The Confounding Effect of River Discharge on Estuarine Response to Nutrient Loading
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The Confounding Effect of River Discharge on Estuarine Response to Nutrient Loading. Craig A. Stow NOAA Great Lakes Environmental Research Laboratory Ann Arbor, MI.

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The Confounding Effect of River Discharge on Estuarine Response to Nutrient Loading

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The confounding effect of river discharge on estuarine response to nutrient loading

The Confounding Effect of River Discharge on Estuarine Response to Nutrient Loading

Craig A. Stow

NOAA Great Lakes Environmental Research Laboratory

Ann Arbor, MI

Borsuk, M. E., C. A. Stow, and K. H. Reckhow. 2004. Confounding effect of flow on estuarine response to nitrogen loading. Journal of Environmental Engineering, 130: 605-614.

Additional Insights and Inputs provided by Conrad Lamon and Song Qian


The neuse river basin

The Neuse River Basin

Courtesy USGS


The confounding effect of river discharge on estuarine response to nutrient loading

Vollenweider Cross-Sectional Lake Nutrient Loading Model

  • Single Lake Relationship:

  • Positive

  • Negative

  • Nonlinear

Brazenly stolen from:

Vollenweider, R.A. 1976. Advances in defining critical loading levels for phosphorus in lake eutrophication. Mem. Ist. Ital. Idrobiol., 33:53-83.


The confounding effect of river discharge on estuarine response to nutrient loading

Residence Time

Turbidity

Salinity

Temperature

River Flow

Nutrient

Concentration

Eutrophication

Nutrient Loading

Estimated

Nutrient Loading

Estimated

Concentration=

f(Flow)


The confounding effect of river discharge on estuarine response to nutrient loading

River discharge highly variable – even on relatively long time-scales

Drives Nutrient Load Variability at this scale


The confounding effect of river discharge on estuarine response to nutrient loading

Concentration:Flow relationships idiosyncratic: positive, negative, or non-monotonic

In the Neuse the relationship was negative

Log concentration

Log flow

  • High load = low concentrations

Data Provided by:

NC DENR DWQ – nutrient concentrations

USGS – daily flow


The confounding effect of river discharge on estuarine response to nutrient loading

0

10

20

Upper

30

New

Bern

40

50

Middle

180

60

170

l

70

Bend

80

160

l

90

150

100

140

l

110

Water Quality Station

Hydrographic Station

l

130

120

l

l

l

l

N

10 miles

10 kilometers

Model Sections

River

Upper

Middle

Lower

Bend


The confounding effect of river discharge on estuarine response to nutrient loading

Chlorophyll a Model

(Bayesian multilevel piecewise lognormal model)


The confounding effect of river discharge on estuarine response to nutrient loading

Estuarine N Concentrations vs. Annual N Load

Ft. Barnwell

Swift Creek

New Bern

Broad Creek

Oriental

Pamlico


The confounding effect of river discharge on estuarine response to nutrient loading

Estuarine P Concentrations vs. Annual P Load

Ft. Barnwell

Swift Creek

New Bern

Broad Creek

Oriental

Pamlico


The confounding effect of river discharge on estuarine response to nutrient loading

Summary

Nonlinear chlorophyll, flow (~ load) relationship on short time-scales

Relationship differs systematically along spatial gradient

Maximum differs systematically along spatial gradient

No relationship between nutrient load, concentration on medium time-scales

This may differ among systems


The confounding effect of river discharge on estuarine response to nutrient loading

TMDLs

Nutrient Loading

Nutrient Loading

Eutrophication

Eutrophication

Hypoxia

Hypoxia


The confounding effect of river discharge on estuarine response to nutrient loading

  • Nutrient load targets appropriate on longer (multi-year) time scales

  • Short-term (yearly or less) misleading

  • Assuming stationary flow (long-term)


The confounding effect of river discharge on estuarine response to nutrient loading

Mississippi River Flow – Seasonal Trend Decomposition Using Loess


The confounding effect of river discharge on estuarine response to nutrient loading

April 2006 - U.S. Court of Appeals District of Columbia Circuit ruled that EPA-approved plan to limit pollution into Anacostia River contrary to Clean Water Act requirements to set "total maximum daily loads" of pollutants.

January 2007 -- United States Supreme Court let stand lower court ruling requiring limits on pollution allowed in Anacostia River each day. 


The confounding effect of river discharge on estuarine response to nutrient loading

River Flow

Nutrient

Concentration

Eutrophication

Nutrient Loading

?

Hypoxia

Upper Trophic Level

Effects


The confounding effect of river discharge on estuarine response to nutrient loading

The End


The confounding effect of river discharge on estuarine response to nutrient loading

River Flow

Hypoxia

Nutrient Loading

Estimated

Nutrient Loading


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