Useful storage of a reservoir:

The useful storage of a reservoir refers to the volume of water that is stored between the normal pool level and the minimum pool level. This storage is considered useful because it can be utilized for various purposes, such as supplying water for domestic, industrial, and agricultural needs, generating hydroelectric power, and maintaining ecological balance.

Explanation:

Reservoirs are man-made structures that are created by constructing dams across rivers or streams. They serve as a storage facility for water, which can be used for various purposes. The storage capacity of a reservoir is determined by the difference in water levels between the maximum pool level and the minimum pool level.

Maximum pool level:
The maximum pool level is the highest water level that the reservoir can reach without causing any damage to the dam or the surrounding areas. It is usually determined based on the design specifications of the dam and the maximum flood level that the reservoir is expected to experience.

Normal pool level:
The normal pool level is the desired water level in the reservoir under normal operating conditions. It is determined based on the water demand, the availability of inflow, and the desired storage capacity. The normal pool level is usually maintained for a significant part of the year to ensure a reliable water supply.

Minimum pool level:
The minimum pool level is the lowest water level that the reservoir should not go below. It is determined based on various factors, such as the minimum water level required for maintaining ecological balance, preventing saltwater intrusion in coastal areas, and ensuring the functioning of water intakes and turbines.

Useful storage:
The useful storage of a reservoir is the volume of water that is stored between the normal pool level and the minimum pool level. This storage is considered useful because it can be withdrawn from the reservoir for various purposes without causing any adverse effects on the dam, the environment, or the operation of the reservoir.

Importance of useful storage:
The useful storage of a reservoir is crucial for meeting the water demands of various sectors, such as agriculture, industry, and domestic use. It also plays a significant role in the generation of hydroelectric power, as the water stored in the reservoir can be released through turbines to produce electricity. Additionally, the useful storage helps in maintaining the ecological balance of the downstream ecosystem by regulating the flow of water and supporting aquatic life.

In conclusion, the useful storage of a reservoir is the volume of water stored between the normal pool level and the minimum pool level. It is an essential component of reservoir design and management as it provides water for various purposes while ensuring the safety of the dam and the sustainability of the environment.