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City of Austin Invasives Control
Texas Invasive Species
Coordinating Committee Austin Texas
March 12, 2013
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Lake Austin and Lady Bird: ‘Run of the River’ reservoirs Last two in chain of 7 ‘Highland Lakes’ 1600 acres, 490 acres respectively Flood and irrigation water conveyance High-use recreational areas
Lake Walter E. Long 1270 acres Cooling water for Decker Creek PP Water pumped from Colorado River City of Austin owns shoreline Bank and boat fishing
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Lake Austin Aquatic Vegetation • Eurasian watermilfoil (Myriophyllum spicatum) dominant
– Controlled by biennial winter drawdowns – In less than 12 ft
• July 1999 – 23 acres Hydrilla (Hydrilla verticillata), 10 % of total veg – First found at boat ramps
• July 2002 – 320 acres, bank to bank
• Impacts to recreation and property owners
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Control Challenges Drawdowns
Fairly low cost Winter only, 12’ depth limit Tubers, deep growth not impacted Limited re-fill water
Harvesting
Short term, targeted control Cost & disposal issues
Herbicides
• Relatively rapid control • High flows, potable water intakes • Contact type only = re-growth • High cost in deep water • Negative public perception
Grass Carp Long term, deep water control Downstream escapement “All or nothing” stocking rate Opposed by some fishermen
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Hydrilla
Tom Miller Dam
Mansfield Dam
Lake Austin Hydrilla Coverage (Source: Texas Parks and Wildlife Department, May 2002)
2 4 miles
Quinlan Park
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Hydrilla
Lake Austin Hydrilla Coverage (Source: Texas Parks and Wildlife Department, Aug 2002)
Mansfield Dam
Tom Miller Dam
2 4 miles
Quinlan Park
July 2002 Major flood Hydrilla backed up flood waters Flooded homes Clogged hydro-intakes, Shut down power production, > $30K
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Lake Austin Hydrilla Management Plan
Partners: • COA, TPWD, LCRA, FOLA
Objectives: • Pre-hydrilla condition • Maintain lake ecosystem
Integrated Efforts: • Winter drawdown • Harvesting/herbicides on mats • Incremental grass carp stocking • Stocking based on veg surveys
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sLake Austin Hydrilla Overview
HydrillaPeriods of Grass Carp Stockings47,770 total fish
8,100 4,700 4,400 13,200 17,370
< 28 fish/ac
> 52 fish/ac < 40 fish/ac
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Why the recent increase? • Drought
– Lower water levels on Travis – LCRA limiting releases – Lake Austin warmer, slower – Last scouring flood- 2007
• Fish migration & mortality – 47,700 stocked – est 25,000 alive – 43 fish/ hydrilla acre
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Taking Stock • Grass carp play critical
role in hydrilla control • Other factors:
– Non-palatable vegetation – Floods and drawdowns
• Current conditions require higher stocking rate
• Stock 9,000 fish this spring • 55 fish/acre
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Lake Long Aquatic Vegetation • Stable diverse native plant community • Good fish habitat and fishing (bank and boat)
• Hydrilla impacts – Cooling water intake screens for power plant – Shoreline & dock access
• 2000- treated w/ Sonar • 2013- spot treat 5 ac w/Aquathol K
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Lady Bird Lake Aquatic Vegetation
• Historically very limited < 3 % cover • Eurasian watermilfoil dominant (5-10 acres) • 2011- Drought= less run-off, increased clarity
• Milfoil increased to 25 ac
• Fanwort Cabomba carolinia Spread from Barton Creek to lake
• 2012 no flow, cover increased
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2011 • 32 acres 7 % cover
• 7 acres Cabomba
2012 • 94 total acres 19 % cover • 78 acres Cabomba
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Problem or Positive Addition? • Aquatic vegetation provides ecosytem benefits • Dense growth only impacts some lake users • Public education (not hydrilla, not lake-wide) • City PARD and WPD Plan
• Control options and funding sources • Criteria for specific action (special events, etc)
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Lady Bird Riparian Restoration
• Improve habitat, wq – Remove invasives – Plant natives if needed
• Model for city-wide effort
• Grow Zones – Limit mowing – Passive re-growth – Plant seedlings
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Arundo donax • Limits lake’s riparian diversity and public use • 3.4 acres, spread along entire 5 mile shoreline • Typically on steep slopes • Ranges from single plant to 150 ft long patch • Monoculture or in mixed stands of hardwoods
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2011 Control Efforts • Cut plants first to limit biomass in areas with
– Woody vegetation – Public access
• Composted material at City facility
• Treated min 4 ft re-growth: – Mixed woody stands
• 5 % Imazamox
– Monoculture • 2 % Imazamox + 1 % Glyphosate
– Both used 1% MSO
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2012 Control Efforts • Poor results from 2011
– Drought limited re-growth – October application – Winter dormancy – Less herbicide uptake
• 2012 No prior cutting • August application • Increased use of glyphosate mix w/ targeted spraying • Results pending
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Elephant ear, wild taro Colocasia esculenta
• Covers at least 50 % of shoreline • Shades out native grasses • Little to no wildlife or public benefit • Traps trash and debris • Provides some erosion control
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Pilot Project • Two herbicides
– Imazamox (Clearcast), with MSO – Glyphosate (Refuge) with NIS
• Three application techniques – Cut and paint – Wick or glove-in-glove – Foliar spray
• Best results w/ foliar spray • Little diff b/w herbicides • Small buffer zone (.5 m) b/w plots • Possible herbicide translocation • Imazamox – more targeted
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Invasive Species Management Plan April 2010 – City Council Resolution
• Wildflower Center working group – City,TPWD, stakeholders
• Five year goals: • Prevention • Early Detection • Rapid Response
• Recommendations for staffing, monitoring, education – 24 priority species – Fact sheets and BMPs
• Cities of Service $25K Grant – Spring 2013 volunteer trainings – Summer 2013 mapping invasives
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Questions?