2012 Annual Report 1a.Objectives (from AD-416): Principal focus of the CEAP Watershed Studies is to evaluate the effects and benefits of conservation practices at the watershed scale, in support of policy decisions and program implementation. 1b.Approach (from AD-416): The effects of conservation activities on water and soil quality will be assessed at the watershed scale using models such as ARS' Soil and Water Assessment Tool, in combination with ARS long-term watershed data sets, expertise, and resources. 3.Progress Report: Watershed-scale data were collected at the Walnut Creek Watershed, in Story County, Iowa, Walnut Creek in Jasper County, Iowa, and the Southfork of the Iowa River, Hamilton and Hardin Counties, Iowa. Measurements of water flow, dissolved oxygen, temperature, and pH were made, as well as nitrate and phosphorus concentrations, E. coli and Enterococcus, and sediment. These data and meteorological data were placed in the Sustaining the Earth's Watersheds Agricultural Research Data System (STEWARDS) database. The effect of temporal variability of nitrate loads over multiple years and within years was analyzed with respect to estimating wetland and bioreactor installations in Walnut Creek and South Fork. Work on the use of light detection and ranging (LiDAR) derived terrain maps for conservation practice placement was also continued. This research was presented at the Soil and Water Conservation Society Meeting in Fort Worth, Texas, July 23, 2012, to National Resources Conservation Service (NRCS), Environmental Protection Agency (EPA) and university scientists as part of a special symposium on Conservation Effects Assessment Project (CEAP).