20250903-003: Reservoir Update 24-25 — original pdf

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The Reservoir Update – FY 2024 and 2025 B r e n t B e l l i n g e r, P h . D . C o n s e r v a t i o n P r o g r a m S u p e r v i s o r Wa t e r s h e d P r o t e c t i o n D e p a r t m e n t S e p t e m b e r, 2 0 2 5 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Overview • A u s t i n L a ke s I n d e x • Goal – understand conditions and drivers impacting our waterways • Policy Relation – make management recommendations to protect and/or improve ecological conditions • A q u a t i c v e g e t a t i o n ( h o t t o p i c ) • Management challenges • S h o re zo n e h a b i t a t • Efficacy of code-and-criteria mitigation rules • M i c ro p l a s t i c s • Recent collaborative effort with University of Texas C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 2 Austin Lakes Index Score Scores remain fair-to-good • • Summarize: water and sediment chemistry, biological communities, habitat Influenced by: land-use, pollutant inputs, climate, flow C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Lake Austin • Aq uatic vegetation • Native and non-native plants • Grass carp populations • 358 grass carp stocked in July • Boater and homeowner per spective • Want more plant management • Fishermen per spective • Want less plant management C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 4 Moving forward • Vegetation sur veys continue to inform management • Decisions • In collaboration with Texas Parks and Wildlife • In consideration of ecological value, uses, hydrilla and stakeholders • Goal - balance vegetation with competing perspectives Triploid grass mechanical harvesting C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 5 Lady Bird Lake • Fa n w o r t g r o w t h f r o m Re d B u d t o I - 3 5 , B a r t o n C r e e k • Floating vegetation move, but are not flushed, by winds and flows • S e a s o n a l d y n a m i c s • October(ish) – June • growth below surface (low user conflict) • July – September • Plants reach surface (highest user conflict) • U s e a n d Pe r c e p t i o n i m p a c t s • Evening cruises, rowers, paddleboarders • Aesthetics • Collecting trash • Cyanobacteria (blue-green algae) mat growth around plants fanwort C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Walter E. Long C u r r e n t l y d r a w n d ow n f o r d a m r e p a i r s E l eva t e d n u t r i e n t c o n c e n t r a t i o n s • Elevated algal biomass • • • Ro bu s t , i n t a c t s h o r e l i n e a n d a q u a t i c ve g e t a t i o n • Supports exceptional fishery • M i n i m a l a c t i ve m a n a g e m e n t o f s y s t e m C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T The (Lake Austin) shore zone Example: Natural Exa mple: Cleared /modified C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 8 Middle ground Enabling development while p reser ving ecological functions C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 9 Development rules • Code-and-criteria specific to projects impacting shoreline, critical water quality zone, critical environmental features, floodplain • This project focused on Lake Austin developments post-2010 (contemporary code) • Impor tance of vegetation integrity • Water quality • Riparian habitat • U.S.EPA findings • Ecological integrity negatively correlated with shore zone development C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 10 Intent of CoA code/criteria Preser ve vegetation (where possible) and provide mitigation plantings in Critical Water Quality Zone • Number of plants and species commensurate with project type and size C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 11 Research project • Goal: determine the p er sistence of required mitigation plantings • Evaluated 84 sites where mitigation plantings had been installed since 2010 code changes • Scored sites 1 – 6 based on abund ance and diver sity required C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 12 Above expectations 2017 2022 Site score = 6 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 13 Met expectations Site score = 4 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 14 Below expectations 2017 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 15 Site score = 1 2019 Key Finding • Number of obser ved plants consistently lower than what wa s req uired • Some sites had a lot of plants and protected them! • Most sites…did not • Process gap in post-project tracking C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 16 Microplastics – a global issue • Size <5mm • Derived from breakdown of plastic or rubber materials • Found throughout food web • Inc luding humans ! • Another defining attribute of the Anthropocene epoch C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 17 Under the microscope Types of microplastics counted: Road/tire particles, Plastic fragments/“Fibers” C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Lake Austin FM 620 Mansfield Dam Panther Hollow Coldwater Cr. Bull Cr. Turkey Cr. Loop 360 Taylor Cr. Bee Cr. Tom Miller Dam C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Lady Bird Lake Tom Miller Dam MoPac Eanes Cr. Shoal Cr. Barton Cr. Lamar Blvd Bouldin Cr. 1st St. Waller Cr. I-35 Congress Ave Longhorn Dam C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 20 Microplastic abundances: Note the scale differences! Lake Austin Lady Bird Lake Flow Flow C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Microplastics (#/100g DW)510152025303505001000150020002500tire/road fibers fragments Taylor SloughTurkey Cr.Panther HollowBee Cr.River km246810Microplastics (#/100g DW)020004000600080001000012000Lamar Blvd.Waller Cr.Shoal Cr.I-35 Summary • Austin Lakes Index • Composite score that captures a lot of ecological complexity • Reser voir-focused • Vegetation management of a multiuse reservoir with an aggressive non-native plant difficult and unpopular • Reser voir-adjacent • Efforts to protect shore zones from development impacts through code-and-criteria need more evaluations and reassessment • Reser voir water shed -contributing • Car and road abundance evident in the surface sediments – implications? C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 22 Questions? C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 23