Reservoir storage zoning: From bottom to top, what is the correct order of storage zones in a reservoir used for water resources projects?

Introduction / Context:
Reservoirs are conceptually divided into storage zones to guide operation and design. Correct identification of these zones ensures reliable supply while providing flood cushion and sediment management.

Given Data / Assumptions:

• Conventional reservoir with low-level outlet(s) and a designated full-reservoir level (FRL) and maximum water level (MWL).
• Sediment accumulation occurs primarily in lower zones over time.

Concept / Approach:

Dead storage lies at the bottom and cannot be released by gravity through normal outlets (often allocated for sediment deposition). Above it is useful or live storage, which can be utilized for supply/power/irrigation. At the top is surcharge storage, a temporary flood cushion above FRL up to MWL, not normally used for conservation storage.

Step-by-Step Solution:

Verification / Alternative check:

Reservoir operation manuals and design textbooks consistently adopt this stratification for storage accounting and rule-curve development.

Why Other Options Are Wrong:

• Any option placing surcharge or useful storage below dead storage is physically inconsistent with outlet control and gravity release.

Common Pitfalls:

• Confusing “useful” with “active” or “live”—they refer to the same releasable volume.
• Assuming surcharge is part of dependable supply.

Final Answer:

dead storage → useful storage (live storage) → surcharge storage.