Multiple choice

Direction: One hour triangular unit hydrograph of a watershed has the peak discharge of 60 m3/sec.cm at 10 hours and time base of 30 hours. The $\phi$ index is 0.4 cm per hour and base flow is 15 m3m/sec.

The catchment area of the watershed is

  1. 3.24 km2

  2. 32.4 km2

  3. 324 km2

  4. 3240 km2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Peak discharge of unit hydrograph = 60 m^3/s. Time base = 30 hours. Area under triangular hydrograph = 0.5 * base * height = 0.5 * 30 * 3600 * 60 = 3,240,000 m^3. Since it is a 1 cm unit hydrograph, 1 cm = 0.01 m. Area = Volume / Depth = 3,240,000 / 0.01 = 324,000,000 m^2 = 324 km^2.

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