Williams, Mark W听1听;听Hill, Ken听2听;听Caine, Nel听3
1听颁鲍-叠辞耻濒诲别谤
2听National Park Service
3听颁鲍-叠辞耻濒诲别谤
Potential climate impacts on the hydrochemistry of two seasonally snow covered catchments is evaluated using 24 years of data from Niwot Ridge Long Term Ecological Research Site, Colorado. At the larger (220 ha), higher elevation (3570 m) GL4 catchment annual discharge did not change signi铿乧antly based on nonparametric trend testing. However, October stream铿俹w volumes and groundwater storage did increase, despite drought conditions near the end of the record in 2000-2004. In contrast, at the smaller (8 ha), lower elevation (3400 m) MART catchment, annual discharge decreased signi铿乧antly over the study period with the most substantial changes in July-September. The study period was separated into "wet", "normal", and "dry" years based on the 75th and 25th quartiles of annual precipitation. Results indicate that MART is particularly sensitive to changes in precipitation with dry years exhibiting decreased snowmelt peak 铿俹ws, earlier snowmelt timing, decreased annual discharge, and reduced late-season 铿俹ws. GL4 was less susceptible to changes in precipitation and surprisingly late-season 铿俹w volumes (Sept.-Oct.) were not signi铿乧antly different between wet, normal, and dry conditions. Surprisingly, during dry years both the concentrations and annual fluxes of Ca2+ and SO42- increased in the outflow of GL4, but not at the Martinelli catchment. These differeneces in hydrochemistry were particularly pronounced during the low-flow period. Streamwater chemistry in GL4 during drought years resembled that of permafrost, suggesting augmented flow during the fall due to permafrost melt. This study shows that seasonally snow covered catchments are particularly sensitive to changes in climate, but the hydrochemical response may depend on landscape characteristics.