[Rockhounds] US rivers are changing from blue to yellow and green, satellite images show

[Kreigh Tomaszewski]

A third of U.S. rivers have significantly changed color over the last 36
years, turning from blue to  yellow and green, striking new images reveal.

Researchers analyzed 235,000 satellite images — taken over a 34-year period
between 1984 and 2018 — from NASA and the U.S. Geological Survey (USGS)
Landsat program. The changing hues can be viewed in an *interactive map*
<https://cuahsi.shinyapps.io/RiverColor/>.

More than half of those satellite images showed rivers with a dominant hue
of yellow,  while more than a third of images were mostly green. Just 8% of
river pics were mostly blue.

"Most of the rivers are changing gradually and not noticeable to the human
eye," lead author John Gardner, a postdoctoral researcher in the global
hydrology lab at University of North Carolina, told Live Science. "But
areas that are the fastest changing are more likely to be man-made."

Rivers can appear to be shades of blue, green, yellow or other colors
depending on the amount of suspended sediment, algae, pollution or
dissolved organic matter in the water. As a general rule, river water turns
green as more algae blooms, or when the water carries less sediments.
Rivers tend to turn yellow when they carry more sediment.

"Sediment and algae are both important, but too much or too little of
either can be disruptive," Gardner said.

https://www.livescience.com/us-rivers-changing-color.html