Abstract:There is growing interest in evaluating the impacts at the watershed scale of agricultural best management practices (BMPs) designed to improve water quality. Many approaches to impact assessment require detailed information about actual BMP use by farmers and landowners in a watershed. This paper examines the strengths and weaknesses of using formal USDA Natural Resources Conservation Service records of conservation program participation as an indicator of spatial and temporal patterns of BMP implementation and maintenance. Field interviews with conservation program participants revealed potential limitations with official records regarding (1) documentation of the incidence of successful BMP implementation, (2) the nature of the BMPs that were implemented, (3) accurate measurement of the timing and location of BMP implementations, and (4) information about the long-term use and maintenance of implemented BMPs. The results suggest that official records should be field-verified before being used as indicators of BMP use. The findings also point to a larger need for development of more robust and accurate systems for tracking BMP implementation and maintenance over periods of time. Key words: best management practice (BMP) implementation-maintenance-measurement-official records-watershedThere is growing interest among policymakers, farmers, and researchers in documenting the impacts of conservation practice adoption on environmental outcomes (Helmers et al. 2007;James and Cox 2008;Mausbach and Dedrick 2004;Van Liew et al. 2007). Numerous approaches to measuring the impacts of best management practices (BMPs) on water quality have been used, ranging from controlled experiments on small research plots or individual farm fields, monitoring of paired watersheds, empirical models that derive output coefficients for broad classes of land use, and process models that simulate the dynamics of watershed physical and hydrologic processes (Cherry et al. 2008). National-level estimates of the impacts of conservation programs have also been developed based on estimates of BMP adoption from large-scale representative sample surveys of farmers (Lambert et al. 2007; USDA NRCS 2009a, 2009b.Efforts to quantify the impacts of realworld agricultural BMPs on water quality at the watershed scale can benefit from the availability of accurate information about the current and past conservation behaviors of farmers and landowners. However, methods for gathering data on conservation behaviors and actual BMP use within watersheds vary widely, and strategies to integrate this information with detailed biophysical monitoring data in analytical models are still in their infancy. One recent initiative designed to address this situation is the USDA Conservation Effects Assessment Program (CEAP) that has coordinated the efforts of 14 existing USDA Agricultural Research Service (ARS) watershed research sites and allocated almost $8 million between 2004 to 2007 to fund another 13 non-ARS watershedscale research projects to develop innovat...