What is "pondage"

Pondage usually refers to the comparably small water storage behind the weir of a run-of-the-river hydroelectric power plant. Such a power plant has considerably less storage than the reservoirs of large dams and conventional hydroelectric stations which can store water for long periods such as a dry season or year. With pondage, water is usually stored during periods of low electricity demand and days when the power plant is inactive, enabling its use as a peaking power plant in dry seasons and a base load power plant during wet seasons. Ample pondage allows a power plant meet hourly load fluctuations for a period of a week or more.