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

[Alan Goldstein]

>From my perspective looking over the Ohio River at the Falls of the Ohio 5 days / week for the last 35 years, I can’t say I’ve seen much “long-term” changes in water color. But I’m not a satellite. Of course, the Ohio is second only to the lower Mississippi in terms of water volume, so it tends to average things out compared to smaller rivers.

One change that predates me, is the deposition of clay on the limestone fossil beds. I’ve seen photos taken in the 1950s where fossils and the limestone are clean. With the construction of the high lift dam and lower water velocities, clays from soil are clinging to the rocks. It’s thin – a fraction of a millimeter (more in backwater areas). No doubt more soil is in the water, though there are significant efforts to mitigate field and construction runoff into feeder streams. The fossil beds are clean when gravel washes over. Also, the summer after the coal barge accident just above the dam, the fossil beds were extraordinarily clear of clay.

When the river is running (dam gates are open), the water contains much suspended sediment. The water is brown. I’ve never seen yellow river water (snow, yes!). When the gates are closed (mostly or completely), the water is pretty clear, albeit with a green tinge. These gates move water from the bottom of the river where sediment should be maximized. This is a single point perspective. Five miles down or up river may have a different perspective.

Zebra mussels may have a role in removing microscopic algae from the water, reducing the green color. Populations were large but reduced and seem to have stabilized based on what I’ve seen. One summer (1999, a drought year?) our water tasted funny because the river was so clear that the water company couldn’t get the algal ‘flavor” out.

Regards,
Alan G.


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From: Kreigh Tomaszewski<mailto:kreigh at gmail.com>
Sent: Wednesday, December 30, 2020 11:48 AM
To: Rockhounds at drizzle.com: A mailing list for rock and gem collectors<mailto:rockhounds at rockhounds.drizzle.com>
Subject: [Rockhounds] US rivers are changing from blue to yellow and green, satellite images show

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://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcuahsi.shinyapps.io%2FRiverColor%2F&data=04%7C01%7C%7C46d15a1cb34942fe918908d8ace2c87e%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449437330931464%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=QBHoVhZRApmk%2FdmIvj7hJjBFjydCSoT5HZ3%2FLb0OpVA%3D&reserved=0>.

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.

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