Reservoir Storage and Flood Control MCQ with answer and solution

Concept

Surcharge storage is the volume between normal pool level (NPL) and maximum pool level (MPL). It temporarily holds flood water and reduces the flood peak going downstream.

Step-by-step solution

1. Recall reservoir zones: dead storage (below minimum pool level), useful or live storage (between minimum pool level and NPL), surcharge storage (between NPL and MPL). 2. So the Assertion matches the definition of surcharge storage. It is true. 3. During a flood, water rises above NPL and is held for some time while the spillway passes it out. 4. This temporary holding lowers the flood peak downstream. So the Reason is true. 5. The Reason gives the purpose of this storage, so it explains the Assertion. Answer is A.

Explanation

The volume of water between normal pool level and maximum pool level is called surcharge storage. It fills only during floods and holds flood water for a short time, so the flood peak reaching downstream areas becomes smaller. So both statements are true, and the Reason explains the Assertion.

Why the other options are wrong

B: The Reason is not false, because surcharge storage does reduce the downstream flood peak. C: The Assertion is the standard definition of surcharge storage, so it is true. D: The Reason states the purpose of surcharge storage, so it does explain the Assertion.

Shortcut

Dead storage is below MPL(min), live storage is MPL(min) to NPL, surcharge storage is NPL to MPL(max).

Common mistake

Mixing up surcharge storage with live (useful) storage, or thinking surcharge storage can be used for normal supply. It is uncontrolled and lasts only during a flood.