The elevation of Grant PUD’s two reservoirs, Wanapum and Priest Rapids, can vary up or down within the maximum and minimum levels of our operating license, for several reasons.
These include marketing opportunities, operation and maintenance activities at each dam, environmental constraints, and river flow. Over the past few years, with the growth in the volume of variable energy generating resources in our region, Grant PUD has seen an increase in the hourly fluctuation of both the Wanapum and Priest Rapids reservoirs due to our ability to help balance these resources with fast‐ramping hydropower.
For example, to support the use of a variable energy resources such as solar, our reservoirs are sometimes kept at the lower end of our minimum operating levels to provide storage capacity while solar power is being generated. As the reservoirs re‐fill, the fast‐ramping ability of hydropower and the capacity in the reservoir is used to meet energy demands when solar power is no longer available or viable.
Grant PUD believes this trend will continue as more and more renewables are added in the region to meet compliance targets under new legislation aimed at addressing climate change. This means there are times when the reservoirs may be kept in the lower end of our minimum operating range for extended periods of time.
