2007 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative agreement is to develop and test computer software that may be used to predict the fate and transport of agricultural chemicals (salts, toxic trace elements, pathogenic microorganisms, pharmaceuticals) in the subsurface, and to test several parts of the software against experimental data. 1b.Approach (from AD-416) As part of this project, several new processes will be incorporated in the windows-based HYDRUS computer programs simulating water, heat and solute movement in soils and groundwater. Among these are (1) improved provisions for simulating three-dimensional transport problems, (2) preferential flow as modeled with alternative dual-permeability models, (3) multicomponent solute transport as applied to toxic trace elements, (4) an energy balance at the soil surface (using the Penman-Monteith or alternative methods), (5) overland flow to improve the design of surface irrigation systems, and (6) colloid and colloid-facilitated transport. The various features will be tested internally to ensure correct mathematical programming. Modeling results will be compared to selected data sets to ensure applicability to a variety of transport problems, and to identify strengths and weakenss of the conceptual formulations incorporated into the software. Closely related objectives of the project are to (a) develop or improve windows-based graphical interfaces of the 1D, 2D and 3D flow transport modules within the HYDRUS software, (b) use model abstraction techniques involving a hierarchy of process-based modules within HYDRUS to analyze a large experimental data set on water flow in a heterogeneous field soil, and (c) develop alternative pedotransfer functions for implementation in HYDRUS, and for application to the NASIS soil hydraulic database of the National Resources Conservation service (NRCS). 3.Progress Report This report serves to document research conducted under a Specific Cooperative Agreement between the Agriculture Research Service and the University of California, Riverside. The research assists in completing objectives associated with parent project 5310-61000-014-00D, Improved Knowledge and Modeling of Water Flow and Chemical Transport Processes in Irrigated Soils, as well as projects 5310-61000-014-02R, Model Abstraction Techniques for Soil Water Flow and Transport, and 5310-61000-014-03T, Technology Transfer Support for Multi-Agency Memorandum of Understanding. Additional details of the research can be found in the reports for those projects. Research progress during FY 2007 included developing several improvements in the windows-based HYDRUS-1D software package for predicting water, heat and solute movement in soils and groundwater. Of particular significance are new capabilities for simulating the transport of emerging contaminants such as pathogens and pharmaceuticals, and improved modules for simulating water flow and solute transport through macro-porous soils. Additionally, work continued on the development of model abstraction techniques that will permit the analysis of large experimental data sets through a hierarchy of process-based modules within HYDRUS. This software, which can be downloaded from the Salinity Laboratory's web site, is being used by a large number of scientists, engineers, and soil and groundwater professionals dealing with water and pollutant movement in the subsurface. Research progress was confirmed through regular meetings, phone conversations, and email correspondence.