STORAGE ZONES OF A RESERVOIR

1. Dead Storage. The volume of water stored below the minimum pool level of the reservoir is know dead storage. This storage is not of such use in the operation of the reservoirs.

2. Useful Storage. The volume of water stored in a reservoir between minimum pool level and normal pool level is know useful storage. The useful storage may be further classifie into conservation storage and flood mitigation storage in a multi-purpose reservoir.

3. Surcharge Storage. The volume of water stored between normal pool level and the maximum pool level is know surcharge storage. This storage is an uncontrolled storage. It exists only till floods are in progress and cannot be retained for later use.

4. Bank Storage. When reservoir is full of water some amount of water seeps in the permeable banks of the reservoir. This seeped water comes out as soon the reservoir level gets deplete. This amount of seeped water which becomes available after the reservoir is deplet is know Bank storage. Amount of bank storage may amount to several per cent of the reservoir storage depending upon the geological formations of the banks. This storage increases the capacity of the reservoir above that indicated by the elevation-volume curve

5. Valley Storage. Some amount of water is stored by the stream channel even before a dam is constructed. This storage is know valley storage. Amount of valley storage is variable as it depends upon the rate of flow in the reservoir. After the construction of dam the valley storage increases. The net increase in the storage is equal to the storage capacity of the reservoir and less than natural valley storage. The valley storage thus reduces the effective storage capacity of the reservoir. This storage is not of much consequence in conservation reservoirs, but the available storage for flood mitigation is reduced as follows:

Effective storage for flood mitigation = Useful storage + Surcharge storage – Valley storage.