1. Management to Mitigate Environmental Effects of Dams
David Rosenberg
CEE 6490 – Integrated River Basin / Watershed Planning & Management

2. Learning Objectives
Quantify effects of dams on river channels and indicator species
Describe major approaches to mitigate effects
Determine effects of mitigation approaches on key indicators
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3. Environmental Effects
Altered flow regimes
Flood frequency and duration
Mean annual flow
Base (minimum) flows
Temperature
Channel degradation
Sediment trapping
Watershed fragmentation
Key indicator species
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4. Historical Longitudinal Bed Profile Glen Canyon Dam, 1956 (Schmidt)
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5. Bed Degradation Glen Canyon Dam, 1956 to 2000 (Schmidt)
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6. Maximum Bed Degradation below some Large Dams (Williams and Wolman, 1984)
Colorado
Glen Canyon: 7.3 m/9 years
Hoover: 7.5 m/13 years
Davis: 5.8 m/26 years
Parker: 4.6 m/27 years
Jemez
Jemez Canyon: 2.8 m/12 years
Arkansas
John Martin: 0.9 m/30 years
Missouri
Fort Peck: 1.8 m/36 years
Garrison: 1.7 m/23 years
Fort Randall: 2.6 m/23 years
Gavin’s Point: 2.5 m/19 years
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7. Key Indicator Species
Typically describe environmental impacts on key indicator species (often a fish!) – NEPA and ESA driven
June sucker, Provo River, Utah
Azraq killfish, Azraq, Jordan
Bonneville cutthroat trout, Bear River
Delta smelt, Sacramento & San Joaquin Delta, CA
Coho and chinook salmon, Klamath River, CA
And many, many, many others
Environmental management typically mitigates for species of concern – improve habitat
Avoid focus on ecosystem function
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8. Key Indicator Species Salmon Spawning and Ocean Counts, CA
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9. Mitigation Approaches
Operational
Change timing and duration of releases
Structural
Multi-stage elevation releases
Temperature control structures
Thermal curtains
Fish screens
Fish ladders
Management
Environmental water accounts
Remove dams (possibly in April)
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10. Changing Reservoir Releases Glen Canyon Dam, Colorado River (J
Changing Reservoir Releases Glen Canyon Dam, Colorado River (J. Schmidt)

11. Sediment Reduction (mmt)
(A) Pre- and (B) Post-Dam Sediment Fluxes
Location
Dist. below Dam (km)
Sediment Reduction (mmt)
Marble Canyon 25
57 to 0.3
Upper Grand Canyon
170
83 to 14
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12. Significance of Fine-Sediment Deposits
Distinctive attribute of the pre-dam riverscape
Campsites
Creates stagnant flow and backwater habitat at some discharges
Riparian ecosystem substrate
Deposits contain archaeological resources or stabilize those resources
Transport creates turbidity
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13. General Pattern of Sand Bar Change (Badger Creek Rapids)
1956
1999
Sand eroded from eddies
Sand eroded by wind; not replaced by flood deposition
In the case of Grand Canyon, matched photography and field surveys have allowed us to develop a time series of sand bar elevation that has been pushed back to the 1880s.

14. Glen Canyon Dam Release Experiments
Reduce range of daily fluctuations (erosion control)
Spiked “floods” (rebuild high elevation sand bars)
Sustain low flows (trap fine sediment)

15. lost hydropower revenue ~ $1 million
November 2004 Sediment Mobilization Flows
lost hydropower revenue ~ $1 million
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16. Costs of Modified Releases
Release Regime
Cost (lost hydro revenue)
[$ Millions]
Interim low fluctuating flows (per year)
$36
Modified low fluctuating flows (per year)
$44
1996 controlled flood $4
2003/2004 experimental releases
$2.85 (autumn)
$1.6 (winter)
Restoration budget
(FY 2004)
$11.1
Annual revenue in 2003/2004
~ $140 million/yr
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17. Glen Canyon Dam Postscript
But …
Newly built sand bars were immediately eroded by the large flow fluctuations, designed to disadvantage spawning trout
Cutbank 1 day after resumption of large fluctuations
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18. Temperature-Controlled Release Tower Shasta Dam, Sacramento River, CA
4.5 MAF storage
Dam height 602 ft.
Max. tower depth 350 ft.
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19. Thermal Curtain (Burgi, 1995; Vermeyan, 1995)
Lewiston Lake, Clear Creak, California
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20. Comparing Temperature Control Methods (Burgi, 1995)
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21. What did the fish say when it ran into the wall?
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22. Fish Ladders Oroville Dam (right) John Day Dam (bottom right)
Bonneville (below)
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23. Fish Ladder at Coleman Fish Hatchery Sacramento River, CA
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24. Fish Screens
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25. Environmental Water Accounts (Hollingshead, 2006)
Sac. & San Joaquin Delta
500 plants & animals
Supplies
2/3 residential and commercial users
7 million ac farmland
21 Federal & State agencies (i.e, CALFED)
Major water exports
CVP: 8,000 af/day
SWP: 15,000 af/day
Endangered species
Chinook salman, delta smelt, steelhead rainbow trout
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26. CALFED Operations Purchase assets (year round)
Long-term, spot market, and options to water on CA market
Storage in reservoirs South of Delta
500 cfs capacity to move purchased assets South of Delta (July to August)
Curtail export pumping (critical times to fish)
Reimburse projects (SWP and CVP) for cutbacks
Deploy purchased assets which are stored South of Delta
Real-time operations that respond to ecological and fish events
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27. CALFED Actions $19 – 65 million/year in purchases 155 – 230 TAF/year
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28. Conclusions
Can quantify environmental impacts of dams and reservoirs with numerous indicators
Site-specific factors determine type and extent of impacts
Regulation-imposed mitigation often required
Structural, operational, and management approaches to mitigate impacts
Often pose significant costs
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29. References
Burgi, P. H. "The Evolving Role of Hydraulic Structures - From Development to Management of Water." Issues and Directions in Hydraulics - An Iowa Hydraulics Colloquium, Iowa City, Iowa,
Hollinshead, S. P., and Lund, J. R. (2006). "Optimization of environmental water purchases with uncertainty." Water Resources Research, 42, W08403,
Mostafa, M. G. (1957). "River-bed degradation below large capacity reservoirs." American Society of Civil Engineers Transactions, 122,
Vermeyen, T. B. "Use of Temperature Control Curtains to Modify Reservoir Release Temperatures." ASCE's First International Conference on Water Resources Engineering, San Antonio, Texas,
Williams, G. P., and Wolman, M. G. (1984). "Downstream effects of dams on alluvial rivers." Professional Paper 1286, U.S. Geological Survey, Washington, D.C.
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