1. General Model Information

Name: QUAL2Kw A framework for modeling water quality in streams and rivers using a genetic algorithm for calibration.

Acronym: QUAL2KW

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Author(s):

Abstract:

QUAL2Kw is a framework for the simulation of water quality in streams and rivers. Dynamic diel heat budget and water quality kinetics are calculated for one-dimensional steady-flow systems. The framework includes a genetic algorithm to facilitate the calibration of the model in application to particular waterbodies. The genetic algorithm is used to find the combination of kinetic rate parameters and constants that results in a best fit for a model application compared with observed data. The QUAL2Kw framework allows up to three steady-flow synoptic survey data sets to be simultaneously calibrated to the same set of kinetic rate parameters and constants.

QUAL2Kw is a modernized version of the QUAL2E model (Brown and Barnwell 1987). QUAL2Kw is adapted from the QUAL2K model that was originally developed by Dr. Steven C. Chapra of Tufts University (Chapra and Pelletier, 2003). The QUAL2Kw framework includes the following elements:

• 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 variables are simulated on a diel time scale.
• Heat and mass inputs. Point and non-point loads and abstractions are simulated.
• Software Environment and Interface. QUAL2Kw is implemented within the Microsoft Excel environment. It is programmed in Visual Basic for Applications (VBA). Excel is used as the graphical user interface for input, running the model, and viewing of output. The numerical integration during a model run is performed by a compiled Fortran 95 executable program that is run by the Excel VBA program.
• Model segmentation. QUAL2Kw allows for unequally-spaced reaches to simulate the mainstem of a river. In addition, multiple loadings and abstractions can be input to any reach segment.
• Carbonaceous biochemical oxygen demand (CBOD) speciation. QUAL2Kw uses two forms of CBOD to represent organic carbon. These forms are a slowly oxidizing form (slow CBOD) and a rapidly oxidizing form (fast CBOD).
• Anoxia. QUAL2Kw 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. These algae have variable stoichiometry of N and P.
• Light extinction. Light extinction is calculated as a function of phytoplankton, detritus, and inorganic solids.
• pH. Both alkalinity and total inorganic carbon are simulated. The river\x{2019}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.
• Hyporheic metabolism. Hyporheic exchange and sediment pore water quality may be simulated, including optional simulation of the metabolism of heterotrophic bacteria in the hyporheic zone.
• Genetic algorithm. A genetic algorithm is included to determine the optimum values for the kinetic rate parameters to maximize the goodness of fit of the model compared with measured data.

II. Technical Information

II.1 Executables:

II.2 Source-code:

II.3 Manuals:

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

• Temperature
• Conductivity
• Inorganic suspended solids
• Dissolved oxygen
• Slowly reacting CBOD
• Fast reacting CBOD
• Organic nitrogen
• Ammonia nitrogen
• Nitrate nitrogen
• Organic phosphorus
• Inorganic phosphorus
• Phytoplankton
• Detritus
• Pathogen
• Alkalinity
• Total inorganic carbon
• Bottom algae (periphyton) biomass
• Bottom algae (periphyton) nitrogen
• Bottom algae (periphyton) phosphorus

III.2.1 Input

• Location, date, numerical integration control options
• Headwater boundary flow and concentrations
• Boundary conditions of flow and concentration for tributary point sources and diffuse sources
• Reach segment lengths, elevations, hydraulic geometry (rating curve or Manning equation inputs for depth and velocity)
• Air temperature, dew point temperature, wind speed, cloud cover, shade
• Light attenuation paramters
• Options for models of solar radiation, evaporation, and longwave radiation
• Parameters for water quality kinetics rates and constants
• Parameters to control the genetic algorithm for optional automatic calibration of water quality kinetics rates and constants

III.2.2 Output

• Longitudinal predictions of diel minimum, average, and maximum concentrations for state variables
• Diel predictions of state variables in the water column and hyporheic pore water

IV. References

V. Further information in the World-Wide-Web

• QUAL2Kw and other models from the Department of Ecology
  
• QUAL2K - EPA version at the Ecosystems Research Division
  

VI. Additional remarks

Go back to Register of Ecological Models (R E M)