The GATE Grind

GATE 2025 CE (CE1) – Question 20

Hydrology · Reservoir capacity, flood estimation and routing, surface runoff models · 1 mark · Multiple choice

To derive the total flood hydrograph at a catchment outlet from an isolated storm, the order in which the following methods are applied, from the first method to the last method, is

P. Obtaining the hyetograph

Q. Addition of baseflow

R. Estimation of initial and infiltration losses

S. Application of unit hydrograph

  1. PRSQ
  2. PQRS
  3. RPSQ
  4. PSQR

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Show answer and explanation

Correct answer: (A) PRSQ

Explanation

First the rainfall hyetograph is obtained (P). The initial and infiltration losses are then subtracted from it to get the effective rainfall (R). The unit hydrograph converts the effective rainfall into direct runoff (S). Finally the baseflow is added to get the total hydrograph (Q). The order is P, R, S, Q.