What Is the Importance of the Lower Snake River Dams for Future Hydropower Generation?

Salah Alsharari

doi:10.7273/000006381

There is a growing controversy behind the Lower Snake River dams (Ice Harbor, Lower Monumental, Little Goose, and Lower Granite). While originally built and still critical for navigation purposes, these dams produce a significant percentage of renewable energy to the region in the form of hydropower. With a total powerhouse capacity of more than 3,000 megawatts, the hydropower generators located in all four dams produced 6.8 billion kilowatt hours of energy in 2015. However, the public perception is that there are negative impacts on anadromous fish populations, including several that are listed on the Environmental Protection Agency’s Endangered Species Act list (Steelhead Trout and Chinook, Coho, Chum, and Sockeye Salmon). The extent to which fish populations have been impacted by the dams is beyond the scope of this study. Herein, we examine just one aspect of this debate, which is, “How important are the Lower Snake River dams for regional hydropower production historically, and how might this change in a future climate?” We had three objectives to address this question, which were as follows. 1) Update an existing hydropower simulation model (RColSim) with the newest information related to hydraulic capacity, net head, and turbine efficiency. 2) Evaluate the model by comparison of observed and modeled streamflow and hydropower generation. 3) Address the research question by simulating the hydropower generated by the four Lower Snake Dams (we will call this SRB) and compare this to the hydropower generated over the U.S. portion of hydropower generated from the Snake and Columbia mainstem dams (we will call this CRB). Despite the fact that our research indicates that climate change is increasing the ratio of SRB to CRB hydropower output, this rise is still minor, meaning that the relative contribution of SRB to CRB in hydropower generation has merely raised by less than 0.5%. We show that the increase of this ratio is due to changing streamflow patterns, which is likely primarily due to precipitation increasing in the SRB faster than in the CRB. This could also partly be due to temperature increasing faster in the CRB as a whole compared to the SRB, possibly resulting in a relative increase in ET in the CRB as compared to just over the SRB. We also show that there is consistent pattern in the SRB/CRB ratio at the monthly scale. Both of these river systems are snowmelt dominant and respond to warming by a shift in the streamflow peak from summer towards winter. Because the SRB has a warmer baseline climate, it responds more quickly to warming than does the CRB as a whole, causing the ratio of SRB to CRB hydropower to increase in the winter and decrease in the summer. Even though our results show that the importance of SRB to CRB in hydropower generation would remain the same, their contribution raises questions about adaptability for the remaining US CRB if these dams were removed. While this study does not incorporate the impacts of the dams on fish populations, we recognize that this is a crucial part of the story and should be rigorously investigated by wildlife scientists.

What Is the Importance of the Lower Snake River Dams for Future Hydropower Generation?

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