MODFLOW is a three-dimensional finite difference groundwater model. It uses modular structure, which makes it easy to modify to adapt to specific application code. Modflow-2000 simulates stable and unsteady flow in irregular flow systems. Aquifers can be closed or unclosed, or a combination of the two, flowing under external pressure, such as flowing to wells, surface recharge, evaporation, flowing to drainage channels, and flowing through riverbed. In addition to simulating groundwater flow, some related functions are extended, such as sediment transport.

DSSAT is a software application program, which contains dynamic crop growth simulation models of more than 40 crops. DSSAT is supported by a range of utilities and applications, including weather, soil, genetic, crop management and observational experimental data, as well as sample datasets for all crop models. Crop simulation models simulate growth, development and yield as a function of soil plant atmosphere dynamics. DSSAT has been used in many applications, from genetic modeling to farms and precise management, to regional assessment of climate change and its impacts. DSSAT has been used for more than 30 years by researchers, educators, consultants, promoters, growers, private enterprises, policy and decision makers, and many people in more than 150 countries around the world.

Calite model is an interactive screening model planned and managed by the state water project (SWP) and the Central Valley Project (CVP) in California. It simulates the hydrology of the Central Valley, reservoir operation and delivery allocation decisions to SWP and CVP, delta salinity response to changes in river flow and outlet, and resident ecosystem index. The power of filtering models like callite is the ability to quickly simulate system operations and merge changes relatively easily. The current version of calite simulates the operation of the system on a monthly basis. On the latest modeling computer, it takes about 6 minutes (compared with 30 minutes of calsim), recording a full 82 years of records (water year 1922-2003). Scenarios can be run using a variety of different user specified parameters related to hydrometeorology, requirements, facilities and infrastructure, regulations, and system operations. Through the integrated post-processing tools of the model, we can observe, compare and analyze the results.

Class model, as the "second generation" surface model that people need, was developed for Canadian GCM in the late 1980s. The model will fully deal with the effects of vegetation, snow cover and soil on the heat and temperature of the atmosphere. Various land surface parameterization schemes are compared in international projects. The class model is tested in the coupling model with GCM and various experiments with pilps. In such an operating environment, class is proved to perform quite well.