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LAKE CAPACITY MODELING The GOOD, the BAD and the UGLY

LAKE CAPACITY MODELING The GOOD, the BAD and the UGLY. 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. Problems with Model s. Expectations are for an exact number in an imperfect science

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LAKE CAPACITY MODELING The GOOD, the BAD and the UGLY

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  1. LAKE CAPACITY MODELINGThe 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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