Rain or shine, the battle of the Mississippi rages on. The vital shipping lane that supports middle-American economies from the Upper-Midwest to New Orleans is once again in dire straits as the Army Corps of Engineers struggles to control Big Muddy--this time by making it deeper. Wracked by the worst (and longest) droughts in memory, the Midwest and the river are critically short on water, so short that the shallowest stretch of the river between Cairo, Ill. and St. Louis could become unnavigable in the next month, and the Corps of Engineers is just about out of geoengineering options to mitigate the problem, NPR reports.