Tucson Water Rainwater Rebate Site Plan Calculator

Fill in the roof area you will be collecting from and the calculator will show your rainwater harvesting potential. Note that these calculations are based on average rainfall in Tucson, Arizona. 

Enter your name and email at the bottom of the calculator to have these results sent to you. 

Roof Area

1 Inch Storm Data

Formula: Roof area (sf) x 1/12(ft) x 7.48 (gal/cubic foot)
Assumes your basin is 8" deep 
Formula: 1 in roof supply / (.667 ft * 7.48 gal/cubic foot) 

2.5 Inch Storm Data

The Tucson Water Rainwater Harvesting Rebate is requires capturing a 1 inch rainfall. Historically, 95% of our storms have dropped 1 inch or less of rain. 

As our rains have become more erratic, our storms have also been becoming more intense. Planning for 2.5 inch rain events will allow you to capture as much of what falls in your catchment area as possible and is a way of preparing for shifts in our weather patterns. 

Formula: Roof area (sf) x 2.5/12(ft) x 7.48 (gal/cubic foot)
Assumes your basin is 8" deep 
Formula: 2.5 in roof supply / (.667 ft * 7.48 gal/cubic foot) 

Annual Data

Formula: Roof area (sf) x 11(in) x 7.48 (gal/cubic foot) x 0.9 (runoff coefficient)
Formula: Roof area (sf) x 9(in) x 7.48 (gal/cubic foot) x 0.9 (runoff coefficient)

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