Nuisance Aquatic Vegetation Control in Water Delivery Systems: Low-Dose Metered Herbicide Application

Project ID: 3968
Principal Investigator: Kevin Kelly
Research Topic: Supporting Irrigation Districts
Funded Fiscal Years: 2016
Keywords: None

Research Question

Can we modernize and further implement a Reclamation patented technology to control nuisance aquatic
vegetation (NAV) in water delivery systems?

Need and Benefit

NAV issues are wide-spread and can be very costly to control. The western U.S. is predominantly arid and highly
dependent on a network of reservoirs and delivery canals for agricultural water distribution. NAV, such as
filamentous algae and rooted aquatic macrophytes, are a growing problem in these canal systems. Flow through
water delivery systems can be greatly reduced or completely obstructed by the growth of NAV. In addition, NAV
can impair the performance of intake structures and pumps, or could otherwise cause serious damage to the
system. Increased sedimentation rates in canals and drainage systems are also exacerbated due to the changes in
design velocity effected by NAV.
Recently, drought conditions have reduced reservoir levels that serve as a source of water supply to the irrigation
districts. In some cases, water supplies have reached historical lows. Indeed, some districts were not able to divert
water into some canals during the past few years. This has renewed interest in tools that will help stretch and
minimize impacts on the limited water supply - such as the low dose metering system.
Canal operators and irrigation districts must hire physical labor to continuously remove the material from the
systems and/or purchase and apply aquatic herbicides. According to irrigation districts, 20% to 30% of their
budget goes toward controlling NAV. Costly control diverts funds and resources that otherwise could be applied
to other critical maintenance and improvement projects.
Many NAV were identified, including, but not limited to, Southern Niad, Horned Niad, Sago Pondweed, American
Pondweed, Curly Leaf, Cattails, Souring and Spike Rush, and filamenteous algae. A multitude of aquatic herbicides
have been developed. Therefore, this proposal does not plan to investigate new herbicides or study the various
species of NAV themselves, since it doesn't change the fact that all aquatic herbicides can be metered using the
low dose metering system.
Instead, the need is modernization of the prototype low dose metering system using current available technology.
For example, a low-dose metering system that can be programmed for different herbicide use pattern (varying
Factor recommendations - i.e. Factor 24 application such as 4 ppm applied for 6 hours, 2 ppm applied for 12
hours, etc.) would make it more applicable and beneficial. A low dose metering system that can also be
programmed to administer multiple combinations of herbicides (multiple stocks) would also be of great benefit.
Being able to program different herbicide use pattern in the control of different NAV species is necessary to
address current NAV infestations. As an example, the herbicide Cascade is touted as a 'silver bullet' for Sago
pondweed in a Factor 24 application. But as Sago pondweed is controlled, there is a species shift in the canals
giving rise to populations of Elodea, Southern naiad, and Horned pondweed. These other species require a Factor
36 application of Cascade or a Factor 36 application of a combination of mono- and di-potassium salts of
endothall (i.e., the herbicides Teton and Cascade, respectively) to then control these other species.
Other needs for being able to program combinations and levels of herbicides include changing dosage regimens
to address synergistic or discordance responses seen in the application of herbicides. It does not appear
Reclamation inventors has ever looked at whether a different concentration exposure time (CET) of the same
Factor would have provided greater control (0.4 ppm/80 hrs versus 4 ppm/8 hrs). Also, it's well know that there
is a synergistic response using combinations of chelated coppers (i.e. Captain XTR) and copper formulations are
directly impacted by water hardness. Copper treatment that will reliably carry 10 miles in Nebraska waters may
only carry 8 miles in Colorado waters. Having the ability to program would improve the applicability of the low
dose metering syst

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Nuisance Aquatic Vegetation Control in Water Delivery Systems: Low-Dose Metered Herbicide Application (final, PDF, 461KB)
By Kevin Kelly
Publication completed on September 30, 2016

Nuisance aquatic vegetation growth may detrimentally impact water flow and water quality in delivery systems. A traditional method of control is the use of federally-approved herbicides, which are commonly added to the water by slug or surface applications. However, these chemicals may not be as efficacious in flowing water systems due to rapidly diluting concentrations and insufficient exposure time. The problem is further compounded when the flow rate is fluctuating. A prototype automated chemical metering system was developed in 1996 by Reclamation scientists to address these challenges. A U.S. patent was granted in 1999. However, this system has been left in storage in a state of disrepair for nearly 20 years. The Research and Development Office requested an assessment of the current condition of the existing prototype and recommendations for modernizing the system.

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Last Updated: 6/22/20