Rivers becoming warmer with rising temperature: Study

Ecologists at the University of Maryland Center for Environmental Science in Solomons claimed that over the past few decades, 20 major streams and rivers in the US have warmed significantly with temperatures in some rivers have risen by over three degrees Celsius.

Such warmer river conditions, the scientists said, could threaten both the biodiversity of waterways and the livelihood of people who depend on them, especially in cities where heat-island effects accelerate warming, the Discovery.com reported.

Sujay Kaushal, an ecologist at the university and the lead author of the study, said: "Even modest changes in temperature can have big biological effects."
"We're seeing the fastest rates of temperature increase in the most highly urbanised areas. That leads us to believe it's a one-two punch of global warming and development."

For their research, Kaushal and his colleagues pieced together all the long-term water temperature data they could find for 40 streams and rivers around the country.
Sources included old drinking water records, monitoring programmes, and water-quality studies conducted by the United States Geological Survey.

Reporting their findings in the journal Frontiers in Ecology and the Environment, the researchers said the data, in 20 rivers they looked at, clearly showed warming, ranging from about 0.01 degree to 0.08 degree C per year.

Those are small numbers but the fractions added up over time -- to as much as a 3 degree C rise in Maryland's Patuxent River in less than 60 years, and probably more in other places, they said.

According to the findings, fastest rates of warming occurred near urban areas in the Mid-Atlantic States, including along the Potomac River outside of Washington DC, the Delaware River near Chester, Penn, and the Patuxent River.

Temperatures have also been rising in streams and rivers across the West, Midwest and Southeast, the researchers said.

They believe that warmer air is partly responsible for warmer river temperatures and pointed out the removing shade trees from waterways for development work as a major contributor for it.

Paving green spaces with asphalt also leads to more heat reflection, which boosts the temperature of air and water even more, the said and predicted that consequences of such warming for the food chain could be catastrophic.

Earlier, a British study had predicted that insect numbers in some rivers will drop by 21 per cent with every 1 degree C rise in water temperature.
Other worries include species extinctions, invasions of alien species, and blooms of algae that could reduce the quality of drinking water and make recreation less enjoyable.
To give rivers a break, Kaushal said, city planners might want to think about planting more trees around urban rivers and making efforts to reduce the islands of heat that build up around cities.