Concerns about the Current Approach to Nutrient Criteria

Concerns about the Current Approach to Nutrient Criteria

GROUP Criteria A1-7 Large Ozark Reservoirs TP & CHL B Big River Lakes TN & CHL C1 Plains FR<.4 TP & CHL C2 Plains FR .4 - .6 TP & CHL C3 Plains FR >.6 TP D1 St. Francois TP D2 Ozark Highland TP D3 Oz Border & Plateau TP

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.

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

GROUP Criteria A1-7 Large Ozark ReservoirsTP & CHL B Big River Lakes TN & CHL C1 Plains FR<.4 TP & CHL C2 Plains FR .4 - .6 TP & CHL C3 Plains FR >.6 TP D1 St. Francois TP D2 Ozark Highland TP D3 Oz Border & Plateau TP

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 approach1) 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.

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

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.) 75% Approach looks at the range of values found in reference lakes.

Missouri’s 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 75% Approach looks at the range of values found in two reference reservoirs. Less rain

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 (?)

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 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.

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-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/Plateau (eutro) 37 1.6 43% 7.4% 29%

Problem with this approach1) Differences in water quality may be related to land-cover and not “regional hydrology and geology”

Level of Concern over the Current Matrix GROUP A1-7Large Ozark Reservoirs B Big River Lakes C1 Plains FR<.4 C2 Plains FR .4 - .6 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.

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

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 49% 26% Annual Values TP 33% 6% CHL 17% 11%

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% CHL 50% 25% Annual Values TP 53% 12% CHL 59% 6%

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% 15%

Concerns about the Current Approach to Nutrient Criteria