期刊
WATER RESOURCES RESEARCH
卷 50, 期 11, 页码 8694-8713出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2013WR015243
关键词
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资金
- NSF [EAR1032295, EAR1032308]
- NSF's Boulder Creek Critical Zone Observatory
- Direct For Biological Sciences
- Division Of Environmental Biology [1242626] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Earth Sciences [1124576, 1141764] Funding Source: National Science Foundation
This study compares stream nitrate (NO3-) concentrations to spatially distributed snowmelt in two alpine catchments, the Green Lakes Valley, Colorado (GLV4) and Tokopah Basin, California (TOK). A snow water equivalent reconstruction model and Landsat 5 and 7 snow cover data were used to estimate daily snowmelt at 30 m spatial resolution in order to derive indices of new snowmelt areas (NSAs). Estimates of NSA were then used to explain the NO3- flushing behavior for each basin over a 12 year period (19962007). To identify the optimal method for defining NSAs and elucidate mechanisms underlying catchment NO3- flushing, we conducted a series of regression analyses using multiple thresholds of snowmelt based on temporal and volumetric metrics. NSA indices defined by volume of snowmelt (e.g., snowmelt <= 30 cm) rather than snowmelt duration (e.g., snowmelt <= 9 days) were the best predictors of stream NO3- concentrations. The NSA indices were better correlated with stream NO3- concentration in TOK (average R-2 = 0.68) versus GLV4 (average R-2 = 0.44). Positive relationships between NSA and stream NO3- concentration were observed in TOK with peak stream NO3- concentration occurring on the rising limb of snowmelt. Positive and negative relationships between NSA and stream NO3- concentration were found in GLV4 with peak stream NO3- concentration occurring as NSA expands. Consistent with previous works, the contrasting NO3- flushing behavior suggests that streamflow in TOK was primarily influenced by overland flow and shallow subsurface flow, whereas GLV4 appeared to be more strongly influenced by deeper subsurface flow paths.
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