The purpose of the test is to make sure wastewater treatment plant improvements are meeting provincial government water quality policies, the city said.

The red dye being put into the Whitson River is known as a dye tracer test. It used to study the mixing of treated wastewater and river water where a wastewater treatment plant discharges to the environment.

The dye will be released into the Whitson River for several hours, while measurement and visual observations are made at a number of locations in the river.