ORIGINAL RESEARCH article
Front. Water
Sec. Water and Hydrocomplexity
Volume 7 - 2025 | doi: 10.3389/frwa.2025.1539177
This article is part of the Research TopicAdvances in Integrated Surface—Subsurface Hydrological ModelingView all 8 articles
On the Emergent Scale of Bedrock Groundwater Contribution to Headwater Mountain Streams
Provisionally accepted
- 1Department of Geosciences, College of Humanities and Sciences, University of Montana, Missoula, Massachusetts, United States
- 2Department of Forest Management, W A Franke College of Forestry & Conservation, University of Montana, Missoula, Massachusetts, United States
Select one of your emails
You have multiple emails registered with Frontiers:
Notify me on publication
Please enter your email address:
If you already have an account, please login
You don't have a Frontiers account ? You can register here
We investigated the contribution of bedrock groundwater to streamflow as a function of catchment scale in a headwater stream. Synoptic surveys were carried out at hydrologically important times of the year for multiple environmental tracers in stream water, soil water, and bedrock groundwater along a first-order montane stream in west-central Montana. Sampled analytes included 222 Rn, used to constrain total subsurface flux, and major and minor elements, used in End Member Mixing Analysis (EMMA) to identify the contributions of soil and bedrock groundwater to the stream. Partitioning between soil derived and bedrock derived groundwater was then analyzed as a function of the incremental and accumulated sub-catchment size. Radon results indicated that subsurface water contributions accounted for the majority of streamflow at all surveyed times. EMMA results indicate that the bedrock groundwater contribution to streamflow varied between 26% during peak snowmelt, to 44% during late summer. Streamflow generation was dominated by soil groundwater contribution along the entire reach, but the bedrock groundwater contribution increased consistently with accumulated sub-catchment size. However, groundwater contributions were not well correlated with incremental sub-catchment size. The scale at which increased bedrock groundwater discharge can be correlated with subcatchment size appears to be >1 km 2 for our study. Our results are consistent with a conceptual model where streamflow is predominantly generated by a 3D subsurface nested flow system. Local subsurface heterogeneities control the stream source at local scales but begin to average out at scales greater than 2 km 2 . Our study indicates that even though soil groundwater is the dominant source, bedrock groundwater is an important and predictable contributor to streamflow throughout the year, even in a snow-dominated, mountainous headwater catchment.
Keywords: Groundwater - surface water interactions, Stream flow generation, mountain hydrology, Environmental tracers, Mountain aquifer
Received: 03 Dec 2024; Accepted: 09 Jun 2025.
Copyright: © 2025 von Trapp, Jencso, Hoylman, Livesay and Gardner. 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) or licensor 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: W. Payton Gardner, Department of Geosciences, College of Humanities and Sciences, University of Montana, Missoula, MT 59812, Massachusetts, United States
Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.