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Model Report

STREAM WATER QUALITY MODEL

Last Revision Date: 08/25/2009 View as PDF
General Information Back to Top
Model Abbreviated Name:

QUAL2K
Model Extended Name:

STREAM WATER QUALITY MODEL
Model Overview/Abstract:
QUAL2K (or Q2K) is a river and stream water quality model that is intended to represent a modernized version of the QUAL2E (or Q2E) model (Brown and Barnwell 1987). Q2K is similar to Q2E in the following respects:
  • One dimensional. The channel is well-mixed vertically and laterally.
  • Steady state hydraulics. Non-uniform, steady flow is simulated.
  • Diurnal heat budget. The heat budget and temperature are simulated as a function of meteorology on a diurnal time scale.
  • Diurnal water-quality kinetics. All water quality variables are simulated on a diurnal time scale.
  • Heat and mass inputs. Point and non-point loads and abstractions are simulated.
The QUAL2K framework includes the following new elements:
  • Software Environment and Interface. Q2K is implemented within the Microsoft Windows environment. It is programmed in the Windows macro language: Visual Basic for Applications (VBA). Excel is used as the graphical user interface.
  • Q2E segments the system into river reaches comprised of equally spaced elements. In contrast, Q2K uses unequally-spaced reaches. In addition, multiple loadings and abstractions can be input to any reach.
  • Carbonaceous BOD speciation.Q2K uses two forms of carbonaceous BOD to represent organic carbon. These forms are a slowly oxidizing form (slow CBOD) and a rapidly oxidizing form (fast CBOD). In addition, non-living particulate organic matter (detritus) is simulated. This detrital material is composed of particulate carbon, nitrogen and phosphorus in a fixed stoichiometry.
  • Anoxia.Q2K accommodates anoxia by reducing oxidation reactions to zero at low oxygen levels. In addition, denitrification is modeled as a first-order reaction that becomes pronounced at low oxygen concentrations.
  • Sediment-water interactions. Sediment-water fluxes of dissolved oxygen and nutrients are simulated internally rather than being prescribed. That is, oxygen (SOD) and nutrient fluxes are simulated as a function of settling particulate organic matter, reactions within the sediments, and the concentrations of soluble forms in the overlying waters.Bottom algae. The model explicitly simulates attached bottom algae.
  • Light extinction. Light extinction is calculated as a function of algae, detritus and inorganic solids.
  • pH. Both alkalinity and total inorganic carbon are simulated. The river ?s pH is then simulated based on these two quantities.
  • Pathogens. A generic pathogen is simulated. Pathogen removal is determined as a function of temperature, light, and settling.
Keywords:
Model Technical Contact Information:
Tim Wool
U.S. EPA ORD/NERL-ERD
Watershed and Water Quality Modeling Technical Support Center
Athens, GA
wool.tim@epa.gov
706-355-8312
Model Homepage: http://www.epa.gov/athens/wwqtsc

User Information Back to Top
Technical Requirements
Computer Hardware
Standard Desktop System. Higher performance machine maybe need for large simulations.
Compatible Operating Systems
Microsoft Windows 98 or Higher
Other Software Required to Run the Model
QUAL2K requires Microsoft Office/Excel 2000 or Higher
Download Information
The QUAL2K model is available to be downloaded.
Using the Model
Basic Model Inputs
Stream/River is broken down into branches and computational elements, forcing functions such as: flow, boundary concentrations, meteorological conditions, light, kinetic constants. More complex the application the greater the input requirements.
Basic Model Outputs
User can give all model output within the Excel environment.
User Support
User's Guide Available?
Watershed and Water Quality Modeling Technical Support Center maintains a QUAL2K Users Manual and is included with the installation package. The Users Manual is periodically updated as the model is enhanced.

Model Science Back to Top
Problem Identification
QUAL2K (or Q2K) is a river and stream water quality model that is intended to represent a modernized version of the QUAL2E (or Q2E) model (Brown and Barnwell 1987).
Summary of Model Structure and Methods
  • Carbonaceous BOD speciation.Q2K uses two forms of carbonaceous BOD to represent organic carbon. These forms are a slowly oxidizing form (slow CBOD) and a rapidly oxidizing form (fast CBOD). In addition, non-living particulate organic matter (detritus) is simulated. This detrital material is composed of particulate carbon, nitrogen and phosphorus in a fixed stoichiometry.
  • Anoxia.Q2K accommodates anoxia by reducing oxidation reactions to zero at low oxygen levels. In addition, denitrification is modeled as a first-order reaction that becomes pronounced at low oxygen concentrations.
  • Sediment-water interactions. Sediment-water fluxes of dissolved oxygen and nutrients are simulated internally rather than being prescribed. That is, oxygen (SOD) and nutrient fluxes are simulated as a function of settling particulate organic matter, reactions within the sediments, and the concentrations of soluble forms in the overlying waters.
  • Bottom algae. The model explicitly simulates attached bottom algae.
  • Light extinction. Light extinction is calculated as a function of algae, detritus and inorganic solids.
  • pH. Both alkalinity and total inorganic carbon are simulated. The river ?s pH is then simulated based on these two quantities.
  • Pathogens. A generic pathogen is simulated. Pathogen removal is determined as a function of temperature, light, and settling.
Model Evaluation
Model results have been compared to analytical solution and other models.


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