KNOW YOUR STREAMFLOW: How minerals and sediment change rivers

A stream like the Uncompahgre River transports many substances as it flows through a variety of geologic, land use, vegetation, and urban areas. The substances include suspended bits of soil and rock, organic material, nutrients, bacteria, and dissolved and undissolved metals. 

Suspended materials, particularly those containing metals like iron, can produce different colors in streams and degrade water quality. Water quality specialists are particularly interested in the concentrations of bacteria, nutrients, and metals that can be harmful to aquatic life and humans.

What might cause the color in the river in the left photo? Does the clear water in the right photo indicate the water is healthy and safe to drink and for aquatic organisms?

Left photo: The Uncompahgre River in Ouray. The clear water comes from Canyon Creek, just upstream, while the yellow-brown water is from the Uncompahgre River above Ouray that has been shunted through the Ouray Hydro Plant and returned to the river. Right: Commodore Gulch is a stream above Red Mountain Creek where the water is clear, but the streambed has been colored by minerals in the water. Melting snow on the bank can deposit soil and rock particles into the stream.

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