Climate Change Modeling Needs and Efforts for Hydroelectric System Operations in the Pacific Northwest

Abstract:

This presentation will outline ongoing, multi-year hydroclimate change research between the Columbia River Management Joint Operating Committee (RMJOC), The University of Washington, Portland State University, and their many regional research partners and stakeholders. Climate change in the Columbia River Basin is of particular concern to the Bonneville Power Administration (BPA) and many Federal, Tribal and regional stakeholders. BPA, the U.S. Army Corp of Engineers, and U.S. Bureau of Reclamation, which comprise the RMJOC, conducted an extensive study in 2009-11 using climate change streamflows produced by the University of Washington Climate Impacts Group (CIG). The study reconfirmed that as more winter precipitation in the Columbia Basin falls as rain rather than snow by mid-century, particularly on the U.S. portion of the basin, increased winter runoff is likely, followed by an earlier spring snowmelt peak, followed by less summer flows as seasonal snowmelt diminished earlier in the water year.

Since that initial effort, both global and regional climate change modeling has advanced. To take advantage of the new outputs from the Fifth Coupled Model Intercomparison Project (CMIP-5), the RMJOC, through BPA support, is sponsoring new hydroclimate research which considers not only the most recent information from the GCMs, but also the uncertainties introduced by the hydroclimate modeling process itself. Historical streamflows, which are used to calibrate hydrologic models and ascertain their reliability, are subject to both measurement and modeling uncertainties. Downscaling GCMs to a hydrologically useful spatial and temporal resolution introduces uncertainty, depending on the downscaling methods. Hydrologic modeling introduces uncertainties from calibration and geophysical states, some of which, like land surface characteristics, are likely to also change with time. In the upper Columbia Basin, glacier processes introduce yet another source of uncertainty. The latest joint effort attempts to ascertain the relative contributions of these uncertainties in comparison to the uncertainties brought by changing climate itself.