Climate Change and Stream Temperature in the Willamette River Basin: Implications for Fish Habitat

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World Scientific Series on Asia-Pacific Weather and Climate

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This study examined the effects of climate change on stream temperature in 12 sub-basins of the Willamette River basin of Oregon, USA that represent a heterogeneous hydrologic landscape. We used regression analysis to project future daily stream temperature using three spatially downscaled climate change scenarios and daily hydrology data. Daily maximum stream temperature was best explained by a combination of the 15 day moving average of daily air temperature and daily streamflow. Together with a reduction in summer streamflow, rising air temperature may increase stream temperature 1–4°C by the 2080s. Stream temperature rises modestly in groundwater-fed streams in high elevations, illustrating that groundwater-fed streams could be more resilient to climate warming and reduced surface flow. In contrast, lowland surfacewater-fed streams that lack riparian vegetation will be most vulnerable to climate change since stream temperature is projected to increase most (up to 4°C) under the highest climate change scenario. Such changes will have negative consequences for cold-water fishes that are already listed as endangered species. The exceedance probability of threshold temperature (17.8°C and 21°C) increased substantially, particularly in the lowland areas, suggesting future management practices for threatened and endangered fish species should focus on improving thermal conditions in those reaches.


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Published in World Scientific Series on Asia-Pacific Weather and Climate: Volume 10



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