PRZM to Predict Hydrology, Atrazine Concentrations, & BMP Effectiveness

Lula Ghebremichael, Clint Truman, Sunmao Chen, Mark White

Syngenta Crop Protection, LLC

SWCS 2015 Conference July 26- 29, 2015, Greensboro, NC

2

Outline

● Goal

● Model description

● MO-07 watershed

● Model performance

● BMP effectiveness

Classification: Public

3

Goal

Evaluate BMPs using a modeling approach to select effective BMPs

and enhance stewardship programs

Classification: Public

4

Model Description

● PRZM (Pesticide Root Zone Model)

● Developed by U.S.EPA (Carsel et. al.1985)

● Official core model for pesticide registration at U.S. EPA

Classification: Public

Hydrological & Erosion Processes

Surface runoff SCS curve number

Water balance (Inflow = Outflow + ΔStorage)

Erosion MUSLE

Pesticide Processes

Application method Various methods

Partitioning (Sorption/desorption) Equilibrium; Linear

Degradation First-order

Plant Uptake, Runoff, Erosion, Volatilization, Foliar Wash-off

Mo

del F

ea

ture

s

5

PRZM Application for Regulatory Environmental Exposure Assessment

● Runoff Events and Pesticide loading Pesticide Concentration in

Standard pond

● Pesticide mass predicted for Runoff Events only

Classification: Public

PRZM EXAMS

1 hectare

(2 m pond)

10 hectare

field area

6

PRZM Application On MO-07 Watershed

Classification: Public

PRZM Model

Atrazine mass from runoff events (multiple fields in a watershed)

Stream flow “measured”

Atrazine Concentration

7

PRZM Model Inputs

Classification: Public

Land use

Soil Inputs

Precipitation (cm/day)

Pan evaporation data (cm/day)

Temperature (Celsius)

Wind speed (cm/sec)

Solar radiation (Langley)

Weather

Chemical

Legend

OM_MO07N_proj

SdvOutpu_1

1.25 - 1.5

1.50 - 2.0

2.00 - 2.4

2.4 - 2.6

2.60 - 3.0

Legend

BD_MO07N_proj

SdvOutpu_1

1.29 - 1.31

1.31 - 1.4

1.4 - 1.480

Legend

ST_MO07N_proj

(Surface Layer), {DCD, <}

Clay loam

Fine sandy loam

Loam

Loamy sand

Sandy loam

Silt loam

Silty clay loam

Not rated or not available

BD OM Texture

8

Model Evaluations

Classification: Public

Hydrology

Atrazine concentrations

Lack of field-level data for model evaluation

Runoff events aggregated from watershed

compared to “measured runoff” (baseflow

separation)

9

Predicted Atrazine Concentration: 2010-2014

Limitations

● Incomplete to reflect stream

flow concentrations

● Used single atrazine

application date for all fields

in the watersheds

● Need to use crop planting

progress data to schedule

application dates across corn

fields

● Runoff timing and travel time

Classification: Public

10

Best Management Practices Modeled

● Soil Incorporation (e.g. Phillips Harrow spray followed by

incorporation in one pass, ~ 5 cm incorporation depth and complete

mixing)

● Split application (pre-, post-emergence)

Classification: Public

11

Model Predicted BMPs Effectiveness

Classification: Public

Concentration vs. Mass

2010

2011

2012

2013

2014

Concentration vs. Mass

12

Summary

● PRZM performances in predicting hydrology and atrazine concentration

- incomplete picture of flow and atrazine conc. in streams

- may be beneficial to add baseflow, runoff timing & travel time

components

- need refinement to model inputs (e.g. application date; rainfall)

● PRZM application for assessing BMPs effectiveness

- relative BMPs effectiveness at field-level in surface runoff

- limited number of BMP can be assessed

● BMP effectiveness

- incorporation (~43%); split application (~ variable)

- concentration vs. mass

Classification: Public