Concerns about the Current Approach to Nutrient Criteria

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Concerns about the Current Approach to Nutrient
Criteria
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GROUP Criteria A1-7 Large Ozark
Reservoirs TP CHL B Big River Lakes TN
CHL C1 Plains FRlt.4 TP CHL C2 Plains
FR .4 - .6 TP CHL C3 Plains FR
gt.6 TP D1 St. Francois TP D2 Ozark
Highland TP D3 Oz Border Plateau TP
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Current Approach for Large Ozark Reservoirs
Median and 75th percentile of chlorophyll values
from each individual reservoir were used to set
Assessment and Action Levels for that reservoir.
Phosphorus Assessment and Action Levels were then
back-calculated from the chlorophyll values.
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Problems with this approach 1) Using historic
data from an individual reservoir to set criteria
for that reservoir Status Quo 2) Each reservoir
ends up with different Assessment and Action
Levels, a different range of values that make up
the Assessment range, and A/A Levels fall in
different places along the distribution of data
3) Currently no rationale given for this
approach
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GROUP Criteria A1-7 Large Ozark
Reservoirs TP CHL B Big River Lakes TN
CHL C1 Plains FRlt.4 TP CHL C2 Plains
FR .4 - .6 TP CHL C3 Plains FR
gt.6 TP D1 St. Francois TP D2 Ozark
Highland TP D3 Oz Border Plateau TP
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Current Approach for Big River Lakes
TN instead of TP criteria because the NP ratios
are generally low. Chlorophyll Assessment and
Action Levels set at 25 and 65/90ug/L TN
Assessment and Action Levels back-calculated from
chlorophyll.
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Problems with this approach1) Low NP may be
misleading as some phosphorus is bound to NVSS
and not readily available for uptake.2) Light
limitation of algae is likely in these lakes,
weakening the Chlorophyll - nutrient
relationship. 3) No mention of where the
chlorophyll assessment and action levels come
from in rationale.
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GROUP Criteria A1-7 Large Ozark
Reservoirs TP CHL B Big River Lakes TN
CHL C1 Plains FRlt.4 TP CHL C2 Plains
FR .4 - .6 TP CHL C3 Plains FR
gt.6 TP D1 St. Francois TP D2 Ozark
Highland TP D3 Oz Border Plateau TP
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Current Approach for Plains Reservoirs with low
flushing rates
Chlorophyll Assessment Levels for each group are
based on median values from two reference
reservoirs, while Action Levels are set at 20 and
25 ug/L chlorophyll. Phosphorus Assessment and
Action Levels are then back-calculated from the
chlorophyll values.
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Problem 1 Misuse of the reference approach
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EPA Reference Approach
Lake 10 mean Lake 9 mean Lake 8 mean Lake 7
mean Lake 6 mean Lake 5 mean Lake 4 mean Lake 3
mean Lake 2 mean Lake 1 mean
Difference in data associated with differences in
waterbodies (i.e. disturbances in watershed,
hydrology, etc.)
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Approach looks at the range of values found in
reference lakes.
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Missouris Version
Reservoir X value 10 value 9 value 8 value
7 value 6 value 5 value 4 value 3 value 2 value 1
More rain
Difference in data associated with climate and
timing of sample collection
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Approach looks at the range of values found in
two reference reservoirs.
Less rain
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A data set made up of individual values from one
or two reservoirs is not the same as a data set
containing mean values from multiple waterbodies!

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Problem 2 Use of reservoirs with forested
watersheds as reference for reservoirs built in
prairie landscape is inappropriate.
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The 10 of Plains reservoirs with lowest TP
concentrations (lt22 ug/L)
Rest of Plains reservoirs (TP gt22 ug/L)
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Proportion of watershed that is forest in
reference reservoirs Lincoln 84Forest
67Deer Ridge 54Nehai Tonkeia 49
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Problem 3 Action Levels of Unknown Origin
Currently the rationale states that the
chlorophyll action levels are based
on literature values (no citations) BPJ
(whose?) examination of data set (?)
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GROUP Criteria A1-7 Large Ozark
Reservoirs TP CHL B Big River Lakes TN
CHL C1 Plains FRlt.4 TP CHL C2 Plains
FR .4 - .6 TP CHL C3 Plains FR
gt.6 TP D1 St. Francois TP D2 Ozark
Highland TP D3 Oz Border Plateau TP
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Current Approach for Plains Reservoirs with high
flushing rates
Assessment and Action Levels are based on the
Phosphorus-Flushing Rate relationship. Assessment
Level is based on regression line (50 of
reservoirs above, 50 below). The Action Level
is set at alpha 0.05 (about 5 of reservoirs in
data set will be above the line).
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Problem with this approach1) The stakeholders
group has not really discussed where the
Assessment and Action Levels should be. These
lines can be placed anywhere within the relation
by changing the alpha value.
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GROUP Criteria A1-7 Large Ozark
Reservoirs TP CHL B Big River Lakes TN
CHL C1 Plains FRlt.4 TP CHL C2 Plains
FR .4 - .6 TP CHL C3 Plains FR
gt.6 TP D1 St. Francois TP D2 Ozark
Highland TP D3 Oz Border Plateau TP
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Current Approach for smaller Ozark reservoirs
Sub-regional approach, with different regions
being held to oligotrophic, mesotrophic or
eutrophic conditions based on hydrology and
geology.
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Are the differences in water quality related to
hydrology and geology?
Sub-Region TP FR Forest Crop Grass St.
Francois (oligo) 10 0.7 67 0.4 15 Ozark
Highlands (meso) 15 2.4 71 0.8 17 Border/Plate
au (eutro) 37 1.6 43 7.4 29
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Problem with this approach1) Differences in
water quality may be related to land-cover and
not regional hydrology and geology
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Level of Concern over the Current Matrix
GROUP A1-7 Large Ozark Reservoirs B
Big River Lakes C1 Plains FRlt.4 C2 Plains
FR .4 - .6 C3 Plains FR gt.6 D1 St.
Francois D2 Ozark Highland D3 Ozark Border
Plateau
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Lake Woodrail Columbia, MO
Horizontal lines represent Assessment and Action
Levels for C1 lakes.
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Lake Woodrail Columbia, MO
Summertime means (mid-May to mid-August)
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Lake Woodrail Columbia, MO
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Symbols represent individual values, lines are
current Assessment and Action Levels
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Symbols represent annual geometric means, lines
are current Assessment and Action Levels
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Symbols represent individual values, lines are
current Assessment and Action Levels
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Symbols represent annual geometric means, lines
are current Assessment and Action Levels
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Symbols represent individual values, lines are
current Assessment and Action Levels
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Symbols represent annual geometric means, lines
are current Assessment and Action Levels
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Symbols represent individual values, lines are
current Assessment and Action Levels
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Symbols represent annual geometric means, lines
are current Assessment and Action Levels
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Above Above
Assessment Action Pomme de
Terre Individual Values TP 46 22 CHL 49
27 Annual Values TP 50 17 CHL 50 17
Stockton Individual Values TP 38 11 CHL 4
9 26 Annual Values TP 33 6 CHL 17 11

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Above Above
Assessment Action Wappapello Individual
Values TP 32 12 CHL 43 25 Annual
Values TP 29 0 CHL 35
6 Clearwater Individual Values TP 61 12 C
HL 50 25 Annual Values TP 53 12 CHL 5
9 6
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Above Above
Assessment Action Table Rock Individual
Values TP 74 37 CHL 56 26 Annual
Values TP 79 32 CHL 63 16 Lake of
the Ozarks Individual Values TP 56 39 CHL
52 22 Annual Values TP 65 40 CHL 50
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