ESS postdoctoral researcher Darren Ficklin, in collaboration with professors Stewart-Frey (ESS) and Maurer (Civil Engineering), has assessed the impact of expected 21st century climatic changes on mountain streams in the Sierra Nevada.
Sierra Nevada snowmelt and runoff is a key source of water for many of California’s 38 million residents. The researchers used output from 16 global climate models (GCMs) and two emission scenarios (which give an estimate of future concentrations of greenhouse gases in the atmosphere based on economic development and population growth) to drive a hydrologic model at the sub-watershed scale and analyze all hydrologic components relevant for streamflow, which had not been undertaken before. The results showed that by the end of the century, annual streamflow is likely to decrease and snowmelt is likely to come earlier by several weeks. In addition, the timing and amounts of evapotranspiration, surface water flow and soil water flow will likely be affected. Most notably, Spring and Summer streamflow will likely decrease by 25 to more than 75% (median estimate). Flow decreases of this magnitude would have substantial impacts on both the human water supply and aquatic ecosystems.
A paper detailing the results of this study has just been accepted for publication in the Journal of the American Water Resources association (Ficklin DL, Stewart IT, Maurer EP, 2012. Projections of 21st century Sierra Nevada local hydrologic flow components using an ensemble of General Circulation Models, JAWRA, in press). It is part of a study investigating changes in streamflow and streamwater quality in mountain basins throughout the west that has been funded by the US Environmental Protection Agency.