On the emergent scale of bedrock groundwater contribution to headwater mountain streams
We investigated the contribution of bedrock groundwater to streamflow as a function of catchment scale in a headwater stream. Synoptic surveys were conducted during hydrologically important periods of the year using multiple environmental tracers in stream water, soil water, and bedrock groundwater,...
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Frontiers Media S.A.
2025-07-01
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| Series: | Frontiers in Water |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/frwa.2025.1539177/full |
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| author | Isabellah von Trapp Kelsey G. Jencso Zachary H. Hoylman Robert Livesay W. Payton Gardner |
| author_facet | Isabellah von Trapp Kelsey G. Jencso Zachary H. Hoylman Robert Livesay W. Payton Gardner |
| author_sort | Isabellah von Trapp |
| collection | DOAJ |
| description | We investigated the contribution of bedrock groundwater to streamflow as a function of catchment scale in a headwater stream. Synoptic surveys were conducted during hydrologically important periods of the year using multiple environmental tracers in stream water, soil water, and bedrock groundwater, along a first-order montane stream, in west-central Montana. Sampled analytes included 222Rn, 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 sizes. Radon results indicated that subsurface water contributions accounted for the majority of streamflow at all surveyed times. EMMA results revealed that the bedrock groundwater contribution to streamflow varied between 26% during peak snowmelt and 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 sub-catchment size appears to be >1 km2 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 >2 km2. Our study indicates that, while soil groundwater is the dominant source, bedrock groundwater remains an important and predictable contributor to streamflow throughout the year, even in a snow-dominated, mountainous headwater catchment. |
| format | Article |
| id | doaj-art-a72ef0c6aff841d5800a687594cf7cc8 |
| institution | Matheson Library |
| issn | 2624-9375 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Water |
| spelling | doaj-art-a72ef0c6aff841d5800a687594cf7cc82025-07-15T05:25:01ZengFrontiers Media S.A.Frontiers in Water2624-93752025-07-01710.3389/frwa.2025.15391771539177On the emergent scale of bedrock groundwater contribution to headwater mountain streamsIsabellah von Trapp0Kelsey G. Jencso1Zachary H. Hoylman2Robert Livesay3W. Payton Gardner4Department of Geosciences, University of Montana, Missoula, MT, United StatesDepartment of Forest Management, Franke College of Forestry and Conservation, Missoula, MT, United StatesDepartment of Forest Management, Franke College of Forestry and Conservation, Missoula, MT, United StatesDepartment of Forest Management, Franke College of Forestry and Conservation, Missoula, MT, United StatesDepartment of Geosciences, University of Montana, Missoula, MT, United StatesWe investigated the contribution of bedrock groundwater to streamflow as a function of catchment scale in a headwater stream. Synoptic surveys were conducted during hydrologically important periods of the year using multiple environmental tracers in stream water, soil water, and bedrock groundwater, along a first-order montane stream, in west-central Montana. Sampled analytes included 222Rn, 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 sizes. Radon results indicated that subsurface water contributions accounted for the majority of streamflow at all surveyed times. EMMA results revealed that the bedrock groundwater contribution to streamflow varied between 26% during peak snowmelt and 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 sub-catchment size appears to be >1 km2 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 >2 km2. Our study indicates that, while soil groundwater is the dominant source, bedrock groundwater remains an important and predictable contributor to streamflow throughout the year, even in a snow-dominated, mountainous headwater catchment.https://www.frontiersin.org/articles/10.3389/frwa.2025.1539177/fullgroundwater—surface water interactionsstreamflow generationmountain hydrologyenvironmental tracersmountain aquifer |
| spellingShingle | Isabellah von Trapp Kelsey G. Jencso Zachary H. Hoylman Robert Livesay W. Payton Gardner On the emergent scale of bedrock groundwater contribution to headwater mountain streams Frontiers in Water groundwater—surface water interactions streamflow generation mountain hydrology environmental tracers mountain aquifer |
| title | On the emergent scale of bedrock groundwater contribution to headwater mountain streams |
| title_full | On the emergent scale of bedrock groundwater contribution to headwater mountain streams |
| title_fullStr | On the emergent scale of bedrock groundwater contribution to headwater mountain streams |
| title_full_unstemmed | On the emergent scale of bedrock groundwater contribution to headwater mountain streams |
| title_short | On the emergent scale of bedrock groundwater contribution to headwater mountain streams |
| title_sort | on the emergent scale of bedrock groundwater contribution to headwater mountain streams |
| topic | groundwater—surface water interactions streamflow generation mountain hydrology environmental tracers mountain aquifer |
| url | https://www.frontiersin.org/articles/10.3389/frwa.2025.1539177/full |
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