Catchment Capacity

Catchment Capacity (scaled to respond to a Large Storm Event) = gal
Volume of water per cubic foot = 7.48 gal
Runoff Coefficient (RC) accounts for 20% loss (splash/evap)
Local High of a storm event ie. 6"

Catchment Area(ft^2) x Local High Storm(ft) x 7.48 gal/ft^3 x RC(.80)

ie.
100 ft^2 x (.5)ft x 7.48 gal/ft^3 x (.80) = ~300 gal


(Calculation source: Rainwater Harvesting, Brad Lancaster)