Status, Trends, Distribution, and Functions of Wetlands in the New York City Water Supply Watershed

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Status, Trends, Distribution, and Functions of
Wetlands in the New York City Water Supply
Watershed
Laurie Machung, Bureau of Water Supply, Watershed
Protection and Planning
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Mapping and Research Programs

• National Wetlands Inventory
• Wetlands Status and Trends
• Wetland Characterization and Preliminary
  Functional Assessment
• Reference Wetlands Monitoring Program

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National Wetlands Inventory (NWI)

• USFWS first completed in 1996 using 158,000
  scale mid 1980s aerial photography
• Updated in 2005 using 140,000 scale 2003 and
  2004 aerial photography
• Provides base data on the distribution,
  characteristics, and extent of wetlands

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Wetland Status and Trends

• Completed for the Croton Watershed in 1999,
  updated in 2005
• 1968 1984
• 1984 1994
• 1994 2004
• Completed for Catskill and Delaware 12/08
• Mid 80s mid 90s
• Mid 90s 2004

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• Wetland Characterization

• USFWS added LLW codes to each wetland polygon in
  the NWI database to depict
• Landscape Position
• Lotic
• Lentic
• Terrene
• Landform
• Water flow path
• Throughflow
• Outflow
• Isolated
• Other modifiers (hw)

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• Wetlands Monitoring Program

• East of Hudson 6 reference sites
• West of Hudson 22 reference sites
• Water Quality
• Water Table
• Vegetation
• Soils

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• Catskill/Delaware Reference Wetlands

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Croton Watershed Palustrine Wetlands
Approximately 15,355 acres (6 of land surface)
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Catskill/Delaware Watersheds Palustrine
Wetlands
Approximately 9,565 acres (1 of land surface)
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NWI vs. Delineated Area

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Wetland Trends East and West of Hudson Watersheds
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Wetland Landscape Positions in East and West of
Hudson Watersheds
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• Wetland Characterization

• Describes Wetland landscape settings
• Enables an estimate of wetlands potentially
  lacking federal regulatory protection
• SWANCC
• Isolated wetlands
• Rapanos and Carabel
• Significant nexus analysis required for
  Non-navigable, non-relatively permanent
  tributaries and adjacent wetlands
• To determine if they significantly affect the
  chemical, physical, and biological integrity of
  TNWs

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Wetland Characterization

• Used USFWS LLW codes to estimate abundance of
  wetlands lacking perennial connections
• Two approaches
• Water Flow path modifiers
• IS, IN isolated
• OI, TI, OU intermittent
• Headwater modifiers
• IN and IS isolated
• Headwater modifier - 1st and 2nd order streams

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Croton Watershed Flow Path Method Predicts that
24 of wetlands are vulnerable isolated
(5) intermittently connected (19)

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Croton Watershed Headwater Method Predicts that
43 of wetlands are vulnerable Headwaters
38 Isolated 5

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Catskill/Delaware Watersheds Flow Path
Method Predicts that 38 of wetlands are
vulnerable isolated (13) intermittently
connected (25)

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Catskill/Delaware Watersheds Headwater
Method Predicts that 71 of wetlands are
vulnerable Headwaters (58) Isolated (13)

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Proportion of NWI Wetlands not included on NYS
FWW Maps
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68
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Percent of Non-DEC wetlands without perennial
connections
40
68
52
70
(11)
(15)
(27)
(46)
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DOC Export
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DOC Export
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DOC vs Color East of Hudson Wetland Outflows
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Conclusions

• According to the NWI, Wetlands occupy
• 15,355 acres, or 6 of Croton Watershed
• 9,565 acres, or 1 of the Catskill and Delaware
  Watersheds
• Reference Wetland monitoring identified margin of
  error in NWI mapping
• Net rates of wetland loss have declined over the
  time periods studied
• Pond construction was leading cause of wetland
  loss in all time periods, though rates have
  declined

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Conclusions

• Based USFWS LLW modifiers, an estimated
• 24 to 43 of Croton Watershed Wetlands and 38
  to 71 of Catskill/Delaware Wetlands could lose
  federal protection and
• 11 to 15 of Croton Wetlands and
  27 to 46 of Catskill/Delaware wetlands would
  lack federal or state protection

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Conclusions

• Reference wetland monitoring is a valuable tool
  to assess whether wetlands have a nexus to
  traditional navigable waters

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