GATE 2016 CE (CE2) – Question 56
The ordinates of a one-hour unit hydrograph at sixty minute interval are 0, 3, 12, 8, 6, 3 and 0 m3/s. A two-hour storm of 4 cm excess rainfall occurred in the basin from 10 AM. Considering constant base flow of 20 m3/s, the flow of the river (expressed in m3/s) at 1 PM is _________.
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Correct answer: 59 to 61
Explanation
Assuming uniform excess rainfall, the4cm over2hours splits into two1-hour pulses of2cm. At1PM,3hours after the first pulse began, their runoff contributions are2U3+2U2=2·8+2·12=40m³/s. Add base flow20 to get **60m³/s**. The uniform temporal split is implicit in the keyed result.