AGNPS and AnnAGNPS

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AGNPS and AnnAGNPS

• Developed by USDAARS and NRCS
• Agricultural NonPoint Source (AGNPS) single event
  model
• Annualized Agricultural NonPoint Source
  (AnnAGNPS) continuous simulation model
• Available for download at
• http//www.ars.usda.gov/Research/docs.htm?docid51
  99

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What is AGNPS?

• Watershed-scale water quality model
• Characteristics
• Spatially distributed
• Continuous simulation
• Surface runoff pollutant model
• Source accounting

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AGNPS Framework

• Watershed is divided into subwatersheds or cells
  (homogeneous drainage areas)
• Cells are connected by streams/channels
• One-dimensional channel routing
• Route runoff and pollutants downstream
• GIS interface used to
• Characterize watershed
• Set model parameters

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AGNPS watershed
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AGNPS Components

• Meteorology
• Uses GEM ( others) to generate daily weather for
  specified years
• Pollutant loading
• Surface-runoff water (rainfall, snowmelt,
  irrigation)
• sediments by size (clay, silt, sand) and source
  (land or stream channel) RUSLE and HUSLE
• nutrients (nitrogen, phosphorus, organic carbon
• source accounting

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AGNPS Components (contd)

• Hydrology
• Soil moisture balance
• Runoff (SCS curves)
• Evapotranspiration (Penman equation)
• Lateral subsurface flow (Darcys eqn or tile
  drain flow)
• Salmonid models

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AGNPS Applications

• Assess BMPs
• Develop TMDLs
• Perform Risk Assessments
• Estimate pollutant export

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Goodwin Creek, MS Study
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Goodwin Creek Study (contd)
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AQUATOX

• Developed and distributed by USEPA
• Available for download at
• http//www.epa.gov/waterscience/models/aquatox/

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What is AQUATOX?

• Simulation model that links environmental
  stressors and their impact on aquatic ecosystems
• Characteristics
• predicts effects of multiple stressors
  (nutrients, organic toxicants, temperature,
  suspended sediment, flow)
• Represents a variety of aquatic ecosystems

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AQUATOX Framework

• Time-variable
• Spatially simple
• thermal stratification
• salinity stratification
• Modular and flexible
• model only what is necessary
• Control vs. perturbed simulations

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AQUATOX Conceptual Model
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AQUATOX Modules

• Plants
• Phytoplankton
• Periphyton
• Macrophytes
• Moss
• Animals
• Zooplankton
• Zoobenthos
• Fish

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AQUATOX Modules (contd)

• Inorganic sediments (stream only)
• Scour, deposition and transport of sediments
• River reach assumed short and well mixed
• Feedback to biota (light limitation
  sequestration of chemicals)
• Nutrients and remineralization
• Detritus
• Nutrients
• Variable pH
• Dissolved oxygen and anoxia
• Stratification

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AQUATOX Modules (contd)

• Toxicant loading
• Chemical fate
• Biotransformation
• Bioaccumulation
• Chronic and acute toxicity

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AQUATOX Applications

• Evaluate water quality criteria and standards,
• Develop TMDLs
• Identify cause(s) of biological impairment where
  there are multiple stressors
• Perform ecological risk assessments

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Coralville, Iowa Study
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Coralville Study (contd)
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Coralville Study (contd)
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Coralville Study (contd)