Gulf of Mexico Hypoxia and Mississippi River Basin Nutrient Losses

Herb Buxton, USGS Rob Magnien, NOAA

Co-Chairs, Monitoring, Modeling, and Research Workgroup, Mississippi

River/Gulf of Mexico Watershed Nutrient Task Force

What Causes Gulf Hypoxia?“Hypoxia in the Northern Gulf of Mexico is caused primarily by excess N delivered by the MARB in combination with stratification of Gulf Waters.” – Integrated Assessment, 2000

Hypoxic Zone• Measured since 1985• Largest extent, 2002

Gulf Hypoxia

NOAA, Rabalais et al.

Area of Hypoxic Zone (km2 x1000)

20

18

16

14

12

10

8

6

4

2

22

85 87 89 91 93 95 97 99 01 03

Hypoxic Zone Extent, July 21-25, 200430

29

8994 93 92 91 90

Rabalais, LUMCON

o

o

o o o o o o

NITRATE LOAD, ANNUAL STREAMFLOW AND N

CONCENTRATION

1955-70 Avg. = 350,000 t/yr 1980-99 Avg. = 950,000 t/y

0.0

1.0

2.0

3.0

Conc. (mg/l)

0

20

40

60

80

1900 1920 1940 1960 1980 2000

Artificially DrainedLand, MRB

Mill

ions

of A

cres

Nitrogen Cycling

• N Inputs and Outputs (Million metric Tons).

• Landscape changes.

Urban Runoff??

INPUTS

OUTPUTS

MR/GM Watershed Nutrients Task Force

• Federal Agencies (USEPA*, NOAA, USDA, USACE, DOI)

• States (Agriculture and Environment Departments)

• Tribal representatives

Task Force Organization

Coordinating Committee (Implementation)– Finance/Budget Workgroup

– Monitoring, Modeling and Research Workgroup

– Management Response Workgroup• Point Sources• Non Point Sources• Restoration

CENR Science Assessment

IntegratedAssessment,

May 2000

A Science-based Action Plan

• Adaptive management.

• Consider all causal and mitigating factors.

• Voluntary Basis.

Task Force Action Plan,January 2001

Action Plan Goals

• Coastal Goal: By 2015, reduce the 5-yr average zone to < 5,000 Km2.

• Within Basin Goal: To restore and protect the waters of the 31 States and 77 Tribes in the Basin.

• Quality of Life Goal: Improve the communities and economic conditions across the Mississippi Basin.

5,000 km2

Area of Hypoxic Zone (km2 x1000)

20

18

16

14

12

10

8

6

4

2

22

85 87 89 91 93 95 97 99 01 03

Reducing Nutrient Loads

Decreasing

N losses

Reducing Point Sources and Urban Runoff

Filter Strips

Farm N Management

Riparian Forest Buffers

Reducing Nutrient Loads

Diversions to Coastal Wetlands

Davis Pond Diversion Structure

IncreasingDenitification

Lock & Dam Management Restoring Wetlands

Ohio32%

Missouri15%Upper

Mississippi10%

Middle Mississippi

28%

Arkansas/Red7%

Lower Mississippi

7%USGS Gaging Station

Nitrogen Loads,

1980-96

1500 Water-Quality Measurementson 9 large sub-basins.

1.6M metric tons per year

Yield on 42 small Sub-basins calculated from >4000 additional water-quality measurements.

Nitrogen Yield, 1980-96

N Input From Wet Deposition

N Input From Fertilizer

N Input From Point Sources

Component Nitrogen Inputs

Statistical extrapolation from representative basins (from 42 measured Sub-basins to 133 Sub-basins of entire Mississippi Basin).

InferenceNitrogen Yield, 1980-96

YIELD

Model Estimation of Total Nitrogen Delivered to the Gulf of Mexico (SPARROW)

A - Municipal and Industrial DischargesB - Atmospheric Deposition , and C - Fertilizer and Livestock Wastes.

A

CB

6% +/- 3

64% +/-2118% +/- 10

Inc

rea

sin

g y

ield

Fraction of In-Stream Nitrogen Delivered to Gulf

Alexander et al. Nature, 2000

MMR Strategy

A Science Strategy to Support Management Decisions Related to Hypoxia in the Northern Gulf of Mexico and Excess Nutrients in the Mississippi River Basin

Available on the Internet:toxics.usgs.gov/hypoxia/task_force_workgroup.html

Chapters/Topical Groups (leads)

Gulf

• Monitoring and Reporting (Rex Herron, NOAA)

• Modeling and Research (Kenric Osgood, NOAA)

• Social and Economic Issues (Rita Curtis, NOAA)

Watershed

• Monitoring and Reporting (Joe Engeln, MO DNR)

• Modeling and Research (Rich Alexander, USGS)

• Social and Economic Issues (Marc Ribaudo, USDA)

Coordination and Information Needs

Resource Needs

Management Questions

THE WATERSHED

What are the major sources and causes of excess nutrients within the Mississippi River Basin?

BASIN MONITORING FRAMEWORK

Nested scales to address and integrate processes from landscape to Basin-Gulf interrelationships.

MRB MOUTH Large Sub basins Small Sub basins Smaller watersheds

BASIN MONITORING: Level 1

MRB MOUTH • High Frequency data.

• Nutrients, carbon and other related data.

• Explain cause-effect linkages to Hypoxic zone.

BASIN MONITORING: Level 2

Large Sub basins

• Estimate annual loads.

• Monitor Sub-basin management strategies.

• Explain variations in loads at the mouth.

USGS Gaging Station

Small Sub basins• Annual loads.

• Explain load variations due to climate, sources.

• Representative sites useful for model extrapolations.

• Response of cumulative management actions.

• Explain time lags.

BASIN MONITORING: Level 3

Smaller watersheds• Quantify specific source contributions and

evaluate specific management actions.

• Useful for model extrapolations.

• Explain time lags in response to management actions.

• Explain processes affecting larger basins.

BASIN MONITORING: Level 4

Priorities for Basin Monitoring and Reporting

• Adopt a four-level watershed monitoring system…

• Supplement existing monitoring efforts …on smaller rivers and streams…

• Coordinate monitoring and reporting through leadership at the federal level…

• Link watershed monitoring to management actions…

Next Step: Action Plan: short-term action 11

By December 2005, and every 5 years thereafter, the Task Force will assess the nutrient load reductions achieved and the response of the hypoxic zone, water quality throughout the Basin, and economic and social effects. Based on this assessment, the TF will determine appropriate actions to continue to implement this strategy or, if necessary, revise the strategy.

Info On the Internet

USGS Hypoxia in the Gulf of Mexico: http://toxics.usgs.gov/hypoxia/

USEPA Hypoxia Task Force:http://www.epa.gov/msbasin/hyp2.htm

NOAA Science Assessment:http://www.nos.noaa.gov/products/pubs_hypox.html