Soil information is one of the crucial inputs needed to assess the impacts of existing and alternative agricultural management practices on water quality. Therefore, it is important to understand the effects of spatial scale at which soil databases are developed on water quality evaluations. In the United States, STATSGO (State Soils Geographic) and SSURGO (Soil Survey Geographic) are the most commonly available soil databases. The purpose of this paper was to quantify the effect of scale by employing STATSGO (1:250,000) and SSURGO (1:24,000) soil databases in predicting and comparing flow, sediment, nitrate and phosphorus losses for High Island Creek. This watershed is predominately agricultural and located in south-central Minnesota. The ADAPT (Agricultural Drainage and Pesticide Transport), model was calibrated for flow, sediment, nitrate and phosphorus losses over two years (2001-2002) using STATSGO and SSURGO soil databases. Then the calibrated model was used to evaluate alternative tillage and fertilizer management practices such as adoption of conservation tillage, and rate, timing and method of N- and P-fertilizer applications. Statistical comparison of calibration results with observed data indicated excellent agreement for both soil databases (STATSGO with r2 of 0.95, 0.97, 0.77 and 0.92 and SSURGO with r2 of 0.90, 0.97, 0.82 and 0.99 for flow, sediment, nitrate and phosphorus losses, respectively). However, STATSGO based predictions of annual nitrate-N losses were consistently greater than those with SSURGO database and vice-versa for predicted annual phosphorus losses for the alternative management practice that were evaluated.
 M. Di Luzio, J. G. Arnold and R. Srinivasan, “Integration of SSURGO Maps and Soil Parameters within a Geographic Information System and Nonpoint Source Pollution Model System,” Journal of Soil and Water Conservation, Vol. 59, No. 4, 2004, pp. 123-133.
 A. C. Mednick, “Does Soil Data Resolution Matter? State Soil Geographic Database versus Soil Survey Geographic Database in Rainfall-Runoff Modeling across Wisconsin,” Journal of Soil and Water Conservation, Vol. 65, No. 3, 2010, pp. 190-199. doi:10.2489/jswc.65.3.190
 R. M. Anderson, V. I. Koren and S. M. Reed, “Using SSUR-GO Data to Improve Sacramento Model a Priori Parameter Estimates,” Journal of Hydrology, Vol. 320, No. 1-2, 2006, pp. 103-116. doi:10.1016/j.jhydrol.2005.07.020
 M. Geza and J. E. McCray, “Effects of Soil Data Resolution on SWAT Model Stream Flow and Water Quality Predictions,” Journal of Environmental Management, Vol. 88, No. 3, 2008, pp. 393-406. doi:10.1016/j.jenvman.2007.03.016
 J. M. Peschel, P. K. Haan and R. E. Lacey, “Influences of Soil Dataset Resolution on Hydrologic Modeling,” Journal of the American Water Resources Association, Vol. 42, No. 5. 2006, pp. 1371-1389. doi:10.1111/j.1752-1688.2006.tb05619.x
 V. Nangia, “Field- and Watershed-Scale Evaluation of Water Quality Trends Due to Changes in Landscape and Management Practices,” Ph.D. Dissertation, University of Minnesota, Minneapolis, 2005, 157 p.
 A. D. Ward, E. D. Desmond, N. R. Fausey, T. J. Logan and W. G. Logan, “Development Studies with the ADAPT Water Table Management Model,” 15th International Congress on Irrigation and Drainage, The Hague, 1993, pp. 235-245.
 P. H. Gowda, A. D. Ward, D. A. White, J. G. Lyon and E. D. Desmond, “The Sensitivity of Stream Flows to Model Input Parameters Used to Define Hydrologic Response Units,” Transactions of the ASAE, Vol. 42, No. 2, 1999, pp. 381-389.
 D. M. Davis, P. H. Gowda, D. J. Mulla and G. W. Randall, “Modeling Nitrate Nitrogen Leaching in Response to Nitrogen Fertilizer Rate and Tile Drain Depth or Spacing for Southern Minnesota, USA,” Journal of Environmental Quality, Vol. 29, No. 5, 2000, pp. 1568-1581. doi:10.2134/jeq2000.00472425002900050026x
 B. J. Dalzell, P. H. Gowda and D. J. Mulla, “Evaluating Feasibility of TMDLs with Alternative Management Prac- tices on an Agricultural Watershed,” Journal of the American Water Resources Association, Vol. 40, No. 2, 2004, pp. 533-543. doi:10.1111/j.1752-1688.2004.tb01048.x
 K. Updegraff, P. H. Gowda and D. J. Mulla, “Watershed Scale Modeling of the Water Quality Effects of Cropland Conversion to Short Rotation Woody Crops,” Renewable Agriculture and Food Systems, Vol. 19, No. 2, 2004, pp. 1-11. doi:10.1079/RAFS200072
 D. R. Petrolia and P. H. Gowda, “An Analysis of the Role of Tile-Drained Farmland under Alternative Nitrogen Abatement Policies,” Journal of Agricultural and Resource Economics, Vol. 31, No. 3, 2006, pp. 580-594.
 P. H. Gowda, B. J. Dalzell and D. J. Mulla, “Model Based Nitrate TMDLs for Two Agricultural Watersheds of Southeastern Minnesota,” Journal of the American Water Resources Association, Vol. 43, No. 1, 2007, pp. 1-10. doi:10.1111/j.1752-1688.2007.00020.x
 P. H. Gowda, D. J. Mulla and D. B. Jaynes, “Modeling Impact of Timing and Amount of Nitrogen Fertilizer on Water Quality for an Iowan Agricultural Watershed,” Agricultural Water Management, Vol. 95, No. 5, 2008, pp. 616-624. doi:10.1016/j.agwat.2008.01.004
 V. Nangia, P. H. Gowda, D. J. Mulla and G. R. Sands, “Water Quality Modeling for Impacts of Fertilizer Management Practices on Nitrate-N losses in Tile Drains at the Field-Scale,” Journal of Environmental Quality, Vol. 37, No. 2, 2008, pp. 296-307. doi:10.2134/jeq2007.0224
 V. Nangia, D. J. Mulla and P. H. Gowda, “Precipitation Changes Impact Stream Discharge, Nitrate-Nitrogen Load More than Agricultural Management Changes,” Journal of Environmental Quality, Vol. 39, No. 6, 2010, pp. 2063-2071. doi:10.2134/jeq2010.0105
 W. J. Gburek, A. N. Sharpley, L. Heathwaite and G. J. Fohan, “Phosphorus Management at the Watershed Scale: A Modification of the Phosphorus Index,” Journal of Environmental Quality, Vol. 29, No. 1, 2000, pp. 130-144. doi:10.2134/jeq2000.00472425002900010017x
 D. N. Moriasi, J. G. Arnold, M. W. Van Liew, R. L. Bingner, R. D. Harmel and T. L. Veith, “Model Evaluation Guidelines for Systematic Quantification of Accuracy in Watershed Simulations,” Transactions of ASABE, Vol. 50, No. 3, 2007, pp. 885-900.