Over the last century large increases in water yield, nitrogen export, and inorganic carbon export have been documented for a number of North American rivers. Particularly, increases in water yield, nitrogen export, and inorganic carbon export from agriculturally dominated watersheds in the Mid-Western United States have been linked to concurrent increases in the Mississippi River. These increases are most notable in cropland dominated watersheds and, as such, land cover changes have been hypothesized as a likely driver. However, in many agricultural regions shifts in land cover have occurred along with increases in artificial drainage and increased rates of fertilization. Also, conversion of native land covers to agriculture has generally occurred because of underlying soil characteristics. Over the same time period as land use and land cover changes have occurred, precipitation has also increased in many watersheds. For this reason the mechanisms driving the above mentioned relationships have remained poorly defined.
Using spatial and temporal analysis of historical water quantity, water quality, land cover, land use, and climate data we will attempt to separate the likely impact of each of the above mentioned environmental changes on water yield and material export. This research will focus on a diversity of North American watersheds with contrasting histories of development, varying soil characteristics, and differing climate characteristics.