2007 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative research project is: (1) to derive mathematical relationships of rain infiltration into heterogeneous soil profiles consisting of cracking soils and soils with vertical macropores or bio-channels, (2) to conduct experimental studies for validating derived relationships for soils with simulated, fixed crusts and developing dynamic seals, and (3) to conduct experimental and theoretical infiltration studies on sloping soils for assessing the incidence of seepage. 1b.Approach (from AD-416) Significant progress has been made in predicting infiltration into swelling/cracking and sealing/crusting soils. However, there is a need to improve existing relationships and to make them more applicable to relevant naturally occurring conditions and to validate derived relationshsips with experimental data. This study will consist of improving mathematical derivations by using polar coordinates for predicting infiltration into cracking soils and to use rainfall simulation approaches for validation purposes. A slope adjustable flume equipped with a rainfall simulator and soil water content and tension measurements will be used to determine the subsurface flow regime and points of water seepage. 3.Progress Report This report serves to document research conducted under a Specific Cooperative Agreement between ARS and the University of Mississippi Dept. of Civil Engineering. Additional details of research research can be found in the report for the in-house project 6408-13000-017-00D, "Integrated Assessment and Analysis of Physical Landscape Processes that Impact the Management of Agricultural Watersheds." The analysis of rainfall infiltration into swelling/shrinking/cracking soils was completed, the results were summarized, written up and published in the peer-reviewed journal, Agricultural Water Management. Progress was monitored as work was performed on the National Sedimentation Laboratory (NSL) premises with daily contact with the Univerity of Mississippi principal investigator and documented in presentations, proceedings, and journal papers.