Climate strongly affects energy supply and demand in the Pacific Northwest (PNW) and Washington State (WA). We evaluate potential changes in the seasonality and annual amount of PNW hydropower production and changes in energy demand in a warming climate by linking simulated streamflow scenarios produced by a hydrology model to a simulation model of the Columbia River hydro system. Energy demand, and potential changes therein, are assessed estimates of heating degree days (HDD) and cooling degree days (CDD) for both the 20th century climate and projections of climate in three future periods (2010-2039, 2030-2059, and 2070-2099) and two emissions scenarios (IPCC A1B and B1). The gridded HDD and CDD values are then combined with population projections to create energy demand indices that respond both to climate, future population, and changes in air conditioning market penetration. We find that substantial changes in the amount and seasonality of energy supply and demand in the PNW are likely to occur over the next century in response to warming, precipitation changes, and population growth. In the 2020s, regional hydropower production increases by 0.5-4% in winter, decreases by 9-11% in summer, with annual reductions of 1-4%. Slightly larger increases in winter, and summer decreases, are projected for the 2040s and 2080s. In the absence of warming, population growth is projected to result in considerable increases in heating energy demand, however, the combined effects of warming and population growth are projected to result in net increases that are approximately one-half those associated with population growth alone. On the other hand, population growth combined with warming greatly increases the projected demand for cooling energy, notwithstanding that by the 2080s, total cooling energy requirements will still be substantially lower than heating energy demand.
Alan F. Hamlet, Se-Yeun Lee, Kristian E.B. Mickelson, Marketa M. Elsner
The Pacific Northwest (PNW) hydropower resource, central to the region's electricity supply, is vulnerable to the impacts of climate change. The Northwest Power andConservation Council (NWPCC), an interstate compact agency, has conducted long termplanning for the PNW electricity supply for its 2005 Power Plan. In formulating its power portfolio recommendation, the NWPCC explored uncertainty in variables that affect theavailability and cost of electricity over the next 20 years. The NWPCC conducted an initialassessment of potential impacts of climate change on the hydropower system, but these results are not incorporated in the riskmodel upon which the 2005 Plan recommendations are based. To assist in bringing climate information into the planning process, we present an assessment of uncertainty in future PNW hydropower generation potential based on a comprehensive set ofclimate models and greenhouse gas emissions pathways. We find that the prognosis for PNW hydropower supply under climate change is worse than anticipated by the NWPCC's assessment. Differences between the predictions of individual climate models are found to contribute more to overall uncertainty than do divergent emissions pathways. Uncertainty in predictions of precipitation change appears to bemore important with respect to impact on PNW hydropower than uncertainty in predictions of temperature change. We also find that a simple regression model captures nearly all of the response of a sequence of complex numerical models to large scale changes in climate. This result offers the possibility of streamlining both top-down impact assessment and bottom-up adaptation planning for PNW water and energy resources.
In ungauged basins, predicting streamflows is a major challenge for hydrologists and
water managers, with approaches needed to systematically generalize hydrometric
properties from limited stream gauge data. Here we illustrate how a geologic/geomorphic
framework can provide a basis for describing summer base flow and recession behavior at
multiple scales for tributaries of the Willamette River in Oregon. We classified the basin
into High Cascade and Western Cascade provinces based on the age of the underlying
volcanic bedrock. Using long-term U.S. Geological Survey stream gauge records, we
show that summer streamflow volumes, recession characteristics, and timing of response
to winter recharge are all linearly related to the percent of High Cascade geology in
the contributing area. This analysis illustrates how geology exerts a dominant control on
flow regimes in this region and suggests that a geological framework provides a useful
basis for interpreting and extrapolating hydrologic behavior.