U.S. Department of the InteriorU.S. Geological Survey

Regional scale point source nutrient load estimation in support of SPARROW* modeling

Gerard McMahon, USGS

Larinda Tervelt and Mike Donehoo, US EPA

2006 National Water Quality Monitoring Conference

May 11, 2006

*SPAtially Referenced Regression On Watershed Attributes

Summary of talk objectives

How can PCS data be used to estimate annual, discharger-specific, point source nutrient loads across the southeastern United States?

Summarize results of load estimation.

Identify several take home messages about undertaking a similar project in the future.

National Water Quality Assessment Program

What kinds of point source data are needed for the SPARROW model?

Sources

Overlandtransport

SPARROW model approach:Regress monitored load against variables characterizing sources, overland transport and instream transport

Monitored load

How can PCS data be used to estimate annual, discharger-specific nutrient loads across the southeastern United States?

Data availability Methodology overview Data preparation Load calculation

Where do we get data?

How are point source discharge data generated?

Decisions that focused the data development effort.

How many dischargers?

Methodology overview

Overall concept similar to EPA Miss. R. point source nutrient load project (1998)

4-step load estimation process for southeastern U.S.

Prepare data for load calculations

Prepare single flow value.

Prepare single TN and TP concentration value

• Discharger specific

• Typical pollutant concentration – SE region

• Typical pollutant concentration – National

What is allocation of PCS/state flow data between major and minor dischargers?

NPDES monthly flow observations, 2000-2002, by treatment plant size

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

state AL FL GA MS NC SC TN

Per

cen

t o

f fl

ow

ob

erva

tio

ns,

200

0-20

02

> 5 MGD

1-5 MGD

0-1 MGD

What are sources of NPDES TN and TP concentration data?

Sources of TN concentration data

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

AL FL GA MS NC SC TNPer

cen

t o

f al

l o

bse

rvat

ion

s w

ith

flo

w d

ata,

200

0-20

02

TPC-2

TPC-1

Plant specific data

Calculate loads

• Load calculation approach

• Three load calculation scenarios

1. 12-months of flow data

2. Flow data during 3 or 4 quarters, but less than 12 months.

3. Flow data during less than 3 quarters

Dischargers with nutrient load, 2000

Number of dischargers, 2000

Minor Major TotalAL 53 94 147FL 137 106 243GA 152 98 250MS 467 64 531NC 670 123 793SC 224 84 308TN 185 86 271Total 1,888 655 2,543

What is allocation of TN and TP load between major and minor dischargers?

Percent of point source TN discharged, 2000, by treatment plant size

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

AL FL GA MS NC SC TN

> 5 MGD

1-5 MGD

0-1 MGD

What is allocation of TN and TP load by size of receiving streams?

TN 2000 load allocation by receiving waterbody drainage area

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

AL FL GA MS NC SC TN

Sta

te p

oin

t so

urc

e lo

ad (

%)

coastal

>10,0000 km2

1,000-10,000 km2

0-1,000 km2

What are the primary sources of TN and TP load, in terms of SIC code?

SIC SIC description TN4952 Sewerage Systems 77%2611 Pulp Mills 6%2621 Paper Mills 5%2631 Paperboard Mills 4%2011 Meat Packing Plants 2%2015 Poultry Slaughtering and Processing 1%9711 National Security 1%2869 Industrial Organic Chemicals, 1%2874 Phosphatic Fertilizers 1%2899 Chemicals and Chemical Preparations 0%

What is the allocation of TN and TP load from sewerage treatment plants by size of discharges?

Point source TN load discharged, 2000, by treatment plant size

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

AL FL GA MS NC SC TN

Per

cen

t T

N p

oin

t so

urc

e lo

ad d

isch

arg

ed

> 5 MGD

1-5 MGD

0-1 MGD

Conclusions Success in a census approach to calculating

annual nutrient loads from point source dischargers across a large region is dependant on several factors.

The load results to date highlight several lessons important to modelers.

Need exists for long-term cooperative approach involving state and federal agencies to generate annual nutrient loads for the entire country using uniform procedures and assumptions.