Determining How Critical Zone Structure Constrains Hydrogeochemical Behavior of Watersheds: Learning From an Elevation Gradient in California's Sierra Nevada
Document Type
Article
Publication Date
8-21-2020
Department
College of Forest Resources and Environmental Science
Abstract
Concentration-discharge (C-Q) relations can provide insight into the dynamic behavior of the Critical Zone (CZ), as C-Q relations integrate the spatial distribution and timing of watershed hydrogeochemical processes. This study blends geomorphologic analysis, C-Q relations and reactive-transport modeling using a rich dataset from an elevation gradient of eight watersheds in the Southern Sierra Nevada, California. We found that the CZ structure exerts a strong control on the C-Q relations, and on the hydrogeochemical behavior of headwater watersheds. Watersheds with thin regolith, a large stream network, and limited water storage have fast mean transit times along subsurface flow lines, and show limited seasonal variability in ionic concentrations in streamflow (i.e., chemostatic behavior). In contrast, watersheds with thicker regolith, a small stream network and more water storage have longer transit times along subsurface flow lines, and exhibit greater chemical variability (i.e., chemodynamic behavior). Independent estimates of mean transit times and water storage from other isotopic, hydrologic and geophysical studies were consistent with results from modeling C-Q relations. The stream chemistry and its variability were controlled by lateral flow within the regolith, and no mixing with deep groundwater was needed to explain the observed chemical variability. This study opens the possibility to estimate water-storage capacity and mean transit times, and thus drought resistance in watersheds, by using quantitative modeling of C-Q relations.
Publication Title
Frontiers in Water
Recommended Citation
Ackerer, J.,
Steefel, C.,
Liu, F.,
Bart, R.,
Safeeq, M.,
O'Geen, A.,
Hunsaker, C.,
&
Bales, R.
(2020).
Determining How Critical Zone Structure Constrains Hydrogeochemical Behavior of Watersheds: Learning From an Elevation Gradient in California's Sierra Nevada.
Frontiers in Water,
2.
http://doi.org/10.3389/frwa.2020.00023
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/16646
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Version
Publisher's PDF
Publisher's Statement
© 2020 Ackerer, Steefel, Liu, Bart, Safeeq, O'Geen, Hunsaker and Bales. Publisher’s version of record: https://doi.org/10.3389/frwa.2020.00023