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Understanding the Whisper of Headwaters

Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Ecol. Evol. | doi: 10.3389/fevo.2019.00046

Spatiotemporal Heterogeneity of Water Flowpaths Controls Dissolved Organic Carbon Sourcing in a Snow-dominated, Headwater Catchment

 Anna G. Radke1,  Sarah E. Godsey1*,  Kathleen A. Lohse1, Emma McCorkle1, Julia Perdrial2, Mark S. Seyfried3 and  W. S. Holbrook4
  • 1Idaho State University, United States
  • 2University of Vermont, United States
  • 3Watershed Management Research, United States Department of Agriculture, United States
  • 4Virginia Tech, United States

The non-uniform distribution of water in snowdrift-driven systems can lead to spatial heterogeneity in vegetative communities and soil development, as snowdrifts may locally increase weathering. The focus of this study is to understand the coupled hydrological and biogeochemical dynamics in a heterogeneous, snowdrift-dominated headwater catchment (Reynolds Mountain East, Reynolds Creek Critical Zone Observatory, Idaho, USA). We determine the sources and fluxes of stream water and dissolved organic carbon (DOC) at this site, deducing likely flowpaths from hydrometric and hydrochemical signals of soil water, saprolite water, and groundwater measured through the snowmelt period and summer recession. We then interpret flowpaths using end-member mixing analysis in light of inferred subsurface structure derived from electrical resistivity and seismic velocity transects. Streamwater is sourced primarily from groundwater (averaging 25% of annual streamflow), snowmelt (50%), and water travelling along the saprolite/bedrock boundary (25%). The latter is comprised of the prior year’s soil water, which accumulates DOC in the soil matrix through the summer before flushing to the saprolite during snowmelt. DOC indices suggest that it is sourced from terrestrial carbon, and derives originally from soil organic carbon (SOC) before flushing to the saprolite/bedrock boundary. Multiple subsurface regions in the catchment appear to contribute differentially to streamflow as the season progresses; sources shift from the saprolite/bedrock interface to deeper bedrock aquifers from the snowmelt period into summer. Unlike most studied catchments, lateral flow of soil water during the study year is not a primary source of streamflow. Instead, saprolite and groundwater act as integrators of soil water that flows vertically in this system. Our results do not support the flushing hypothesis as observed in similar systems and instead indicate that temporal variation in connectivity may cause the unexpected dilution behavior displayed by DOC in this catchment.

Keywords: Dissolved organic carbon (DOC), Hydrologic connectivity, soil water, Ground water, Snow, Critical zone observatory, dryland ecosystems

Received: 01 Sep 2018; Accepted: 07 Feb 2019.

Edited by:

Timothy P. Burt, Durham University, United Kingdom

Reviewed by:

Yong Liu, Hunan Academy of Agricultural Sciences (CAAS), China
Joseph Holden, University of Leeds, United Kingdom  

Copyright: © 2019 Radke, Godsey, Lohse, McCorkle, Perdrial, Seyfried and Holbrook. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Sarah E. Godsey, Idaho State University, Pocatello, 83209, Idaho, United States, godsey@isu.edu