HR)0 - 22 - 4Rainfall (cm)6.25.0 \(\therefore \phi - index = \frac{{P - R}}{t}\)whereP = Rainfall depthR = Runoff deptht = Duration of rainfallR = P - ϕindex × tR = (6.2 + 5.0) - 1.2 × 4R = 11.2 - 4.8R = 6.4 cmRunoff volume = 6.4 × 10-2 × 250 × 106Runoff volume = 1600 × 104 m3Runoff volume = 1600 hectare - meter(1 hectare = 104 m2)