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Naches River
Photo Credit: Courtesy of Oregon State University
Scientific Frontline: Extended "At a Glance" Summary: Climate-Driven Acceleration of Water Transit Times
The Core Concept: Warmer winter temperatures are causing "snow droughts" where precipitation falls as rain rather than snow, significantly accelerating the rate at which water transits through western United States landscapes and river basins.
Key Distinction/Mechanism: Unlike traditional snow-dominated hydrologic systems that slowly release stored water through a delayed spring melt, warmer conditions cause immediate precipitation runoff. This transition from snow to rain is projected to accelerate "water transit times"—the duration between precipitation falling and leaving as streamflow—by an estimated 18% on average by the late century.
Major Frameworks/Components:
- Advanced Hydrologic Modeling: Researchers coupled field-collected water samples with complex computational hydrology models to estimate past and future water transit timelines without relying entirely on continuous field sampling.
- Isotopic Tracing: The foundational method for calculating water transit variability relies on analyzing natural chemical tracers, specifically stable water isotopes, found in both precipitation and subsequent streamflow.
- Climate Change Projections: The research incorporates regional predictive models forecasting environmental shifts, such as an anticipated 16% decrease in snow and a 25% increase in rain in the targeted basin between 2036 and 2050.
Branch of Science: Hydrology, Climatology, Earth Sciences, and Environmental Science.
Future Application: The modeling framework developed in this study can be applied globally to predict water transit times in other climate-sensitive basins. This data will be critical for informing municipal water management, shaping agricultural planning, and updating future hydrologic assessments in regions experiencing frequent weather disturbances.
Why It Matters: Faster water transit times deplete essential summer water reserves required for drinking, agriculture, and aquatic species survival (such as salmon and trout). Furthermore, accelerated transit damages water quality by causing spikes in shallow-subsurface contaminants during high-water events, a critical concern given that 53% of water runoff in the western United States originates as snowmelt.
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| Water sampling Photo Credit: Courtesy of Oregon State University |
As future shifts in climate lead to more rain and less snow in the western United States, new research finds that water will move faster through a landscape, likely leading to negative impacts on summer water levels and water quality.
The study is especially relevant at this moment because the western United States experienced similar snow drought conditions this past winter, with generally typical precipitation amounts, but less snow because of warmer temperatures.
“This winter has been exactly like what our paper had said the future will be like,” said Zach Butler, a postdoctoral scholar at Oregon State University and lead study author, who has a part-time job forecasting winter weather in Oregon for the site OpenSnow.
The research can help inform future water management decisions. While the timing of water release relative to snowpack has long informed water planning, understanding how long it takes for water to travel through a landscape is not well understood and is important, especially at a time of increasing weather disturbances and extreme conditions.
In the new study, recently published in Scientific Reports, Butler and a team of researchers from Oregon State, Pacific Northwest National Laboratory and the National Center for Atmospheric Research in Colorado estimated “water transit times” – the time between rain or snow falling on the landscape and leaving as streamflow – will be 18% faster on average in the late century.
Faster water transit times have been shown to negatively influence water quality because during high-water events there are often spikes of contaminants that have been stored for a shorter period in shallow subsurface layers. Additionally, during low-water conditions, contaminants can be stored for a longer period of time.
The seasonal shift to faster water transit times in the winter will also likely lead to less water in streams, rivers, lakes and reservoirs in the summer, which could have negative implications for aquatic species such as salmon and trout and less water for drinking and agriculture.
The study focused on the Naches River, the main tributary of the Yakima River in Washington. The river basin is one of the most climate-sensitive basins within the Columbia River basin due to projected warming and snowpack declines, the researchers note.
Snowpack declines in the Naches River basin from 1991-2020 have already resulted in discharge peaking earlier in the spring. Other research has projected a 16% decrease in snow and a 25% increase in rain by 2036-2050.
While the researchers focused on that one basin, the framework they developed can be used to predict historical and future water transit times in other parts of the western United States and the world. Their work builds and aligns with studies conducted by other scientists in the Rocky Mountains and Europe.
The research is important because one-sixth of the world’s population Link downloads document relies on snowmelt water for drinking or agriculture, the researchers note. In the United States west of Colorado, 53% of water runoff originates as snowmelt.
Variability of water transit times is traditionally calculated by analyzing natural chemical tracers, such as stable water isotopes, found in precipitation and streamflow. This is costly and logistically challenging because it requires collecting water samples in the field.
Butler and scientists from the Pacific Northwest National Laboratory collected samples from the Naches River and coupled those in a novel way with an advanced hydrologic model to estimate water transit times both in the past and future.
“This study provides a crucial step in improving projections of water resource responses to climate change and underscores the value of integrating water transit time dynamics into future hydrologic assessments,” Butler said.
Good is an associate professor in the College of Agricultural Sciences and director of the interdisciplinary Water Graduate Resources Program. Raleigh is an assistant professor in the College of Earth, Ocean, and Atmospheric Sciences. Segura is a professor in the College of Forestry.
Published in journal: Scientific Reports
Title: Shifts in rain-snow partitioning drive faster water transit times in the US Pacific Northwest
Authors: Zachariah Butler, Stephen P. Good, Huancui Hu, Xingyuan Chen, Mark S. Raleigh, Catalina Segura, and Aubrey Dugger
Source/Credit: Oregon State University | Sean Nealon
Reference Number: es041626_01
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