One-dimensional river and stream water quality model with steady state hydraulics, non-uniform steady flow, and diel heat budget/water-quality kinetics.


One-dimensional vertical lake model that is designed to compute seasonal trends of water quality in stratified lakes.


One-dimensional lateral benthic algae model that computes the distribution of biomass in rivers according to temperature, attenuated light, and available nutrients.

News Feed

Updated 01.01.2021

Thanks EPA...

The U.S. Environmental Protection Agency (EPA) just funded a QUAL2K model update. This includes the addition of sensitivity and uncertainty analysis (UNCAS), enhanced model outputs, benthic algae and phytoplankton upgrades, and real-time simulations.

New version of LAKE2K coming shortly

A python version is being developed by PhD candidate Greg Coyle in conjunction with Dr. Chapra. We will let you know when it is available.

Dr. Chapra just retired!

Please email him your best wishes to his new phase of life (Professor Emeritus) that will include additional research, model development, and potentially wine tasting, in no particular order.

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Disclaimer: The software provided on this website must be used at the user's own risk. Neither the U.S. Environmental Protection Agency nor the program authors can assume responsibility for model operation, output, interpretation or usage. The creators of these programs have used their best efforts in preparing this code. They are not absolutely guaranteed to be error free. The author/programmer makes no warrantees, expressed or implied, including without limitation warrantees of merchantability or fitness for any particular purpose. No liability is accepted in any event for any damages, including accidental or consequential damages, lost of profits, costs of lost data or programming materials, or otherwise in connection with or arising out of the use of this program.