Environmental Simulations International (ESI) provide training, consulting and software development in groundwater modeling. They are the developers of Groundwater Vistas.

The International Ground Water Modeling Center is an internationally oriented information, education and research center for ground-water modeling.

The Hydrogeology Group is coordinated by Chunmiao Zheng (author of MT3DMS) and is affiliated with the faculties of Geological Sciences, Civil & Environmental Engineering, Mathematics, and Aquatic Biology in the University of Alabama. Download MT3DMS free of charge.

The USEPA Center for Exposure Assessment Modeling (CEAM), was established in 1987 to meet the scientific and technical exposure assessment needs for the USEPA and state environmental resource management agencies.  CEAM provides proven predictive exposure assessment techniques for aquatic, terrestrial, and multimedia pathways.

RockWare - Earth Science software specialists, providing a large range of mapping, data analysis, modeling, and educational software.

Schlumberger Water Services - Developers of WinPEST and Visual PEST-ASP.

Environmental Modeling Systems, Inc. (EMS-I) provides software, support, training, and consulting services for water resources modeling using the Groundwater Modeling System (GMS, Surface-water Modeling System (SMS), and Watershed Modeling System (WMS) software. These state-of-the-art graphical user interfaces for environmental and water resource modeling are developed at Brigham Young University's Environmental Modeling Research Laboratory (EMRL). 

Scientific Software Group sell a comprehensive range of groundwater, surface-water, bioremediation, geotechnical, air-pollution and environmental software.

AzTechSoft - software and resources for the Engineering, Architectural, and AutoCAD Communities.

Kumar Links to Hydrology resources provides a comprehensive set of links to important surface and ground water sites.

National Ground Water Association is a non-profit organization providing a range of educational, information and other services to the groundwater industry.

United States Geological Survey (USGS) water resources applications software. USGS public domain software can be downloaded free of charge from this site.

US Army Corps of Engineers Hydrologic Engineering Center was established to support hydrologic engineering and water resources planning and management. HEC software can be downloaded from here.

Directory of Groundwater Online Resources provides an enormous range of information on matters pertaining to groundwater.

Earthsoft develops and markets EquiS, a comprehensive groundwater, chemical, geological and environmental database package.

C-Tech Development Corporation developed EVS (Environmental Visualization System), a powerful groundwater, geological and environmental visualization and data analysis package.

Argus ONE (open numerical environments) is a generalized spatial modeling interface that supports a wide range of GIS functionality. Interfaces to many popular groundwater models are available.

WASY Institute for Water Resources Planning and Systems Research LTD are the developers of the comprehensive finite-element, groundwater and transport model, FEFLOW. The latest version of FEFLOW includes a PEST interface.

Richard B. Winston's home page (includes an enormous number of links to water resources, modeling, and other information).

Download UNCERT, a geostatistical uncertainty analysis package applied to groundwater flow and contaminant transport modeling. Includes some visualization capabilities. Developed by William L. Wingle, Eileen P. Poeter and Sean A. McKenna.

The Geotechnical & Geo-environmental Software Directory catalogues programs in the fields of geotechnical engineering, soil mechanics, rock mechanics, engineering geology, foundation engineering, hydrogeology, geo-environmental engineering, data analysis and data visualization and lists worldwide suppliers and publishers of these programs.

GSLIB software library. GSLIB is available as part of the book "GSLIB: Geostatistical Software Library and User's Guide" by Clayton Deutsch and Professor Andre Journal which is available from Oxford University Press.

The Center for Subsurface Modeling Support (CSMoS) provides public domain ground-water and vadose zone modeling software and services to public agencies and private companies.