What is Rainwater Harvesting?
Rainwater harvesting is collecting the run-off from a structure or other impervious surface in order to store it for later use. Traditionally, this involves harvesting the rain from a roof. The rain will collect in gutters that channel the water into downspouts and then into some sort of storage vessel. Rainwater collection systems can be as simple as collecting rain in a rain barrel or as elaborate as harvesting rainwater into large cisterns to supply your entire household demand.
The idea of rainwater harvesting usually conjures up images of an old farm cistern or thoughts of developing countries. The reality is that rainwater harvesting is becoming a viable alternative for supplying our households and businesses with water. It's not just for the farm anymore! There are many countries such as Germany and Australia where rainwater harvesting is a norm. Due to the green building movement, you will be seeing rainwater harvesting systems become more popular here in America.
The collection of rainwater is known by many names throughout the world. It ranges from rainwater collection to rainwater harvesting to rainwater catchment. In addition, terms such as roofwater collection or rooftop water collection is also used in other countries.
We believe that rainwater harvesting is a viable technology in an urban setting. All that is necessary to take advantage of this resource is to capture the free water falling on your roof and direct it to a rainwater storage tank. By doing this, you can take control of your water supply and replace all or at least a substantial portion of your water needs. Rainwater harvesting systems can be configured to supply your whole house and/or your landscape needs.
You can essentially use rainwater anywhere you use tap water. The idea of using drinking water to flush our toilets and water our lawns is wasteful and irresponsible, especially in light of population growth and water shortages across the country. Rainwater collection is a technique to green your home and to lessen your environmental footprint.
There are basically three areas where rainwater can be used:
Here are some ideas for specific uses of rainwater:
The amount of rainfall that you can collect is governed by the following formula:
1" of rain x 1 sq. ft. = 0.623 gallons
Or put in an easy form to remember :
1" of rain from 1,000 sq. ft. will provide 623 gallons
To calculate the amount of rainwater you can collect, you need to know your annual average precipitation for your area. You can use the precipitation map below to find an approximate amount for your area (click for a zoomed image).
Alternatively, you can find an exact precipation amount by looking at the NCDC Monthly Precipitation Probabilities and Quintiles. Find the closest weather station to you and use the 0.5 row to determine your annual average precipitation.
Once you have the annual average rainfall in your area and the square footage of your collection surface, you can plug these values into our rainwater collection calculator.
So you're convinced that rainwater collection is a technology that you want to implement at your house. Next, we will discuss the various methods and components of rainwater harvesting. Even though rainwater catchment is an old technology, there have been many improvements over time through product development.
Go to the next step: How to Collect Rainwater