The researchers came to this conclusion after studying the 34-year period of the existence of water flows.
Scientists analyzed 235,000 satellite images taken between 1984 and 2018. After that, they reflected all the observed observations on an interactive map called “Visualization of the color of rivers in the United States.” The map is available to everyone – you can see it too.
More than half of the satellite images show rivers with a predominantly yellow tint, and more than a third of the images show rivers with a green tint. Only 8% of the photos of the river were mostly blue.
Rivers can have shades of blue, green, yellow or other colors, depending on the amount of suspended sediment – these are small mineral particles carried by the water flow. In addition, color is influenced by the presence of algae (and their flowering state, for example) and various contaminants.
Typically, river water turns green when a lot of algae blooms or when there is less sediment in the water. And the yellow color appears when flows, on the contrary, carry more sediment.
In the north and west of the United States, rivers tend to become greener, while in the eastern regions of the country, streams tend to turn yellow. Larger waterways, such as the Ohio Basin and the Upper Mississippi Basin, have also turned blue-green.
The changing color of rivers is worrying, scientists say. Of course, in some cases this process can be explained by natural factors, but satellite images clearly show “hot spots” – places where human influence, for example, the construction of dams, reservoirs, urban development and agriculture, can aggravate the situation with rivers.
So far, researchers continue to study the data obtained to determine how accurate the color of the river in each area is and how it affects the development of the ecosystem in one place or another.