A third of U.S. grain and oilseed exports move through New Orleans and nearly 40 percent if one includes the Texas Gulf ports. Another 15 percent moves out the PNW to Asia. But what happens when the Mississippi dries up? In older literature, USDA’s Agricultural Marketing Service does not even show the Great Lakes ports moving cargo out of the Midwest. But when a conventional egress is blocked, find another route.  U.S. wheat exports are about on par with last year, but corn and soybean exports are both off by about a fifth. Thus far this year, U.S. grain exports moving out through the Great Lakes and the St. Lawrence Seaway to the North Atlantic are up 40 percent and potash is up over 260 percent. Some of this moved prior to the...