Version 4.5.5 available now

Model the water,
in two dimensions.

CE-QUAL-W2 is a free, laterally averaged 2D (longitudinal–vertical) hydrodynamic and water-quality model trusted worldwide for rivers, lakes, reservoirs, estuaries and entire river-basin systems.

2D Longitudinal–Vertical Hydrodynamics + Water Quality Open & Free Continuously Developed
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What is CE-QUAL-W2

One model for the whole waterbody — surface to bed, headwater to outlet.

CE-QUAL-W2 couples a hydrodynamic engine and a rich water-quality kinetics library in a single, laterally averaged framework. Because it resolves the vertical dimension, it captures the thermal stratification, selective withdrawal and density currents that dominate the behavior of deep reservoirs and stratified estuaries.

  • ●Two coupled engines — hydrodynamics (water levels, velocities, temperature) and water quality (oxygen, nutrients, algae and more) solved together.
  • ●Branched, multi-waterbody grids — link rivers, reservoirs and estuaries into a single basin-scale network.
  • ●Backed by decades of research — developed through a Portland State University–USACE ERDC partnership and applied on well over a thousand projects worldwide.

See what it can simulate →

SCHEMATIC · LONGITUDINAL–VERTICAL GRID
inflow withdrawal distance along branch → depth ↓
Why modelers choose it

Capabilities that scale from a pond to a river basin

A compact selection of what makes CE-QUAL-W2 a workhorse for water-resources studies.

See the latest features & what's new →

Water-quality state variables & groups

Modern versions allow an arbitrary number of algae, epiphyton, zooplankton, CBOD and user-defined generic constituents.

Hydrodynamics & water quality

Temperature, oxygen, nutrients, algae — coupled and consistent

The hydrodynamic solution drives transport for every constituent, so stratification, mixing and residence time feed directly into the water-quality kinetics. Simulate the full oxygen and nutrient cycle, multiple algal and zooplankton groups, organic-matter pools, pH and carbonate chemistry, sediment oxygen demand and sediment diagenesis.

Full capability reference →

Where it's used

From drinking-water reservoirs to TMDL studies

CE-QUAL-W2 is applied across the world by agencies, consultants and universities.

Latest release

What's new in version 4.5.5

The model is actively developed — each release adds kinetics, numerics and usability improvements driven by real project needs.

    Full release notes →

    Version history

      Community & support

      Stuck on a boundary condition? Ask the community.

      Join the discussion forum to trade calibration tips, report issues and request features — or reach the developers directly for technical support.

      Open the discussion forum Report an issue
      References

      Sources & further reading

      This portal compiles publicly available information about CE-QUAL-W2. Always defer to the official model documentation for authoritative guidance.