The Great River Crisis

“Declining oxygen in rivers, or deoxygenationalso drives the emission of greenhouse gases and leads to the release of toxic metals.”

By Annette J Beveridge

Rivers are the lifeblood of any country. Who hasn’t taken a walk alongside a river or stream or relaxed on the river bank releasing the stresses of the day? Yet, these precious river systems are greatly at risk and as this new study shows, will impact both aquatic life and people.

New research published in the journal Nature Climate Change revealed that rivers are warming and losing oxygen faster than oceans.

The Penn State-led study published on September 14 2023 revealed that out of almost 800 rivers, warming occurred in 87% of them, along with 70% of oxygen loss.

We talk about the warming of oceans, but little has been said about river temperature warming too or the detrimental impact it could have.

The study predicted that within 70 years river systems, particularly those in the American South would experience, low-levels of oxygen. This would lead to acute death for some species of fish and would put at risk aquatic diversity.

Li Li, Penn State’s Lsett Professor of Civil and Environmental Engineering and corresponding author said: "This is a wake-up call. We know that a warming climate has led to warming and oxygen loss in oceans, but did not expect this to happen in flowing, shallow rivers.

“This is the first study to take a comprehensive look at temperature change and deoxygenation rates in rivers -- and what we found has significant implications for water quality and the health of aquatic ecosystems worldwide."

Artificial intelligence, (AI) was used by the International Research Team along with deep learning approaches to reconstruct historically sparse water quality data from nearly 800 rivers across the U.S. and central Europe.

The research indicated that the warming of and deoxygenation of these rivers could have serious implications, not just for the aquatic life but for humans too.

Lead author of the study, Wei Zhi said: "Riverine water temperature and dissolved oxygen levels are essential measures of water quality and ecosystem health,"

Wei Zhi is also the assistant research professor in the Department of Civil and Environmental Engineering at Penn State. He said. "Yet they are poorly understood because they are hard to quantify due to the lack of consistent data across different rivers and the myriad of variables involved that can change oxygen levels in each watershed."

Novel deep learning enabled systematic comparison across different rivers.

Life in water relies on temperature and dissolved oxygen. Coastal areas like the Gulf of Mexico often have dead zones in the summer. Research indicated this could happen to rivers as it will not be possible to sustain life.

Li said: “Declining oxygen in rivers, or deoxygenation, also drives the emission of greenhouse gases and leads to the release of toxic metals.”

A computer model trained on a vast range of data, which included annual precipitation rates to soil type to sunlight for 580 rivers in the United States and 216 rivers in Europe revealed 87 per cent had been getting warmer over the last 40 years and 70 per cent had been losing oxygen.

Urban rivers revealed rapid warming, but agricultural rivers had slower warming, but faster deoxygenation. The model used forecast future rates for all of the river studies, with the risk of deoxygenated rates in the future between 1.6 and 2.5 times higher than in the past.

Li said: “Rivers are essential for the survival of many species, including our own, but they have historically been overlooked as a mechanism for understanding our changing climate.

This is our first real look at how rivers throughout the world are faring - and it's disturbing.”

Story Source:

Penn State. "Rivers are rapidly warming, losing oxygen; aquatic life at risk." ScienceDaily.

www.sciencedaily.com/releases/2023/09/230914114710.htm