Groundwater dominates snowmelt runoff and controls streamflow efficiency in the western United States

Paul D. Brooks; D. Kip Solomon; Stephanie Kampf; Sara Warix; Carleton R. Bern; David Barnard; Holly R. Barnard; Gregory T. Carling; Rosemary Carroll; Jon Chorover; Adrian Harpold; Kathleen Lohse; Fabiola Meza; Jennifer McIntosh; Bethany Neilson; Megan Sears; Margaret Wolf

doi:10.1038/s43247-025-02303-3

USGS · 70267407

Groundwater dominates snowmelt runoff and controls streamflow efficiency in the western United States

Paul D. Brooks·D. Kip Solomon·Stephanie Kampf·Sara Warix·Carleton R. Bern·David Barnard·Holly R. Barnard·Gregory T. Carling·Rosemary Carroll·Jon Chorover·Adrian Harpold·Kathleen Lohse·Fabiola Meza·Jennifer McIntosh·Bethany Neilson·Megan Sears·Margaret Wolf

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Abstract

Climate change in seasonally snow-covered mountain catchments is reducing water supply and decreasing streamflow predictability. Here, we use tritium age dating to show that contrary to the common assumption that snowmelt quickly contributes to runoff, streamflow during snowmelt in western US catchments is dominated by older groundwater. The average age of streamwater during snowmelt runoff (5.7 ± 4.3 years) was intermediate to the average age of groundwater (10.4 ± 4.5 years) and recent precipitation, indicating that 58% (±34%) of snowmelt runoff was derived from groundwater. Water ages, streamflow, and groundwater storage were mediated by bedrock geology: low-permeability hard rock/shale catchments exhibited younger ages, less storage, and more efficient streamflow generation than high-permeability sandstone/clastic catchments. Our results demonstrate that snowmelt runoff is the result of multiple prior years of climate mediated by groundwater storage. Including these interactions will be crucial for predicting water resources as climate and landscape changes accelerate.

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Communications Earth & Environment Article

Source-reported bounding extent: 31.337662810224828° to 48.94832156904479° latitude; -125.33002798384842° to -104.0181665891808° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Paul D. Brooks, D. Kip Solomon, Stephanie Kampf, Sara Warix, Carleton R. Bern, David Barnard, Holly R. Barnard, Gregory T. Carling, Rosemary Carroll, Jon Chorover, Adrian Harpold, Kathleen Lohse, Fabiola Meza, Jennifer McIntosh, Bethany Neilson, Megan Sears, Margaret Wolf. 2025-05-03. Groundwater dominates snowmelt runoff and controls streamflow efficiency in the western United States. https://doi.org/10.1038/s43247-025-02303-3

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