TopoFlow

TopoFlow is a powerful, spatially-distributed hydrologic model with a user-friendly point-and-click interface. Its main purpose is to model many different physical processes in a watershed with the goal of accurately predicting how various hydrologic variables will evolve in time in response to climatic forcings.
Modeled processes include:
Channelized flow (kinematic, diffusive or dynamic wave, all 1D and D8-based)
Overland flow
Snowmelt (degree-day or energy balance)
Icemelt (from valley glaciers using GC2D)
Meteorology (including precipitation, air temperature, shortwave and longwave radiation, etc.)
Evaporation (Priestley-Taylor or energy balance)
Infiltration (Green-Ampt, Smith-Parlange or Richards' 1D, multi-layer), *Shallow subsurface flow (Darcy, up to 6 layers)
Flow diversions (sinks, sources or canals)

Each process can have its own timestep. Typical timesteps are:
Channel flow (seconds)
Infiltration (seconds to minutes)
Snowmelt (hours to days)
Subsurface flow (hours to days), etc.
Model can be run for a full year or longer, if necessary.

Overland flow is currently modeled in a nonstandard way. Diffusive wave and dynamic wave routing routines need more testing. The linkage between the unsaturated zone (infiltration component) and saturated zone (subsurface flow component and water table) is not robust.

Available test datat sets:
Treynor watershed, in the Nishnabotna River basin, Iowa, USA. (Two large rainfall events.)
Small basin in Kentucky.
Inclined plane for testing.
Arctic watershed data from Larry Hinzman (UAF).
See /data/progs/topoflow/3.0/data on CSDMS cluster.