|Working Group II: Impacts, Adaptation and Vulnerability|
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15.3.2. Subregional and Extra-Regional Cases
The discussion that follows offers a sample of subregional and extra-regional cases that reflect the unique and changing nature of the relationship between climate and places in the North American context. Six subregions have been defined: Pacific, Rocky Mountains-Southwest United States, Prairies-Great Plains, Great Lakes-St. Lawrence, North Atlantic, and Southeast United States (see Figure 15-9). These subregions represent unique landscapes that have experienced development paths that reflect natural potential for resource development as well as region-specific histories of evolving economies and communities. Some of these cases describe responses to recent extreme events. Others focus on scenarios of future climatic changes. Canada and the United States have a long history of cooperating on resource management concerns in transboundary areas, including the Boundary Waters Treaty of 1909 and more recent agreements on transboundary air pollution, watershed development, and the environmental agreement associated with NAFTA. There also have been binational and subregional conflicts over a wide range of issues that are climate-sensitive, including water resources, wetland protection, trading of forest and agricultural commodities, and harvesting of transboundary fish stocks. Various cooperative management approaches are being considered. Could climate change make a difference in any of these conflicts? Extra-regional issues are considered for the Arctic, U.S.-Mexican, and U.S.-Caribbean borders.
This subregion includes the Columbia River basinthe fourth-largest in North America, and one of the most valuable and heavily developed watersheds. The Columbia system produces 18,500 MW of hydroelectricity; it also is managed for flood control, agriculture, navigation, sport and commercial fisheries, log transportation, recreation, wildlife habitat, and urban, industrial, and aboriginal uses. Climate variability affects the total volume and temporal pattern of natural runoff, although binational management agreements have substantially altered this pattern. Any hydrological changes caused by long-term climatic change will have impacts that may affect the management of the system and the nature of conflicts among various users. Recent management and policy changes have led to changes in system operations; fish habitat protection now is regarded as a high priorityon par with hydroelectricity production and flood control (Cohen et al., 2000).
Climatic change is expected to lead to reductions in annual streamflow. Estimates for three warming scenarios range from a small increase to a decrease of 16% by 2050, with an earlier annual peak, higher winter flows, and lower summer flows (Lettenmaier et al., 1996, 1999; Hamlet and Lettenmaier, 1999; Miles et al., 2000). This would affect system reliability. Results from a reservoir system model for the driest of the three scenarios [based on the Max Planck Institute (MPI) GCM, ECHAM-4] indicate reductions of 15% in reliability for Snake River irrigation, 11% for McNary Dam "biological flow" (to support fish habitat), 14% for firm energy production, and 19% for nonfirm energy production. Reliability for flood control would remain relatively unchanged in this case but would decrease in the wetter scenarios (Hamlet and Lettenmaier, 1999; Miles et al., 2000).
Interviews were held in 1997 with water resources managers and other stakeholders
in the upstream portion of the Columbia, on the Canadian side. Their responses
to the MPI scenario were similar to those obtained from the reservoir system
model. For example, they noted that flood risk would not necessarily be reduced
because upstream storage facilities may be releasing high discharges for fish
habitat protection or other reasons. Similarly, irrigation supply and hydroelectricity
production would be reduced because of lower annual flow combined with fish
protection requirements. In these circumstances, regional utilities might have
to purchase electricity from fossil fuel sources, thereby affecting the region's
ability to meet GHG emission targets (Cohen et al., 2000).
This case study suggests that despite the high level of development and management in the Columbia basin, vulnerabilities would still exist and impacts could still occur in scenarios of natural streamflow changes caused by global climate change. It also suggests that expanded development of hydroelectric facilities, as a means of reducing GHG emissions, will create considerable challenges to management, given increases in the sensitivity of regional energy supplies and other water-related resources to climate.
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