The Viscosity Effect: A Newly Found Connection Between the Riparian Zone and Water Quality

800 450 Stroud Water Research Center
Diane Huskinson

By Diane Huskinson

A new Stroud™ Water Research Center study shows that the density of water plays a previously overlooked role in nutrient and carbon cycling in freshwater ecosystems. 

The research, conducted by scientists Diana Oviedo Vargas, Ph.D., Marc Peipoch, Ph.D., and Charles Dow, Ph.D., underscores the complex and delicate balance that maintains healthy streams and rivers. 

Science has already shown that the organisms living in a stream affect the cycling of chemicals like carbon and nitrogen through the earth, but this recent finding — what the researchers call the “viscosity effect” — shows that water viscosity does too. As temperature rises throughout the day and water becomes less viscous, it more readily percolates through soils on land, enters underground aquifers, and flows up into and through streams. The source water, with its unique chemical makeup at a given time, then shifts the water chemistry in the streams it flows through, in turn affecting water quality.

An EnviroDIY Monitoring Station on the banks of White Clay Creek in Pennsylvania.
An EnviroDIY Monitoring Station on the banks of White Clay Creek in Pennsylvania

The findings, published in the peer-reviewed Journal of Geophysical Research: Biogeosciences, suggest how human-induced changes that impact water temperature, such as a lack of tree shade from deforestation, might trigger more pronounced oscillations in water chemistry. 

The team completed the study in the east branch of White Clay Creek in southeastern Pennsylvania, using EnviroDIY™ Monitoring Stations, which allowed them to automate the collection of water samples over 24-hour periods to look for patterns.

“​​We found seasonal differences,” says Oviedo Vargas. “In the spring and summer, streams have more biological activity — more algae growth, for example. Microorganisms feed on that algae, consuming some chemicals and releasing others in the process. Our study showed that during the warmer months, the changes in water chemistry throughout the day were largely the result of the metabolic activity of microorganisms in the stream. However, during the wintertime, the changes in temperature from daytime to nighttime produced the viscosity effect.”

This work contributes to a larger body of research by Stroud Center scientists that has shaped our understanding of how to protect clean fresh water. You too can protect our most precious life-sustaining resource by supporting our work with a donation today.

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