The quantity of water in a reservoir, which cannot be utilised under normal operating conditions and is stored below the minimum pool level, is known as ___________.
dead storage
Understanding Reservoir Storage: Dead Storage Explained
Reservoirs are designed to store water for various purposes like irrigation, power generation, and water supply. The total volume of water a reservoir can hold is divided into different storage zones based on the water level and its usability under normal operating conditions. The question asks about the water quantity that is stored below the minimum pool level and cannot be utilized under normal operations. Let's look at the different types of storage mentioned in the options.
Types of Reservoir Storage
Reservoir storage is typically categorized into several types:
- Dead Storage: This is the volume of water stored below the minimum pool level. It represents the water that cannot be drained out by gravity through the lowest outlet of the dam. This water is essentially "dead" or unusable under normal operating conditions and is often meant to contain sediment accumulation.
- Live Storage: This is the volume of water stored between the minimum pool level and the normal maximum pool level (or full reservoir level). This is the water that is available for withdrawal and utilization through the outlets and spillways for intended purposes.
- Surcharge Storage: This is the volume of water stored above the normal maximum pool level up to the maximum water level that the reservoir structure can safely contain, typically during flood events. This storage is temporary and is released through the spillway.
- Valley Storage: This term is less commonly used in the context of specific reservoir storage zones within the dam structure itself. It might refer to the natural storage capacity of the valley upstream of the dam site before construction, or the overall storage potential of a valley system. In the context of reservoir operation levels, it's not a standard term like dead, live, or surcharge storage.
Analyzing the Question's Description
The question specifically describes water that is:
- Stored below the minimum pool level.
- Cannot be utilized under normal operating conditions.
Based on the definitions above, this description perfectly matches the definition of dead storage.
Why Other Options Are Incorrect
- Valley storage is not a standard classification for reservoir storage levels defined by operating criteria like minimum or maximum pool levels.
- Surcharge storage is water stored above the normal maximum pool level, specifically during floods, which is the opposite of being below the minimum pool level.
- Live storage is the usable water stored between the minimum and maximum pool levels, which is available for normal operation, contrary to the question's description of unusable water.
Therefore, the quantity of water in a reservoir stored below the minimum pool level and unusable under normal operating conditions is known as dead storage.
| Storage Type | Location Relative to Pool Levels | Usability (Normal Operations) |
|---|---|---|
| Dead Storage | Below Minimum Pool Level | Cannot be Utilized |
| Live Storage | Between Minimum and Normal Maximum Pool Levels | Utilizable |
| Surcharge Storage | Above Normal Maximum Pool Level | Temporarily Stored, Released During Floods |
Revision Table: Key Reservoir Storage Concepts
| Term | Definition | Key Characteristic |
|---|---|---|
| Dead Storage | Water below the lowest outlet, below minimum pool. | Unusable under normal gravity flow. |
| Live Storage | Water between minimum pool and normal maximum pool. | Usable for planned releases. |
| Surcharge Storage | Water above normal maximum pool during floods. | Temporary, accommodates excess flow. |
Additional Information on Reservoir Storage
Understanding reservoir storage types is crucial in water resources engineering and reservoir management. The design of a dam and its outlets directly influences the amount of dead storage. The primary purpose of dead storage is often to account for sediment deposition over the reservoir's lifespan. Sediment carried by incoming rivers settles at the bottom of the reservoir, accumulating in the dead storage zone. While unusable for supply, maintaining dead storage helps protect the live storage capacity from being lost due to sedimentation for a certain period. The minimum pool level is determined by the invert level of the lowest outlet structure used for normal water releases. Surcharge storage plays a vital role in flood control by temporarily holding excess inflow and gradually releasing it downstream, thereby reducing peak flood flows.
Important Questions from Dams and Spillways
Sequentially arrange the following steps which are involved in surveying to build an irrigation structure.
A. Reconnaissance survey
B. Preliminary survey
C. Examine the water availability
D. Final location survey
E. Final survey report
A drop in canal bed is generally provided, if
________ is a kind of passage to allow water from upstream to downstream of a dam which has flood gates to control the flow.
For the upstream face of an earthen dam, the most adverse condition for stability of slope is:
For no tension to develop in the gravity dam the resultant of all external forces should always lie _______.
