What is Rainwater Harvesting?
Rainwater harvesting is the collection of rainwater by “capturing, storing and directing rainwater runoff and putting it to use”, says the Colorado State Extension.
Generally rainwater is collected from a residential roof and stored in a container (barrel or plastic tank) of some kind. Water can also be collected from concrete patios and driveways. Depending on the level of water filtration, collected water can be used in the following ways.
- edible garden irrigation
- lawn & other landscape irrigation
- toilet flushing
Using rainwater saves you money and helps the environment. Win-win!
How to Harvest Rainwater
Designing a catchment system can be as simple or complex as you want, depending on the ultimate intended use of the water. For the purpose of this post, I will be discussing water collection for use in gardens and other landscapes.
You will need:
- Collection Area: likely your roof
- Transportation System: likely a gutter and downspout
- Storage Container: barrel or plastic tank
Types of Containers
“The best barrels are made of an opaque material (metal, wood or colored plastic) to prevent light transmission and inhibit algae and bacterial growth. To stop barrels from becoming mosquito breeding grounds, fasten a tight-fitting top to them, and screen the ends of downspouts leading into the barrels”, says Mother Earth News.
The tank lid will also, “reduce evaporation…More sophisticated systems have “first flush” diverters that are recommended to exclude capture of the initial rain that might carry impurities from the roof”, says the Colorado State Extension.
Location of Container
Where you place the container will impact how much water you collect and how easily the water is distributed. Ideally the container should be placed under a downspout that is close to the parts of your yard that will receive the collected water.
Garden Gate Magazine provides the following how-to description for building your collection system.
“Dig out a 4-inch-deep area the length and width of the cinder block base. Fill the area with 1/4-inch pea gravel. This makes a base to help you level the cinder blocks and drain away water to keep your foundation dry.
The higher you can raise the barrels, the better the water pressure will be. Raising the barrels up also gets the spigot higher off the ground so you can get a watering can under it.
Short lengths of hose can be attached to individual barrels to link them together and boost the capacity of your system. And they can be added over time as you see how much water your garden needs.”
Things to consider
1. Mosquitos & other pests: To prevent your water collection container from becoming a breeding ground for mosquitos and other pests, ensure your container has sealable lid.
2. Water quality: Filters and screens on your container will also help maintain water quality. These can keep out leaves, bird droppings, and (depending on the filter) heavy metals from rain water and your roof.
In addition to physical filters and screens, you can also ensure better water quality by using a “first-flush diverter”. This diverts the first few gallons of rain water, which are more likely to contain leaves, dust, bird droppings, etc. If your intended water use is solely for irrigation of landscape, then water quality is less important.