Determination of Capacity and Observe the Trend of Capacity ‘C’, Elevation ‘E’ and Surface Area ‘A’ Curves.

Reservoir:

            An area occupied by water body due to construction of dam.

Impacts of reservoir:

1.   Reservoirs provide many benefits including water supply, floodwater control, power generation, irrigation and recreational use.
2.   Conversely, there are many disadvantages, such as loss of high quality agricultural land, displacement of people and changes to downstream flow patterns.
3.   Barrier for migratory fishes.
4.   Decreasing flow volumes in tail waters
5.   Stabilization of flow regimes by flood peak cut
6.   Changes in thermal regimes of river water
7.   River bed degradation and increase in substrate grain size by sediment trapping, etc.

Classification of Reservoir Based on Usage

i) Storage reservoir (conservative reservoir)

This reservoir is constructed to conserve the water in rainy season & releases it when river flow is low.

ii) Flood control reservoir

It is constructed for the purpose of flood control & it protects the area on the downstream side from the damage due to flood.

iii) Detention reservoir

This reservoir stores excess water during flood & releases it after the flood. Detention reservoir is similar to storage reservoir but it is provided with large gated spillways & sluice ways to permit the flexibility of operation.

iv) Distribution reservoir

It is a small storage reservoir to tide over the peak demand of water for water supply or irrigation. It stores water during lean period & supplies the same during the period of high demand.

v) Multipurpose reservoir

A reservoir that fulfills multiple functions is called multipurpose reservoir. For example Mangla dam reservoir is used for both storage of water and power generation.

vi) Balancing reservoir

A small reservoir constructed D/S of main reservoir for holding water released from the main reservoir.

Practical importance of surface area(S), elevation (E) and capacity (C) curves

E-S curve:

This curve is use for site selection before the construction & this curve provides information about the land that is required for reservoir, people evacuation, forest cutting & other environmental purposes. This curve needs modification time to time as the available area corresponding to elevation changes frequently due to sedimentation or erosion which will affect the capacity or reservoir.  

       

E-C curve:

These curves are important to calculate the storage capacity by selecting the height & to estimate the following elevation levels:

•   Maximum elevation level
•   Operational elevation level
•   Dead elevation level

S-C curve:

This curve provides information about the area that is under the water.

E-S-C curve:

This curve is used to check the feasibility of the project.