GATE 2022 CE (CE1) – Question 56
A two-hour storm gives 3 cm uniform excess rainfall. At times 0,1,2,3,4,5,6,7 h, streamflows are 10,16,34,40,31,25,16,10 m³/s. With baseflow 10 m³/s, find the peak of the one-hour unit hydrograph.
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: 12
Explanation
Subtract the constant 10 m³/s baseflow and divide by 3 cm to get the 2-hour unit hydrograph: 0,2,8,10,7,5,2,0.
A 2-hour unit hydrograph equals one-half the sum of two 1-hour unit hydrographs separated by one hour. Thus $u_t=2v_t-u_{t-1}$ gives 0,4,12,8,6,4,0,0. The peak is **12 m³/s**.