The Merriam-Webster Unabridged Dictionary defines the term reservoir as 'an artificial lake in which water is impounded for domestic and industrial use, irrigation, hydroelectric power, flood control, or other purposes.' The size and water content of a reservoir are controlled by a dam. The reservoir volume is usually defined by its live or dead storage capacity. Live storage capacity is the entire volume that can be withdrawn from the reservoir, whereas dead storage is the volume of water remaining in the reservoir when it is emptied to its (legislative) low-water level. Live storage capacity can be expressed as a degree of regulation, i.e., the proportion of a river's mean annual discharge that can be stored in a reservoir. Most reservoirs have a fairly low degree of regulation - usually far below 100% - but Lake Volta in the Volta River in Ghana has the world record of 428%, implying that more than 4 years of average discharge can be stored in the reservoir without releasing any water downstream of the dam. Apart from storing water, the function of a reservoir is to raise the level of the water to be diverted into a canal or pipe or to increase the hydraulic head. The head is an expression of water pressure that can be measured as the difference in height between the surface of a reservoir and the river downstream. Hydroelectric stations convert this pressure to electricity.
Was this article helpful?