Spatial Aquatic Model (SAM):

Update on the Regional Pilot 

Project

Presentation to the Environmental Modeling Public 

Meeting (EMPM)

3/19/13

Nelson Thurman, US EPA, OPP, EFED
Spatial Aquatic Model Pilot Project Team

• Nelson Thurman – project manager

• Dirk Young – aquatic model development lead

• Shelly Thawley – GIS, spatial development lead

• Jim Carleton – hydrology, modeling, GIS expertise

• Ron Parker – PRZM, hydrology expertise

• Kurt Pluntke – database, modeling expertise

• Paul Mastradone – modeling, risk management

• Phil Villanueva – management lead

• Gabe Rothman – climate/weather

• Chris Koper – modeling (QA evaluations)
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What Do We Need to Know About 

Pesticide Exposure in Water?

How much? (magnitude)

How long? (duration)

How often? (frequency)

Where? (spatial)

Do the levels of exposure exceed 

the levels of concern?

 ...is actually several questions:
Goal: Become More “Spatially Explicit”

No longer assumes a uniform distribution of the 

pesticide (stressor)

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Spatially Explicit Assessment

Stressor 

distribution

Receptor 

range

Area exceeding level of concern

Considers the overlap between the stressor and 

the receptors (humans, animals, plants)

Pesticide

Where

When

How often

Animals

Plants

Humans
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What We Needed to Move Forward

Nationally available 

spatial data.

Quick, efficient 

modeling.

Sufficient computing 

power, storage. 
Spatial Data for Aquatic Modeling

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b) Soils

d) Weather

a) Hydrology

e) Crop Growth, Management

c) Land Use/ Land Cover
Adapting Our Current Aquatic Exposure 

Modeling Approach

Field or 

watershed 

with pesticide 

applications

Runoff

Drift

Erosion

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Water body 

(pond or 

reservoir)

(PRZM)

(EXAMS)

Pesticide Fate 

and Transport

Pesticide

Loading

Soil, Site, Crop,

Hydrology

Weather 

(rainfall, temp.,

Irrigation)
Incorporating Spatial Heterogeneity into 

the Watershed Modeling Unit

(b) Soil map – land cover patterns

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(a) Single, uniform watershed
Redesigning PRZM for Spatial Modeling

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Pesticide Fate 

and Transport

Pesticide

Loading

Soil, Site, Crop,

Hydrology

Weather 

(rainfall, temp.,

Irrigation)

Pesticide 

Fate & 

Transport 

Routines

Hydrology / 

Scenario 

Generator Water 

Body 

Model
Model Development and Data Quality 

Review model routines

Scientifically sound

Documented

Verified

Functioning as expected

Sensitivity analyses 

Compare any code 

changes against current 

models

Evaluate results 

Compare with robust 

monitoring data

Reasonable, protective
General Flow of the Spatial Model 

Process

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Tabular storage, 

calculations,

manipulations

largely occur outside of 

the spatial environment

Spatial data 

extracted, 

fed into 

models

Results are 

linked back to 

mappable

areas

Heavy 

lifting

Catchment/ 

field with 

pesticide 

applications

Receiving 

water body

Runoff

Drift

Erosion

Pesticide Fate 

and Transport

Pesticide

Loading

Soil, Site, Crop,

Hydrology

Weather 

(rainfall, temp.,

Irrigation)
Spatial 

Scenario 

Inputs

NonSpatial 

Scenario 

Inputs

Hydrology/

Scenario 

Generator

Scenario 

Files

Hydrology

Sediment

Crop 

Specific 

Scenarios

Pesticide Fate/ 

Transport Model

Watershed/ 

Water body 

Coverages

Hydrology, 

Sediment 

Flux

Pesticide 

Fate/Tox 

Properties

Pesticide 

Flux by 

Model Unit

Watershed 

Pesticide 

Flux

Water Body 

Model

Watershed 

Calculator

Summary Outputs:

LOC Exceedances

Pesticide 

EECs

Link Data to 

Water Bodies

Watershed 

Recipe 

Files

User Input 

Interface

Use, 

Application 

Inputs

Calculate

Endpoints

More 

Complex 

Version
Example Outputs

Areas 

exceeding 

toxicity 

threshholds

Exposure 

overlap 

with 

species 

of 

concern

Tables 

summarizing LOC 

comparisons for 

eco, MOE 

comparisons for 

human health

Frequency, 

duration of 

occurrences

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Building SAM in a Phased Approach

Pilot 1: 

Proof of 

Concept 

Model

Pilot 2: Model 

Development 

at a Regional 

Level

Pilot 3: Model 

Expanded to the US
Progress and Plans

• Final stages of data development, 

compilation

• Model components evaluated

• Testing how the model components work 

together will begin soon

• Demonstration model 

• Evaluation of computing, storage needs

• Expand model to national coverage

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