Capital Press

Aquifer recharge, salmon recovery and aquatic herbicides are a few of the topics that will be tackled next month during a water seminar in Idaho.

Sponsored by the Idaho Water Users Association, the water law and resources seminar will run Nov. 5-6 at the Doubletree-Riverside in Boise.

Brian Olmstead, manager of the Twin Falls Canal Co., will discuss the canal company's experience in getting a Section 18 emergency exemption from the Environmental Protection Agency to use an aquatic herbicide called Cascade.

"It took us two full years to get that approval," Olmstead said in a recent interview.

The new aquatic herbicide was used by the canal company this year for the first time as a means of removing moss and other weeds from canals and laterals.

The Twin Falls Canal Co. has been severely restricted in its use of conventional aquatic herbicides because of nearby fish farms.

It has had to rely instead on mechanical methods to rip away the moss, including the use of tractors and heavy chains -- a dangerous and costly practice.

The new aquatic herbicide has allowed the canal company to greatly scale back on its use of drag chains, Olmstead said.

"It has just about eliminated the need for chaining because it doesn't kill fish," he said.

Twin Falls Canal Co. used Cascade on many of its canals this year and hopes to use it on the entire system next year.

"We had phenomenal results," Olmstead said. "We had the best aquatic weed control we've ever had."

Other seminar speakers will discuss the legal and regulatory implications of using aquatic herbicides in general.

Irrigation districts and other entities that use pesticides and herbicides in and around water will have to get National Pollution Discharge Elimination System permits starting in April 2011.

Other topics to be discussed:

* Recent decisions by the Idaho Department of Water Resources, including an order to curtail some junior ground water pumpers.

* A presentation from Idaho Deputy Attorney General Clive Strong called "Idaho's Constitutional Preference for Irrigated Agriculture -- Fact or Fiction."

* An update on the Endangered Species Act and salmon litigation.

* Legal issues facing the dairy industry.

* An update of the state's comprehensive aquifer management plan.

Staff writer Dave Wilkins is based in Twin Falls, Idaho. E-mail:


More on the two-day seminar, including a full agenda, is at the Idaho Water Users Association Web site,, or at 208-344-6690.

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