Nutrient Criteria for Reservoirs

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• Nutrient Criteria for Reservoirs A Review of
  Missouris Proposed Approach
• Daniel V. Obrecht
• Dept. of Fisheries and Wildlife Sciences
• University of Missouri

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Talk Outline

• Review approaches suggested in EPA guidance
  document
• Review some of the dead ends we visited
• Review how we came up with current proposal
• What it means in real terms

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Suggested EPA Approaches
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STEP APPROACH Designated Use Impairment of
use Algal biomass
Nutrient levels Criteria level
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UMBRELLA APPROACH

• 1) Reference reservoirs and lakes 75th
  percentile
• 2) All reservoirs and lakes 25th percentile
• 3) EPAs Regional criteria

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Reference 75 58 All Reservoirs 25 31 EPA
Regional Value 40
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Dead Ends
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Dead Ends

• Relate current land use and hydrology to water
  quality

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Dead Ends

• Relate current land use and hydrology to water
  quality
• Flow Chart divide reservoirs up into various
  groupings

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Dead Ends

• Relate current land use and hydrology to water
  quality
• Flow Chart divide reservoirs up into various
  groupings
• Tried to identify impairment

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Current Approach
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Multi-Pronged Approach

1. Divide state into ecoregions
2. Use morphology and watershed characteristics to
   predict differences in total phosphorus
   concentrations among reservoirs
3. Identify reference reservoirs within each
   ecoregion

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1. Ecoregions
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2. Use morphology and watershed characteristics
to predict differences in total phosphorus
concentrations among reservoirs
Reservoir surface area, reservoir volume, dam
height (measure of depth), watershed area,
pre-European settlement land cover (prairie,
forest, etc.), and hydrology Did not include
current land cover
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Regional Equations for Predicting Total Phosphorus
Plains ecoregion TP ( prairie/4)
(16/residence time in years) (570/dam height in
feet) Ozark Border ecoregion TP 15 (740/dam
height in feet) Ozark Highland ecoregion TP 5
(740/dam height in feet)
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Plains Reservoirs
( prairie/4) (16/ residence time) (570/dam
height in feet)
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3. Reference Reservoirs
1. No point sources or CAFOs within the
watershed 2. lt20 of watershed in combined crop
and urban coverage 3. gt50 of watershed in
dominant historic land cover (Ozark Highlands
forest Plains grassland)
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3. Reference Reservoirs

1. Plains Region has 7 reference reservoirs
2. Ozark Border Region has 7 reference reservoirs
3. Ozark Highlands has 23 reference reservoirs

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Reference Reservoirs in the Plains Region
Reservoir Total Phosphorus (µg/L) Marie 14 Vik
ing 25 Hazel Creek 27 Bethany 30 Elmwood
52 Harrison County 52 Lamar 72
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Reference Reservoirs in the Plains Region
Reservoir Total Phosphorus Marie 14 Viking
25 Hazel Creek 27 Bethany 30 Elmwood 52 Harr
ison County 52 Lamar 72
10th percentile
(of range)
75th percentile
(of range)
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Region Parameter 75 10 Plains Phosphorus
58 20 Nitrogen 911 506 Chlorophyll 33.1
7.5 Border Phosphorus 41 16 Nitrogen 890
451 Chlorophyll 25.5 6.1 Ozarks Phosphorus
26 9 Nitrogen 597 253 Chlorophyll 12
.4 2.6 All values are micrograms per liter
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Plains Reservoirs
( prairie/4) (16/ residence time) (570/dam
height in feet)
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Questions?