PT - JOURNAL ARTICLE AU - K.E. Schilling AU - C.S. Jones AU - C.F. Wolter AU - X. Liang AU - Y.-K. Zhang AU - A. Seeman AU - T. Isenhart AU - D. Schnoebelen AU - M. Skopec TI - Variability of nitrate-nitrogen load estimation results will make quantifying load reduction strategies difficult in Iowa AID - 10.2489/jswc.72.4.317 DP - 2017 Jul 01 TA - Journal of Soil and Water Conservation PG - 317--325 VI - 72 IP - 4 4099 - http://www.jswconline.org/content/72/4/317.short 4100 - http://www.jswconline.org/content/72/4/317.full AB - Many states within the Upper Mississippi River Basin are developing strategies to reduce nutrient loads to rivers. Reliable load estimation methods are needed to track progress toward nutrient reduction goals. We evaluated the variability of commonly used interpolation and extrapolation models to estimate nitrate-nitrogen (NO3-N) loads in 11 Iowa rivers. Results showed that the overall consistency between models of annual mean daily loads was low. Differences among the methods were particularly pronounced in May when the greatest NO3-N loads normally occur. The disparity in N load estimation among different methods is troubling given that states, federal agencies, or interest groups must have confidence in NO3-N load estimation procedures if the public is to believe that the load reductions strategies are working.