High elevation mountain watersheds are undergoing rapid warming
and declining snow fractions worldwide, causing earlier and
quicker snowmelt. Understanding how this hydrologic shift
affects subsurface flow paths, biogeochemical reactions, and
solute export has been challenging due to the entanglement of
hydrological and biogeochemical processes. Coal Creek, a
high-elevation catchment (2,700 3,700 m, 53 km2) in Colorado, is
experiencing a higher rate of warming than surrounding low-lying
areas. This warming corresponds with dynamic and increased
responses from biogenic solutes and dissolved organic carbon
(DOC), whereas the behavior of geogenic solutes and dissolved
inorganic carbon (DIC) has remained relatively unchanged. DOC
has experienced the largest concentration increase (>3x), with
annual average flow weighted concentrations positively
correlated to average annual temperature. This suggests
temperature is the main driver of increasing DOC levels.
Although DOC and DIC response to warming is influenced by many
drivers, the relative contribution of each remains unknown. DOC
and DIC were analyzed to incorporate both carbon component
products of soil respiration (DOC and CO2) and to represent high
solute concentrations transported by shallow (DOC) versus deep
(DIC) subsurface flow. The contrasting behavior of these carbon
solutes indicates climate change and warming are driving changes
in organic matter decomposition and soil respiration. Modeling
results from the process-based model HBV-BioRT show increased
temperatures cause earlier snowmelt and streamflow generation
and lower peak discharge. As stream flow generation occurs
earlier, so do DOC flushing and DIC dilution events.
Additionally, post-snowmelt periods show greater DOC production
and concentrations under warming scenarios. Results indicated
increased production of DOC in post-snowmelt periods. DOC is
then flushed out by earlier snowmelt partitioned through the
shallow soil zone. Most process-based studies lack a
watershed-scale understanding of carbon transformation and flow
path alterations. This work demonstrates complex hydrologic and
biogeochemical coupling at the watershed scale to illustrate how
water flow paths and chemistry are responding to a changing
climate in highelevation mountain watersheds.
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Strontium isotope dynamics reveal streamflow contributions from shallow flow paths during snowmelt in a montane watershed, Provo River, Utah, USA
Quantifying the routing of snowmelt to surface water is critical for predicting the impacts of atmospheric deposition and changing land use on water quality in montane catchments. To investigate solute sources and streamflow in the montane Provo River watershed (Utah, USA), we used time‐series87Sr/86Sr ratios sampled at three sites (Soapstone, Woodland and Hailstone) across a gradient of bedrock types. Soils are influenced by aeolian dust contributions, with distinct87Sr/86Sr ratios relative to siliciclastic bedrock, providing an opportunity to investigate shallow versus deeper flow paths for controlling water chemistry. At the most upstream site (Soapstone), Sr concentrations averaged ~17 μg/L with minimal dilution during snowmelt suggesting subsurface flow paths dominated streamflow. However, a decrease in87Sr/86Sr ratios from ~0.717 during baseflow to as low as ~0.713 during snowmelt indicated the activation of shallow flow paths through dust‐derived soils. In contrast, downstream sites receiving water inputs from Sr‐rich carbonate bedrock (Woodland and Hailstone) exhibited strong dilution of Sr from ~120 to 20 μg/L and an increase in87Sr/86Sr ratios from ~0.7095 to ~0.712 during snowmelt. A three‐component mixing model using87Sr/86Sr ratios and Sr concentrations at Soapstone showed water inputs were dominated by direct snowmelt and flushed soil water during runoff and groundwater during baseflow. At Woodland and Hailstone, a two‐component mixing model showed that the river was a mixture of groundwater and up to 75% upstream channel water during snowmelt. Our findings highlight the importance of flushed soil water for controlling stream water discharge and chemistry during snowmelt, with the signal from the upstream site propagating downstream in a nested catchment. Further, aeolian dust contributes to the solute chemistry of montane streams with potential impacts on water quality along shallow flow paths. Potential contaminants in these surface soils (e.g., Pb deposition in dust) may have significant impacts on water quality during snowmelt runoff.
more » « less- NSF-PAR ID:
- 10366331
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Hydrological Processes
- Volume:
- 36
- Issue:
- 1
- ISSN:
- 0885-6087
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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