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River Colors are Changing

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River Colors are Changing

Much like the sky, rivers are rarely painted one color. Across the world, they appear in shades of yellow, green, blue, and brown. Subtle changes in the environment can alter the color of rivers, though, shifting them away from their typical hues. New research shows the dominant color has changed in about one-third of large rivers in the continental United States over the past 35 years.

“Changes in river color serve as a first pass that tell us something is going on nearby,” said John Gardner, the study’s lead author and a hydrologist at the University of Pittsburgh. “There are a lot of details to parse out on what is causing those changes, though.”

The figure above shows data from the first map of river color for the contiguous United States. The rivers are colored as they would approximately appear to our eye. Gardner and colleagues built the map from 234,727 images collected by Landsat satellites between 1984 and 2018. The dataset includes 67,000 miles (100,000 kilometers) of waterways of at least 200 feet (60 meters) wide. Around 56 percent of rivers were dominantly yellow over the course of the study and 38 percent were dominantly green. The team has released an interactive map where the public can further investigate color trends in individual rivers.

Why they began dyeing the Chicago River green : NPR

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St. Patrick’s Day: Why they began dyeing the Chicago River green : NPR

As the city grew in size, efforts to clean the river increased, including the construction of waste treatment plants and even a canal that permanently reversed the flow of the river, bringing clean water from Lake Michigan into the mouth of the river.

When Richard J. Daley took office as the mayor of Chicago in 1955 he was determined to develop the riverfront and tasked city workers with finding where the sewage was coming from. They used the green dye to help identify the source of the waste.

Dendritic

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‘Dendritic’ means like branches like a tree. It’s often used to describe rivers that have many branches, especially over a small area as seen with the Wateman and Utley Brooks in East Otto State Forest, or even the many small kills and creeks that dominate the landscape near Bethlehem.

Smaller summer harmful algal bloom predicted for western Lake Erie | University of Michigan News

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Smaller summer harmful algal bloom predicted for western Lake Erie | University of Michigan News

University of Michigan researchers and their partners are forecasting that western Lake Erie will experience a smaller-than-average harmful algal bloom this summer.

A relatively dry spring is expected to lead to a repeat of last year’s mild bloom, marking the first time in more than a dozen years that mild Lake Erie blooms have occurred in consecutive summers.

This year’s bloom is expected to measure 3—the same size as last year’s bloom—with a potential range of 2-4.5 out of 10 on the severity index, according to the annual Lake Erie forecast released today by the National Oceanic and Atmospheric Administration, which funds the research. The 2021 bloom is expected to be among the smaller blooms since 2011.