Also in: Disaster Response and Recovery
Rainwater Harvesting Yield
Annual gallons from catchment area, rainfall, and collection efficiency.
Example
You enter
- Catchment area (ft^2) 1000
- Annual rainfall (in) 30
- Collection efficiency (0-1) 0.85
You get
- Annual yield 15894 gal
Checked against published worked examples from: Texas Water Development Board.
Details, formula, and sources
Formula or tableAnnual gallons = catchment_area_ft² × annual_rainfall_in × 0.6233 × collection_efficiency. The 0.6233 constant converts in × ft² to gallons (1 in × 1 ft² = 0.6233 gal).
Source and editionARCSA (American Rainwater Catchment Systems Association) Rainwater Harvesting Manual by name; NOAA precipitation data.
Free accessARCSA materials free at arcsa.org. NOAA precipitation data free at hdsc.nws.noaa.gov.
What governsEstimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
API field namescatchment_ft2, annual_in, efficiency, annual_gal
- Default collection efficiency 0.85 (asphalt-shingle roof) unless user suppliesARCSA typical