Hybrid PRZM

“Filling in the gaps” in field sampling data usrealistic simulation modelingPaul Miller Chris Harbourt William Paul Miller, Chris Harbourt, William Northcott Northcott

Paul Hendley and Jessie J. Prenger

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EMPM Meeting, March 20th

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Why is this needed?

 Concern exists that monitoring programs may be miss

 Tension opposite cost of ultra-frequent monitoring

 Bias factors are promising for extrapolating moderate 

monitoring data to conservatively estimate higher fre

 e.g. estimating 4 day rolling averages from 7-day monitoring da BUT challenge is how to use bias factors

 Multiply entire period, assume “missed peaks” every week......

 Instead, what about using more realistic ways of pred

possible peaks between gaps in measured concentra

 E.g. Including local information on weather, watershe

and agronomy to identify when peaks might have occur

 Developg p p 

ing more accurate representation of peak occu

duration and magnitude and thus 

 Realistically reduce uncertainty of evaluations

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EMPM Meeting, March 20th
Key Enabler: Crop District Modeling/Data Sys

Addit

Plan

Crop 

So

Croplan

Weather Variables

NEXRAD Rain

Temperature

Solar

Database 

Data on Demand

Historical/Current

(Rain Temp GDD 

Modelin

Near Re

C 

Database 

System

(Rain, Temp, GDD,

Moisture)

Summarized by 

District

Crop 

Soil M

Crop Co

Output

Tabular

Graphical

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Key Enabler: LOCAL NEXRAD rainfall data for any 

of i t t f i

n

teres

t

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EMPM Meeting, March 20th
PRZM Hybrid uses tools we understan

 Pesticide Root Zone Model (PRZM) version 3.12.2 

simulate edge-of-field runoff from representative a

soils in each subwatershed soils in each subwatershed.

 Site specific input parameters include Corn and Sorghu

SSURGO soils 

 locally measured weather data, application timing 

l d k bili l i h land wor

k

ability

algorit

hm,

 and a watershed percent treated area (PTA) based 

land-use data and grower survey data (local but n

 PRZM Modeling integrates variables of interest

 PRZM output Site-year specific

 Cropping NEXRAD local rainfall

 Allows comparison to and integration with monitoring

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EMPM Meeting, March 20th
PRZM-Hybrid is Site & Local Event Specific*

 Uses PRZM code

 Atrazine Efate data

 Regional data

 Crop reporting district 

based atrazine application rate

 Watershed & year specific 

loca data l

 SSURGO soils NEXRAD rainfall % Crop (NASS CDL 

( )) NLCD

 Output 

 Uses directly available 

data - No model specific calibration

 Conservative edge-offield concentrations

 Uncertainties defined

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EMPM Meeting, March 20th

*Atrazine: Development of the PRZM-Hybrid Watershed Exposure Modeling System Methodology Report – Miller et al. April 2011
Key Enabler: Algorithm to Simulate Farmer Beha

Agronomic Timing Based on LOCAL Conditions  New application algorithm accounts for land “work

distribution across time and addresses

 LOCAL response f il t i f ll f h th l 

of soil

s t

o rain

f

all for

w

h

ether lan

worked

 Wariness of some farmers not to plant too early Need for seed bed to be prepared in first workable d

fields

 Equipment capacity constraint on applying very large 

the watershed in a day

 Possibilities for post emergent treatments

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EMPM Meeting, March 20th
Key Enabler: Algorithm to Simulate Farmer Beha

Agronomic Timing Based on LOCAL Conditions 

 Workability Approach

 Determine first planting date from 14 day moving average of 

temperature, when >55 degrees (F) and soil moisture is 

≤ 0

is April 1st or later then planting is “Possible” 

 Window for potential applications starts 7 days prior to 630 

 Soil moisture accounting uses water balance (not based on 

estimates) starting March 1st

 Land Workability defined as a ratio of 0.9 or less (soil moistu

moisture at field capacity)

 Applies equal amounts on all workable days in the applicatio

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EMPM Meeting, March 20th
Not accounting for local variation gives “OK” pred

In earlier method, application won growing degree days. This predictions through the season

Green bars reflect a fraction of the total seasonal chemical load being applied in an even pattern across a GDD defined window defined window

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EMPM Meeting, March 20th
Using LOCAL conditions to help predict farmer be

agronomy improves things!

With chemical applications not bewould not allow field operation, efrealistic estimates of mass availa“next “ rainfall happens

Green bars reflect a fraction of the total seasonal chemical load being applied on each day application is judged feasible judged feasible

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EMPM Meeting, March 20th
PRZM Hybrid Land Workability Approach:

Additional Examples

Not as accurate

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EMPM Meeting, March 20th
PRZM Hybrid Land Workability Approach:

Additi l E l Additional Examples

Fairly Accurate

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EMPM Meeting, March 20th
How well do we predict applicatio

across planting season??

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EMPM Meeting, March 20th
PRZM-Hybrid vs. old “best available” approach (1

But still not perfect !!

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EMPM Meeting, March 20th
PRZM-Hybrid vs Old “Best Available” Approac

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EMPM Meeting, March 20th
Using PRZM-Hybrid to enhance 

existing monitoring data

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EMPM Meeting, March 20th
Sequential PRZM HYBRID Logic

Grab and Autosample

Measured Conc. 

Data record

Grab and Autosample

Measured Conc. 

Data record

Watershed 

Variables

Rainfall

GDD Application

Watershed 

Variables

Rainfall

GDD Application 

Day with 

Field sample?

GDD Application

Window

Application Data

Soils

Window

Application Data

Soils Apply rule.

Add Grab/Auto 

Data To Daily 

Series

Yes

PRZM Modeled 

EOF

PRZM

EOF

Series

Add PRZM 

EOF Conc to 

No

Yes

EOF EOF Event ?

Conc.

EOF

Conc.

EOF Conc.to

Daily Series

Interpolate Add

No

Add

Interpolated 

value to 

Daily Series

Interpolate

Linearly to 

next measured 

value

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EMPM Meeting, March 20th
PRZM-Hybrid Uses Local Soils/Rainfall to Drive Realistic Simula

Potential Events between Monitored Data. 

A

C

nfall

2

B

verted Rain

1

4

3

5

ow and Inv

D

Fl

Time (t) l

PRZM‐Hyb Interpolated Line PRZM‐Hyb Conc.

Monitored Sample Conc. Flow

Sample Interpolated Line

Rainfall Event
Conclusions

 PRZM-Hybrid shows considerable promise for supp

day data

 Predicts peak occurrence/relative magnitude but ov

>20 ppb

 Reflects reality - peaks only predicted when runoff eve

occur

 New land workability approach provides improved e

expected atrazine application timing

 PRZM-Hy pp g brid ties application together with local rain

estimate runoff using well established regulatory mo

 Incorporates effect of degradation and “soaking” rains

 Model output compared to measured values indica

approach improves on previous best available appr

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EMPM Meeting, March 20th
PRZM-Hybrid - Next Steps

 Evaluate enhancing Land Workability approach for a

dates with NASS planting progress data

 Evaluate optimal approaches for larger CWS-relevan

of area >800 sq. mi.

 Divide into smaller units and do simple routing Apply a simple dilution model Due to “area averaging”, transition from mechanistic t

models

 Apply PRZM Hybrid thinking to other types of Agroch

patterns

 Preventative and curative fungicide applications  Insecticide treatments

 Evaluate approaches for linking PRZM-Hybrid to Pro

weather data for evaluating year-to-year variation 

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EMPM Meeting, March 20th
Thank you

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EMPM Meeting, March 20th

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