Section 4: Soil and Water Conservation Engineering
Hydrology
Subtopic: Flood routing, hydrological reservoir and channel routing
Question Statement:
In uncontrolled reservoir flood routing (level pool routing), the peak outflow discharge occurs exactly at:
Options:
(A) The point of intersection of the outflow hydrograph with the receding limb of the inflow hydrograph
(B) The exact time of the inflow hydrograph peak
(C) The start of rainfall excess on the reservoir water surface
(D) The end of baseflow recession in the tailwater channel
Answer Key:
A
Step-by-Step Solution & Explanation
From the continuity equation $\frac{dS}{dt} = I - O$, the peak storage (and hence peak outflow $O$, since $S = f(O)$ is a monotonic function) occurs when $\frac{dS}{dt} = 0$, which requires $I = O$. This equality occurs at the point where the outflow hydrograph intersects the recession limb of the inflow hydrograph. Option A is correct.