Estuaries in PEI Why are some more susceptible to nutrient loads - - PowerPoint PPT Presentation

WRIG - Community Stakeholder Consultations 16/03/2011

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Estuaries in PEI

Why are some more susceptible to nutrient loads than others?

WRIG - Community Stakeholder Consultations 16/03/2011

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Nutrient Susceptibility

 It has been apparent for

some time that each estuary in PEI has a specific load that it can tolerate

 Some have re-occurring

anoxia and “small” loads

 Some have little or no

anoxia despite high loads

 Something in the estuary

itself is driving this

 Biological/Chemical  Physical

Oyster mortality following anoxic event – Southwest River, PEI. July 2006

WRIG - Community Stakeholder Consultations 16/03/2011

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Island Estuaries with Re-Occurring Anoxic Events 2002 - 2010

>6 Anoxic Events 3-6 Anoxic Events 1-2 Anoxic Events

> 6 anoxic events 3-6 anoxic events 1-2 anoxic events

WRIG - Community Stakeholder Consultations 16/03/2011

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Nutrient Target Setting for PEI Estuaries

 Ambient tidal ranges appeared to be driving much of

the susceptibility to nutrients in PEI estuaries

 A very simple model developed (Gary Bugden, DFO-

BIO Estuary Load FW Volume + SW Volume

 Model appears to work for most estuaries on PEI

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Results

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

BDR BRA BRE BRR BWR CAB CAS COL COV ENM FLA FRE GDR HBR IND KIL MGR MIR MOR MUR NLB NLC NOR ORB PIN RUS SPB SSH SWR TRB TRY WES WIL WIN

Estuary Delta-N (mg/l) Anoxia Not Reported Anoxia Reported

0.06 mg/l 0.10 mg/l

Critical N Range

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Issue - Tidal Flushing



Causeways and Bridges

–

Many of them date from the 50’s and 60’s

–

Small openings easier and cheaper to build

–

Not always engineered for a full opening



lack of planning



• ther reasons (freshwater impoundments)

WRIG - Community Stakeholder Consultations 16/03/2011

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Wheatley River Has A Bridge!



Was constructed ~1972. There was also a bridge there prior to that. Bridge is in good shape.



Opening (gap) is 20m. Effective water depth is 1.7 m (was 1.3 m)



Studied in 2009 for TIF, (Mark MacNeil)



Results

–

No sill present

–

Admitted 95% of the tide (all but the highest tides)

–

Restriction due to the bridge channel and not downstream or upstream shoal area

–

Debris from previous structure present. Removal

• f debris recommended increasing depth under

bridge by 0.4 m and restoring 100% of tide.

–

Tidal currents under the bridge have decreased slightly as a result.

–

Work has been carried out (2009)

From MacNeil. 2009

WRIG - Community Stakeholder Consultations 16/03/2011

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Wheatley River Tidal Ranges

• 0.6
• 0.4
• 0.2

0.2 0.4 0.6 0.8 1 30/06/2009 04/07/2009 08/07/2009 12/07/2009 16/07/2009 20/07/2009 24/07/2009 28/07/2009 01/08/2009 Date Tide Height (m) Hunter River Rustico Bay Above Oyster Bed Bridge

WRIG - Community Stakeholder Consultations 16/03/2011

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Wheatley River Tidal Ranges

• 0.6
• 0.4
• 0.2

0.2 0.4 0.6 0.8 1 03/07/2009 07/07/2009 11/07/2009 Date Tide Height (m) Hunter River Rustico Bay Above Oyster Bed Bridge

WRIG - Community Stakeholder Consultations 16/03/2011

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Vernon River Restricted Tide Heights

below causeway above causeway

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Other Studies

 1986 “A Study of Water Quality Issues at Selected Prince

Edward Island Causeways” For PEI Department of Transportation and Public Works (P. Lane and Jacques Whitford)

 1996. “Numerical Modelling of Rustico Inlet, PEI” for Parks

Canada (Baird and Associates)

 1998. “Computer Modelling of Rustico Bay Hydrodynamics” for

Parks Canada (Baird and Associates)

 1998. “Assessment of Potential Water Quality Impacts

Resulting from Removal of Rustic Island Causeway”. For Parks Canada (Mike Brylinsky)

WRIG - Community Stakeholder Consultations 16/03/2011

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Other Physical Factors in Estuary Susceptibility



Residence time

–

How long does it take a molecule of water entering at the upper end to exit the lower?



Bathymetry

–

Relative size of photic zone

–

Presence of stratification



Size/Shape

–

Are there tidal flats?

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Long and skinny may force water in rather than out



Orientation

–

Prevailing wind direction

–

Movement of sediments/sand



Presence of Sills

–

Upstream Stagnation

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END

 Questions?

Cindy Crane Surface Water Biologist PEI Department of Environment, Energy and Forestry 902-368-5179 cscrane@gov.pe.ca