Water experts are set to turn the River Clyde red as part of a revolutionary environmental check-up.
Fluorescent dye will be placed in the river
The red dye will be tracked downstream to allow scientists to work out how long it would take for effluent from a sewer overflow to mix into the river.
Officials from Scottish Water and Sepa (Scottish Environment Protection Agency) said the dye will not harm fish or other wildlife in the waterway.
A Sepa spokesman said regular water users should not be alarmed.
Scottish Water project manager Iain McMillan explained: "We believe this is the first time such a comprehensive survey of the Clyde has been carried out.
"It may look quite dramatic when the liquid dye is first released, but the material will have no effect on the river or its ecology other than to change the colour of the water, although it will dissipate as it moves downstream.
"The survey will monitor nine waste water treatment works and a number of sewer outfalls and provide comprehensive information on how water quality is affected by waste water discharges."
Sepa spokesman George Rattray added: "Regular water users should not be alarmed at the release of this dye and be aware that monitoring equipment will be deployed at various locations along the Clyde.
"It is essential that this equipment is not disturbed so that as much scientific data is possible can be gathered."
The month-long survey begins this weekend.