Capturing rainwater from your roof, parking lot or driveway
In many parts of the world, capturing rainwater from roof tops is common. In Oregon,
unlike some other western states, you do not need a water use permit to do so.
“ORS 537.141 - Uses of water not requiring water right application, permit or certificate;
rules. (1) The following water uses do not require an application under ORS 537.130 or
537.615, a water right permit under ORS 537.211 or a water right certificate under
ORS 537.250:
(h) The collection of precipitation water from an artificial impervious surface and the use
of such water;”
Some useful figures and calculations for rain water catchment:
Inches rainfall x Square feet of catchment area x 0.625 = gallons of
water captured
The 0.625 Factor = (7.5 gallons per cubic foot of water / 12-inch depth
per cubic foot = 0.625)
Example:
30-inches per year is equivalent to 18.75 gallons per of water
collected from each square foot of surface area.
30-inches of rainfall collected from the roof of a 1,600 square
foot home = 30,000 gallons water
30-inches of rainfall collected from the roof of a 2,500 square
foot home = 46,875 gallons water
Storage tank capacity will depend on total rainfall, surface area
collected, seasonal rainfall patterns, and seasonal water use patterns.