The Kings River Experimental Watershed (KREW) in the southern Sierra Nevada of California contains watersheds at the rain-snow interface and watersheds that are snow dominated.  The higher elevation watersheds are likely to become similar to the lower watersheds given the future climate predictions for this area—a 1.6^°C increase and 33% loss of snowpack by 2060.  The six years of measurement at KREW contain two years of high precipitation and two years of below average precipitation.  What is the current variability among watersheds and between the two sites for stream discharge; precipitation; carbon (C) and nitrogen (N) inputs, pools, and outputs?

Results/Conclusions Although there is over a 1,000 m difference in elevation between the KREW research sites, the total precipitation is similar, but almost all of the precipitation comes as snow at the higher elevation watersheds.  While atmospheric concentrations of N pollutants are moderately elevated, there is no evidence that significant amounts of N are moving through the soils into the streams.  Atmospheric concentrations at the lower watersheds were 2 µg/m³ for nitric acid and 4 µg/m³ for ammonium (background levels should not exceed 0.4 µg/m³ for nitric acid or 1 µg/m³ for ammonium).  Concentrations at the higher watersheds were less than half of that measured at the lower elevations.  Wet season throughfall deposition of N ranged from 0.5 to 1.7 kg/ha/year.  Most N samples from stream water and shallow soil water are below detection levels (0.05 mg/l).  A consistent pattern of a slight increase in N is present during spring in soil water, possibly caused by snowmelt processes.  Forest vegetation seems to be taking up most available N; however, N concentrations in the mineral soil are high in surface horizons (routinely in excess of 50 mg/kg).  Soil C and N contents will be compared, and stream dissolved organic matter values reported.