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Developing alternatives to toxic herbicides for controlling aquatic vegetation in irrigation canal systems.
Headwaters Heritage Initiative
TALENT IRRIGATION DISTRICT COLLABORATION
Water quality research has found that streams can carry a witch’s brew of chemicals, including pesticides, herbicides, hydrocarbon compounds, heavy metals, and pharmaceuticals. This unnatural cocktail can make it impossible to recover salmon and steelhead, even where significant money has been spent to restore physical habitat conditions.
Locally, open irrigation canals with dirt bottoms are common. These types of canals are affected by growth of aquatic weeds during the summer months when there is sufficient water and warm weather. The conventional response to this problem is to poison the weeds in the canals at regular intervals throughout the irrigation season with herbicides.
Our Clean Water Act court ruling determined that irrigation districts need a permit to apply herbicides to irrigation canals. This caused some irrigation districts to start thinking of alternative methods for removing aquatic weeds, and precipitated our collaboration with the Talent Irrigation District (TID) to reduce their dependency on chemical herbicides. The main component of our collaboration has been the development of a moss cutter, which uses high pressure water jets to manually remove vegetation from the canal bottom without structurally damaging the canal prism or chemically poisoning the water.
The TID purchased basic plans for the machine from Warm Springs Irrigation District and then modified the design to better accommodate the District's needs. As a more urban irrigation district, Talent Irrigation District required a machine with a jet arm that could lift out of the water when they had to work past automobile bridges.
Throughout the prototype design process, TID experienced many setbacks and cost increases. Problems with the cut vegetation from the canal clogging up sprinkler systems was partially alleviated by the installation of large trash racks that remove the cut vegetation from the canals and deposit it on the banks. The District's work must be commended for holding to the larger goal of herbicide reduction. In the end, the effort created a system that delivers clean water to the farmers while protecting the fish in the Bear Creek Watershed. Since this collaboration started, the TID has not applied chemical herbicides to control aquatic vegetation growth in their canals. In 2005, the TID received one of our annual stewardship awards for their efforts to reduce their dependence on chemical pesticides.
The initial collaboration has spawned additional projects aimed at improving fish access to tributary streams during the irrigation season when the irrigation district is withdrawing water from the streams. With funding assistance from the National Center, temporary fish ladders have been installed on Wagner and Neil Creeks to allow fish access past irrigation diversions during the summer.
This project has funded in part by generous support from the Carpenter Foundation and the National Fish & Wildlife Foundation.
Photo of moss cutter by Tonya Graham.
Photos of fish ladders by Talent Irrigation District.
