Publication Date: 
December 2009
Viers, JH, G Epke, S Yarnell, and JF Mount. Characterization of the Unregulated Spring Snowmelt Recession in the Sierra Nevada, California, and Potential Changes with Regional Climate Warming. EOS TRANS. AGU, 90(53): H12D-06

In previous work, we developed a conceptual model for the ecology and management of the spring snowmelt recession in Mediterranean-montane catchments. This conceptual model focused on three components of the Natural Flow Regime: magnitude, timing, and rate of change. Here we provide a model definition and develop synthetic hydrographs of the spring snowmelt recession for unregulated catchments of the Sierra Nevada, California. By modeling the exponential decay of snowmelt pulses, we show the scalability of the spring snowmelt recession limb slope at multiple temporal scales and explore empirical evidence for stationarity found in unregulated rivers in contrast with regulated river systems. Lastly, we show the results of spring snowmelt recession dynamics for climate altered hydrologies simulated in the WEAP21 rainfall-runoff model for the entire western Sierra Nevada. Our results show that with regional climate warming the present rate of change in the snowmelt recession will significantly decrease due to substantial reductions in snowpack and increased duration of low flow conditions. These results suggest potential impacts to freshwater and riparian organisms, which currently respond to the spring snowmelt period and accompanying flow conditions as a favorable window of opportunity for reproduction and population expansion.