Tough Love for Lakes lake management strategies

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Tough Love for Lakeslake management strategies

• Frank X. Browne, Ph.D., P.E.
• F. X. Browne, Inc.

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Eutrophication Trophicmeans food or energy
level Oligotrophicecologically young lake with
low nutrients, low populations of algae and
macrophytes (aquatic plants), usually high levels
of dissolved oxygen, and a fair
fishery. Mesotrophicecologically middle-aged
lake with medium nutrients, medium populations of
algae and macrophytes, usually somewhat lower
dissolved oxygen in lower waters of lake, and a
pretty good fishery. Eutrophicecologically old
lake with high nutrients, high populations of
algae and/or macrophytes, usually depleted
dissolved oxygen in lower waters of lake, and a
poor fishery.
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Lake Succession Natural aging of a lake lake
gradually fills in, becomes wetland/bog, and
eventually becomes a forest. Cultural
eutrophicationaging of the lake is quickened by
mans activities, including Development Agricul
ture Forestry Activities Wastewater Roads/Highw
ays/Streets
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Lake Problems

• Excessive Algae (algal blooms)
• Excessive Macrophytes (Aquatic Plants)
• Siltation
• Loss of Clarity
• Dissolved Oxygen Depletion
• Fish Impacts and Changes

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Impacts of Eutrophication

• Loss of Lake Capacity sedimentation
• Reduction in lake depth
• Loss of Aesthetics
• Decrease in Recreational Value
• Decrease in Home Values
• Health Affects due to toxins

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Causes of Eutrophication

• Wastewater
• Septic systems
• Treatment plants
• Soil Erosion
• Stormwater Runoff
• All land uses

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Algae

• Product oxygen
• Provide food source for all animal life in lake
• zooplankton
• fish

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Macrophytes

• Product oxygen
• Provide habitat
• fish spawning and protection
• waterfowl
• Provide food source
• Provide substrate for attached algae (periphyton)
• Provide aesthetics

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Lake Habitats
Plankton
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Controlling Macrophytes
Macrophyte Map

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Controlling Macrophytes

• In-Lake Controls
• Physical
• Biological
• Chemical
• Watershed Management

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Physical Controls

• Dredging
• Lake drawdown
• Benthic barriers
• Shading
• Mechanical weed treatment

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Dredging

• Full lake or partial dredging
• Non-selective
• Removes all macrophytes
• Removes nutrients
• Disruptive to lake ecosystem
• Strict permitting requirements
• Expensive
• Usually effective

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Lake Drawdown

• Non-selective
• Sometimes effective
• Duration of drawdown
• Climate
• Types of macrophytes
• Inexpensive if outlet structure available
• Short to intermediate term solution

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Lake Drawdown Potential Impacts

• Loss of lake use during drawdown
• Aesthetics
• Reduction in benthic macroinvertebrate
  population
• Dissolved oxygen depletion in remaining pool
  areas of lake
• Reduction in beneficial macrophytes
• Potential algal blooms after refilling lake

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Benthic Barriers

• Usually used around docks, etc.
• Effective
• Several seasons

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Shading

• Chemical shades
• Depends on hydraulic resident time of lake
• Not practical for most flow-thru lakes
• Trees
• Sometimes effective

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Mechanical Weed Treatment

• Hand cutting/pulling
• Time/people intensive
• Cutting and shredding
• Dead weeds left in lake to recycle
• Harvesting
• Removes weeds and nutrients from lake
• Does not remove roots
• Potential to spread some weeds
• Rotavating
• Tills sediment and removes weeds roots from
  lake
• Weed rolling
• Compresses soil and vegetation

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Biological Controls

• Weevils/Beetles
• Fungal Pathogens
• Native Plans
• Grass Carp
• Eat invasive and native plants
• Can remove too much vegetation
• Eat selective plants

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Source Pennsylvania Lake Management Handbook
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Chemical Controls

• Kills macrophytes
• Not always selective
• Can kill native species
• Macrophytes remain in lake
• Plants die and recycle nutrients
• Short-term solution

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Source Pennsylvania Lake Management Handbook
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Source Pennsylvania Lake Management Handbook
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Aquatic Plant Management Program

• Prevention citizen watch program
• Assessment state problem w/o assuming a
  solution
• Site-specific management develop integrated
  management program
• Evaluation evaluate results and costs
• Monitoring plants, algae, fish, chemistry
• Education

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Watershed Management

• The ultimate lake management approach
• Control nutrients and sediments from entering
  lake
• Control soil erosion and stormwater
• Control existing and new development and land
  uses
• Control wastewater

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Existing Development

• Retrofit existing stormwater facilities
• Add new stormwater controls
• All land uses (agriculture, developed land,
  roads, commercial, forests)
• Stabilize eroded streambanks
• Add/improve riparian buffers
• Upgrade wastewater facilities
• Maintain stormwater facilities

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Shoreline Zones
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Unhealthy Lawn
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Healthy Riparian Buffer
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Riparian Buffer Convert grass area to natural
vegetative Buffer Eliminate grass Modify
slope Add natural vegetation
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New Development

• Implement low impact development approach
• Reduce impervious area
• Infiltrate and evaporate stormwater
• Reduce volume of stormwater
• Treat stormwater
• Develop and adopt stormwater management ordinance

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Wastewater Management

• Fix or replace failing septic systems
• Implement septic system management program
• Upgrade existing treatment plants
• Implement decentralized wastewater management
  systems for new developments

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Suitability of Soils for Septic Systems
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Suitability of Soils for Drip, Spray Mound
Treatment Systems
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Centralized Wastewater System
Decentralized Wastewater System
Source F.X. Browne, Inc.
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- Need to evaluate both in-lake and watershed
management options - Need to develop an
integrated management program
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Frank Browne, Ph.D., P.E.F. X Browne,
Incwww.fxbrowne.comLake and Watershed
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