through the soil and is made available to plant roots. The use of wicking beds can be a very good idea—especially in drier climate zones where less rainwater is available.

Placing wicking beds close to the rainwater collection point means that these effectively expand your water storage capacity, while also giving you additional space to grow.

Wicking beds are just one option. You might also tie in a rainwater harvesting system to a small-scale hydroponics or aquaponics system—providing an influx of freshwater to these largely closed-loop, low-water-use systems.

Diverting Rainwater to a Filtration System

In certain areas, and for certain uses, it can be a good idea to think about diverting rainwater through a filtration system. Simple filters of straw/charcoal, sand, and gravel can remove particulates prior to use. Reed beds or other phytoremediation areas can use plants and micro-organisms to filter further impurities out of the water before it is used.

Should you wish to do so, it is also possible to use more sophisticated modern filtration systems to turn rainwater into water that will be suitable for use inside your home. This can be a useful option to consider in off-grid situations. To harvest rainwater for drinking, consulting a professional for guidance can help ensure you set up a safe system.

Diverting Rainwater to a Rain Garden or Swale

rain garden with flowering meadow
RBC Rain Garden at the London Wetland Centre has water management as its key focus.

Marathon / geograph

Another simple and useful way to make use of rainwater and naturally filter the water on your property is to make a rain garden. A rain garden is a basin to which rainwater is directed from driveways, areas of hard paving, or the roof of your home. In this basin is loose soil, planted with (usually) native plants. In the base of the basin are plants that like wetter conditions, and a periodic soaking. While more drought-tolerant planting is placed around the sides.

A vegetated swale is another type of earthwork designed to allow water to slowly drain into the soil in your garden. On-contour swales—small "canals" dug into the earth following the contours of the landscape—with flat bottoms and adjacent downhill berms are planted up with appropriate plants. These fill with water during rainfall, keeping water in the landscape, then drain over time into the soil, and as water is taken up by the nearby plants. Drainage swales or drainage ditches slope slightly, allowing water to pass along them to a rain garden, or another part of the garden.

A rain garden or vegetated swale that is carefully designed for your specific site can keep water around, using it to grow beneficial native plants for wildlife and garden ecology. And it can also help filter water through soil and plants to remove pollutants before that water drains off to rivers or the sea or ocean. 

Diverting Rainwater to a Garden Pond

Finally, in a higher rainfall area, it can also be helpful to direct rainwater from high rainfall periods to a permanent catchment pond or reservoir in your garden. There are a great many reasons why creating a permanent pond on your property can be beneficial. One of these is that a garden pond will keep water around for when it is needed, rather than simply allowing it to drain away.

A permanent pond can be particularly beneficial for water catchment where there are periods of heavy rain followed by periods of drought. In cold winter areas, a pond can also be useful for catching snow-melt at the end of the winter, keeping that water around for summer, when precipitation levels may be low.

Thinking about where to divert the rainwater from your roof can help you determine the best ways to manage freshwater on your property. The above suggestions are just some of the interesting options to consider.