1. Stanford Homecoming
October 12, 2007
Is Dilution the Solution to Pollution?
At any scale?
Karan Venayagamoorthy
Oliver Fringer
Jeff Koseff
Environmental Fluid Mechanics Laboratory
Civil and Environmental Engineering
Support from the Lenfest Ocean Program

2. How do we locate the fish pens?
Typical dimensions:
• 150 ,000 fish/cage
• ~ 20 m diameter
• ~ 15 m tall

3. Understanding the potential impact of a fishfarm is strongly
dependent upon proper assessment of the mixing of the
discharge from the cage with the local receiving waters!
Tides
Plus: Density variability Wind
Complex Bathymetry and Topography Riverine Discharges
Earth’s Rotation SSA Applications Inc

4. Critical Question and Needs
Where and in what concentrations will the dissolved waste from
aquaculture pens located in near-shore and off-shore environments be
found?
Need a science-based tool to determine:
- “after the fact” the impacts of a specific pen location
- “before the fact” where pens could be located to minimize effluent
concentrations at shoreline
More specifically…
For a given pen locations, what are the effects of tidal range, wind, riverine
discharges, earth’s rotation, bathymetry, and water column stratification on:
- the overall distribution of the pollutant field
- the concentration of pollutants at specific locations as a function of time
- the overall cross-shore and along-shore fluxes of pollutants

5. Transport of Effluent in a Fictitious
Two-Dimensional Embayment
Tide+Current

6. Transport of Effluent in a Fictitious
Two-Dimensional Embayment
B
A
BA

7. Transport of Effluent in a Fictitious
Two-Dimensional Embayment

8. Transport of Effluent in a Fictitious
Two-Dimensional Embayment
Tide+Current

9. Transport of Effluent in a Fictitious
Two-Dimensional Embayment

10. The importance of capturing the
physical processes fully and correctly
Tide+Current
Turn off the effects of the Earth’s Rotation

11. The importance of capturing the
physical processes fully and correctly
Tide+Current
Freshwater Inflow

12. The importance of capturing the
physical processes fully and correctly
Incomplete characterization of the flow
around and through the fishpens
Tide+Current

13. Summary and Implications
• Strong non-Gaussian behavior
• High concentrations at
significant distances from source
• Intermittency in space and time-
very large variability in
concentrations at a single point
and from point to point
• Importance of accounting for all
physics correctly

14. Aquaculture: Law and Policy
Meg Caldwell
Environmental and Natural Resources Law & Policy
Stanford Law School
Woods Institute for the Environment

15. Nonpoint
Source
Pollution
Point Sources
Pollution
Invasive Species
Aquaculture
Ocean Commissions Identify
Major Threats to Our Oceans

16. Coastal
Development
Overfishing
Habitat
Alteration
Bycatch
Climate Change
Major Threats to Oceans cont’d

17. The Ocean Commissions
Agree on Aquaculture
• Aquaculture must be
environmentally
responsible
• Not all fish farms
are created equal
• We need national
standards for
aquaculture
U.S. CommissionU.S. Commission
on Ocean Policy 2004on Ocean Policy 2004
Pew OceansPew Oceans
Commission 2003Commission 2003

18. U.S. Policy Embraces
Aquaculture
To promote the
development of
robust and
environmentally
sound aquaculture
in U.S. waters . . .

19. U.S. Aquaculture Legislation is
“In the Works”
But, NOAA’s bill contains no national standards for
environmentally responsible fish farming…
What else is Missing?
• Process to establish appropriate sites for fish farms
• Transparency and opportunities for public comment on
permits
• Clear authority to police facilities and rescind permits for
violations

20. California’s Approach:
A Model for the Nation
SB 201 (Simitian 2006)
• Requires environmental impact assessment
• Prohibits adverse impact on fishing, other uses,
wildlife and marine habitats
• Prevents discharge of pollutants
• Minimizes drug and chemical use
• Prevents and reports escapes
• Restores damage to marine environment
• Grants authority to monitor & inspect facilities
• Imposes reasonable lease fees

21. Non-Regulatory
Approaches

22. Our Challenge:
Develop the Industry While Protecting the
Oceans
Like fisheries,
offshore fish
farming has great
potential….Can
we learn from
history?