Concerns about the Current Approach to Nutrient Criteria

GROUPCriteria A1-7 Large Ozark ReservoirsTP & CHL B Big River LakesTN & CHL C1 Plains FR<.4TP & CHL C2 Plains FR.4 -.6TP & CHL C3 Plains FR >.6TP D1 St. FrancoisTP D2 Ozark HighlandTP D3 Oz Border & PlateauTP

Current Approach for Large Ozark Reservoirs Median and 75 th 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.

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

GROUPCriteria A1-7 Large Ozark ReservoirsTP & CHL B Big River LakesTN & CHL C1 Plains FR<.4TP & CHL C2 Plains FR.4 -.6TP & CHL C3 Plains FR >.6TP D1 St. FrancoisTP D2 Ozark HighlandTP D3 Oz Border & PlateauTP

Current Approach for Big River Lakes TN instead of TP criteria because the N:P 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.

Problems with this approach 1) Low N:P 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.

GROUPCriteria A1-7 Large Ozark ReservoirsTP & CHL B Big River LakesTN & CHL C1 Plains FR<.4TP & CHL C2 Plains FR.4 -.6TP & CHL C3 Plains FR >.6TP D1 St. FrancoisTP D2 Ozark HighlandTP D3 Oz Border & PlateauTP

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.

Problem 1 – Misuse of the 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.) EPA Reference Approach 75% Approach looks at the range of values found in reference lakes.

Reservoir X value 10 value 9 value 8 value 7 value 6 value 5 value 4 value 3 value 2 value 1 Difference in data associated with climate and timing of sample collection Missouri’s Version 75% More rain Less rain Approach looks at the range of values found in two reference reservoirs.

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!

Problem 2 – Use of reservoirs with forested watersheds as reference for reservoirs built in prairie landscape is inappropriate.

The 10% of Plains reservoirs with lowest TP concentrations (<22 ug/L) Rest of Plains reservoirs (TP >22 ug/L)

Proportion of watershed that is forest in “reference” reservoirs: Lincoln – 84% Forest – 67% Deer Ridge – 54% Nehai Tonkeia – 49%

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 (?)

GROUPCriteria A1-7 Large Ozark ReservoirsTP & CHL B Big River LakesTN & CHL C1 Plains FR<.4TP & CHL C2 Plains FR.4 -.6TP & CHL C3 Plains FR >.6TP D1 St. FrancoisTP D2 Ozark HighlandTP D3 Oz Border & PlateauTP

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).

Problem with this approach 1) 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.

GROUPCriteria A1-7 Large Ozark ReservoirsTP & CHL B Big River LakesTN & CHL C1 Plains FR<.4TP & CHL C2 Plains FR.4 -.6TP & CHL C3 Plains FR >.6TP D1 St. FrancoisTP D2 Ozark HighlandTP D3 Oz Border & PlateauTP

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.”

Are the differences in water quality related to hydrology and geology? Sub-RegionTPFRForestCropGrass St. Francois (oligo) %0.4%15% Ozark Highlands (meso) %0.8%17% Border/Plateau (eutro) %7.4%29%

Problem with this approach 1) Differences in water quality may be related to land-cover and not “regional hydrology and geology”

Level of Concern over the Current Matrix GROUP A 1-7 Large Ozark Reservoirs B Big River Lakes B Big River Lakes C1 Plains FR<.4 C2 Plains FR C3 Plains FR >.6 D1 St. Francois D2 Ozark Highland D3 Ozark Border & Plateau

Lake Woodrail – Columbia, MO Horizontal lines represent Assessment and Action Levels for C1 lakes.

YearTP (ug/L) Overall Average18 Lake Woodrail – Columbia, MO Summertime means (mid-May to mid-August)

Lake Woodrail – Columbia, MO

Symbols represent individual values, lines are current Assessment and Action Levels

Symbols represent annual geometric means, lines are current Assessment and Action Levels

Symbols represent individual values, lines are current Assessment and Action Levels

Symbols represent annual geometric means, lines are current Assessment and Action Levels

Symbols represent individual values, lines are current Assessment and Action Levels

Symbols represent annual geometric means, lines are current Assessment and Action Levels

Symbols represent individual values, lines are current Assessment and Action Levels

Symbols represent annual geometric means, lines are current Assessment and Action Levels

Above Above Assessment Action Pomme de Terre Individual Values TP46%22% CHL49%27% Annual ValuesTP50%17% CHL50%17% Stockton Individual ValuesTP38%11% CHL49%26% Annual ValuesTP33%6% CHL17%11%

Above Above Assessment Action Wappapello Individual Values TP32%12% CHL43%25% Annual ValuesTP29% 0% CHL35% 6% Clearwater Individual ValuesTP61%12% CHL50%25% Annual ValuesTP53%12% CHL59% 6%

Above Above Assessment Action Table Rock Individual Values TP74%37% CHL56%26% Annual ValuesTP79%32% CHL63%16% Lake of the Ozarks Individual ValuesTP56%39% CHL52%22% Annual ValuesTP65%40% CHL50%15%