Chapter Five - Lake Management|
EVERYLAKE is unique. Specific strategies to address a lake's water quality
problems should focus on activities in the watershed and/or in-lake
restoration techniques, depending on the nature and extent of the
Lake management approaches fall into two categories, the "quick-fix" and
long-term management. The quick-fix offers a short-term solution such as
the application of herbicides to kill unwanted algae or macrophytes
(large plants). It treats the biological symptoms of a lake problem, but
does not address the underlying causes. Plant and fish productivity are
dependent on the chemical and physical processes going on in and around
the lake, and these must be considered in any plan to change the biology
of a lake.
Long-term management considers all of the environmental, cultural, and biological
factors affecting the lake and sets a priority on finding lasting
solutions. If immediate in-lake restoration techniques are necessary,
they should be followed by appropriate long-term management actions to
control sediment, nutrient, and toxic inputs.
Lake management is a complicated job and likely will be a joint effort of community
groups, individuals, landowners, and government. To be effective, lake
management is a long-term commitment and investment. This and following
sections briefly summarize various methods to improve a lake's water
quality and indicate necessary permits and possible grants and loans.
In-Lake Restoration: Cleaning up problems
Controlling pollution sources will not improve lake water quality immediately in
many cases. Years may pass before lakes cleanse themselves of accumulated nutrient loads and wastes. For this reason, in-lake restoration techniques have been developed to accelerate recovery. In-lake restoration techniques are briefly described in the table below. Consult the references at the end of this web-site for more details on these techniques.
In-Lake Restoration Techniques
Flush with low nutrient water
||Reduces nutrient levels. Washes out surface algae.
||Requires large volumes of water.Does not eliminate sources of phosphorous from sediments or watershed.
sulfate (alum) treatment
lake phosphorus content. Inhibits release of phosphorous from
sediment. Increases water column transparency.
measure. Potential toxic impacts during application. Increased
macrophyte growth due to water clarity.
or prevents stratification. Provides aeration and oxygenation.
Increases aerobic habitat.
not decrease algal biomass. May decrease water clarity. Adverse
impact on cold-water fish. No effect on macrophytes.
oxygen in hypolimnion. Limits release of phosphorous from sediments.
Increases habitat and food supply.
to supply adequate oxygen. Potential for destratification and subsequent
algal blooms. No effect on macrophytes.
aquatic vegetation, deepens lake. Increases lake volume. May improve water
resuspension of sediments. Temporary destruction of habitat. Disposal
concerns. High cost.
macrophytes. Consolidates sediments. Facilitates dredging or excavation.
Facilitates dock repairs.
effectiveness in mild, wet climates. Short-term benefit. Intensifies algal
blooms. Temporary adverse impacts on fish and invertebrates. May leave
docks high and dry.
|Biomanipulaton: Adjust fish species composition
growth of zooplankton, which eat algae.
experimental. Not effective where blue-green algae dominate.
Aquatic Plant Control
techniques have been developed for controlling aquatic plants and are briefly described in the table below. Additional information on advantages, disadvantages, permits, costs, and contacts for each technique are available at this link and in references provided at the end of this web-site.
Aquatic Plant Control Techniques
Manual Methods: (Handpulling, raking and cutting)
||Inexpensive. Flexible. Easy to use around docks, swim areas.
||Not practical for large areas. Stirs up sediment. Disturbs bottom-dwellers.
|Inhibits or prevents growth. Nontoxic. Low environmental impact in small applications. Ability to target problem areas. Can be installed in areas that are inaccessible to harvesters.
||High cost. Prone to damage, displacement, and plant regrowth. Must be correctly installed to prevent flotation. Maintenance required.|
Rolls plants flat or detaches them from bottom sediment
||Inexpensive, easy to operate. Can give season-long control.
||Detached plants need to be removed from water. Good only for limited area around dock.
|Mechanical Cutting: Cutters clip plants several feet below surface
||Hand-held cutters easily maneuvered. Fish habitat retained. Low cost for individuals/associations.
Plant fragments must be removed to prevent rerooting. Several cuts required in growth season.
plant material from lake. Requires no toxic substances. Vegetation
may be composted.
intensive, seasonally dependent. Access constraints. May facilitate
colonization of new areas due to fragmentation. High costs. Repeat
treatments needed. Depth restriction (.5m-5ft.) Plant disposal
Rotovation: "Roto-tilling" to dislodge plants and roots
||2-3 acres can be rotovated daily. Removes roots.
||Large equipment, high costs. Disrupts sediment, causing turbidity, nutrient and toxic release. Disturbs bottom dwellers. For milfoil control.|
Sterile Grass Carp
some aquatic vegetation. Requires no toxic substances.
impacts on other organisms. May increase nutrient cycling and
stimulate algal blooms due to grazing and digestive activities.
Possible escape and infestation of nontarget areas. Introduction of
parasites. May prefer native plant species over exotics.
Herbicides: Apply chemicals to kill or control plants.
||Inexpensive. Easy to apply. May control macrophyte and algae growth.
||Potential toxic effects. Decomposing plant material releases nutrients to water column. Short-term benefit may require temporary restriction on recreational activities. Dissolved oxygen depletion due to decomposing plants. Repeat applications needed.