Tolley-Mann et al. (2026) Flowing cold and shallow: snowmelt controls on spring temperature and resilience to climate change

Identification

• Journal: Journal of Hydrology
• Year: 2026
• Date: 2026-08-06
• Authors: Loren Tolley-Mann, Emilio Grande, Ate Visser, Jory Chapin Lerback, Alexander Jake Harm, Jean E. Moran
• DOI: 10.1016/j.jhydrol.2026.136181

Research Groups

• Department of Earth, Environmental, and Sustainability Sciences, California State University East Bay
• Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory

Short Summary

This study used a multi-tracer framework combining stable water isotopes, noble gases, and thermal budgeting to reconstruct recharge elevations, temperatures, and flow path depths of six major springs in Northern California's Cascade region. The results indicate that recharge occurs at high elevations (1800-2900 m) with cold recharge temperatures (1.5-7.0 °C), suggesting a significant warming of spring water as it flows through the subsurface.

Objective

• Reconstruct recharge elevations, temperatures, and flow path depths of six major springs in Northern California's Cascade region using a multi-tracer framework combining stable water isotopes, noble gases, and thermal budgeting.

Study Configuration

• Spatial Scale: Regional scale, focusing on the Cascade region in Northern California.
• Temporal Scale: Long-term, with samples collected between July 2023 and August 2025.

Methodology and Data

• Models used: PANGA (inverse modelling approach) for noble gas analysis, and a regional δ18O lapse rate regression for recharge elevation estimation.
• Data sources: Stable water isotope samples from 31 springs, and dissolved noble gas concentrations from 18 of those samples.

Main Results

• Recharge elevations ranged from 1800 to 2900 m across the spring complexes, with a median effective Hr ranging from 1728 m at McCloud Big Springs to 2666 m at Mt. Shasta City Park Site A.
• Noble gas recharge temperatures varied between 1.5 °C and 6.9 °C, with sample-level 95% uncertainty intervals spanning 0.4–8.0 °C.
• Theoretical flow path depths ranged from 19 m to 289 m, depending on the geothermal gradient used.

Contributions

• This study provides a transferable approach for evaluating climate sensitivity in mountain spring systems using a multi-tracer framework combining stable water isotopes, noble gases, and thermal budgeting.
• The results highlight the importance of considering recharge elevation and temperature when assessing the vulnerability of springs to climate change.

Funding

• This research was supported by [insert funding agency/program/project codes].

Citation

@article{TolleyMann2026Flowing,
  author = {Tolley-Mann, Loren and Grande, Emilio and Visser, Ate and Lerback, Jory  Chapin and Harm, Alexander  Jake and Moran, Jean E.},
  title = {Flowing cold and shallow: snowmelt controls on spring temperature and resilience to climate change},
  journal = {Journal of Hydrology},
  year = {2026},
  doi = {10.1016/j.jhydrol.2026.136181},
  url = {https://doi.org/10.1016/j.jhydrol.2026.136181}
}