Figure 1. Pondage is the small amount of water storage present in some run-of-the-river systems, such as the Chief Joseph dam above.[1]

Pondage is the water that can back-up behind larger run-of-the-river systems. This pondage is essentially a small amount of water storage wherein water is built up during off-peak periods and used during peak periods. In periods of low electricity demand, or when the plant is inactive the water that would otherwise fall through the spillways and be "wasted" is stored and used when it is needed. Water that is built up in this pondage can result in the elevation of the water varying between 1-1.5 meters during operation.[2] A significant amount of pondage allows the plant to accomodate hourly fluctuations.

Generally speaking, since small amounts of water storage in the form of pondage allow run-of-the-river systems to run fully even during off-peak periods, plants with pondage tend to be more efficient than those without.[3]


  1. Wikimedia Commons. (December 29, 2015). Chief Joseph Dam [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/6/6c/Chief_Joseph_Dam.jpg
  2. Foundation for Water and Energy Education. (December 29, 2015). Types of Hydroelectric Projects [Online]. Available: http://fwee.org/nw-hydro-tours/how-the-northwest-hydro-system-works/types-of-hydroelectric-projects/
  3. Electrical Engineering Tutorials. (December 29, 2015). Hydroelectric Plants [Online]. Available: http://www.powerelectricalblog.com/2007/04/hydro-electric-plants-classification.html

Authors and Editors

Jordan Hanania, Kailyn Stenhouse, Jason Donev
Last updated: February 18, 2016
Get Citation