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  • Writer's pictureKhalana Gocken

How much water does my landscape use?*

Landscapes consisting primarily of turf use approximately 25 gallons/sq ft. per year. A 750 sq ft lawn uses approximately 18,750 gals/year.

Edible landscapes use approximately 20 gallons/sq ft per year. A 750 sq ft edible landscape uses approximately 15,000 gals/year.

Landscapes with an even mix of plantings and turf use approximately 16 gallons/sq ft per year. A 750 sq ft yard uses approximately 12,000 gals/year.

Xeriscape landscapes use approximately 7 gallon/sq ft per year. A 750 sq ft xeriscape uses approximately 5250 gals/year.

How much water does your landscape use? If you live in Denver and have a 750 sq ft roof, you may be able to divert approximately 9493 gallons of rainwater per year into your landscape. That would support an entire xeriscape of 1356 sq ft!

*These figures were pulled from a presentation given by Harold Smethills, Managing Director, Sterling Ranch, LLC. at the "Landscape 2030: Imagine a Water Smart Denver" event on July 31, 2013 at the Denver Botanic Gardens.

Calculating Runoff:

In Denver the average annual rainfall is 15.81". Historically this annual number has been as low as 7" and as high as 25". In order to calculate the amount of rainwater runoff coming through your downspouts each year follow this formula..

1. Measure the surface area of your roof as if you were looking directly down upon it. (The rain falls directly down, not at the angle of the pitch of your roof. Google Earth is a great place to get this calculation.)

2. Multiply that number by .8 for composite roofing or .9 for metal roofing. (This accounts for efficiency.)

3. Multiply by rainfall in feet.

4. Multiply by 7.48 conversion rate. (To get to gallons.)

5. This equals the gallons of rainwater available annually.


1225 sq ft aluminum roof in a 1.25” rain event

1125 sq ft x .9 efficiency factor x .104’ rainfall x 7.48 conversion rate = 787.64 gallons of rainwater

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