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Big picture

Big picture. Focus on watershed scale where suspended algae are most prevalent Watershed planning fine tunes limits for small streams Long-term average, not driven by critical flow. Considerations. Critical condition/flow Downstream impacts Transport Non-point reductions Compliance point

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Big picture

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  1. Big picture • Focus on watershed scale where suspended algae are most prevalent • Watershed planning fine tunes limits for small streams • Long-term average, not driven by critical flow

  2. Considerations • Critical condition/flow • Downstream impacts • Transport • Non-point reductions • Compliance point • Immediate reach • 8 digit HUC

  3. Background • Current “background” is above standards • Assume reductions from proposed lake TMDLs • Assume reductions from approved turbidity TMDLs • Modeling in MN R basin for turbidity predicts dramatic improvements for TP

  4. Draft river eutrophication criteria (summer-means). • Future assessments based on: • Minimum of 2 summers & 6 or more obs./summer; • Data from most recent 10 years; • Must exceed cause & one or more response (stressors)to be deemed impaired (303(d) listed)

  5. Draft criteria compared to RNR-based TP distribution. Reflects distinct regional patterns Based on summer-mean STORET data from 1995-2009 for: 128 (North), 239 (Central) and 209 (South) river sites.

  6. Examples

  7. South Fork Crow

  8. Outlet or every stream mile? 150 ug/L 150 ug/L 150 ug/L 150 ug/L 150 ug/L 150 ug/L 150 ug/L 150 ug/L

  9. Fantasy vs reality 150 ug/L 150 ug/L 150 ug/L 140 ug/L 100 ug/L 150 ug/L 150 ug/L 160 ug/L 145 ug/L 150 ug/L 150 ug/L 175 ug/L 200ug/L 150 ug/L 150 ug/L

  10. Cottonwood HSPF output

  11. Response variables • Set limits based on TP • Modeling response variables will require additional resources and time • Is Chl-a more valuable than BOD

  12. Topics that need attention • Stabilization ponds • Mass vs concentration limits • Calculating non-point reductions • Stressor id is the proposed path for small streams • Biology and periphyton • Habitat, nutrients, tss, contaminents…..

  13. Quantile (piece-wise) regression (with CI) describes relationships & ID threshold concentrations. Mid-point of 2 breakpoints used to interpolate TP.

  14. Threshold Concentrations Threshold concentrations from biological tests for: • Region: north, central, and south • River size: nonwadeable and wadeable • Biological group: Fish and invertebrate

  15. Cottonwood and downstream

  16. Flow considerations

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