Environmental impacts caused by herbicide loss from agricultural production are well documented in the surface runoff-prone claypan region. The most widely known impact was for atrazine, which caused the Mark Twain Lake to be listed in the original 303(d) list for impaired waters. While this lake has since been removed from the 303(d) list, concern remains that the reduction allowing its removal was at least partly caused by dry weather, which would mean that return to wetter weather might cause a renewed environmental impact. The lack of knowledge about factors controlling herbicide loss and transport hinder improved management. The 15-yr dataset on herbicide transport within the Goodwater Creek Experimental Watershed presents an opportunity to examine these factors over a range of weather, hydrology, and agricultural practices. The datasets include concentrations and loads for atrazine, metolachlor, alachlor, and acetochlor and several important metabolites. Observations include consistently high levels of atrazine and its mobile metabolites, DEA and DIA, compared to the acetanelide herbicides (alachlor, metolachlor and acetochlor). Cumulative frequency diagrams will be used to discern long-term trends in transport.