America’s rivers are changing color – and people are behind many of the trends, a new study has said.
One-third of tens of thousands of rivers in the United States have shifted color prominently in satellite imagery since 1984. That includes 11,629 miles that have become greener, or have been turned green. violet head towards the color spectrum, according to its study in this week’s journal Geographical Research Letters. Some river sections became redder.
Only about 5 percent of U.S. river miles are considered blue – a color that is often equated with brass waters by the masses. About two-thirds of America’s rivers are yellow, indicating that they contain a lot of soil.
But 28 percent of rivers are green, which often appears to be choked with algae. And researchers found that 2 percent of U.S. rivers have shifted over the years from yellow to mostly green.
“If things are going greener, that’s a problem,” said study lead author John Gardner, professor of geology and environmental science at the University of Pittsburgh. While rivers may have a slightly green color as usual, Gardener said, it often means large algal blooms that cause oxygen loss and can produce toxins.
The main causes of color changes are the flow of farm manure water, dams, efforts to combat ground erosion and climate change by hand, which increase water temperature and water-related runoff, the study authors said.
“We change a lot on our rivers. Much of that has to do with human activity, ”said study co-author Tamlin Pavelsky, professor of global irrigation at the University of North Carolina.
For example, Pavelsky said, the green at times in the Ohio River indicates a severe algae problem from run – down water while farms are turning yellow to show the success of regulations to prevent erosion. .
The study looked at more than 230,000 NASA satellite images over 35 years, focusing on rivers and reservoirs. The study found that much of the shift to greener rivers occurred in the north and west, while the yellow occurred more in the East and around the Mississippi River. He also discovered that some rivers change colors naturally with the seasons.
Expert experts praised the study, saying that while difficult-to-understand measurements have revealed problems with America’s rivers, this simply illustrates the situation.
The study is “very cool and a bit intuitive (but intuitive),” Martin Doyle, head of water programs at Duke University, wrote in an email. “It shows how humans are affecting most of our planet, now including the basic color of our water. That’s pretty deep if you think about it. ”
“It is also important because it opens up the idea and the ability to use the color of the river as an early stage indicator, or warning of environmental change,” wrote Doyle, who was not part of the study.