NPS Inputs and EOS TargetsDeveloping EOS targets

based on Nutrient Balance in the

Chesapeake Bay Watershed Model

Nutrient Balance EOS Targets

Where do the targets come from? How Are

Targets Distributed? (Why) Do they differ from Phase 4.3?

Fate and transport of N and P Model Scale Refined Land Uses Newer Research Information

How Does This Affect Delivered Loads?

Where Do Targets Come From

Calculated Mass Balance of known inputs and outputs on land uses

Estimates of attenuation/delivery factors: Literature Review Of In-Stream

Concentrations assigned “back-stream” to likely upland sources

Addresses uncertainty in input/output estimates

Calculating Balance: Inputs/Outputs

Pervious Surfaces: Inputs: Fertilizer, Manure, N-fixation,

Atmospheric Deposition Outputs: Crop Removal, de-nitrification,

volatilization Residual: Nitrogen (mobile) and

Phosphorus (mobile and immobile) The residual is that which may reach the

stream

The Mass-Balance Approach

Determine all input types (I): Atmospheric Deposition Fertilizer Application (where applicable) Manure Application (where applicable) Legume Fixation (where applicable)

Determine all outputs (O): Removal via harvest (potentially largest) Volatilization/De-nitrification (low to high) Sequestration in refractory organic matter (small) Sequestration/Attenuation in lower order streams

Eligible for Losses to the watershed outlet (E)

)()( ASVHLMFA OOOOIIIIE

0

0.02

0.04

0.06

0.08

0.1

0 10 20 30 40 50 60 70

Distributing EOS Targets Based on distribution around Median

Balance/Median In-stream Value From lit. review

Addresses uncertainty in the exact application rates, and attenuation of in-stream studies

EOS Target can NOT exceed Eligible Balance

0

0.01

0.02

0.03

0.04

-20 0 20 40 60 80 100

Median Balance (LWM) Median In-Stream (LWM)

Ex: 45.1 Balance => 39.6 EOS

Impervious EOS – Mass Balance

Urban Impervious surfaces a little more difficult to characterize

Inputs: Atmospheric Deposition (from Atmospheric model) Miscellaneous

Direct Automobile Deposition (difficult to estimate) Other Sources (animals, trash spillage, etc.)

Outputs: Little to no attenuation of N and P is expected to occur

on impervious surfaces Outputs are known from urban studies, generally based

on Event Mean Concentration (EMC) Mass Balance:

E = m + A ; A = atmospheric, m = miscellaneous

Estimating M from NURP/NSDQ

Quantify the misc. on impervious surfaces from EMC

Assumptions: Rainfall = runoff on impervious surface = 40” / ac-

year NURP/NSDQ Average EMC on highly impervious

(>80%) 2.2 mg/L This EMC represents mean value in watershed EMCs already include any attenuation Assume that “m” is constant, and the only variable

is atmospheric Acreage of impervious will be the greatest factor in

loading 12.74 lb-N/ac mean atmospheric deposition m = EMC*Runoff - A

Calculations: yrac

lbN

yrac

lbNconv

L

mg

yracM

05.574.12.

2.2"40

Change in TN Land Targets Between Phase 4.3 and Phase 5

Started with similar targets to Phase 4.3

Not enough Nitrogen to calibrate rivers Analysis of targets vs export

We expect Nitrogen targets to be scale dependent. Targets vs river loads Independent studies

TN Comparison Modeled vs. Estimator (using P4.3 targets in P5)

Compared ESTIMATOR loads to upstream EOF targets

0

0.2

0.4

0.6

0.8

1

1.2

Coastal Plain Piedmont VR and Pied Valley and Ridge AP and VR Appalachian Plateau

Delivery F

acto

r

Resolution

Double Nitrogen targets from all land uses in non-coastal plain segments (eyeball estimate).

Phosphorus does not have a similar reduction mechanism and the targets are not scale-dependent

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Coastal Plain Piedmont VR and Pied Valley and Ridge AP and VR Appalachian Plateau

De

liv

ery

F

ac

to

r

Change in scale

Nitrogen is Always Reduced in Rivers

Simulated river miles Phase 4 – 2,479 Phase 5 – 10,237

National SPARROW model (1997): First order rate coefficients are scale dependent Rivers < 1000 cfs = 0.38/day Rivers between 1000 and 10000 cfs = .12/day Rivers > 10000 cfs = 0.04/day

Considerable literature on denitrification Many Seitzinger articles Nitrogen budgets (e.g. Howarth)

Delivered: Phase 5 Versus Phase 4.3

Phase 5 Nitrogen targets are roughly 2X that of Phase 4.3.

Phosphorus remains nearly the same. Attenuation in lower (as compared to 4.3)

order streams is now simulated, thus the EOS must approach the EOF

Consequently, Phase 5 N attenuation is much greater then 4.3

Overall loads are similar, however, they will not be exactly the same since 1) the modeling period is different, 2) the model is more accurately calibrated

Phase 5 Versus 4.3 (delivered)

Old School New School

Similar Lesson: ~4.5 Million Lbs N

~17%

Attenuatio

n

~41% A

ttenuatio

n