Despite advances in modeling, such as graphical user interfaces, the use of GIS layers, and databases for developing input files, the approaches to modeling phosphorus (P) have not changed since their initial development in the 1980s. Current understanding of P processes has evolved and this new information needs to be incorporated into the current models. Filling this need, Modeling Phosphorus in the Environment describes basic approaches to modeling P, how the current models implement these approaches, and ways to improve them.

The book sets the scene with a review of general approaches to modeling runoff and erosion, P in runoff, leaching of P, stream processes that affect P, and an examination of the important issue of model uncertainty. It describes state-of-the-science watershed-scale P transport models including dynamic semi-disturbed models, models of intermediate complexity, and two lumped models. Phosphorus Indexes (PIs) represent one end of the modeling spectrum and the book takes a comprehensive look at PIs developed in each state, and illustrates some of the problems encountered when incorporating PIs into farm-scale manure management software. The book discusses monitoring data, which is critical for calibrating models, and concludes with suggestions for improving the modeling of P.

From researching mechanisms to applying regulations, the uses of phosphorus models have increased as our knowledge of the effects of phosphorus in the environment has increased. Drawing on contributions from experts, the book gives you the tools to select the model that best fits your needs.

Numerical models have become much more efficient, making their application to problems increasingly widespread. User-friendly interfaces make the setup of a model much easier and more intuitive while increased computer speed can solve difficult problems in a matter of minutes. Co-authored by the software's creator, Dr. Jirka Simunek, Soil Physics with HYDRUS: Modeling and Applications demonstrates one- and two-dimensional simulations and computer animations of numerical models using the HYDRUS software. Classroom-tested at the University of Georgia by Dr. David Radcliffe, this volume includes numerous examples and homework problems. It provides students with access to the HYDRUS-1D program as well as the Rosetta Module, which contains large volumes of information on the hydraulic properties of soils. The authors use HYDRUS-1D for problems that demonstrate infiltration, evaporation, and percolation of water through soils of different textures and layered soils. They also use it to show heat flow and solute transport in these systems, including the effect of physical and chemical nonequilibrium conditions. The book includes examples of two-dimensional flow in fields, hillslopes, boreholes, and capillary fringes using HYDRUS (2D/3D). It demonstrates the use of two other software packages, RETC and STANMOD, that complement the HYDRUS series. Hands-on use of the windows-based codes has proven extremely effective when learning the principles of water and solute movement, even for users with very little direct knowledge of soil physics and related disciplines and with limited mathematical expertise. Suitable for teaching an undergraduate or lower level graduate course in soil physics or vadose zone hydrology, the text can also be used for self-study on how to use the HYDRUS models. With the information in this book, you can run models for different scenarios and with different parameters, and thus gain a better understanding of the physics of water flow and contaminant transport.