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LAKE CAPACITY MODELING The GOOD, the BAD and the UGLY.

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Presentation on theme: "LAKE CAPACITY MODELING The GOOD, the BAD and the UGLY."— Presentation transcript:

1 LAKE CAPACITY MODELING The GOOD, the BAD and the UGLY

2 Lake Capacity Model  Just a tool not a solution to planning issues / concerns  Help to identify those lakes where water quality impacts may be a concern

3 Problems with Models  Expectations are for an exact number in an imperfect science  many modeling assumptions  many different export coefficients (always evolving)  retention coefficients for phosphorus in septic beds now being applied  evolution of the way the LCSM is applied – 50% rule

4 Changing PWQO(s)  10 ug/L TP cold water or 20 ug/L TP warm water  also background + 50 % rule for TP; lake at 8 ug/L can go to 12 ug/L; new objective becomes 12 ug/L.  Oxygen PWQO was 5.0 mg/L then 6.0 mg/L now MVWHDO value of 7.0 mg/L.

5 Implementation Problems: What do we do with at capacity lakes?  Stop Development or have more Strict Protective Measures for development  Larger lot frontages  Larger setbacks more restrictive building code requirements re: septics.

6 Implementation Problems: What do we do with at capacity lakes?  What about development on upstream lakes – often in different municipalities with different planning rules in their OP(s).  Do we stop development on the upstream lakes based on nutrient loading arguments?

7 Implementation Problems: What do we do with at capacity lakes?  What about existing vacant lots of record?  What about lots where:  septic beds are >300 metres from the water  or achieve a surficial flow > 300 metres to the lake  or have drainage to a different watershed?

8 What If:  Water quality improves such that the PWQO(s) are not exceeded, say from 11 ug/L TP to 9 ug/L  The science becomes conclusive that nutrient migration away from septic beds on Precambrian Shield lakes is negligible.

9 What Capacity Models do not address:  Models do not address urbanization of shorelines  Incremental near shore habitat loss both in-water and on land  Vegetation removal (nursery habitat for fish)  Substrate alteration – spawning for bass, lake trout pike etc.  Visual impacts  Tree removal etc. etc.


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