# Advances in modeling urban/residential pesticide runoff W. Martin Williams Amy M. Ritter Megan L. White J. Mark Cheplick Waterborne Environmental, Inc. Leesburg, Virginia USA2 

# Status of Regulatory Modeling

• The UK Pesticides Safety Directorate: Excel spreadsheet model (HardSPEC ca 2003) -- first tier to predict concentrations of herbicides on hard surfaces (e.g. concrete, asphalt, railway ballast) in surface water and 

### groundwater • The U.S. Environmental Protection Agency (USEPA) 

### began conducting risk assessments for residential pesticide use ca 2004 with PRZM - EXAMS3 

## UK Pesticides Safety Directorate



## HardSPEC • Empirical model based on washoff studies of six herbicides (atrazine, diuron, oxadiazon, glyphosate, oryzalin, isoxaben) on asphalt, concrete, and railway ballast • Four regulatory scenarios: 1. Surface water stream receiving surface drainage from a major road in a rural setting 2. Surface water stream receiving surface drainage from an urban catchment 3. A pond receiving surface drainage waters from an urban catchment 4. Ground water aquifer receiving herbicide leached from a double railway track HOLLIS, J.M., RAMWELL, C.T. and HOLMAN, I.P. (2003). HardSPEC: A First -tier Model for Estimating Surface - and Ground -Water Exposure resulting from Herbicides applied to Hard Surfaces. NSRI research report No. SR3766E for DEFRA PL0531, 79 pp + 3 Appendices. http://www.pesticides.gov.uk/approvals.asp?id=7134 

## U.S. Environmental Protection Agency’s



## Residential Scenario • 10- ha watershed draining into 1 - ha by 2 - m pond 

### • Watershed simulated with PRZM model

– 30-year simulation 

### • Pond simulated with EXAMS

– Pesticide mass added to pond

– Runoff water not added to pond 

### • Two PRZM simulations (pervious and impervious)

– 70% pervious (turf) -- 50% treated

– 30% impervious (roofs, driveways, sidewalks, roads)

– 1% of application rate on impervious area (over spray) USEPA ,2007. Pesticides: Science and Policy. Red Legged Frog MetaData.. Last updated 20 - Sep-2007. http://www.epa.gov/oppefed1/models/water/pe5_rlf.htm5 

# CLA Model Evaluation 2006 • Stormwater Management Model (SWMM)

– USEPA urban runoff model

– Highly sophisticated in its ability to simulate hydraulic processes and urban features

– Limited in water quality components, especially in its ability to represent pesticide applications and sorption kinetics 

## • Pesticide Root Zone Model (PRZM)

– USEPA agricultural runoff/leaching model

– Relatively sophisticated in its ability to represent pesticide applications and sorption kinetics

– Limited in its ability to simulate urban drainage features; unknown ability to simulate pesticide sorption kinetics Cheplick, J.M., S. Dasgupta, A.M. Ritter, and W.M. Williams, 2006. Model Review and Scenario Development for Urban/Residential Pesticide Runoff Model. Prepared by Waterborne Environmental, Inc. for Crop Life America. http://www.epa.gov/oppefed1/models/water/empm_top.htm 

## • Stormwater Management Model (SWMM)

– USEPA urban runoff model

– Highly sophisticated in its ability to simulate hydraulic processes and urban features

– Limited in water quality components, especially in its ability to represent pesticide applications and sorption kinetics 

## • Pesticide Root Zone Model (PRZM)

– USEPA agricultural runoff/leaching model

– Relatively sophisticated in its ability to represent pesticide applications and sorption kinetics

– Limited in its ability to simulate urban drainage features; unknown ability to simulate pesticide sorption kinetics6



# Objective • Present recent advances in modeling pesticide 

## runoff urban/residential landscapes

– Pesticide applications and pesticide washoff from hard surfaces with SWMM



### – Runoff and pesticide washoff from hard surfaces with PRZM7



# Pesticide Application

Time in days SWMM

PRZM Time in days 0 0 - 1,000 Target Rate 0

## Simulation of Storm Water Runoff with SWMM and PRZM

Source: Google Maps9 

# Portland Oregon Dataset
• 115 single -family residential lots totaling 6.8 hectares with 35% impervious area. • Monitored extensively for runoff from November 1998 through May 1999 at 5 - minute intervals. 

### • SWMM was used to simulate and connect all source water, including runoff from individual roof, driveway, and lawn surfaces to lateral and main storm sewers.
Huber, W.C., Cannon, L., and M. Stouder, 2006. BMP Modeling Concepts and Simulation. EPA/600/R -06/033, Office of Research and Development, USEPA, July 2006. www.epa.gov/ORD/NRMRL/pubs/600r06033/epa600r06033chp14.pdf10 

# Portland Oregon Dataset

Source: Google Maps11 

## Detailed Model 

## Simple Model 

# SWMM Set Up12 

## Observed vs. Modeled Discharge (SWMM)13



# PRZM Set Up

• Impervious (roof, sidewalk, road) • Pervious (lawn, ornamentals) 4.4 ha 2.4 ha Ia = 0.005 cm CN = 98 BD = 2.2 FC = 0.08 Ia = 0.2 cm CN = 83 BD = 1.5 FC = 0.4714 

## Observed vs. Predicted Discharge 

## (SWMM and PRZM)

## Simulation of Herbicide Runoff with SWMM and PRZM16



# UK Roadway Study

HEATHER, A.I.J., SHEPHERD, A. & HOLLIS, J.M. (1998). Losses of six herbicides from a kerb-and-gully pot road drain. Soil Survey and Land Research Centre report JF4085- 1, for the Hard Surfaces Project Consortium. 28 pp. . http://www.pesticides.gov.uk 

### • Natural rainfall study • Six herbicides applied to curb edge of asphalt road

– Atrazine , glyphosate , diuron (Oct 14 - Nov 11)

– Atrazine, oxadiazon, oryzalin (Dec 9 - Dec 25) 

### • Spray was applied in a continuous swath approximately 0.3 m wide along the full length of the section 

### • Measurements included rainfall, temperature, runoff volume, and herbicide concentration over time.17 

# SWMM Water Results18 

# SWMM Washoff Coefficients
• Exponential equation:

• C 1 

### – chemical specific? • C 2 

### – land cover specific (grass, asphalt, concrete, etc.)? W = C 1 

### x q C2 

### x B C 1 

### = washoff coefficient 

### C 2 

### = washoff exponent q = runoff rate per unit area B = pollutant buildup19 

# SWMM Pesticide Results

W = C 1 

### x q C2 

### x B Herbicide 1: C 1 = 0.20, C 2 = 0.95 Herbicide 2: C 1 = 0.10, C 2 = 0.9520



# PRZM Water Results

Ia = 0.005 cm CN = 98 BD = 2.2 FC = 0.0821 

# PRZM Pesticide Application
Application = CAM 4 with 0.1 cm Application = CAM 122 

## PRZM Pesticide Runoff Algorithm 

## Modified for Impervious Surface

WIN - PRZM23 

# PRZM Pesticide Results

Application = CAM 4 with 0.1 cm Pesticide runoff extraction = 0.9 Kd1 = 0.0 Kd2 = 0.124



# Washoff Coefficients What Kd to use with PRZM? What coefficients to use in SWMM?25 

# Washoff Database Growing Agency Study Chemicals CDPR Formulation effects and off-target

transport of pyrethroid insecticides from urban hard surfaces. UC - Davis – 2009 cyfluthrin, λ cyhalothrin, esfenvalerate, bifenthrin CDPR Pesticide hard surface wash -off study.

UC - Riverside – 2009 bifenthrin, permethrin, cyfluthrin, λcyhalothrin, fipronil, CDPR Washoff of formulated pyrethroid

insecticides from concrete, turf, bare soil. UC - Davis – 2009 B -cyfluthrin, esfenvalerate PWG Washoff/runoff of cypermethrin residues

from slabs of external building material surfaces using simulated runoff – 2008 cypermethrin CDPR Runoff of diazinon from paved plots -

2001 Diazinon Soil Survey and Land Research Centre Herbicide partitioning to concrete,

asphalt and railway ballast – 2002 fuoranthene, phenanthrene, atrazine, diuron, oryzalin, isoxaben, isoproturon, dichlorophen Small Catchment report – 1999 atrazine, diuron, oxadiazon, glyphosate, oryzalin, isoxaben Road Wash -off Study – 1999 atrazine, diuron, oxadiazon, glyphosate, oryzalin, isoxaben26 

# Summary / Conclusions
• SWMM (beta) now has the ability to simulate discrete 

### applications of chemicals • PRZM (WinPRZM wdv

### ) now has the ability to simulate hard surface runoff of chemicals 

### • SWMM and PRZM reasonably simulated hydrologic response of UK roadway and Oregon residential area • SWMM and PRZM reasonably simulated atrazine and 

### glyphsate runoff from UK roadway • Data is becoming available to develop washoff coefficients for hard surfaces (pesticide properties/formulations vs. surface conditions)27



# Acknowledgements • Paul Hendley (on behalf of Pyrethroid Working Group) 

### • Wayne Huber (Oregon State University) • Scott Jackson (on behalf of Crop Life America) • Lewis Rossman (USEPA-ORD)28 

# Questions?

Photo credit: D. Rosen