What IS that in Modesto-area canals?

Water has been turning red in Modesto Irrigation District canals, thanks to a dye that tracks aquatic herbicides.

The sight might be jarring — a crimson tint to this life-sustaining resource — but MID said it’s a safe way of dealing with algae and weeds that could clog the system.

“This is the second irrigation season in which we’ve used the tracking red dye, and we understand its look can be alarming,” spokeswoman Melissa Williams said by e-mail Monday. “It’s harmless and doesn’t affect the water quality and is safe for irrigation (swimming and fishing too, but we discourage such in our canals).”

The treatments started Thursday at the top of channels that branch off the main canal from Modesto Reservoir. This round will go through the end of this week and will be followed by another in six to eight weeks, said another spokeswoman, Samantha Wookey.

The dye takes about two days to make its way down a canal and eventually ends up on farm fields, she said.

Riverbank resident Lena Wright sent The Modesto Bee a photo of a red canal near her town. She raised concern about the health effects for joggers and dogs along the waterway.

“The red is just dye to track a carcinogenic herbicide that DOES have risks,” she said. “... I think the public should be told before these are flushed through our backyards and communities.”

MID’s canals serve about 58,000 acres of farmland bounded generally by the Tuolumne on the south, the San Joaquin River to the west and the Stanislaus River to the north. The district also treats river water for Modesto and a few smaller locales, but this is separate from the branch canals.

This story was originally published May 1, 2017 at 12:15 PM with the headline "What IS that in Modesto-area canals?."