# Development of Conceptual Models for Estimating Aquatic Exposure from the Use of Pesticides on Rice using the Pesticide Flooded Application Model

By: Melanie Biscoe, Marietta Echeverria, Meridith Fry, Jim

Hetrick, Greg Orrick, Chuck Peck, Mohammed Ruhmann, Andrew Shelby, Nelson Thurman, Katrina White, and Dirk Young

Presentation to EMPM, March 24, 2014

U.S. Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division

# Outline

• The physical model (PFAM)

• Site selection

• California Site

– Inputs for conceptual model

– Spray drift

– Spread of applications and flood releases



# • Arkansas/ Missouri site

• Monitoring analysis

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# Pesticide in Flooded Application Model (PFAM)

Potential Overflow

Water Input Pesticide Application Volatilization

degradation

degradation mass transfer Evaporation/ Precipitation

Adjustable Weir

Leaching Receiving Water Body or Mixing Cell

3 PFAM provides pesticide concentration in paddy water and receiving water body or mixing cell (daily average value)

# Site Selection

• Main rice growing area

• Surface water drinking water intake influenced by rice

• Monitoring data to validate conceptual model development approach

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# Where is rice grown?

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# 2007 AgCensus

– Rice Acres Harvested

State Acres Harvested % of Acres in U.S.

AR 1,326,377 48% CA 531,075 19% LA 377,115 14% MS 185,076 7% MO 179,300 7% TX 145,006 5% FL 11,376 0.4% TN 2,317 0.1%

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# Areas of Interest

• Arkansas and California are the major rice growing areas

• Both have at least one surface water intake that could be influenced by rice

• Monitoring data are available for the Sacramento River in California to validate the conceptual model

• Some monitoring data available in Arkansas

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### • Drinking water intake of interest: near Sacramento, CA on Sacramento River

• 511,824 acres of rice in watershed

• 14.4 million total acres in watershed

• Rice positioned in lower part of watershed

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# Conceptual Model for Drinking Water

Flow from surrounding watershed and river

Flow from rice paddy water released over paddy draining duration Rice Field

Drinking Water Intake Spray Drift of pesticide

Direct Application of Pesticide

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# Inputs to Define for Conceptual Model

• Receiving mixing cell

– Width, depth, length

– Base flow



## • Area of watershed

• Area of rice in watershed

– Amount of pesticide applied

– Volume of paddy water



## • Spray drift fraction

• Dates of applications

• Dates of flood release

• Depth of paddy

• Agronomic practices

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# Inputs to Define for Conceptual Model

• Receiving mixing cell

– Width, depth, length

– Base flow



## • Area of watershed

• Area of rice in watershed

– Amount of pesticide applied

– Volume of paddy water



## • Spray drift

• Dates of applications

• Dates of flood release

• Depth of paddy

• Agronomic practices

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# Summary of flow at USGS Site 11425500 Sacramento River at Verona, CA

Parameter Discharge (cubic feet per second)

2011 2012 1946

- 2012

Annual Mean 24,490 14,970 19,750 Highest Daily Mean 67,700 (Mar 26) 46,100 (Mar 18) 95,600 (Jan 3, 1997) Lowest Daily Mean 9,870 (Nov 11) 7,610 (May 18) 3,590 (June 24, 1992)
Annual 7

- day minimum 10,000 (Nov 5) 8,020 (May 15) 3,960 (June 22, 1992)

Maximum peak flow

-- 46,900 (Mar 18) 102,000 (Jan 2, 1997)



### Data were calculated by the USGS and reported in Water

- Data Report 2012 for the site. Flow from paddies is potentially double

- counted.

Lowest flows occur during rice growing season. This impact is minimized by using a low flow estimate.

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# PFAM Conceptual Model: CA

• Mixing Cell:

– Width, depth, length (194m × 5.1m × 30m)

– Base flow

– Based on USGS data

– Residence time of water in mixing cell (seconds to minutes)



# • Area of Watershed: 14.4 million acres

• Area of Rice: 511,000 acres

• Sacramento, CA weather file and latitude

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# Usage and Monitoring: Molinate in the Sacramento River

14 0 1 2 3 41-Apr8-Apr15-Apr22-Apr29-Apr6-May13-May20-May27-May3-Jun10-Jun17-Jun24-Jun1-Jul8-Jul15-Jul22-Jul29-Jul

Sampling Date Molinate Concentration in ppb (Site 34_12)

# Water Management Practices for Rice in CA

• Emergency releases are rare

– 1 in 2009; 33 in 2002, a flood year 1



# • Seepage from the berm is also rare

– 97% of inspected paddies had no seepage in 2009 1



## – 3% of inspected paddies had seepage of <5 gallons/day 1



# • Flood depth 4 inches (range is typically 3

- 5 inches)

• Post

- application hold times specified on pesticide label

1 California Regional Water Quality Control Board Central Valley Region. Resolution No. R5

- 2010

- 9001. Rice Pesticides Program

– Control of Rice Pesticides. 15

# Inputs to Define for Conceptual Model

• Receiving mixing cell

– Width, depth, length

– Base flow



## • Area of watershed

• Area of rice in watershed

– Amount of pesticide applied

– Volume of paddy water



## • Spray drift fraction

• Dates of applications

• Dates of flood release

• Depth of paddy

• Agronomic practices

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# Spray Drift to Canals

• 23 rice paddies selected from the Colusa Basin to represent the typical canal and paddy orientation

• AgDRIFT was used to determine the spray drift fraction for a 10, 50, 100, 200, and 300 meter zone from edge

- of

- paddy

• NHD+ was intersected with each drift zone to determine the area of water in each zone, assuming a 3m canal width

• Area of water in buffer zone x spray drift faction = area of water receiving full application rate for that buffer zone

• Sum the areas and scale to total paddies

• Area of water receiving full app rate ÷ area of rice = spray drift fraction

1718 Rice Paddy receiving full application

Drift Zone (10 m) 

### Area of water X 0.29 = y Area of water x 0.15 = z

Drift Zone 50 m



## Area water with 100% application rate= z+y Canals flowing through drift zones

# Spray Drift Fraction for Canals

Canal contribution Aerial Ground

– High Boom Very Fine

to Fine Fine to Medium Fine/Very Fine

Summed area of water in each

zone adjusted by each buffer spray drift value (m 2 ) 87950.79 47152.41 88922.94

Spray drift value (fraction) 0.0308 0.0201 0.0312

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# Spray Drift Fraction for Rivers

River and Stream contribution Aerial Ground

– high boom Very Fine

to Fine Fine to Medium Fine/Very Fine

Weighted spray drift on typical river (fraction) 0.11 0.046 0.050

Spray drift value (fraction) 0.0036 0.0015 0.0016 Canal contribution Aerial Ground

– High Boom Very Fine

to Fine Fine to Medium Fine/Very Fine

Summed area of water in each

zone adjusted by each buffer spray drift value (m 2 ) 87950.79 47152.41 88922.94

Spray drift value (fraction) 0.0308 0.0201 0.0312



## Total Fraction of amount applied that is applied directly to the receiving water body flow: 0.015 to 0.034. With 500,000 acres receiving applications, even this small fraction can have a big impact on EDWC. 20

# Spread of Applications and Flood Releases

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# Arkansas/ Missouri Conceptual Model

Only one surface water drinking water intake of interest

USGS station near DWI: Black River, Pocahontas, Arkansas

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# PFAM Conceptual Model: AR/MO

• Mixing Cell:

– Width, depth, length (98m × 2.3m × 30m)

– Base flow

– Based on USGS data



# • Area of Watershed: ~3 million acres

• Area of Rice: 102,345 acres

• Little Rock, Arkansas weather file and 36 o 

# N

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# Monitoring Data for CA

• Monitoring data available on Sacramento River and Calusa Basin Drain

– CADPR

– NAWQA



# • Will analyze both acute and annual average results

• Will examine results with and without the use of a bias factor

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# Monitoring Data for Arkansas/Missouri

• Little data available on Black River

• Data are available on nearby streams and rivers

• Data are also available for Mississippi River near Baton Rouge that have shown to be influenced by rice

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# PFAM Conceptual Model Team

• Management Lead: Jim Cowles

• Model Developer: Dirk Young

• Senior Science Advisor: Nelson Thurman

• Team Lead: Katrina White

• Other Team Members: Melanie Biscoe Meridith Fry Jim Hetrick Greg Orrick Chuck Peck Mohammed Ruhmann Andrew Shelby

• Acknowledgement: Jim Breithaupt, Jim Carleton

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# Questions27 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000Monthly Mean Data 1946-2012Cubic feet per second Mean

Max

Min 

# Flow in Sacramento River

# Black River at Pocahontas, Arkansas

Parameter Discharge (cubic feet per second)

2011 2012 1936

- 2012

Annual Mean 8,734 4,520 5,638 Highest Daily
Mean 83,700 (Apr 28) 15,800 (Dec 7) 83,700 (Apr 28, 2011)
Lowest Daily
Mean 1,820 (Jan 31) 1,200 (Jul 6) 1,080 (Oct 16, 1956)

Annual 7

- day minimum 1,840 (Jan 25) 1,250 (Jul 2) 1,090 (Oct 15, 1956)
Maximum peak flow -- 16,000 (Dec 7) 86,600 (Apr 28, 2011)

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* Data were calculated by the USGS and reported in Water

- Data Report 2012 ( USGS, 2012a , 2012b )

.

# Flow in Black River

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## USGS gage station near West Sacramento DWI

30 USGS Gage on Sacramento River at

Verona