Butler et al. (2026) Shifts in rain-snow partitioning drive faster water transit times in the US Pacific Northwest

Identification

• Journal: Scientific Reports
• Year: 2026
• Date: 2026-04-01
• Authors: Zachariah Butler, Stephen P. Good, Huancui Hu, Xingyuan Chen, Mark S. Raleigh, Catalina Segura, A. L. Dugger
• DOI: 10.1038/s41598-026-46539-1

Research Groups

• Water Resources Graduate Program, Oregon State University, Corvallis, OR, USA
• School of Civil and Construction Engineering, Oregon State University, Corvallis, OR, USA
• Department of Biological and Ecological Engineering, Oregon State University, Corvallis, OR, USA
• Atmospheric, Climate, and Earth Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA
• College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
• Forest Engineering, Resources and Management, Oregon State University, Corvallis, OR, USA
• National Center for Atmospheric Research, Boulder, CO, USA

Short Summary

This study estimated historical and future water transit times in five headwater catchments in the U.S. Pacific Northwest. It found that water transit times are projected to be 18% (35–64 days) faster on average under the RCP 8.5 climate scenario due to shifts in rain-snow partitioning.

Objective

• To estimate historical and future water transit times in mountainous regions of the U.S. Pacific Northwest and determine how they may shift under future climates, particularly due to rapid snowpack declines and changes in rain-snow partitioning.

Study Configuration

• Spatial Scale: Five headwater catchments within the U.S. Pacific Northwest.
• Temporal Scale: Historical (2006–2013) and future (2086–2093) periods.

Methodology and Data

• Models used: Water Tracer enabled version of the Weather Research and Forecasting Hydrologic model (WRF-Hydro) with Sequential Precipitation Input Tagging (SPIT) framework.
• Data sources: Model outputs, observed delta Q data, and climate projections based on the Representative Carbon Pathways (RCP) 8.5 scenario. All codes and data are published on the River Corridor and Watershed Biogeochemistry SFA, ESS-DIVE repository (doi:10.15485/2562910).

Main Results

• Water transit times are projected to be 18% faster on average under the RCP 8.5 climate scenario.
• This acceleration corresponds to a reduction of 35–64 days in transit time.
• The primary driver for faster transit times is shifts in rain-snow partitioning.
• Future conditions show higher fractions of younger water during the wet season and older water during the dry season.
• These shifts are expected to impact regional water quality, temperature, and hydrologic seasonality.

Contributions

• Quantifies the projected shifts in water transit times in snowmelt-dominated mountainous regions of the U.S. Pacific Northwest under future climate change.
• Identifies shifts in rain-snow partitioning as a critical mechanism driving changes in water transit times.
• Provides insights into the potential consequences of altered water transit times for regional water quality, temperature, and seasonal hydrologic response.

Funding

• U.S. Department of Energy (DOE), Office of Science Biological and Environmental Research (BER) program, Environmental System Science program.
• River Corridor Scientific Focus Area (SFA) at Pacific Northwest National Laboratory (PNNL).
• PNNL operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RL01830.
• Distinguished graduate research fellowship between PNNL and Oregon State University (through the PNNL River Corridor SFA).

Citation

@article{Butler2026Shifts,
  author = {Butler, Zachariah and Good, Stephen P. and Hu, Huancui and Chen, Xingyuan and Raleigh, Mark S. and Segura, Catalina and Dugger, A. L.},
  title = {Shifts in rain-snow partitioning drive faster water transit times in the US Pacific Northwest},
  journal = {Scientific Reports},
  year = {2026},
  doi = {10.1038/s41598-026-46539-1},
  url = {https://doi.org/10.1038/s41598-026-46539-1}
}