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Water: Water Quality Models

Water Quality Models

We provide access to a number of specialized models and tools for water quality managers.

DMR Pollutant Loading Tool: The Discharge Monitoring Report (DMR) Pollutant Loading Tool is a new tool designed to help you determine who is discharging, what pollutants they are discharging and how much, and where they are discharging. The tool calculates pollutant loadings from permit and DMR data from EPA‘s Permit Compliance System (PCS) and Integrated Compliance Information System for the National Pollutant Discharge Elimination System (ICIS-NPDES). Data is available for the years 2007 through 2010. Pollutant loadings are presented as pounds per year and as toxic-weighted pounds per year to account for variations in toxicity among pollutants. The tool ranks dischargers, industries, and watersheds based on pollutant mass and toxicity, and presents “top ten” lists to help you determine which discharges are important, which facilities and industries are producing these discharges, and which watersheds are impacted.


Water quality models are tools for simulating the movement of precipitation and pollutants from the ground surface through pipe and channel networks, storage treatment units and finally to receiving waters. Both single-event and continuous simulation may be performed on catchments having storm sewers and natural drainage, for prediction of flows, stages and pollutant concentrations.

Each water quality model has its own unique purpose and simulation characteristics and the reader is advised to thoroughly review downloading and data input instructions for each model.

  • AQUATOX: A Simulation Model for Aquatic Ecosystems
    AQUATOX is a freshwater ecosystem simulation model. It predicts the fate of various pollutants, such as nutrients and organic toxicants, and their effects on the ecosystem, including fish, invertebrates, and aquatic plants.
  • CORMIX for Mixing Zones
    A mixing zone model that can be used to assess water quality impacts from point source discharges at surface or sub-surface levels.
  • WASP7
    WASP7 is an enhanced version of the Water Quality Analysis Simulation Program (WASP). This version includes kinetic algorithms for
    1. eutrophication/conventional pollutants,
    2. organic chemicals/metals,
    3. mercury, and
    4. temperation, fecal coliform, and conservative pollutants.
  • QUAL2K model
    A river and stream water quality model, intended to represent a modernized version of the QUAL2E (or Q2E) model (Brown and Barnwell 1987)


Water quality tools include maps and methods.

  • Analytical Methods
    Methods used by industries and municipalities to analyze the chemical and biological components of wastewater, drinking water, sediment, and other environmental samples.
  • BASINS: A Powerful Tool for Managing Watersheds
    A multi-purpose environmental analysis system that integrates a geographical information system (GIS), national watershed data, and environmental assessment and modeling tools into one convenient package.
  • DFLOW: A Tool for Low Flow Analysis
    A tool to calculate design flow statistics. It also includes several pages explaining how to use the tool and provides detailed background information.
  • Economics & Benefits
    Estimating the benefits of our water quality programs.
  • Mercury Maps: A Quantitative Spatial Link Between Air Deposition and Fish Tissue
    Mercury Maps is a tool that relates changes in mercury air deposition rates to changes in mercury fish tissue concentrations, on a national scale. Mercury Maps can be used to help identify those waterbodies expected to attain state water quality standards as a result of air deposition reductions, or to assist in Total Maximum Daily Load (TMDL) analyses for individual or multiple watersheds.
  • National Lake Fish Tissue Study
    We are conducting a screening-level study to estimate the national distribution of selected persistent, bioaccumulative and toxic chemical residues in fish tissue from lakes and reservoirs of the continental United States.

Training and meetings

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