Alternative Dam Management

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Alternative Dam Management A Different Type of
Flood Management Policy
Kaytee Manchester March 7, 2006BEE694
EcoHydrology
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Overview of Topics

• Natural Floods Effects
• Managed Floods Effects
• Using Frequency Analysis to Manage Floods
• What next?

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Flood Regime in Regulated Rivers

• Upper Mississippi River System

• Illinois River
• Upper Mississippi River
• Maintains seasonal flood pulses
• 50 of original floodplains
• About half a million hectares unleveed

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Flood Regime in Regulated Rivers

• Overview of River System

• 126 Million tons cargo transported along 2,167 km
  annually
• Supports 485 species of mussels, fishes,
  amphibians, reptiles, birds, and mammals
• 50 species are rare, threatened, or endangered
• 2.5 M worth of fish plundered annually
• 88 90, substantial amounts of mussels shells
  taken used in marine oysters to create pearls
• Recreational benefits estimated at 1.2 B
• 18,000 jobs to support outdoor recreation

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Flood Regime in Regulated Rivers

• Changes in Natural Flooding

Daily Water Levels from 1878 1899, 1975 - 1996
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Flood Regime in Regulated Rivers

• Changes in Natural Flooding

• 1880 - upland drainage for agriculture increased
• More dams for navigation water diversions
  created
• Major floods have higher peaks and are more
  frequent
• Fewer years with stable water levels during
  growing season
• Horizontal line flood elevation that causes
  damage

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Flood Regime in Regulated Rivers

• Changes in Natural Flooding

• Early upland drainage did not affect biota
• Changes in upland and mean low water level, not
  flow
• Including seasonal timing, duration, frequency
  of flows have the most affect on floodplain
  ecosystems

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Flood Regime in Regulated Rivers

• Effects of Dams Levees

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Flood Regime of Regulated Rivers

• Effects of Dams Levees

• 33 low navigation dams constructed in 1930s
• Permanent effects of navigation dams
• permanent flooding immediately upstream
• natural vegetation replaced with aquatic
  vegetation
• Seasonal Effects
• reduces water level variation along river length
• floodplain floods during growing season
• but drains during fall and spring floods

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Flood Regime of Regulated Rivers

• Effects of Dams Levees

4 miles upstream of Dam 26
36 miles upstream of Dam 26
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Flood Regime of Regulated Rivers

• Effects of Dams Levees

• Minor floods have effects too
• Floods in summer drown seeds tubers
• Abrupt drops can strand kill fish gtltgt gtltgt gtltgt
• Or raise temperatures, lower DO
• Aye, so dams have negative effects, but they are
  sort of necessary

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Flood Regime of Regulated Rivers

• Naturalization vs Restoration

Restoration is the returning of an ecosystem to
a close approximation of a condition that existed
prior to human alteration. (NRC
definition) Naturalization is to shift some
components of an altered ecosystem closer to a
natural condition, while maintaining or enhancing
existing economic and social uses of the
ecosystem.
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Flood Regime of Regulated Rivers

• Flood of 1993

• Had many effects on populations, communities,
  succession
• But nutrient loading
• Nutrient rich-sediments deposited upstream of
  delta
• If more floodplains allowed to flood, more
  nutrients would have been deposited, less
  carried to Gulf of Mexico
• Despite reduction in nutrient loading to the
  Gulf, levels have not fallen all that much
• Perhaps more flooding can help this?

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Flood Regime of Regulated Rivers

• Managed Floods Floodplain Compartments

• In the Fall, water is pumped into compartments
  or
• Flows into compartments if river rises gates
  opened
• Flooding patterns usually tailored to soil
  moisture pattern of native vegetation
• In the Summer, pumped out to preferred soil
  moisture levels in compartments
• In the Spring, during spring floods
• Fish can access compartments to spawn
• Return of adults young to river before summer
  pumping?

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Flood Regime of Regulated Rivers

• Managed Floods Controlled Drawdown

• More infrequent extreme than compartment
  drawdown
• Periodic drawdown compaction of sediments
• May restore sediment-filled backwaters, devoid
  of aquatic life
• 1994, a floodplain lake pumped dry for
  maintenance
• 77 species not seen in 5-6 years appeared
• Records amounts of visiting waterfowl
• Aquatic vegetation grew in submersed
  construction ruts
• Prompted 4 small scale drawdown projects

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Flood Regime of Regulated Rivers

• Managed Floods Controlled Drawdown

• Results from 4 projects
• Increased abundance diversity of aquatic
  plants
• Ecological benefits worth temp constraints on
  navigation recreation?
• Logistical problems to be overcome in future
  drawdowns
• Maintenance of intermittently run pumps for long
  time periods
• Rain, levee seepage, groundwater inflows
• Effects from animals on levees, materials, etc

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Flood Regime of Regulated Rivers
Managed Floods Using Navigation Dams

• ACOE project, to hold water level at 0.15 m
  lower than max regulated level for 20 days
• Still able to meet minimum navigational depth
  levels
• Results Drawdowns in 3 areas
• Abundant growth of emergent species in 202-243
  ha
• Further experiments in progress in different
  areas
• Value of water level variation in
  river-floodplain ecosystem interaction beginning
  to be accepted

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Flood Regime in Regulated Rivers
Conclusions Recommendations

• Restoration of large river systems is not a
  viable policy
• But naturalization may be!
• Relaxing constraints on high low water levels
• Lots of ideas about what would actually work,
  are risks worth it, etc
• No one knows for sure, especially on such a
  large scale
• Key is adaptive management

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Flood Regime in Regulated Rivers
Conclusions Recommendations

• Adaptive Management let Nature have a say
• Engineering planning to incorporate variation
  across time space
• If drought year allow drying to occur
• If flood year allow flooding to be protracted
• Both have benefits
• Use experts knowledge, especially when data
  about original state is not available (including
  socioeconomic know how)

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Forecast-based Advanced Release
Advanced Release as a Management Strategy

• Folsom Reservoir
• On an individual event basis
• Use data from NWS streamflow forecasts
• Release water from a reservoir in advance of a
  flood
• Goal is to make later, high releases unnecessary
• 2 Modes of failure
• Advance release is higher than would have been,
  w/o prep
• Failure to refill conservation pool by end of
  event

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Forecast-based Advanced Release
Advanced Release as a Management Strategy
(a) without Advance Release (b) with Advance
Release
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Forecast-based Advanced Release
Uncertain Streamflow
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Forecast-based Advanced Release
Basic Idea Advance Release Triggers

• Forecasted peak streamflow of certain magnitude
• Forecasted event volume of certain magnitude
• A forecasted quantile meets either above trigger
• Forecasted event results in release larger than
  channel capacity w/o advance release
• Also have a discontinue trigger for Advanced
  Release

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Forecast-based Advanced Release
Simulation Results

• Actual 1997 event
• Total event volume 1,135,517 acre-ft
• Peak flow 252,538 cfs
• Use 1997 event 150 (to force release above
  channel capacity)

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Forecast-based Advanced Release
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Forecast-based Advanced Release
Conclusions Recommendation

• Need to weigh potential effectiveness with risk
  of impacts to other reservoirs objectives
• This is just being explored, no decisions have
  yet been made
• Further study is needed

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Alternative Dam Management

• Agreement that variation is good, but how to
  create effective variation?
• Controlled flooding could be good, start on
  smaller dams?
• Other thoughts?