Also known as
Model type Single
Model part of larger framework
Note on status model
Date note status model
Spatial dimensions 1D
Spatial extent Watershed-Scale
Model domain Terrestrial
One-line model description A Modeling Framework for Simulating River and Stream Water Quality
Extended model description 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.

biogeochemistry, water quality,

Name Steve Chapra
Type of contact Model developer
Institute / Organization Tufts University, Civil and Environmental Engineering Dept.
Postal address 1 200 College Avenue
Postal address 2
Town / City Medford
Postal code 02155
State Massachusetts
Country United States
Email address

Name Greg Pelletier
Type of contact Model developer
Institute / Organization
Postal address 1
Postal address 2
Town / City
Postal code
Email address

Name Hua Tao
Type of contact Model developer
Institute / Organization
Postal address 1
Postal address 2
Town / City
Postal code
Email address

Supported platforms
Other platform
Programming language


Other program language Visual Basic (VBA), Excel
Code optimized Single Processor
Multiple processors implemented
Nr of distributed processors
Nr of shared processors
Start year development 1987
Does model development still take place? Yes
If above answer is no, provide end year model development
Code development status
When did you indicate the 'code development status'?
Model availability As code
Source code availability
(Or provide future intension)
Through web repository
Source web address
Source csdms web address
Program license type Other
Program license type other NOT SURE
Memory requirements --
Typical run time --

Describe input parameters Too many to mention here
Input format
Other input format
Describe output parameters --
Output format
Other output format
Pre-processing software needed? No
Describe pre-processing software
Post-processing software needed? No
Describe post-processing software
Visualization software needed? No
If above answer is yes
Other visualization software

Describe processes represented by the model The QUAL2K framework includes the following new elements:
  • Software Environment and Interface. Q2K is implemented within the Microsoft Windows environment. Numerical computations are programmed in Fortran 90. Excel is used as the graphical user interface. All interface operations are programmed in the Microsoft Office macro language: Visual Basic for Applications (VBA).
  • Model segmentation. Q2E segments the system into river reaches comprised of equally spaced elements. Q2K also divides the system into reaches and elements. However, in contrast to Q2E, the element size for Q2K can vary from reach to reach. In addition, multiple loadings and withdrawals can be input to any element.
  • 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).
  • 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 can be 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.
  • 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 computed based on these two quantities.
  • Pathogens. A generic pathogen is simulated. Pathogen removal is determined as a function of temperature, light, and settling.
  • Reach specific kinetic parameters. Q2K allows you to specify many of the *Weirs and waterfalls. The hydraulics of weirs as well as the effect of weirs and waterfalls on gas transfer are explicitly included.
Describe key physical parameters and equations Too many to mention here. See manual.
Describe length scale and resolution constraints --
Describe time scale and resolution constraints --
Describe any numerical limitations and issues --

Describe available calibration data sets
Upload calibration data sets if available:
Describe available test data sets
Upload test data sets if available:
Describe ideal data for testing

Do you have current or future plans for collaborating with other researchers? --
Is there a manual available? Yes
Upload manual if available: Media:Q2KDocv2 11b8.pdf
Model website if any
Model forum / discussion board
Comments Questionnaire is filled out by Albert Kettner

This part will be filled out by CSDMS staff

OpenMI compliant No but possible
BMI compliant No but possible
WMT component No but possible
PyMT component
Is this a data component
Can be coupled with:
Model info
Steve Chapra
Pelletier, Tao
Nr. of publications: 115
Total citations: 1283
h-index: 18
m-quotient: 0.82
Qrcode QUAL2K.png
Link to this page




Nr. of publications: 115
Total citations: 1283
h-index: 18
m-quotient: 0.82

Featured publication(s)YearModel describedType of ReferenceCitations
Chapra, S.C.; Pelletier, G.J.; Tao, H.; 2008. QUAL2K: A Modeling Framework for Simulating River and Stream Water Quality, Version 2.11: Documentation and Users Manual. .
(View/edit entry)
2008 QUAL2K

Model overview

See more publications of QUAL2K



Input Files

Output Files