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Weed issues putting stress on irrigation district

Posted on July 30, 2014 by Taber Times

With the summer growing season now in full swing for local producers, water usage in the Taber Irrigation District (TID) has reached normal levels for the area.

“We’ve had a significant uptake in water usage with the warmer weather, and we finally got rid of those June rains,” said TID district manager Chris Gallagher.

“We’ll have normal winter water levels. We’re in the process of using water now, and they’ll eventually have to release some water to draw down to normal winter levels. We’re in a good storage situation right now.”

Although water is being consumed at an above average current rate of usage, cumulative usage is below average.

“It’s a little bit higher (than average), in terms of current rate of usage, however, our cumulative usage is down compared to previous years. We’re just under 33,000 acre/feet this year, and we were just under 40,000 acre/feet at this time last year. A significant amount of that difference was prior to July,” said Gallagher.

A consistent annual problem for most irrigation districts, aquatic weeds have been wreaking particular havoc this year for the TID.

“At this point, we’re struggling with the water that we’re receiving from the St. Mary’s River Irrigation District (SMRID),” said Gallagher. “Normally, by this time, they will have done a magnacide (herbicide) treatment downstream of Stafford Reservoir. They have been unable to do that due to high turbidity from the rain events, and the quick ramp-up of water usage after that.

“The ideal time to apply magnacide-H is when you have fairly clear water at relatively low flows. Because it’s concentration based, once the irrigation demand ramped up, the economics become unfeasible. Basically, they would have had to use almost their entire magnacide-H stockpile in order to treat the main canal.”

Weed treatments are only effective against growing plants, not detached plant material that has made its way into the district via the SMRID system.

“To make a long story short, the treatment that they had planned to do this year, they were unable to do. In addition, the strong wind events we’ve had has caused the detachment of a lot of aquatic weeds from the bottoms of the reservoirs, both from SMRID and our own reservoirs. That’s created a lot of problems for us. There’s a lot of floating weeds going through our district. Even our own magnacide program, internally within TID, can’t do much about that. It will treat the stuff that’s growing in our own canals, but it can’t do much for anything that is already suspended,” said Gallagher.

Weed issues can cause significant problems for irrigation districts, requiring careful monitoring to ensure fouled infrastructure remains free of clogs.

“It clogs up our works. In particular, we had a recent incident where it accumulates at some of our headworks structures, forms a clog, and then all comes through the headworks in one shot,” said Gallagher. “Then our ditchrider has to go out and clean the whole canal system. It also clogs up our pipeline inlet grates — the trash racks — and can starve pipelines if we don’t get on that quick enough.”

Other than struggling against weeds, the TID has had a relatively smooth water delivery season thus far, according to Gallagher.

“For the most part it has gone fairly well. We’ve been able to meet our water delivery requirements with no major events. We had some original start-up issues, with the rain and the late frost conditions, but since then we’ve had no pipe leaks or major canal events or anything like that. It’s been a good delivery season.”

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