GATE 2022 ES – Question 56
A 3-hour storm covers zones15%,35%,50% with φ-indices .5,1.0,.8 cm/h. Their hourly rainfall triples (cm) are(.4,2.5,1.6),(.8,3.0,2.1),(.6,2.6,1.9). Find area-weighted rainfall excess in cm, to one decimal.
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Correct answer: 3.0 to 3.0
Explanation
Only positive hourly excess counts. Zone totals are0+2.0+1.1=3.1,0+2.0+1.1=3.1,and 0+1.8+1.1=2.9 cm. Weighted excess=$.15(3.1)+.35(3.1)+.50(2.9)=\mathbf{3.0}$ cm. Rainfall below the φ-index gives zero excess, not a negative contribution.