Environmental Assessment Program - Models for TMDLs

Environmental Assessment > Models for TMDLs

Models for Total Maximum Daily Load Studies

A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. Computer models are used extensively for water quality management and TMDLs. Models are used to predict the water quality in a water body in response to changes in pollutant loading and various allocation strategies.

Models and tools supported by the Department of Ecology

• QUAL2Kw - A modeling framework written in Excel/VBA for simulating river and stream water quality. The QUAL2Kw framework has the following characteristics:
  • One dimensional. The channel is well-mixed vertically and laterally.
  • Steady flow. Non-uniform, steady flow is simulated.
  • Diel heat budget. The heat budget and temperature are simulated as a function of meteorology on a diel time scale.
  • Diel water-quality kinetics. All water quality state variables are simulated on a diel time scale for biogeochemical processes.
  • Heat and mass inputs. Point and non-point loads and abstractions are simulated.
  • Phytoplankton and bottom algae in the water column, as well as sediment diagenesis, and heterotrophic metabolism in the hyporheic zone are simulated.
  • Variable stoichiometry. Luxury uptake of nutrients by the bottom algae (periphyton) is simulated with variable stoichiometry of N and P.
  • Automatic calibration. Includes a genetic algorithm to automatically calibrate the kinetic rate parameters.
• PIKAIA - A general purpose function optimization subroutine based on a genetic algorithm written in Excel/VBA. PIKAIA was originally developed in fortran by Charbonneau and Knapp.
• SolRad - A solar position and solar radiation calculator for Excel/VBA.
• Sunrise/Sunset - An Excel workbook with seven VBA functions for sunrise/sunset and solar position: dawn, sunrise, solar noon, sunset, dusk, solar azimuth, solar elevation.
• Shade - A tool for estimating shade from riparian vegetation written in Excel/VBA.
• tTools for ArcGIS - An ArcGIS project with tools for sampling geospatial data to obtain input data for the calculator for shade from riparian vegetation and topography.
• rTemp - A simple model written in Excel/VBA to predict a time-series of water temperatures in response to heat fluxes determined by meteorological data, groundwater inflow, hyporheic exchange, and conduction between the water and sediment.
• SedFlux - An Excel/VBA model of sediment nutrient fluxes and sediment oxygen demand (SOD) from diagenesis that is based on a method that was originally developed by Dominic DiToro.
• CO2SYS - A calculator for the CO2 system in seawater written in Excel/VBA. This program takes any two parameters of the CO2 system in seawater (alkalinity, total inorganic carbon, pH, and fugacity or partial pressure of CO2), and calculates the other two parameters for given input and output conditions of temperature and pressure. Calcium solubility is also calculated for both calcite and aragonite. This Excel/VBA application is based on the original DOS program named CO2SYS by Lewis and Wallace (1998).
• COARE - Coupled Ocean Atmosphere Response Experiment. Bulk air-sea heat flux algorithm, version 3.0b (Excel/VBA translation of Fortran 77 program from Chris Fairall's FTP site at NOAA).
• Seawater properties - Properties of water (and seawater) for Excel/VBA, using the UNESCO equation of state. VBA functions include potential temperature (theta), in-situ density (rho), sigma-t, sigma-theta, thermal expansion coefficient (alpha), saline contraction coefficient (beta), compressibility, freezing temperature, and specific heat.
• Manning's n calculator - An Excel/VBA program to calculate Manning's n (or depth) from cross-section data for trapezoidal or rectangular channels based on equation 14.32 in Chapra's Surface water quality modeling textbook.
• PWspread - Spreadsheets for water quality-based NPDES permit calculations.

Links to other models and resources used by the Department of Ecology

• USEPA Center for Exposure Assessment Modeling - Models supported by the US Environmental Protection Agency, inlcuding WASP, QUAL2E, SMPTOX3, and others.
• USEPA DFLOW tool for low flow analysis - DFLOW is a Windows-based tool developed to estimate user selected design stream flows for low flow analysis
• USEPA Ecosystems Research Division Watershed/Water Quality Modeling Technical Support Center - Tools and approaches that can be used in the development of Total Maximum Daily Loads (TMDL), waste load allocations, and watershed protection plans. Includes: water quality models (QUAL2K, WASP,EPD-RIV1, AQUATOX), watershed tools and/or models (BASINS, Watershed Characterization System, Loading Simulation Program, HSPF, WAMView), and hydrodynamic models (EFDC, EPD-RIV1).
• USEPA Guidance for TMDL Modeling - Guidance documents for TMDL modeling by the US Environmental Protection Agency
• USEPA Models - Comprehensive list of models supported by the US Environmental Protection Agency
• USEPA OWOW Guidance - Guidance documents for TMDL modeling by the US Environmental Protection Agency Office of Wetlands, Oceans, and Watersheds
• USEPA Quality System Guidance - Agency-wide quality system guidance documents that apply to internal USEPA organizations
• USEPA Rates, Constants, and Kinetics Formulations Manual - A USEPA publication that is an essential reference for water quality model calibration.
• USEPA Visual Plumes Model - Visual Plumes model system is a Windows-based software application for simulating surface water jets and plumes.
• CORMIX - CORMIX is a mixing zone model and decision support system for environmental impact assessment of regulatory mixing zones resulting from continuous point source discharges.
• USGS techniques for water resource investigations - The USGS publishes a series of manuals for planning and conducting water resource investigations.
• Oregon DEQ - Tools for analysis of water quality by the Oregon Department of Environmental Quality
• HeatSource - A model developed by Matthew Boyd at Oregon DEQ and Oregon State University that simulates stream and river water temperature via dynamic heat and mass transfer.
• CE-QUAL-W2 - Information about the CE-QUAL-W2 model from Portland State University
• EFDC - For information on obtaining or using the current public version of the Environmental Fluid Dynamics Code (EFDC) and supporting documentation and auxiliary software tools, contact John Hamrick at TetraTech at 703-385-6000 or john.hamrick@tetratech-ffx.com (inlcude your real name, affilitation, mailing address, phone number, and valid institutional, business or government email address).
• GEMSS - Generalized Environmental Modeling System for Surfacewaters (GEMSS) is an integrated system of 3-D hydrodynamic and transport models developed by J.E. Edinger Associates Inc.
• Ecology's Mixing Zone Guidance - Guidance for conducting mixing zone analyses
• Ecology's Permit Writers Manual - Technical guidance and policy manual for NPDES permit writers in Washington State
• Ecology's TMDL Technical Guidance - Guidelines for selected technical topics were prepared to ensure consistency in developing TMDL reports in Washington State
• Ecology's TMDL Development Guidance - Guidance for Determination and Allocation of Total Maximum Daily Loads (TMDL) in Washington State

Links to meteorological data

• Office of the Washington State Climatologist - The function of the State Climatologist is to collect, disseminate, and interpret climate data. This new web site provides links to sources of climate data and seasonal forecasts for the state of Washington.
• NOAA National Weather Service - The latest observations (up to 7 days of data) from NOAA's National Weather Service stations across the northwest (data provided by NOAA's National Weather Service forecast office in Missoula Montana).
• University of Washington Live from Earth and Mars - Continuous weater data (1996 to present) from selected stations in Washington and Oregon from an educational Web site provided by the University of Washington.
• Evergreen State College - Weather data from the campus of the Evergreen State College in Olympia, WA.
• NOAA National Weather Service - Seattle office (western Washington).
• NOAA National Weather Service - Spokane office (eastern Washington).
• Past weather data from NOAA - Access point for all of NOAA's past weather data.
• DAYMET GIS data for daily meteorology summaries - DAYMET is a model by the University of Montana. Using a digital elevation model and daily observations of minimum and maximum temperatures and precipitation from ground-based meteorological stations, an 18 year daily data set (1980 - 1997) of temperature, precipication, humidity and radiation has been produced as a continuous surface at a 1 km resolution.
• NCAR GIS data for climate change scenarios - This GIS data portal provides access to global datasets of climate change scenarios by National Center for Atmospheric Research.

Links to stream flow data

• USGS surface water data for Washington - Data from all USGS surface water stations in Washington.
• Department of Ecology's flow monitoring network - Data from all Department of Ecology stream gaging stations in Washington.

Links to tide and bathymetry data and tools

• Puget Sound Tide Model - The Puget Sound Tide Channel Model is a research tool for studying the tides of the Sound. It was developed by Lavelle et al. (1988) at NOAA PMEL and subsequently updated by H. Mofjeld to include the full suite of standard tidal constituents.
• Puget Sound Digital Elevation Model - Combined bathymetry and topography of Western Washington, including the Straits of Juan de Fuca, Puget Sound and Hood Canal.
• NOAA VDatum transformation tool - VDatum transforms coastal elevations between 28 different vertical datums consisting of tidal, orthometric, and ellipsoidal (3-D, three dimensional) datums.