Managing Aquatic Plants In Guntersville Reservoir
A Long-Term Action Plan
This plan lays out a strategy for future management of plants that grow in the waters of Guntersville Reservoir. It was developed primarily by the people who live on the reservoir or benefit from the recreational and economic development opportunities it provides. A stakeholder group made up of various reservoir user interests—fisherman, boaters, homeowners, industry, tourism councils, local governments, environmental groups, TVA, and others⎯evaluated control options for aquatic plants and recommend the following management strategy tailored to the unique needs and preferences of Guntersville Reservoir users
The proposed strategy calls for a combination of mechanical harvesters to provide access to open water areas and herbicide treatments to manage aquatic plant populations in near-shore areas. These methods were used in combination 1998 through 2009 and have been effective in providing a satisfactory level of control.
This plan reflects a commitment to managing aquatic plants in Guntersville Reservoir in a way that is both responsive and responsible—in a way that achieves the related goals of meeting the recreational needs of as many lake users as possible and protecting the reservoir’s ecological health and natural beauty.
Aquatic plants have been abundant and widespread in Guntersville Reservoir since the 1960s. The most abundant species on the reservoir are exotic, or non-native, species such as Eurasian water-milfoil, hydrilla, and spinyleaf naiad—all introduced to the United States from other regions of the world. Native species such as coontail, small pondweed, American pondweed, southern naiad, eelgrass, and muskgrass also grow in the reservoir but seldom colonize large areas like non-native species.
These plants provide many benefits. They provide food and cover for waterfowl, fish, and smaller aquatic organisms. They benefit the sport-fishing industry by increasing the growth and numbers of pan fish and bass , which helps attract more recreational and professional anglers. They reduce the effects of wave action, filter sediments suspended in the water, add oxygen to the water, and help protect shorelines from erosion.
However, aquatic plants cause significant problems when they reach excessive levels. They can interfere with swimming, skiing, and bank fishing, clog boat propellers, and make it hard for boaters to reach ramps and docks. Large colonies are unsightly, which impacts the aesthetic quality of the area for visitors and companies looking for relocation sites. They can also clog water intake screens, reduce local property values, decrease native plant diversity, and create mosquito habitat.
Aquatic Plant Growth
Populations of aquatic plants, whether native or exotic, undergo dramatic fluctuations in response to weather-related conditions, such as reservoir levels, river flow, and water clarity. During a record drought period from 1984 to 1988, for example, aquatic plants increased to an historical high in the Tennessee River system. This was followed by a dramatic decline during a period of high flows that began in early summer 1989 and culminated in the early 1990s.
During peak years of vegetation coverage in the late 1980s, aquatic plants colonized as much as 20,000 acres—or about 30 percent—of the total surface area of the 69,000 acres of Guntersville Reservoir. This was followed by significant declines in aquatic plants to about 5,000 acres in 1991. Since the early 1990s, aquatic plants have increased significantly—to a maximum of about 19,000 acres in 2012. Fluctuations can be expected from year to year, but aquatic plant populations are almost certain to colonize large areas of Guntersville Reservoir in the foreseeable future.
From the 1960s until about 2010, the non-native Eurasian water-milfoil was the dominant submersed plant on Guntersville Reservoir. In recent years, the dominant submersed species has become hydrilla—a more aggressive and difficult to control non-native species—which increased from about 400 acres in 1996 to about 4,000 acres in 1998, to about 11,000 acres in 2012. Hydrilla currently infests an estimated 80 percent of developed shoreline areas. Because hydrilla requires less light, it can grow at greater depths than Eurasian water-milfoil and has spread into areas of deeper water not previously colonized by aquatic plants.
Aquatic Plant Management
After the widespread colonization of Eurasian water-milfoil on Guntersville Reservoir in the late 1960s, TVA tried to eradicate it from the reservoir with large-scale herbicide treatments. While these treatments significantly reduced the amount of milfoil, the plants re-grew. The failure of eradication efforts—and a growing recognition of the benefits of water-milfoil to waterfowl, fish, and other aquatic life—caused a change in strategy in the early 1970s. Instead of trying to completely eradicate the species, TVA began a management program of controlling water-milfoil only in areas where it caused conflicts with reservoir use—primarily along developed shoreline. These areas were designated as “priority treatment areas” in the Guntersville Master Plan prepared by the U.S. Army Corps of Engineers and TVA in 1992.
In addition to the use of herbicides and normal reservoir level fluctuations which provide some control of aquatic plants, TVA introduced 100,000 sterile grass carp into Guntersville Reservoir in 1990 to curtail the spread of aquatic plants. More recently, mechanical harvesters have been used to provide access to developed shoreline areas by cutting lanes through colonies of aquatic vegetation. Harvesters cut aquatic plants and collect the fragments for disposal along the shore or in shallow water areas.
The Planning Process
Increasing plant populations and growing concerns about their impact on reservoir recreation prompted the formation of a stakeholder group in February 1998. The group’s goals were to help develop a process for involving local residents in addressing aquatic plant management issues on Guntersville Reservoir and to provide relief to homeowners and reservoir users without adverse ecological and economic impacts to the reservoir. Fishermen, boaters, homeowners, industry, tourism councils, local governments, environmental groups, and other reservoir interests were represented. To accomplish their goals, the stakeholder group developed a short-term strategy for managing aquatic plants in the summer of 1998 and then drafted a long-term management plan for 1999 and beyond for public input and review.
As a first step in the planning process, the stakeholder group asked TVA to conduct an independent public opinion survey to obtain new information about the needs for additional or different approaches to aquatic plant management on Guntersville Reservoir. TVA contracted this work to The Capstone Poll of the University of Alabama, which interviewed more than 400 area residents in June 1998. Survey respondents were randomly selected and screened to ensure some reservoir-related experience in the previous two years.
Ecological health, habitat for wildlife and waterfowl, and clear shoreline areas emerged as top priorities—consistent with the results of surveys conducted in 1994 on other reservoirs. Sixty percent of the respondents said they approved of the use of herbicides. (For a complete report on the survey results, please contact TVA’s Public Land Information Center 800-882-5263)
Survey results were presented to the stakeholder group for consideration and used in developing a short-term management strategy, announced by the stakeholder group in July 1998. This interim strategy called for the expanded use of mechanical harvesters and for the resumption of herbicide treatments in near-shore areas along developed shorelines too shallow for mechanical harvesting.
Work on the long-term management plan began in earnest in October 1998, when two focus groups were convened by the mayors of Guntersville and Scottsboro at the stakeholder group’s request. These focus groups were asked to identify existing problem areas—resulting from new construction or different property uses, for example—and to compare these areas with the map of priority treatment areas included in the 1992 Guntersville Master plan.
The stakeholder group received public comments on the draft long-term plan, including the location of priority treatment areas at two public meetings in February 1999. Suggested modifications and public comments were incorporated into the long-term management plan, described below. Implementation began with the start of the 1999 growing season.
In November 2008, TVA announced a change in its approach for managing aquatic plants in its reservoirs. In 2009 TVA funded treatments during the months of June and July along private residential and commercially developed shorelines. In 2010, TVA discontinued all private and commercial treatments and focused on a Valley wide plan to manage aquatic plants solely at public use areas. Due to this change in the scope of work and the absence of TVA funding for treatments along private residential and commercially developed shoreline areas, the Guntersville Stakeholder Group became inactive.
A “new” Stakeholder Group was formed and the first meeting was held in April 2014. During these meeting, the Group endorsed the long-term aquatic plant management plan developed in 1998 with minor modifications that reflected changes in aquatic plant growth and abundance and additional development of shoreline areas on Guntersville Reservoir. The 2014 long-term plan is outlined below.
Aquatic plants in Guntersville Reservoir will be managed to achieve three goals: to protect the ecological health of the reservoir, to meet the needs of as many recreation users and homeowners as possible, and to preserve the reservoir’s aesthetic and economic value. Consistent with these goals, this plan calls for continued targeted management of aquatic plants—not eradication. Recognizing the natural cycles affecting plant populations in large reservoirs along major rivers, it outlines a flexible strategy aimed at (1) suppressing aquatic plants in designated areas of the reservoir where they cause conflicts with reservoir use, (2) protecting aquatic habitat, and (3) improving communication and public involvement.
Managing Plant Populations
Of the 3,100 acres identified for potential treatment by the stakeholder group’s plan criteria, only approximately 1,350 to 1,400 acres have historically had aquatic plant issues within the Guntersville Reservoir (69,000 surface acres). This acreage is expected to be managed annually during implementation of the long term management plan. Typically, this is about 7 to 10 percent of the overall aquatic plant population. Identified treatment areas fall into four major categories and will be given treatment priority as follows: Priority 1 - Public Access/Recreation; Priority 2 - Residential; Priority 3 - Commercial; Priority 4 - Aesthetic. Maps on display at local public facilities (local Court House, City Hall, Chamber of Commerce) show the areas on Guntersville Reservoir which have been designated for aquatic plant management.
Plant populations in these areas will be controlled by two methods: mechanical harvesters and herbicides. Mechanical harvesters will be used to open boat access lanes and to clear small areas near drinking water intakes and around some public ramps. Herbicides will be used in near-shore areas along developed shorelines and to open access lanes in a few areas inaccessible to a mechanical harvester. In years with unusually high aquatic plant growth and abundance, herbicides may be selectively used in a few areas to open boating access lanes.
Use of these two methods in combination provides some distinct advantages. Harvesters are used to provide site-specific and immediate reductions in aquatic plants and can be used in close proximity to water treatment plants, where herbicide use is restricted. Herbicides are used to reduce aquatic plants in shallow water areas and confined areas around docks, where harvesters cannot operate efficiently.
Two other control methods were considered, but rejected: increasing the amplitude, time and duration of reservoir drawdown on Guntersville Reservoir and use of biological control agents. The current reservoir drawdown of about two feet, conducted as part of TVA’s normal reservoir operations, provides minimal control of aquatic plants. However, a deeper drawdown would cause significant problems for overall reservoir operation and commercial navigation. Biological control agents, such as herbivorous fish (grass carp), insects, and plant pathogens were not included in the plan because their use does not meet current management goals, or they have not been proven to be effective in large reservoirs.
TVA will remain abreast of research related to aquatic plant management and share information on improvements and innovations with the stakeholder group. Demonstrated advancements in technology will be evaluated jointly by TVA and the stakeholder group for possible incorporation in future Guntersville plant management operations.
Mechanical Harvesters — Mechanical harvesters will be used to cut and maintain access lanes 20 to 50 feet wide through colonies of aquatic plants near developed areas—for example, residential areas, commercial marinas and campgrounds, public and private boat ramps, and scout and church camps—and through colonies of mid-river vegetation to connect near-shore areas with deeper, open water. Harvesters also will be used to remove vegetation around potable water intakes and private boathouses and piers near drinking water intakes, to improve access to fishing areas, and to remove vegetation from small areas around public ramps where the water is deep enough. An estimated 50 acres of aquatic plants could be controlled with harvesters.
Mechanical harvesters will be operated from June through late September. Access lanes will be re-cut as needed—probably at two to four week intervals—to keep them open for boat traffic. Lanes will be cut in roughly the same locations as in 1998 through 2009 and in new locations identified during the stakeholder review process. The schedule for cutting and maintaining access lanes will be determined and coordinated by TVA and the Stakeholder Group.
Herbicide Treatments — Aquatic vegetation in designated areas (see maps on display at local public facilities) will be controlled with herbicides approved by EPA for use in the aquatic environment. Herbicides, including 2,4-D, endothall, diquat, glyphosate, and chelated copper compounds, will be selected based on their effectiveness in controlling the target plant species. In some cases, these herbicides may be used in combination or with EPA-approved adjuvants to improve the effectiveness of control. All herbicide treatments will be on an as needed basis as determined by TVA and applied in accordance with Pesticide General Permit ALG870022 issued to TVA by the Alabama Department of Environmental Management for management of aquatic plants in TVA reservoirs in northern Alabama.
Annual herbicide treatments are expected to be 1,350 to 1,400 acres based on 1998 to 2009 treatments applied during implementation of the long-term aquatic plant management plan for Guntersville Reservoir and inclusion of new areas of residential development. Because regrowth is likely to occur in some areas following treatment, some areas may be treated more than once during the growing season. Many of the herbicides available for use in the aquatic environment do not kill the underground rootstock of the plants and regrowth can occur within about five to eight weeks. In other instances, removal of one species - Eurasian water-milfoil, for example - may allow a different species or group of plants to grow in the treated area.
Herbicide treatments will extend from the shoreline to about 50 feet beyond the end of docks, boathouses, and other facilities. Thus, most herbicide treatments on Guntersville Reservoir areas with residential development, public access and recreational facilities, and commercial businesses will be within 150 to 200 feet of the shoreline. In areas managed for aesthetics, aquatic plants will be controlled up to a maximum of 600 feet from the shoreline or highway causeways. Vegetation reduction along causeways will increase fishing opportunities for bank anglers. Herbicides will also be used to open and maintain access lanes in a few areas that are inaccessible to a mechanical harvester. An example being embayments upstream of highway causeways that have bridges with low clearance and that lack ramps suitable for launching a harvester.
Herbicides will be applied from boats, or rarely from the shoreline using wheeled vehicles or back packer sprayers. All herbicide treatments will be by licensed contractors with certified applicators according to guidelines specified on the herbicide label and Alabama Pesticide General Permit ALG870022. All treatment boats will be clearly marked with identifiable numbers and a flashing light or other method that indicates when the boat is actually applying herbicides. Treatments will be monitored by TVA personnel familiar with standard application techniques and safe handling procedures. The schedule and order of shoreline areas to be treated with herbicides will be determined by TVA. All treatments made in the vicinity of potable water intakes will be coordinated with the managers of water treatment plants to insure that drinking water supplies are not affected.
Herbicide treatments are expected to begin about the first of June and continue through September. Treated areas will be posted with signs that include the date of treatment, name of herbicide applied, appropriate water-use restrictions, and telephone number of the contract applicator.
Protecting Aquatic Habitat
TVA and the Alabama Department Conservation and Natural Resources will regularly evaluate fish stocks to ensure that Guntersville Reservoir has healthy populations of black bass and other sport fish. TVA also will continue to monitor the overall ecological condition of the reservoir as part of its Reservoir Monitoring Program. This program includes five important ecosystem components: dissolved oxygen, chlorophyll, sediment quality, benthic macroinvertebrate community, and fish community. Monitoring results will be compared to information collected on Guntersville in previous years and to conditions observed in other TVA lakes to identify changes and to determine if they are widespread or specific to Guntersville Reservoir.
Improving Communication and Public Involvement
During the summer season, the herbicide treatment schedule for the coming week will be published in local newspapers. The stakeholder group website www.lakeguntersvillestakeholders.org will contain information such asthe treatment schedule and a lake map identifying treatment areas, details of the long-term management plan, educational information about aquatic plant species specific to the Guntersville Reservoir, brief updates on work accomplished, contact information for stakeholder representatives and other useful information designed to keep all lake users and the general public engaged and informed. Also included will be brief updates on work accomplished, he stakeholder group will work with TVA to develop and distribute information materials about aquatic plants and management strategies.
Active public involvement and open communication are essential to ensure that aquatic plant management activities respond to changing reservoir user needs. The public will be encouraged to provide input on ongoing plant management activities and suggest ideas for future improvement through the stakeholder group or mayors' offices in Guntersville and Scottsboro. The stakeholder group and TVA will meet as needed, but at least annually, to review the status of aquatic plants in the reservoir, consider citizen input, and evaluate the need for adjustments in future aquatic plant management operations.