Blann, Kristen, L.Anderson, James, L.Sands, Gary, R.Vondracek, Bruce2017-01-202017-01-202009https://hdl.handle.net/11299/183566The North American landscape has been profoundly altered to promote agricultural development since European settlement (“settlement”) at the end of the nineteenth century. More than 98% of the North American prairie and vast areas of forest have been replaced with croplands. Bringing much of this land into production under modern agricultural systems has been associated with extensive modifications to natural drainage networks. Extensive networks of surface ditches and subsurface drains (“tiles”) have been constructed to remove excess water from the field soil surface or soil profile (Spaling & Smit, 1995). By 1987, the most recent year for which survey data were collected, more than 17% of U.S. cropland (up to 30% in the Upper Midwest) had been altered by artificial surface or subsurface drainage (Pavelis, 1987).enwater qualitywetlandsnutrientshydrologyfishmacroinvertebratesReport