Dr. Sarah Null presented her research at DISCCRS IV.

Dr. Sarah Null presented her research on river temperature impacts of climate warming in California’s Sierra Nevada Mountains at DISCCRS from March 13 – 20 at Saguaro Ranch in Mesa, Arizona. The aim of DISCCRS (DISsertations initiative for the advancement of Climate Change ReSearch) is to foster interdisciplinary work by connecting young researchers to develop creative solutions to problems relating to climate change.

Climate Warming in California’s Sierra Nevada: Potential Water Temperature Impacts and Resiliency
Sarah E. Null, Joshua H. Viers, Jeffrey F. Mount, Michael L. Deas, Stacy K. Tanaka

Water temperatures are an important characteristic of stream ecosystems, and influence the distribution, abundance, and health of aquatic organisms. This study assesses climate warming impacts on unimpaired stream temperatures in west-slope Sierra Nevada watersheds from the Feather River to the Kern River to highlight contributing factors that make rivers more vulnerable or resilient to climate warming, such as elevation, latitude, flow volume, drainage area, and year type. Weekly instream flow estimates from WEAP21, a spatially explicit rainfall-runoff model were passed to RTEMP, an equilibrium water temperature model, to estimate river temperatures using the heat budget, coarse river channel geometry, and exposure time of water to atmospheric conditions. Air temperature was uniformly increased by 2ºC, 4ºC, and 6ºC as a sensitivity analysis to bracket the range of likely outcomes for regional stream temperatures. Other meteorological conditions, including precipitation, were left unchanged from historical values. Overall, water temperatures increase most at middle elevations (1,500 – 2,500 m), where snowfall shifts to rainfall, and rivers may heat by more than 1.6ºC for each 2ºC increase in air temperature. River temperatures are generally most resilient to climate warming at the high elevations of southern Sierra Nevada watersheds. Future changes to river temperatures are likely to impact instream habitat conditions, altering the distribution and abundance of fish and wildlife. This work improves our understanding of water temperature resiliency to climate warming for rivers in the Sierra Nevada, and provides river temperature estimates for water managers who must balance instream habitat protection with human water uses, such as water supply, hydropower, flood control, and recreation.