Reservoir and Lake Nutrient Criteria

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Reservoir and Lake Nutrient Criteria

• A Different Approach

D.V. Obrecht, J.R. Jones M.K. Knowlton MU
Limnology
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UMBRELLA APPROACH

• 1) Reference reservoirs and lakes 75th
  percentile
• 2) All reservoirs and lakes 25th percentile
• 3) EPAs 304(a) criteria

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Oxbow lakes (n12) TP 212 ug/L TN 1.56 mg/L
Reservoirs (n135) TP 45 ug/L TN 0.73 mg/L
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Reservoir TP (µg/L) range of
geomeans Maysville (n10) 182 116
300 Grindstone (n5) 147 90 -
218 Unionville (n10) 98 68 - 155 Long
Branch (n20) 48 30 - 115 Viking (n16)
26 19 - 40 Forest (n19) 23 14
- 44
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STEP APPROACH Designated Use Impairment of
use Algal biomass
Nutrient levels Criteria level
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Drinking Water Supply Impairments -taste and
odor -clogging of filters -algal toxins
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There may be too many factors that influence
water quality and too much variability within and
among systems to allow for the setting of a
single set of criteria to be used by the state
for regulation.
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EPA allows some flexibility (states can)
develop their own criteria which reflect more
locally representative conditions. prioritize
their waters..Such an approach should include a
mechanism for evaluating the sensitivity of all
watersconsidering current and expected land
use EPA memorandum, Nov. 14, 2001
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A Different Approach!
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A lake is a reflection of its watershed.
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Total Phosphorus (µg/L)
Cropland ()
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A reservoir is also a reflection of its
watershed, and the intensity of that reflection
is dictated by hydrology.
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Regression model results Equation r2 TP
4.27 0.36 crop 0.62 TP 5.53 0.33 crop
0.50DH 0.73 TP 5.20 0.35crop - 0.37 DH
0.12 FI 0.77 DH is dam height, a surrogate from
reservoir morphology FI is flushing index
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Proportion crop Short Res. Time Med. Res. Time Long Res. Time
gt 40
20 40
10 20
1 10
lt 1
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Proportion crop Short Res. Time Med. Res. Time Long Res. Time
gt 40 116 ug/L 75 ug/L 47ug/L
20 40 97 ug/L 80 ug/L 53 ug/L
10 20 59 ug/L 54 ug/L 33 ug/L
1 10 40 ug/L 27 ug/L 27 ug/L
lt 1 17 ug/L 17 ug/L 17 ug/L
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Can we use agriculture to classify reservoirs?
USGS photo
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Reservoirs were built into landscapes that had
already been altered. No Restoration Water
quality in a reservoir is a function of
morphology/hydrology and location within the
landscape.
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Harvested acres of corn, 1920
58,000 87,000 ac
7,600 34,000 ac
30 counties
36 counties
34,000 58,000 ac
26 counties
87,000 169,000 ac
22 counties
Between 11 and 21 of total Missouri land
surface dedicated to just corn production in 1920!
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Missouris reservoirs gt10 acres in size Year
completed 1800-1920 122
8 1920-1940 267 18 1940-1960 68
5 1960-1980 909 61 1980-1995 121 8
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This approach allows the state to -Identify and
protect the reservoirs that have low watershed
impacts. -Identify and focus efforts on the
reservoirs that have higher nutrient
concentration than expected, given watershed land
use and hydrology. -Gauge the potential for
successful nutrient reduction by looking at the
factors that control in-reservoir nutrient
concentrations. And focus limited resources ()
on those reservoirs where improvements can be
made.