SOFTWARE REVIEWHYDRUSJohn E. McCray – Colorado School of Mines.
Software Review courtesy of International
Ground Water Modeling Center and Colorado
School of Mines.

The HYDRUS-2D/3D software package
is a major upgrade and extension of the
HYDRUS-2D/MESHGEN-2D software
package originally developed andreleased by the U.S. Salinity Laboratory,
PC-Progress and the International
Ground Water Modeling Center. The
new version, released under the name
HYDRUS, is a Microsoft Windows-basedmodeling environment for analysis ofwater flow, solute, and heat transportin variably saturated porous media.
For flow, the code solves the mixed
form of the Richards’ equation, withmany functions for simulating hydraulicconductivity versus water content (orpressure head) relationships, including
hysteresis. It allows root water uptake withcompensation and spatial root distributionfunctions, and includes new soil hydraulicproperty models. The new code allows
for dynamic, system-dependent boundary
conditions such as switching amongpressure heads, seepage face, zero flux,
or atmospheric boundaries, dependingon the position of the water level.
For solute transport, the code solves
the advection-dispersion equation,but with many processes not usually
included in unsaturated zone codes. For
example, in addition to the typical linear
partitioning between soil, water, andgas phases, the code also simulates thefollowing processes: non-linear and nonequilibrium partitioning between phases;
diffusion in the gas phase; zero- andfirst-order degradation kinetics, including
decay chains (such as for nitrates andradionuclides); advective flow in a dualporosity system allowing for preferential
flow in fractures or macropores
while storing water and dissolved
chemicals in the matrix; transport ofviruses, colloids, and bacteria using an
attachment/detachment model; filtration
theory; blocking functions; and flowing

Review of HYDRUS-2D/3D

Ease of Use:
GUI:
Output/Plotting:Documentation:
Speed:OVERALL RATING:

Application
Vadose zone flow andtransport
Best Features
New GUI
Worst Feature
No optimization in 3D

Rating System:
Excellent
Poor
International Ground Water Modeling Center
Colorado School of Mines

particles in two-dimensional applications.
HYDRUS also includes a new constructedwetland module, only in 2-D.
HYDRUS still allows optimizationin 1-D and 2-D; unfortunately, it isnot provided for 3-D applications.
Another useful new feature is better
print management, allowing the user toprint at regular time intervals or after
a constant number of time steps.

standard for 3-D geometries comprising
flexible 2-D geometries and layers forthe third dimension. A professionalversion that will allow applicationof general, flexible 3-D geometries
is expected in summer 2007.
The original, public-domain version of HYDRUS-1D
is included in the HYDRUS package and may still
be downloaded for free from the IGWMC web site atwww.mines.edu/igwmc/software/igwmcsoft/hydrus1d.
htm. HYDRUS may be purchased by visiting
typhoon.mines.edu/software/igwmcsoft/hydrus3d.htm.

The GUI is much improved with many
new user-friendly functions, such as
drag-and-drop, context-sensitive popup menus after clicking on objects,
selection and editing of multiple
objects in the same dialog window, andallowing multiple projects and views
to be opened at the same time in theHYDRUS main window. One of the best
new features is that time-varying andcumulative fluxes can be calculated anddisplayed across internal meshlines.
The only negatives associated withthe program are that the user’s guide
could be more complete. Not allfeatures are explained well enoughfor a modeler without previous
HYDRUS experience to easily follow.
However, the online discussion forum
is very helpful; it can be found atwww.pc-progress.cz/_Forum/default.asp.
Pricing varies depending on the levelpurchased. Single-computer licenses are$1,500 for HYDRUS that can handle
applications for simple (hexahedral)
geometries, and $1,800 for HYDRUS
January/February 2007 • Southwest Hydrology • 41