5. CONCLUSIONS
Because of their remoteness and inhospitality, high-altitude (as well as
high-latitude) snow-melt dominated catchments remain understudied. These
catchments contribute a significant fraction of global streamflow
(Viviroli et al., 2007) and are also among the most susceptible to the
effects of changing climate (Adam et al., 2009). Mobilization and
downstream transport by river networks are critical processes in carbon
and nitrogen cycles. This makes developing a generalized understanding
of the solute dynamics of snowmelt dominated catchments, and in
particular the response to hydroclimatic perturbation, of global
importance. Como Creek represents one of the highest elevation locations
we yet have data for.
Using big, open-data is the new frontier in hydrological and ecological
sciences (Hampton et al., 2013), and this study relied entirely on
publicly available data. We took a network-of-networks approach to
combine historical and high-frequency precipitation, snowpack,
discharge, and solute data to assess drivers of carbon and nitrogen
export from a high altitude stream in the Rocky Mountains. We found that
DOC and NO3-N fluxes were strongly controlled with
discharge, over time scales ranging from minutes to decades. Seasonal
snowmelt pulses are the dominant driver of annual solute export.
Interannually, the magnitude and timing of the snowmelt pulse, and by
extension solute export, was strongly correlated with both the depth and
persistence of the snowpack. As in prior studies, we found that
clockwise C-Q hysteresis over the snowmelt pulse was suggestive of
seasonal depletion of solute pools. Yet, the high-frequency data
revealed pulses within pulses from individual events wherein
concentrations where enriched and C-Q hysteresis was counter-clockwise -
indicating that additional DOC and NO3-N pools persist
and can be readily mobilized, particularly through rain on snow events.
While the historical low-frequency grab sample data suggest that reduced
snowpack and earlier snowmelt may result in reduced export of DOC and
NO3-N, the sensor data make this conclusion uncertain,
as increasingly prevalent rain on snow events appear equally capable of
mobilizing solutes.