Although diversity is a hallmark of how hydroelectric projects operate, they must work together to maximize efficiency.
One way to think about this is to imagine that all projects in the system had a single owner. That owner would synchronize operations to maximize power production while meeting flood control, navigation, irrigation, recreation, and environmental needs. Coordinated operations also provide benefits such as supplying surplus power to a utility experiencing an emergency because of transmission lines or turbines that are shut down.
Beyond thinking and acting as one, the operational key to achieving maximum efficiency and flexibility is storage. In the Columbia River system, there are 55 million acre-feet of storage. Of this, 42 million acre-feet are available for coordinated purposes. That’s enough to cover the Northwest four inches deep in water. With this storage comes the ability to hold and release water in a way that meets multiple needs while extending the time frame for when power can be generated.
Two agreements, the Pacific Northwest Coordination Agreement (PNCA) and the Columbia River Treaty, underpin how the system functions in a coordinated fashion. The Treaty was signed in 1961 and PNCA took effect in 1964. Both are still in place, although PNCA will end in 2003 if an extension is not negotiated.
The Columbia River Treaty brings Canada into the process as a partner. Canada is where the Columbia begins its journey and where 30 percent of its streamflow originates. With the treaty, there are two important outcomes: the ability to store more water and annual planning for river projects.
In the case of storage, three large storage projects were built in Canada and one was built in the United States. These dams more than doubled the storage capacity of the hydro system and thus introduced much greater operational flexibility. Second, the treaty requires joint annual planning for river operations. Specifically, representatives from the Corps, BPA and B.C. Hydro create one plan that takes a six-year view of storage operations and another that takes a twelve-month view.
The second agreement is the Pacific Northwest Coordination Agreement (PNCA), which was inspired by the Columbia River Treaty. This agreement is signed by the Bureau of Reclamation, BPA, the Corps, and 15 public and private generating utilities. With PNCA comes the ability to coordinate operations among federal, public and private owners.
At the heart of PNCA is a set of operating rules. These rules are then used to create a set of “rule curves” that govern the amount of firm energy that each project can produce during particular months. These parameters form the basis for operating like a single system.
How rule curves are set and the amount of coordination that must occur is, of course, fairly complex. The actual work is carried out by representatives from each participating utility. These representative work together as part of the Northwest Power Pool, which also helps coordinate operation and transmission concerns.