GATE 2021 CE (CE2) – Question 32
A 12-hour, 1 cm unit hydrograph is triangular with base 144 h and peak 23 m³/s. Find catchment area in km², nearest integer.
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Correct answer: 595 to 598
Explanation
Runoff volume is the hydrograph area: $V=\tfrac12(144\times3600)(23)=5961600$ m³. Unit runoff depth is 0.01 m, so catchment area is V/0.01=596160000 m²=596.16 km². **Answer: 596 km².** Hydrograph duration is not substituted for its full 144 h base.