Drivers of Change

We focus on three primary large scale drivers of change within the Minnesota River Basin. First, intensively managed row-crop agriculture has changed the movement of water, nutrients, energy and sediment. Aggregated individual economic decisions such as a crop rotation schedule, how much land to have in production and fertilizer application rates can propagate through a watershed and have unintended consequences. Second, climatic drivers of watershed processes such as temperature and precipitation are concurrently changing the hydrological cycle and impose external forcing on the system. Finally, there continues to be active adjustment of the fluvial network to a geologic scale catastrophic event whichf2_MRBCropTransition2_lowerRes occurred
over 13,000 years ago. We investigate the relative importance of the three underlying drivers of change through both modeling and field methods.

Right: Progression of agricultural changes in the Minnesota River Basin (MRB). Using land-cover data at the county level, we define the ‘‘Land-Cover Transition’’ (LCT) as the year when the percentage of area for growing soybeans exceeded that for hay and small grains (barley, flax, oats, rye, and wheat).  (see examples in (a) Redwood and (b) Whetstone basins). (c) The map demonstrates the southeastern to northeastern progression of this agricultural transition. The Redwood (R), Cottonwood (C), and Whetstone (W) subbasins are shown for reference. Data are from the U.S. Department of Agriculture National Agricultural Statistics Service.  Bottom Left: Non-stationarity in climatic condition introduces many challenges in decoupling drivers of watershed processes.  The photo below is the 2012 Duluth flood caused by an unprecedented 9 inches of rainfall in the area.  Bottom Right: The catastrophic draining of Lake Aggasiz over 13,000 years ago formed the fluvial network of the Minnesota River Basin.

flood 600       lake-aggassiz2