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Santa Cruz River to be dyed red for research project

Santa Cruz River will be running red this week
University of Arizona BIO5 Institute Laboratory
Posted at 6:23 AM, Mar 07, 2022
and last updated 2022-03-07 08:23:22-05

PIMA COUNTY, Ariz. — The Santa Cruz River will be running red starting March 8.

The changing of color for the river is part of a scheduled research project between partner agencies including the University of Arizona and the U.S. Geological Survey.

Researchers will apply dye to river flows near the Tres Ríos Water Reclamation Facility located near Ina Road.

The non-toxic dye, rhodamine WT, will be released into the river and be monitored as it flows downstream in order to aid researchers as they take water samples at selected downstream locations.

Rhodamine WT, the fluorescent red dye used in this study, is commonly used in other hydrologic studies, is non-toxic and safe for the environment.

Since the water in the river flows at different velocities at different locations, the application of the dye will allow researchers to time the variable rates of flow to ensure they are collecting samples of the same sections of water as it moves downstream.

The dye injection is being done by the USGS in coordination with University of Arizona researchers, who plan to use the water-travel data in later laboratory experiments.

For that project, researchers will collect water samples at specific intervals downstream to measure the effects of sunlight on certain organic materials.

Some of the materials researchers are testing for include personal care products, pharmaceuticals, and other chemical compounds.

Researchers hope that by collecting water samples at specific locations, they can measure the cumulative impact of continued exposure to sunlight on destroying or chemically altering the residual organic materials in effluent.

The dye may be visible for several days if ponding at a location were to happen.

University staff should be collecting samples until about March 11.