2007 Annual Report 1a.Objectives (from AD-416) Principal focus of the CEAP effort is to produce a national assessment of environmental benefits of conservation programs to support policy decision and program implementation. 1b.Approach (from AD-416) Utilize ARS historical watershed databases to validate the SWAT model and then utilize this model to determine the impact of conservation practices on water quality, soil quality, air quality, and wildlife habitat. 3.Progress Report This report serves to document research conducted under a reimbursable agreement between the Agricultural Research Service (ARS) and the Natural Resources Conservation Service (NRCS). Additional details of the research can be found in the report for the parent project, CRIS 6206-13610-006-00D, Development of Models and Conservation Practices for Water Quality Management and Resource Assessments. The objective of the research is to assess the watershed scale effects of NRCS conservation practices. A national assessment is being conducted using the Soil and Water Assessment Tool (SWAT). This project serves as a mechanism to coordinate components of the Conservation Effects Assessment Project (CEAP) on a national scale as well as to provide for field and modeling research at the local level. The SWAT model is being used to assess the effects of conservation practices on all major watersheds in the nation. Input data was developed for the SWAT model for 18 river basins and over 2,100 subwatersheds in the coterminous United States. Point sources and APEX (Agricultural Policy/Environmental eXtender) model output from cultivated lands were incorporated into the model. The water balance of each subwatershed was calibrated to long-term USGS (United States Geological Service) data, and monthly streamflow was validated at 50 USGS gage sites. Model output was validated to sediment, nitrogen, and phosphorus at selected gage sites in the upper Mississippi, Ohio, and Missouri River Basins. The validation results give confidence as we begin analysis of conservation practice scenarios. 6.Technology Transfer Number of non-peer reviewed presentations and proceedings 6