Rainwater harvest yield
Annual litres collectable from a roof or paved area given catchment, rainfall and runoff coefficient. First-flush losses deducted.
Annual harvest
106,900litres
= 107 kL·28,240 US gal
Monthly average
8,908L / month
= 8.91 kL
Daily average
293L / day
Average — actual yield is seasonal.
Single rainfall event · catch-tank sizing
Per-event harvest (50 mm)
8,200litres
= 8.2 kL·2,166 US gal
Size the catch tank to hold at least one full event without overflowing.
Peak inflow (1 h notional storm)
137L / min
Use to size gutter capacity and downpipe diameter.
Rainwater yield specification
A 200 m² catchment receiving 650 mm annual rainfall (runoff coefficient 0.85) yields 107 kL/year after first-flush losses — averaging 293 L/day. A 50 mm storm delivers 8,200 L in one event (peak inflow 137 L/min) — size the catch tank accordingly.