Randall Hunt, U.S. Geological Survey, Upper Midwest Water Science Center, Middleton, WI, United States, Esben Auken, University of Aarhus, Aarhus, Denmark, Wade Hampton Kress, U.S. Geological Survey, Lower Mississippi-Gulf Water Science Center, Nashville, TN, United States, Burke J Minsley, USGS Geology, Geophysics, and Geochemistry Science Center, Denver, CO, United States, Elliot D Grunewald, Vista Clara Inc., Mukilteo, WA, United States and Steen Christensen, Aarhus University, Aarhus C, Denmark