What is Rainwater Harvesting?

Rainwater harvesting has been used around the world for centuries. It is the collection of runoff stormwater. When it rains, water will travel along a roof catchment system of gutters and pipes that will fall into a storage container which is stored and used for a later time. Storage tanks are covered to reduce evaporation losses and to prevent the breading of unwanted bugs. Even though rainwater harvesting is legal and even supported in Texas, individuals should check with their country districts for guidance and regulations.

Photo credit: builtsmartresources

Photo credit: builtsmartresources

For many answers to frequently asked questions on rain harvesting, please visit this Texas Water Development Board page.


What is rainwater harvesting used for?

Coming soon.


How to predict your rainwater harvest rate

To size a system for a site, you must choose the water collecting area to supply enough volume of water for the site occupants, given the site's rainfall patterns.  The simplest equation for system sizing is this:

(Volume) = (Area) • (Precipitation) • (% Efficiency)

Volume is the amount of rain harvested in that time period, measured in liters.  Area is the rainwater capture area, measured in m2.  Precipitation is the amount of rainfall in that time period (in mm).  Efficiency is the percent of water actually captured, as opposed to splashing out of the system somewhere; it is usually 75% - 90%.

In English units, a coefficient must be added:

(Volume) = (Area) • (Precipitation) • (0.62 gal/ft2/inch) • (% Efficiency)

Here volume is in gallons, area is in ft2, precipitation is in inches.

(Rainwater Harvesting Rate feature credited to sustainabilityworkshop.autodesk.com)