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Presentation
Stream Temperature Sensitivity to Climate Warming in California's Sierra Nevada
American Geophysical Union, Fall Meeting 2010, abstract #GC51D-0773 (2010)
  • Sarah Null, Utah State University
Abstract

Water temperatures influence the distribution, abundance, and health of aquatic organisms in stream ecosystems. Improving understanding of climate warming on the thermal regime of rivers will help water managers better manage instream habitat. This study assesses climate warming impacts on unregulated stream temperatures in California’s west-slope Sierra Nevada watersheds from the Feather River to the Kern River. We used unregulated hydrology to isolate climate induced changes from those of water operations and land use changes. A 21 year timeseries of weekly instream flow estimates from WEAP21, a spatially explicit rainfall-runoff model were passed to RTEMP, a simplified model based on equilibrium temperature theory, to estimate stream temperatures using net heat exchange, coarse river channel geometry, and exposure time of water to atmospheric conditions. Air temperature was uniformly increased by 2○C, 4○C, and 6○C as a sensitivity analysis to bracket the range of likely outcomes for stream temperatures. Other meteorological conditions, including precipitation, were left unchanged from historical values. Overall, stream temperatures increased by an average of 1.6○C for each 2○C rise in air temperature, and increased most at middle elevations. Thermal heterogeneity existed within and between basins (Figure 1). The high watersheds of the southern Sierra Nevada and the Feather River watershed were less vulnerable to changes in the thermal regime of rivers from climate warming. Precipitation as rainfall instead of snowfall, and low flow conditions were two characteristics that drove water temperatures dynamics with climate warming. These results suggest the thermal regime of rivers will change with climate warming. Viable coldwater habitat will shift to higher elevations and will likely be reduced in California. Understanding potential changes to stream temperatures from climate warming will affect how fish and wildlife are managed, and must be incorporated into modeling studies, restoration assessments, environmental impact statements, and licensing operations of hydropower facilities to best estimate future conditions and achieve desired outcomes. Average annual number of weeks stream temperature exceeds 24°C with incremental uniform 2°C air temperature increases

Disciplines
Publication Date
2010
Citation Information
Sarah Null. "Stream Temperature Sensitivity to Climate Warming in California's Sierra Nevada" American Geophysical Union, Fall Meeting 2010, abstract #GC51D-0773 (2010)
Available at: http://works.bepress.com/sarah_null/47/