Transboundary Implications of Climate Change for the Columbia River Basin Richard N.Palmer, Alan F. Hamlet, Philip W. Mote, Nate Mantua, Dennis P. Lettenmaier JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering University of Washington

Science of climate change Thousands of peer-reviewed scientific papers Intergovernmental Panel on Climate Change (IPCC) Major reports in 1990, 1996, 2001, 2007 2001 report involved 637 contributing authors, 420 peer-reviews, then another review by government experts and policy-makers Conclusions: “An increasing body of observations gives a collective picture of a warming world and other changes in the climate system.” “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.” The basis for scientific understanding are the thousands of papers published in peer-reviewed journals. These papers usually focus on small pieces of the overall subject. Selective choices of a handful of papers can be used to support various points of view, but do not necessarily represent the broadest perspective nor the best expert judgment. It is the function of a scientific assessment to collect the disparate and sometimes conflicting pieces, to reconcile different points of view where possible and note them where not, and to summarize the state of knowledge in a lengthy document. On the subject of climate change, this function has been performed since 1988 by the Intergovernmental Panel on Climate Change (IPCC), which was formed under the auspices of the United Nations Environment Programme and the World Meteorological Organization. It has issued three major reports, most recently a three-volume report issued in 2001. The first volume, which runs to 881 pages, covered the scientific basis of climate change and involved 639 expert authors and over 300 reviewers. It was a monumental undertaking and represents the best available statement of the world’s climate experts. In the summary for policymakers, the IPCC stated that Earth is indeed warming and that humans are probably partly responsible. These conclusions were underscored for President Bush last June in a special report by the National Academy of Sciences. In a press conference on June 11, 2001, he quoted the report’s conclusions, apparently accepting that Earth is warming and that humans are partly responsible. (My understanding is that it was Senator Larry Craig (R-ID) who urged President Bush to turn to the NAS for answers to some key questions.) Sources: The IPCC report is available through Cambridge University Press. The Summary for Policymakers is available as a pdf online from www.ipcc.ch. The NAS report is available from www.nap.edu/catalog/10139.html President Bush’s speech on June 11 is available from the White House web site, www.whitehouse.gov/

Science of climate change 2001 White House request for advice from the US National Academy of Sciences “… are there any substantive differences between the IPCC Reports and IPCC Summaries?” National Research Council convened a panel of 11 leading US climate scientists to write the report Conclusions: “Greenhouse gases are accumulating in Earth’s atmosphere as a result of human activities, causing temperatures to rise … The committee generally agrees with the assessment of human-caused climate change presented in the IPCC scientific report …” The basis for scientific understanding are the thousands of papers published in peer-reviewed journals. These papers usually focus on small pieces of the overall subject. Selective choices of a handful of papers can be used to support various points of view, but do not necessarily represent the broadest perspective nor the best expert judgment. It is the function of a scientific assessment to collect the disparate and sometimes conflicting pieces, to reconcile different points of view where possible and note them where not, and to summarize the state of knowledge in a lengthy document. On the subject of climate change, this function has been performed since 1988 by the Intergovernmental Panel on Climate Change (IPCC), which was formed under the auspices of the United Nations Environment Programme and the World Meteorological Organization. It has issued three major reports, most recently a three-volume report issued in 2001. The first volume, which runs to 881 pages, covered the scientific basis of climate change and involved 639 expert authors and over 300 reviewers. It was a monumental undertaking and represents the best available statement of the world’s climate experts. In the summary for policymakers, the IPCC stated that Earth is indeed warming and that humans are probably partly responsible. These conclusions were underscored for President Bush last June in a special report by the National Academy of Sciences. In a press conference on June 11, 2001, he quoted the report’s conclusions, apparently accepting that Earth is warming and that humans are partly responsible. (My understanding is that it was Senator Larry Craig (R-ID) who urged President Bush to turn to the NAS for answers to some key questions.) Sources: The IPCC report is available through Cambridge University Press. The Summary for Policymakers is available as a pdf online from www.ipcc.ch. The NAS report is available from www.nap.edu/catalog/10139.html President Bush’s speech on June 11 is available from the White House web site, www.whitehouse.gov/

Example of a flawed water planning study: The Colorado River Compact of 1922 The Colorado River Compact of 1922 divided the use of waters of the Colorado River System between the Upper and Lower Colorado River Basin. It apportioned **in perpetuity** to the Upper and Lower Basin, respectively, the beneficial consumptive use of 7.5 million acre feet (maf) of water per annum. It also provided that the Upper Basin will not cause the flow of the river at Lee Ferry to be depleted below an aggregate of 7.5 maf for any period of ten consecutive years. The Mexican Treaty of 1944 allotted to Mexico a guaranteed annual quantity of 1.5 maf. **These amounts, when combined, exceed the river's long-term average annual flow**.       

What’s the Problem? Despite a general awareness of these issues in the water planning community, there is growing evidence that future climate variability will not look like the past and that current planning activities, which frequently use a limited observed streamflow record to represent climate variability, are in danger of repeating the same kind of mistakes made more than 80 years ago in forging the Colorado River Compact. Long-term planning and specific agreements influenced by this planning (such as long-term transboundary agreements) should be informed by the best and most complete climate information available, but frequently they are not.

Trends in April 1 SWE 1950-1997 Mote P.W.,Hamlet A.F., Clark M.P., Lettenmaier D.P., 2005, Declining mountain snowpack in western North America, BAMS, 86 (1): 39-49

spring flows rise and summer flows drop As the West warms, spring flows rise and summer flows drop Stewart IT, Cayan DR, Dettinger MD, 2005: Changes toward earlier streamflow timing across western North America, J. Climate, 18 (8): 1136-1155 Spring snowmelt timing has advanced by 10-40 days in most of the West, leading to increasing flow in March (blue circles) and decreasing flow in June (red circles), especially in the Pacific Northwest.

Observed 20th century variability Curves are fits to ln(CO2) for A2 (solid) and B1 (dashed) Warming ranges are shown for 2020s, 2040s and 2090s relative to 1990s. Central estimates: 0.7C by 2020s, 1.7C by 2040s, 3.2C by 2090s. Pink box shows +/- 2 sigma for annual average temperature (sigma=0.6C). Red lines show previous generation of change scenarios. 0.4-1.0°C Pacific Northwest

Observed 20th century variability % -1 to +3% +6% +2% +1% Curves are fits to ln(CO2) for A2 (solid) and B1 (dashed) Precip changes are shown for 2020s, 2040s and 2090s relative to 1990s. Central estimates: 1% by 2020s, 3% by 2040s, 6% by 2090s. Pink bar shows +/- 2 sigma for PNW annual precip. Observed 20th century variability -1 to +9% -2 to +21% Pacific Northwest

Global Climate Change Scenarios and Hydrologic Impacts for the PNW

The warmest locations are most sensitive to warming +4.5% winter precip

Changes in Simulated April 1 Snowpack for the Canadian and U. S Changes in Simulated April 1 Snowpack for the Canadian and U.S. portions of the Columbia River basin (% change relative to current climate) 20th Century Climate “2020s” (+1.7 C) “2040s” (+ 2.25 C) -3.6% -11.5% -21.4% -34.8% April 1 SWE (mm)

Naturalized Flow for Historic and Global Warming Scenarios Compared to Effects of Regulation at 1990 Level Development Historic Naturalized Flow Estimated Range of Naturalized Flow With 2040’s Warming Regulated Flow

Water Resources Implications for the Columbia River Basin

Impacts on Columbia Basin hydropower supplies Winter and Spring: increased generation Summer: decreased generation Annual: total production will depend primarily on annual precipitation (+2C, +6%) (+2.3C, +5%) (+2.9C, -4%) NWPCC (2005)

Warming climate impacts on electricity demand Reductions in winter heating demand Small increases in summer air conditioning demand in the warmest parts of the region From a variety of charts in an NWPCC report (http://www.nwcouncil.org/library/2002/2002-11.pdf; see Fig.15), the monthly electricity demand during the winter is ~25000 MW; during the summer it's more like 20000 MW. So, the changes in winter demand in this figure are probably a reduction ~10% (as a maximum). This jives with some of the graphs from Sailor (I attached one) that calculates the sensitivity of electricity consumption for a 2 degree C warming to be a little less than 10%. NWPCC 2005

Adaptation to climate change will require complex tradeoffs between ecosystem protection and hydropower operations Source: Payne, J.T., A.W. Wood, A.F. Hamlet, R.N. Palmer, and D.P. Lettenmaier, 2004, Mitigating the effects of climate change on the water resources of the Columbia River basin, Climatic Change, Vol. 62, Issue 1-3, 233-256

Flood Control vs. Refill Streamflow timing shifts can reduce the reliability of reservoir refill Full Model experiments (see Payne et al. 2004) have shown that moving spring flood evacuation two weeks to one month earlier in the year helps mitigate reductions in refill reliability associated with streamflow timing shifts. Payne, J.T., A.W. Wood, A.F. Hamlet, R.N. Palmer, and D.P. Lettenmaier, 2004, Mitigating the effects of climate change on the water resources of the Columbia River basin, Climatic Change, Vol. 62, Issue 1-3, 233-256

Temperature thresholds for coldwater fish in freshwater Warming temperatures will increasingly stress coldwater fish in the warmest parts of our region A monthly average air temperature of 68ºF (20ºC) has been used as an upper limit for resident cold water fish habitat, and is known to stress Pacific salmon during periods of freshwater migration, spawning, and rearing +1.7 °C +2.3 °C

Implications for Transboundary Agreements in the Columbia Basin Climate change will result in significant hydrologic changes in the Columbia River and its tributaries. Snowpack in the BC portion of the Columbia basin is much less sensitive to warming in comparison with portions of the basin in the U.S. and streamflow timing shifts will also be smaller in Canada. As warming progresses, Canada will have an increasing fraction of the snowpack contributing to summer streamflow volumes in the Columbia basin. These differing impacts in the two countries have the potential to “unbalance” the current coordination agreements, and will present serious challenges to meeting instream flows on the U.S. side. Changes in flood control, hydropower production, and instream flow augmentation will all be needed as the flow regime changes.

Selected References and URL’s Climate Impacts Group Website http://www.cses.washington.edu/cig/ White Papers, Agenda, Presentations for CIG 2001 Climate Change Workshop http://jisao.washington.edu/PNWimpacts/Workshops/Skamania2001/WP01_agenda.htm Climate Change Streamflow Scenarios for Water Planning Studies http://www.ce.washington.edu/~hamleaf/climate_change_streamflows/CR_cc.htm Northwest Power and Conservation Council Columbia Basin Hydropower Study http://www.nwppc.org/energy/powerplan/plan/Default.htm Refs on Climate Variability and Climate Change http://www.ce.washington.edu/~hamleaf/hamlet/publications.html