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

Estuaries in PEI Why are some more susceptible to nutrient loads than others? 1 WRIG - Community Stakeholder Consultations 16/03/2011

Nutrient Susceptibility  It has been apparent for Oyster mortality some time that each estuary following anoxic event in PEI has a specific load – Southwest River, PEI. that it can tolerate July 2006  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 2 WRIG - Community Stakeholder Consultations 16/03/2011

Island Estuaries with Re-Occurring Anoxic Events 2002 - 2010 Number of Estuaries with Recorded Anoxic Events (2002 - 2010) PEI 25 20 15 Number 10 5 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 Year > 6 anoxic events >6 Anoxic Events 3-6 Anoxic Events 1-2 Anoxic Events 3-6 anoxic events 1-2 anoxic events 3 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 5 WRIG - Community Stakeholder Consultations 16/03/2011

Results 0.40 Anoxia Not Reported Anoxia Reported 0.35 0.30 0.25 Delta-N (mg/l) 0.20 0.15 0.10 mg/l 0.10 Critical 0.06 mg/l  N Range 0.05 0.00 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 6 WRIG - Community Stakeholder Consultations 16/03/2011

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  other reasons (freshwater impoundments)  7 WRIG - Community Stakeholder Consultations 16/03/2011

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 – of debris recommended increasing depth under From MacNeil. 2009 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) – 8 WRIG - Community Stakeholder Consultations 16/03/2011

Wheatley River Tidal Ranges 1 0.8 0.6 0.4 Tide Height (m) 0.2 0 -0.2 -0.4 -0.6 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 Hunter River Rustico Bay Above Oyster Bed Bridge 9 WRIG - Community Stakeholder Consultations 16/03/2011

Wheatley River Tidal Ranges 1 0.8 0.6 0.4 Tide Height (m) 0.2 0 -0.2 -0.4 -0.6 03/07/2009 07/07/2009 11/07/2009 Date Hunter River Rustico Bay Above Oyster Bed Bridge 10 WRIG - Community Stakeholder Consultations 16/03/2011

Vernon River Restricted Tide Heights below causeway above causeway 11 WRIG - Community Stakeholder Consultations 16/03/2011

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) 12 WRIG - Community Stakeholder Consultations 16/03/2011

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? – Long and skinny may force water in rather than out – Orientation  Prevailing wind direction – Movement of sediments/sand – Presence of Sills  Upstream Stagnation – 13 WRIG - Community Stakeholder Consultations 16/03/2011

END  Questions? Cindy Crane Surface Water Biologist PEI Department of Environment, Energy and Forestry 902-368-5179 cscrane@gov.pe.ca 14 WRIG - Community Stakeholder Consultations 16/03/2011